Contains Nonbinding Recommendations 
 
 
Medical Devices and Clinical Trial 
Design for the Treatment or 
Improvement in the Appearance of 
Fungally-Infected Nails 
 
Guidance for Industry and Food and 
Drug Administration Staff  
 
Document issued on: March 7, 2016. 
 
The draft of this document was issued on January 27, 2015. 
  
 
For questions about this document, contact General Surgery Devices Branch 1, 301-796-6970 and 
Mr. Neil Ogden, 301-796-6397, neil.ogden@fda.hhs.gov. 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Devices and Radiological Health 
Office of Device Evaluation 
Division of Surgical Devices 
 
 
  Contains Nonbinding Recommendations 
 
 
 
Preface 
 
Public Comment 
 
You may submit electronic comments and suggestions at any time for Agency consideration to 
http://www.regulations.gov . Submit written comments to the Division of Dockets Management, 
Food and Drug Administration, 5630 Fishers Lane, Room 1061, (HFA-305), Rockville, MD 
20852. Identify all comments with the docket number FDA-2014-D-1849. Comments may not be 
acted upon by the Agency until the document is next revised or updated. 
 
Additional Copies 
 
Additional copies are available from the Internet.  You may also send an e-mail request to CDRH-
Guidance@fda.hhs.gov to receive a copy of the guidance. Please use the document number 
1400009 to identify the guidance you are requesting. 
 
 
  Contains Nonbinding Recommendations 
 
 
Table of Contents 
 
I.  INTRODUCTION............................................................................................................. 1 
II.  BACKGROUND ............................................................................................................... 3 
III.  TEMPORARY INCREASE IN CLEAR NAIL ............................................................. 5 
A.  Regulatory considerations ............................................................................................................. 5 
1. Defining temporary increase in clear nail .................................................................................. 5 
2. Combining treatment with antifungal drugs or debridement ........................................................... 5 
3. Differentiating aesthetic indications from medical indications ....................................................... 6 
4. Special populations .......................................................................................................................... 6 
B.  Clinical trial considerations .......................................................................................................... 7 
1. Special populations .......................................................................................................................... 7 
2. Inclusion/exclusion criteria: recommendations ............................................................................... 7 
3. Adjunctive therapies....................................................................................................................... 10 
4. Endpoints ....................................................................................................................................... 11 
5. Follow-up ....................................................................................................................................... 14 
6. Controls ......................................................................................................................................... 14 
7. Blinding .......................................................................................................................................... 14 
8. Dose considerations ....................................................................................................................... 15 
9. Data analysis ................................................................................................................................. 15 
10.  Adverse event monitoring .......................................................................................................... 16 
C.  Statistical Considerations ............................................................................................................ 16 
D.  Labeling Considerations .............................................................................................................. 19 
IV. TREATMENT OF ONYCHOMYCOSIS .......................................................................... 20 
A.  Regulatory considerations ........................................................................................................... 20 
1. Defining treatment of onychomycosis ....................................................................................... 20 
2. Combining treatment with antifungal drugs or debridement ......................................................... 21 
3. Species-dependent outcomes .......................................................................................................... 21 
4. Special populations ........................................................................................................................ 21 
B.  Clinical trial considerations ........................................................................................................ 21 
1. Special populations ........................................................................................................................ 21 
2. Inclusion/exclusion criteria: recommendations ............................................................................. 22 
3. Adjunctive therapies....................................................................................................................... 23 
4. Endpoints ....................................................................................................................................... 23 
5. Follow-up ....................................................................................................................................... 25 
6. Controls ......................................................................................................................................... 25 
7. Blinding .......................................................................................................................................... 25 
8. Dose considerations ....................................................................................................................... 26 
9. Data analysis ................................................................................................................................. 26 
10.  Adverse event monitoring .......................................................................................................... 26 
C.  Statistical Considerations ............................................................................................................ 26 
D.  Labeling considerations ............................................................................................................... 26
 
  Contains Nonbinding Recommendations 
 
 
 Medical Devices and Clinical Trial 
Design for the Treatment or 
Improvement in the Appearance of 
Fungally-Infected Nails 
 
Guidance for Industry and Food and 
Drug Administration Staff  
 
 
This guidance represents the current thinking of the Food and Drug Administration (FDA or 
Agency) on this topic.  It does not establish any rights for any person and is not binding on 
FDA or the public.  You can use an alternative approach if it satisfies the requirements of the 
applicable statutes and regulations.  To discuss an alternative approach, contact the FDA staff 
responsible for this guidance as listed on the title page.  
 
 
I.  INTRODUCTION  
 
A variety of diseases can affect the appearance of nails, including fungal infection.  This 
guidance is intended to provide recommendations regarding clinical trial design for medical 
devices intended either (1) to provide improvement in the appearance of nails affected by 
onychomycosis, that is, to affect the structure/function of the nails or (2) to treat onychomycosis 
(fungal nail infection).  All marketed devices to date have been 510(k)-cleared for visual 
improvement, with Indication for Use statements such as temporary increase of clear nail in 
patients with onychomycosis (e.g., dermatophytes Trichophyton rubrum and Trichophyton 
mentagrophytes, and/or yeasts Candida albicans).1  Some elements of this guidance will be 
primarily applicable to non-ablative energy-based devices, although the basic principles may be 
broadly applicable to all devices.     
 
The Food and Drug Administration (FDA) distinguishes these two conditions as target outcomes.  
An indication for the treatment of onychomycosis (an infectious disease) requires proof of stable 
                                                           
1 For brevity, this guidance may use the abbreviated phrases temporary increase of clear nail or temporary 
increase in clear nail to refer to the Indication for Use temporary increase of clear nail in patients with 
onychomycosis (e.g., dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes, and/or yeasts 
Candida albicans, etc.).   
1 
  Contains Nonbinding Recommendations 
 
 
elimination of the fungal organism, which is a medical endpoint.  This outcome is distinct from 
outcomes limited to temporary increase in clear nail in nails which are fungally-infected, 
which is considered an aesthetic endpoint, and does not necessarily signify successful eradication 
of fungal infection, but rather an effect on the structure/function of the nails.  The Agency 
recognizes that this endpoint may have functional benefits as well, which may be of some value 
to the patient if the improvement in appearance or function is clinically significant and if the 
benefits outweigh potential risks of the treatment.  Nonetheless, claims related to appearance 
remain distinct from claims of eliminating fungal infection. 
 
This guidance addresses patient populations in the United States as the intended demographic for 
intervention.  The recommendations regarding clinical trial design may be applicable for any 
medical device type that is intended for temporary increase of clear nail or to treat 
onychomycosis (fungal nail infection).  These recommendations would apply to clinical 
performance data submitted in Premarket Notification (510(k)) Submissions, Evaluation of 
Automatic Class III Designations (de novo submissions), and Premarket Approval (PMA) 
applications, as well as for Investigational Device Exemptions (IDEs).2   
 
The need for clinical performance data will be dependent on the design and use of the device.3  
Sponsors are encouraged to discuss this with the agency.  In addition, we recommend that you 
contact the Agency through the pre-submission process prior to starting any clinical study for 
these nail indications.  For information on the pre-submission process see FDAs guidance 
Requests for Feedback on Medical Device Submissions: The Pre-Submission Program and 
Meetings with Food and Drug Administration Staff 
(http://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocu
ments/UCM311176.pdf).   
 
This guidance is not intended to replace the policies described in other guidance documents.  In 
cases where questions arise, consult the appropriate FDA review division directly or the Center 
for Devices and Radiological Health (CDRH) Division of Industry and Consumer Assistance 
(DICE).   
 
FDAs guidance documents, including this guidance, do not establish legally enforceable 
responsibilities.  Instead, guidances describe the Agencys current thinking on a topic and should 
be viewed only as recommendations, unless specific regulatory or statutory requirements are 
cited.  The use of the word should in Agency guidances means that something is suggested or 
recommended, but not required.  
 
 
                                                           
2 Currently marketed devices indicated for temporary increase in clear nail have been cleared through the 510(k) 
pathway.  As such, this guidance refers to clearances and devices cleared.  However, wherever such 
terminology is used in this document, the recommendations and considerations may apply to all premarket 
submission types (e.g., PMA, de novo). 
 
3 One example of a device type that has been cleared for the indication of temporary increase in clear nail is light-
based devices.  Refer to the Appendix for an example of the information that FDA recommends be submitted in a 
regulatory application for this device class. 
2 
  Contains Nonbinding Recommendations 
 
 
II.  BACKGROUND 
 
Nail dystrophy is commonly due to fungal infection (onychomycosis), but approximately 40% of 
nails which appear abnormal may be due to other clinical conditions.4  A wide variety of 
disorders, including inflammatory, metabolic, genetic, and non-fungal infectious diseases, as 
well as physical trauma to the nail, can create abnormal nail structures.  These changes, which 
include separation of the distal nail from the nail bed, nail thickening, and color changes within 
the nail, can be visually indistinguishable from onychomycosis.5  However, it cannot be assumed 
that treatments that alter the appearance of nails are necessarily effective in eliminating 
onychomycosis.  Conversely, it cannot be assumed that treatments that are effective in treating 
onychomycosis would necessarily alter the appearance of nails, if the abnormal nail growth or 
appearance (dystrophy) were caused by a condition other than onychomycosis.  It is therefore 
important to distinguish the indications of temporary increase of clear nail in patients with 
onychomycosis and treatment of onychomycosis, so as to differentiate the treatment goals.   
 
This guidance is intended to provide information related to both indications, when the device is 
applied to nails with confirmed fungal infection.  The considerations in this guidance may not be 
equally applicable to nails whose appearance is altered by non-fungal causes.  Therefore, prior to 
pursuing treatment of abnormally structured or dystrophic nails, it is critical to diagnose the 
underlying cause, and to base treatment decisions on proven therapies for the identified cause.   
 
Temporary increase of clear nail 
Historically, devices have been cleared with the Indications for Use (IFU) of temporary increase 
of clear nail in patients with onychomycosis (e.g., dermatophytes Trichophyton rubrum and/or 
yeasts Candida albicans, etc.).  This indication has been used to highlight that the outcomes for 
which the device has provided support are limited to visual improvement, an aesthetic endpoint, 
and not for mycological cure, which would constitute a medical endpoint.  Several aspects of this 
IFU are noteworthy: 
 
1)  This IFU is not intended to mean that the treatment eliminates fungal infection.  It does, 
however, convey that clinical studies performed in support of the IFU included nails with 
confirmed fungal infection.   
2)  The devices have primarily been assessed for their effectiveness in nails infected with the 
common fungal organisms; the effectiveness may not be comparable in nails infected 
with rare species.   
3)  As stated above, this indication should not be assumed to demonstrate effectiveness in 
other causes of nail dystrophy.  Therefore dystrophic nails should be confirmed as 
fungally-infected prior to initiation of clinical trials or treatments that employ devices 
cleared with this IFU.   
                                                           
4 Gupta AK, Jain HC, Lynde CW, Watteel GN, Summerbell RC.  Prevalence and epidemiology of unsuspected 
onychomycosis in patients visiting dermatologists' offices in Ontario, Canada--a multicenter survey of 2001 patients.  
International Journal of Dermatology.  1997;36(10):783-7. 
5 Fletcher CL, Hay RJ, and Smeeton NC.  Observer agreement in recording the clinical signs of nail disease and the 
accuracy of a clinical diagnosis of fungal and non-fungal nail disease.  British Journal of Dermatology.  2003;148, 
55862. 
3 
  Contains Nonbinding Recommendations 
 
 
4)  Finally, we recognize that some patients seek total clearing of their nails rather than 
partial clearance and this expectation should be clarified.  Labeling and promotional 
materials should provide a transparent portrayal of representative results that were 
achieved in the clinical trials, both in terms of the extent of nail clearance and the 
timeline of effect. 
 
Treatment of onychomycosis 
In contrast to treatments for increase in clear nail, treatments aimed at treating a fungal infection 
require evidence of an antifungal effect.  Specifically, devices marketed with an indication of 
treating fungal infections of the nail are expected to provide evidence that the fungal infection in 
the nail has been eliminated.  For treatment of toenail fungal infection, this indication, in most 
cases, will be supported by evidence of visual improvement in conjunction with negative fungal 
cultures and stains. 
 
Fungal species: geographic and demographic considerations   
Clinical studies performed outside the United States may not be applicable to the U.S. population 
due to different prevailing fungal organisms that may affect the nails.  Therefore, studies 
performed in the U.S. are recommended.  Data from clinical studies performed outside the U.S. 
should include a comprehensive analysis of all fungal species detected in the nails of the 
population screened for enrollment in the clinical study, and the analysis reveals a similar 
spectrum and distribution of fungal species.   
 
Special populations, including individuals with certain chronic diseases, occupational risks, or 
immune compromise, may have different or additional organisms in the nail, and the 
effectiveness demonstrated in clinical studies performed in healthy adults may not be sufficiently 
informative about these populations. 
 
Although indications for use statements in prior clearances have included Candida as an example 
of an organism that may have been present during treatment, Candida is not a toenail pathogen in 
healthy individuals and is involved in only approximately half of fingernail infections.6  Since it 
is recommended that non-healthy individuals be excluded from clinical studies for these 
indications, Candida should not be assessed in clinical studies of toenails for the indication of 
temporary increase in clear nail or of treatment of onychomycosis.  An Indication for Use 
addressing Candida may be considered with specially designed studies assessing the 
performance of the device in nails infected with Candida species.  Future marketing application 
labeling should reflect this information. 
 
Care and re-use of devices which contact fungally-infected nails 
Devices intended for use on infected tissue should be evaluated for design and labeling as 
described in FDAs guidance  Reprocessing Medical Devices in Health Care Settings: 
Validation Methods and Labeling 
                                                           
6 Foster KW, Ghannoum MA, and Elewski BE.  Epidemiologic surveillance of cutaneous fungal infection in the 
United States from 1999 to 2002.  Journal of the American Academy of Dermatology.  2004;50(5):748-52. 
 
4 
  Contains Nonbinding Recommendations 
 
 
(http://www.fda.gov/downloads/medicaldevices/deviceregulationandguidance/guidancedocumen
ts/ucm253010.pdf).  
 
III.  TEMPORARY INCREASE IN CLEAR NAIL 
 
A.  Regulatory considerations 
 
1.  Defining temporary increase in clear nail  
 
Normal appearance of nails is the goal for appearance improvement.  Historically, for medical 
devices, FDA has allowed less than fully clear nails as acceptable for a primary endpoint.  
Although the assessment method for clear nail varied, several medical devices have received 
510(k) clearance on the premise that they improve the appearance of nails by an increase in clear 
nail, observed clinically. These devices have demonstrated that this improvement is maintained 
or increased when assessed at two timepoints (e.g., 3 months and 6 months) after the last 
treatment, to reflect growth of clear nail. All studies were performed on toenails, primarily the 
first toenail.7   
 
By way of comparison, pivotal studies performed in support of oral antifungal treatments have 
shown that the mean time to overall success is 10 months in toenails and 4 months in 
fingernails.8  These studies employed multiple endpoints, including complete visual clearance, or 
for partial responders at least 5 mm increase in clear nail at 36 weeks (9 months) after 
completion of treatment of the toenails and at 18 weeks after completion of treatment of the 
fingernails. 
 
Nails which are structurally abnormal can only clear by outgrowth of the dystrophic component 
and replacement by newly-created, normal-appearing nail.  The mean growth rate for nails in 
healthy U.S. adults is 1.5 mm per month for toenails and 3-3.5 mm per month for fingernails.9  
Based on this mean growth rate, the ideal effective treatment would be expected to yield a fully 
replaced, clear fingernail in a healthy adult after approximately 6 months and a fully replaced, 
clear great toenail approximately 12 months after the initiation of treatment.  However, given the 
length of time after the initiation of treatment, it is possible that the nail would be re-infected 
during this time, in the absence of ongoing treatment.   
 
2.  Combining treatment with antifungal drugs or debridement 
 
Historically, device studies have allowed concomitant debridement and/or use of topical or 
systemic antifungal drug products, aimed at treating the nails or the skin.  The combination of 
debridement and/or antifungal drug therapy confounds the interpretation of the study results in 
determining the relative contribution of the device to the clinical outcome.   
 
                                                           
7 Refer, for example, to K110370 and K110375  
8 Refer to NDA 020539 
9 Yaemsiri S, Hou N, Slining MM, He K.  Growth rate of human fingernails and toenails in healthy American young 
adults.  Journal of the European Academy of Dermatology & Venereology, 2010; 24(4): 420-23. 
5 
  Contains Nonbinding Recommendations 
 
 
The Agency will continue to consider submission of clinical performance data evaluating the 
device with adjunctive interventions, with the exception of oral antifungal drugs.  The use of oral 
drugs will likely confound any device results observed, and as a result, FDA does not believe 
such data should be used to support a substantial equivalence determination.  If topical products 
(not systemic) are used which can have antifungal activity, they should be administered 
according to standard of care dosing and route of administration.   
 
For truthful and transparent labeling, the Agency recommends that the device labeling reflect any 
adjunctive treatment in the Indications and Usage statement.  Recommended wording for a 
device whose clinical trials were performed with topical antifungals and/or debridement, for 
example, would be:  
 
Indicated for adjunctive use in the temporary increase in clear nail in patients 
with onychomycosis (e.g., dermatophytes - Trichophyton rubrum and 
Trichophyton  mentagrophytes).  This device should be used with manual 
debridement and/or topical antifungal products, administered according to 
standard of care dosing and route of administration, whose use may need to be 
continued after completion of device treatment course, as stand-alone 
effectiveness of this device for this indication has not been demonstrated; 
 
or 
 
Indicated for the temporary increase in clear nail in patients with onychomycosis 
(e.g., dermatophytes - Trichophyton rubrum and Trichophyton  mentagrophytes) 
only when used together with topical antifungalproducts, administered according 
to standard of care dosing and route of administration for treating accompanying 
tinea pedis and/or onychomycosis. 
 
For transparency, FDA recommends that the patient and practitioner labeling disclose that the 
device has been assessed as an adjunct to drug therapy or other intervention. 
 
3.  Differentiating aesthetic indications from medical indications 
 
Devices cleared for improvement in the appearance of nails, or an increase in clear nail, could be 
misconstrued to be intended to treat onychomycosis.  To prevent misinterpretation, FDA 
recommends that the labeling for these devices contain clarifying language, to include:  
 
This device has not demonstrated effectiveness in the treatment of fungal 
infections.  It is cleared only for improvement in nail appearance.   
 
4.  Special populations 
 
The distinction between aesthetic improvement of the nail and elimination of a fungal infection 
is of particular clinical relevance for vulnerable populations, who require definitive antifungal 
treatment, and who may remain at ongoing medical risk by postponing definitive treatment.  To 
protect these populations, the labeling should include the following statement:  
6 
  Contains Nonbinding Recommendations 
 
 
 
Warning: These devices should be used with caution in patients with diabetes, 
peripheral vascular disease, or immune-suppression, or with any other medical 
state which warrants definitive antifungal therapy. 
 
Devices that have not been studied in such populations should receive a similar warning. 
 
B.  Clinical trial considerations 
 
The claim of temporary improvement in clear nails is an aesthetic one, but treatments will be 
performed in nails that are infected with a fungus.  Therefore, although the claim is aesthetic, 
clinical trial design should take into account the medical implications of the proposed protocol.  
 
1.  Special populations 
 
Ethical design of clinical studies mandates that risk to special populations be minimized.  Special 
populations may be considered particularly vulnerable and may not be appropriate subjects for 
clinical studies assessing temporary increase in clear nail.  For example, patients with diabetes 
mellitus, peripheral vascular disease, recurrent cellulitis, lymphatic insufficiency, or immune 
compromise (whether due to underlying medical disorders or to immunosuppressive treatments), 
exhibit an increased risk of bacterial infections.  In these patients, the skin breakdown induced by 
a fungus may provide a portal for bacterial infections, which consequently pose a significant 
health risk.  Portals of entry can also be formed at sites of skin breakdown caused by adverse 
events in the course of a device-based treatment.  Furthermore, nails may appear to have an 
increase in clear area but still harbor fungal organisms; this is the distinction between the clear 
nail indication and an indication of treating onychomycosis.  For these reasons, it is 
recommended that patients with diabetes, immune suppression, peripheral vascular disease, 
lymphatic insufficiency, recurrent cellulitis, or other compromised states of health be excluded 
from participating in clinical trials intended to demonstrate improvement in the appearance of 
nails. 
 
Sponsors and investigators are urged to design clinical studies which enroll a cross-section of 
subjects that reflects the U.S. demographic.  This may include variable age, gender, and 
Fitzpatrick skin types (if needed).   
 
Treatment with light sources whose wavelength is absorbed by melanin pose increased risk to 
individuals with darker skin types.  In addition, any modality that can induce injury to skin poses 
an increased risk for post-inflammatory hyperpigmentation in subjects with darker skin.  Since 
the pigmentation of both the nails and the surrounding skin may affect response and treatment 
tolerance, it is recommended that studies be designed to allow assessment of safety and 
effectiveness in the target population.  If the nature of the treatment mandates restriction in 
Fitzpatrick skin phototypes in the clinical study, this should be reflected in the device labeling. 
 
2.  Inclusion/exclusion criteria: recommendations 
 
Clinical involvement 
7 
  Contains Nonbinding Recommendations 
 
 
Nails with 100% dystrophy or with involvement of the lunula can be very resistant to treatment 
due to permanent damage to the nail matrix (root); this may reduce the mean effectiveness 
assessed across a group of subjects.10  Conversely, nails with minimal distal changes may not be 
representative of the target populations for this procedure.  Therefore, it is recommended that the 
study population include nails with at least 25% involvement of the nail area and no more than 
75% involvement of the nail area. 
 
Clinical presentations of onychomycosis 
There are several clinical forms of onychomycosis, differentiated by their appearance.  Some are 
appropriate for inclusion in device clinical trials, while others may be less appropriate for 
inclusion in clinical studies intended to demonstrate improvement in the appearance of nails.   
 
  Distal subungual onychomycosis (DSO):  This type of onychomycosis is the most 
common clinical presentation, in which the distal nail plate is separated from the nail bed.  
This infection is visualized as nails with normal surface texture and thickness but variable 
bays of white nail that extend from the distal nail tip proximally into the area of the nail 
bed.  This form has been the cornerstone of antifungal drug studies.  Since it generally 
does not involve the nail matrix, it is more amenable to improvement in clinical 
appearance than some other forms. 
 
  Proximal subungual onychomycosis (PSO):  PSO is an uncommon form of 
onychomycosis that appears as a white discoloration below the nail plate at the base of 
the nail, near the lunula.  The distal nail retains normal appearance and texture.  PSO 
involves infection near the matrix, deep to the nail.  It may be associated with trauma to 
the nail or to immune compromise.  Therefore, the clinical presence of PSO may hint at 
an underlying medical disorder.  In addition, PSO may reflect different species of fungus.  
Moreover, obtaining samples for mycology studies prior to enrollment is not possible 
without piercing or removing the nail.  It is therefore recommended that this form of 
onychomycosis not be included in device clinical studies.   
 
  Superficial white onychomycosis (SWO):  This form of onychomycosis is defined by the 
appearance of a white coating on the nail surface.  This clinical form can be eliminated 
by filing or buffing the surface of the affected portion of the nail.  Since subjects might 
buff or file the nails during the study and confound the results, and since this form does 
not generally require any other treatment, SWO is not an ideal clinical form of 
onychomycosis for device trials or for post-market treatments. 
 
  Complete dystrophy: Nails which are 100% dystrophic are manifested by yellowing and 
thickening of the entire nail unit.  These nails may be difficult to treat due to irreversible 
damage to the nail matrix.  In such cases even complete eradication of the fungus may 
not lead to normal nail growth rate or appearance.  Such nails may provide data that is 
relevant for subsequent clinical use, but these cases may also be more difficult targets for 
                                                           
10 Gupta A and Daniel III C.  Factors that may affect the response of onychomycosis to oral antifungal therapy.  
Australasian Journal of Dermatology. Nov98, Vol. 39 Issue 4, p222-224 
8 
  Contains Nonbinding Recommendations 
 
 
treatment.  If enrolled, it is recommended that this clinical form of onychomycosis be 
evaluated for improvement in appearance separately from other clinical forms, whose 
appearance may improve more readily with treatment. 
 
  Other nail changes: Nail changes that appear as parallel lines, small pinpoint depressions, 
brown spots, black or brown linear streaks, complete yellowing of all nails without 
textural change, green debris below the nail, or notches in the nail margin may represent 
causes of nail dystrophy that are not fungal.  It is therefore recommended that all nails be 
evaluated by an expert in nail disease prior to enrolling such subjects in device clinical 
trials or post-market treatments.   
 
Confirmation of fungal infection underlying nail appearance 
To support an Indication for Use of temporary increase of clear nail in onychomycosis, it is 
appropriate that all enrolled subjects be confirmed to have nails infected by the common fungal 
organisms implicated onychomycosis.  In the United States, Trichophyton rubrum accounts for 
roughly 80% of toenail onychomycosis, with additional infections caused by Trichophyton 
mentagrophytes or Epidermophyton floccosum; other observed but less common fungal 
infections of the toenails include Candida parapsilosis, and Fusarium species.11  In fingernail 
onychomycosis, Candida albicans accounts for over 50% of cases, with another 25% accounted 
for by Trichophyton rubrum; other Candida species comprise most of the remaining cases.10  By 
enrolling subjects whose nails have been demonstrated to harbor these organisms, studies are 
more likely to generate data that is clinically meaningful.  It is recommended that nails infected 
by rare fungal species or non-fungal organisms such as mold or bacteria be excluded, as their 
data is unlikely to provide information that is widely applicable. 
 
Common methods for identifying the presence and type of fungus present in nails include stains 
(e.g. periodic acid Schiff (PAS); silver stains; potassium hydroxide (KOH)) and fungal culture.)  
Negative stains, particularly PAS and silver stains, provide convincing evidence that the sampled 
portion of the nail is free of fungal organisms.  However, while finding fungal organisms within 
the nail plate using fungal stains provides convincing evidence of the presence of fungus, it does 
not speak to the organisms viability, and it does not identify the type of fungus.  Identification 
of the organism and determination of its viability, both of which are critical pre-treatment data, 
are accomplished by culture.   
 
The best evidence that a nail is suitable for a clinical study would be a concurrent positive stain 
showing septate hyphae and positive culture demonstrating the growth of T. rubrum or other 
common dermatophyte.  Therefore, it is suggested that prior to enrollment, both a stain and 
culture be obtained.   
 
It is known that cultures may yield false negative results.  If the stain exhibits septate hyphae but 
the culture fails to grow a fungus, the culture may be repeated.  If two sequential cultures are 
negative, it is recommended that the nail not be included in the study, as the fungus may be 
partially treated, fastidious, or otherwise not representative of the target strains.  Sponsors may 
                                                           
11Foster KW, Ghannoum MA, and Elewski BE.  Epidemiologic surveillance of cutaneous fungal infection in the 
United States from 1999 to 2002.  Journal of the American Academy of Dermatology.  2004;50(5):748-52. 
9 
  Contains Nonbinding Recommendations 
 
 
wish to stain and culture material from two nails from an affected foot or hand in parallel to 
expedite this process.  The finding of positive stains with negative cultures from two nails would 
suggest the subject is not a good candidate for the study. 
 
Co-morbidities 
Subjects with psoriasis, lichen planus, or other medical conditions known to induce nail changes 
may also have superimposed fungal nail infections.  Trauma from ill-fitting shoes, running, or 
overly-aggressive nail care can also induce changes visually indistinguishable from 
onychomycosis.  These causes of nail breakdown can predispose to secondary fungal infection.  
However, it cannot be predicted whether treatments aimed at increasing clear nail in patients 
with onychomycosis would also improve the appearance of nail changes when those nail changes 
are due to an additional causative condition.  It is therefore advisable to avoid inclusion of 
subjects known to have such medical conditions, as their response may not be indicative of the 
effects of the device on nails that are infected by fungus but are otherwise normal. 
 
Prior or ongoing antifungal drug therapy 
Systemic antifungal drugs are deposited in the nail substance and remain in the nail until the nail 
grows and is trimmed.  Based on the known rates of nail growth in healthy adults, it is expected 
that nails exposed to even one dose of an antifungal drug may contain the drug for 1 year in the 
case of toenails and 6 months in the case of fingernails.  Enrollment of subjects who have been 
exposed to antifungal drugs in the 12 months prior (in the case of toenails) or 6 months prior (in 
the case of fingernails) could confound interpretation of the study data, and it is therefore 
recommended that these subjects be excluded from any device study. 
 
Topical antifungal drugs are less effective in providing clinical clearance of onychomycosis.  
However, their presence can reduce the sensitivity of fungal cultures, even if applied only to the 
skin of the affected hand or foot.  It is therefore recommended that a significant washout period 
be applied when enrolling patients who have undergone topical treatment of the skin or nails, and 
that such treatments be avoided during the clinical trial and follow-up period.   
 
Demographics 
It is recommended that the enrollment include adequate US demographic representation of the 
intended population with regard to gender, age, ethnicity, race, and skin phototype. 
 
3.  Adjunctive therapies 
 
Adjunctive therapies in clinical trials of devices are suboptimal as they may mask the true 
performance of the device.  Nonetheless, if a clinical trial is designed in which antifungal drug 
therapy or other intervention is administered in parallel to the device treatment, the adjunctive 
intervention should be consistent across all study subjects, and the full regimen should be 
included in the recommended treatment protocol as well as the device labeling.  Sponsors might 
consider including a control which utilizes only the adjunctive therapy, in order to identify the 
incremental benefit provided by the device.  For example, studies that include a topical 
antifungal product may be able to provide additional data in support of device effectiveness by 
performing a contralateral controlled study, in which both feet (or hands) are exposed to the 
10 
  Contains Nonbinding Recommendations 
 
 
topical antifungal agent, but only one side is exposed to the device treatment.  Such a study 
design would require special considerations if blinding or placebo were to be incorporated. 
 
It is recommended that debridement not be carried out more proximally than the most proximal 
margin of the dystrophic nail, as this can interfere with assessment of clear nail area attributable 
to the device intervention.  If debridement is used in clinical studies performed in support of a 
device, the debridement procedures should be well described in the clinical protocol, used 
consistently in study subjects, and included in the recommended treatment protocol as well as the 
device labeling. 
 
4.  Endpoints 
 
Based on the nail growth rates described in the regulatory considerations section above, and to 
provide a fair and informative guideline for assessment of the success of a treatment, FDA 
recommends the following effectiveness endpoints be used in a study to demonstrate temporary 
increase in clear nail. Although these endpoints differ from those historically provided for this 
device type for this indication, we believe that the use of data at time points measured after the 
first treatment, rather than the last treatment,  provides a more clinically relevant  result than 
assessment of nails after treatment has been discontinued.  Further, to address variability in nail 
length among different digits, the longest nail (thumb or first toe) is recommended as the target 
nail for measurement.  
 
The 95% one-sided confidence interval (i.e., lower bound only) around the observed response 
rate as described below should be 50%.    
 
Toenails: (based on assessment in the first toe nail) 
 
  To be defined as a responder, a nail would need to meet one of the following 
measurements of clear nail increase: 
  at least 6 mm increase in clear nail measured from the proximal nail fold 
o
to the most proximal area of nail dystrophy, with evidence of distal growth 
of the affected area, 6 months after the first treatment; 
or 
  an additional 60 mm2 of clear nail (based on width of the first toenail), 
o
with evidence of outward growth of the affected area, 6 months after the 
first treatment; 
or 
  complete clearance 6 months after the first treatment if less than 6 mm 
o
distal nail was involved prior to treatment.   
 
  Treatments may be continued, as the clear nail will be measured 6 months after 
the initiation of treatment.   
 
  The response should be progressive in at least 2 sequential timepoints that are at 
least 3 months apart, with a projected increase in clear nail of at least 1 mm per 
month. 
11 
  Contains Nonbinding Recommendations 
 
 
 
Fingernails: (based on assessment in the thumb nail) 
 
  Measurement of clear nail increase: 
  at least 12 mm increase in clear nail, with evidence of distal growth of the 
o
affected area, 6 months after the first treatment; 
or 
  an additional 90 mm2 of clear nail (based on width of the thumb nail), with 
o
evidence of outward growth of the affected area, 6 months after the first 
treatment; 
or 
  complete clearance 6 months after the first treatment if less than 12 mm 
o
distal nail was involved prior to treatment.   
 
  Treatments may be continued, as the clear nail will be measured 6 months after 
the initiation of treatment.   
 
  The response should be progressive in at least 2 sequential timepoints that are at 
least 3 months apart, with a projected increase in clear nail of at least 2 mm per 
month. 
 
These recommended endpoints arise from the combined consideration of the expected response 
to an effective treatment (in which the majority of nails would respond) with the known slower 
nail growth rate in older individuals and in certain disease states.  It is anticipated that at least 
half the treated nails would show a response within the designated time frame for assessment, 
while slower-growing nails would achieve the response later.   
 
FDA may consider alternate endpoints and/or response rates for devices which pose very high or 
very low risk.  If alternate endpoints are being considered, FDA recommends that you contact 
the Agency through the pre-submission process to discuss these endpoints.   
 
Studies performed on fingernails only should only be used to support an IFU in the fingernails.  
Studies which include the toenails can be used to support an IFU of all nails. 
 
The indication of temporary increase in clear nail is an aesthetic endpoint, and as such study 
endpoints will reflect visual improvement in clear nail.  A number of methods can be employed 
to assess the improvement.  In some trials, multiple methods may be employed to offer the most 
accurate assessment. 
 
  Millimeters of clear nail: The simplest method of assessing increase in clear nail is 
sequential measurements of the distance from the proximal nail fold to a predefined distal 
mark, such as the most proximal edge of the nail change.  Effective therapy will allow 
normal nail to replace the affected nail as it grows, leading to a progressive increase in 
the distance from the proximal nail fold to the most proximal portion of the nail change.  
Measurement to the distal margin of the nail is not recommended as nail trimming can 
introduce artifact into the measurement.  The drawback of this technique is that the nail 
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  Contains Nonbinding Recommendations 
 
 
dystrophy may not form a well-demarcated line, nor will it necessarily be parallel to the 
proximal nail margin.  Furthermore, such techniques do not account for variable rates of 
nail growth.  Variations on this method can overcome this limitation.  For example, a nail 
file can be used to etch a shallow horizontal line parallel to the horizontal portion of the 
proximal nail fold; this line would be placed at the most proximal portion of the 
dystrophic nail.  This line can serve as both a marker for nail growth rate, to confirm the 
nail is growing, as well as for marking the most proximal point of the nail dystrophy. 
 
  Clear nail area (mm2):  An increase in the area of the nail that is clear can provide 
clinically-meaningful data, and this method overcomes the limitations imposed by 
uneven margins of a dystrophic nail segment.  This method suffers from more complex 
evaluation methods with standardized photography equipment and dedicated software.  
Providing that methods can be validated, a measurement of area, presented as millimeters 
squared, can yield objective data.  Presentation of the same data as percentage is less 
desirable, as nail trimming or debridement can artificially increase the percent of the nail 
which is clear.  Therefore, measurement of clear nail area in square millimeters provides 
a more reliable, stand-alone objective measurement than percent clear nail. 
 
  Photographic assessment:  Visual evidence of improvement underlies all aesthetic 
treatments, including the indication of temporary increase in clear nail, and therefore 
will represent the bulk of the study data.  FDA recommends submission of all 
photographic data gathered in the performance of a clinical study for this indication, in 
order to assess the visual change.  To ensure adequate photographic quality and to 
maximize the ability to compare photographs across timepoints and across subjects, a 
standardized photography protocol should be put in place.  Photographs should be of high 
quality and high resolution.  An internal scale (e.g. ruler) should be included in all images 
to allow objective measurement of millimeters of clear nail regardless of magnification of 
the image.  Unedited and unretouched photographs are necessary in order to perform an 
accurate assessment.  Images should be assembled and presented in an organized fashion, 
for example pre-treatment and post-treatment images side by side, to facilitate FDA 
review.  Sponsors may choose to score the nail appearance on a numerical scale or use 
another categorization tool.  When such tools are used, they are most reliable when 
photographs are evaluated in a blinded manner and when the scores of multiple 
independent, blinded observers are combined.  The use of training aids, such as 
representative photographs for each score or category, add to the accuracy and reduce 
inter-observer variability and should therefore be considered. 
 
  3-Dimensional improvement: Dystrophic nails may also be thickened.  Means of 
assessing nail thickness, using calipers or photography from an appropriate angle, may be 
used as additional tools in assessing improvement in nail appearance.  Such assessment 
would be less relevant if debridement were used in the treatment protocol. 
 
  Composite endpoints: Methods of assessing overall improvement or multi-axis scoring 
systems can be of use in some aesthetic indications.  However, these endpoints should be 
used with caution as they can be subjective or easily affected by non-quantifiable factors.  
Furthermore, such scales may lack clinical validation.  If a composite endpoint is chosen, 
13 
  Contains Nonbinding Recommendations 
 
 
it is recommended that it be a secondary endpoint and that it be discussed with the FDA 
prior to commencement of the study. 
 
  Nested studies endpoints:  The endpoints for an indication of clear nail may later be used 
to support an indication for treatment of onychomycosis, when combined with 
appropriate mycology studies and controls.  As will be discussed below, a study can be 
designed to provide data in support of a clear nail indication in the first phase, and after 
continued follow-up and analysis of the relevant additional data, further endpoints can be 
used to support an indication of treating onychomycosis in a second phase of the study. 
 
5.  Follow-up 
 
In the absence of fungal re-infection or recurrence, it is anticipated that successful treatment will 
result in stable and progressive increase in clear nail.  To assess the effectiveness of the response 
to treatment, an ideal study would follow the nails until they are completely replaced by clear 
nail.  As discussed above, based on the average growth of nails this follow up duration would 
translate to roughly 6 months after the first treatment for fingernails and 12 months after the first 
treatment for toenails.   
 
The FDA recognizes that there is an inherent rate of re-infection or recurrence, and that the goal 
of studies in support of clear nail indications is to assess the improvement in appearance in 
response to treatment, rather than the ability to prevent re-infection.  However, sponsors are 
reminded that prospective patients and providers will have interest in data about recurrence rates. 
 
6.  Controls 
 
When possible, clinical trials benefit from the use of well-selected controls.  In the design of 
trials assessing body sites which are symmetric, such as the hands and feet, the use of a 
contralateral untreated control can be of great value, provided the two sides have similar 
involvement at baseline.  This type of control is of particular value in studies whose design 
includes the concomitant use of a topical antifungal drug.  When the baseline severity of the two 
sides is not similar, a contralateral control with crossover may allow maximal use of the 
contralateral side as control. 
 
Using the before status or photos of a nail as a control may not be sufficient.  Sponsors are 
encouraged to consider contralateral control design when possible, as this approach reduces 
inter-subject variability.  Additional controls that have been employed include untreated 
individuals or historical controls.  These approaches suffer from multiple limitations; the use of 
such data may not provide adequate comparator data or may necessitate a larger number of 
subjects for adequate statistical power.  Sponsors and investigators are advised to consult with a 
statistician and with the Agency. 
 
7.  Blinding 
 
The use of blinding in clinical trials that assess visual improvement strengthens the data by 
removing conscious or unconscious bias by the observer and by reducing placebo effect in the 
14 
  Contains Nonbinding Recommendations 
 
 
subject when patient reported outcomes or unblinded photographic analysis is used.  When 
possible, the use of a sham strengthens study design.  This may only be possible for treatments 
which cannot be felt by the treated subject, as may be the case in low level laser therapy, for 
example.  Blinding may be difficult when a laser or other energy-based treatment can be 
distinguished by the subject if the active intervention leads to heating or discomfort.  However, 
blinding of the observer is possible and recommended.  This blinding can be accomplished by 
providing unmarked before and after photographs, or by providing unlabeled treated and 
control photographs to independent observers.  The FDA recommends use of blinded 
assessment to provide maximally objective data. 
 
8.  Dose considerations 
 
The Indication for Use of temporary increase in clear nail does not distinguish between 
different nails.  Historically, studies in clear nail were performed on the first toe, which has the 
largest nail, and which nail is most often affected.  However, in practice the treatment will be 
applied to the smaller toenails as well as to fingernails.  The differing thickness and area of these 
nails, together with potential differences in heating of underlying neural and vascular structures, 
may require that different doses of energy be applied to the first versus other toenails and to the 
toenails versus the fingernails.  Clinical trials and labeling should address dose considerations so 
as to assess and ensure substantially equivalent safety and effectiveness in these different body 
sites. 
 
9.  Data analysis 
 
Clinical trial data can be analyzed in several different manners in order to evaluate whether a 
device is as safe and effective as a predicate device, to confirm a response to a particular 
regimen, to identify a dose-response relationship in both safety and effectiveness, to test whether 
different nail changes respond differently, and to unmask sources of confounding.  For trials that 
study the response of a nail whose appearance has been altered by fungal infection, several 
different analyses may be relevant.  Analysis of data as a function of each of these may provide 
information that will assist FDA in evaluating the performance of the device.  Such analyses may 
also provide valuable information to the sponsor with respect to training, marketing, and 
development of devices for clear nail indications.  Suggested analyses include: 
 
  Increase in clear nail at each timepoint of evaluation after the last treatment 
  Increase in clear nail as a function of the number of treatments, energy dose, or other 
controllable variable 
  Subgroup analysis of response by clinical subtype (e.g., distal subungual onychomycosis, 
total dystrophy) 
  Subgroup analysis by fungal species isolated prior to enrollment 
  Subgroup analysis by baseline severity 
  Subgroup analysis by degree of response (e.g., complete response or clearing, >75% 
clear, 50-75% clear) 
  If multiple nails are affected, subgroup analysis of toenails  vs. fingernails, or first nail vs. 
smaller nails 
15 
  Contains Nonbinding Recommendations 
 
 
  If relevant, device alone vs. device with adjunctive topical antifungal product or 
debridement 
 
When responder analysis is reported on a per nail basis, per subject analysis should be included.  
 
10. Adverse event monitoring 
 
Post-market monitoring of devices cleared for temporary increase of clear nail has identified 
several adverse events which may be device-related.  These adverse events include edema, 
burn/blister, disfigurement of nails, infection of soft tissue, infection of the underlying bone, 
deep tissue damage and nerve damage, and delayed wound healing.  Some of these events were 
associated with device output failure or use error, while others occurred when the device was 
used and operating within specifications. 
 
In light of these reports, sponsors, investigators, and practitioners are urged to be mindful that 
energy-based treatments do pose risks.  In the context of the aesthetic Indications for Use of 
temporary increase in clear nail, the benefit-risk analysis is particularly important.  All adverse 
events related to such procedures should be reported by type, severity, duration, outcome, and 
relationship to the device or procedure in order to develop an accurate understanding of the risks 
and benefits of these procedures.   
 
C.  Statistical Considerations 
 
Like studies for other medical products, clinical studies for devices aimed at treating or 
improving the appearance of fungally infected nails should be well designed with valid 
statistical analysis plans.  Many general statistical principles such as study design, objective 
(e.g., superiority or non-inferiority), randomization, prespecification of analyses (e.g., method, 
covariates), multiplicity control of type I error due to multiple endpoints or analyses, 
determination of analysis populations (e.g., ITT, per protocol), handling of missing data, use of 
interim or subgroup analyses, etc., are issues that need to be addressed for devices intended to 
treat nails in the same way as for other medical devices.  As such, these topics will only be 
briefly discussed here.   
 
1.  The study objective(s) should be clearly stated as superiority, non-inferiority.  The null 
and alternative hypotheses should be stated in text and in statistical notation, including 
the non-inferiority margin (delta), along with appropriate justification if the study is a 
non-inferiority trial. 
 
2.  Study designs with randomized, concurrent controls are recommended whenever 
possible.  For products not expected to have systemic effects, the most efficient design 
would be a within-patient controlled design, where nail(s) on one foot get the 
investigational treatment and nail(s) on the other foot get the control treatment.  This 
split-foot design reduces the patient to patient variability and thus requires a smaller 
sample size.  Another strong design is the controlled parallel group design, where 
treatment (investigation or control) is randomly assigned to subjects in two independent 
16 
  Contains Nonbinding Recommendations 
 
 
groups.  FDA recognizes the inherent limitations with historically controlled studies 
and recommends other study designs be utilized when appropriate. 
 
3.  There should be a statistical justification of sample size, which is typically based on 
type I error, power, and expected outcomes considerations.  In some cases, there may 
be a need to power the study for safety as well, as there may be a low tolerance for 
serious or bothersome adverse reactions.  The final sample size is a judgment and 
depends upon prior experience with the class of products.  If a performance goal is 
being used, such as a 50% response rate, then the (lower bound) 95% one-sided 
confidence interval around the observed success rate in the study population should be 
50%. 
 
4.  The randomization scheme should be fully described, including the randomization 
ratio, and any use of stratification or block size.  It should also be specified whether the 
randomization is centrally controlled or managed at each site.   
 
5.  The level of blinding (patient/investigator/evaluator) should be carefully considered.  
Double-blinded studies should be conducted whenever possible.  However, when this is 
not possible, investigator- or evaluator-blinding should be considered.  The use of 
photographic evaluations may also be used to maintain the blind; however, assessment 
of depth is typically compromised with photographs.  It is prudent to have as much 
blinding as possible due to the degree of subjectivity in assessing endpoints with nail 
products. 
 
6.  Studies for devices intended to treat nails may have a number of assessments that are 
used to define the primary and secondary endpoints.  The number of assessments 
may be due to the multifaceted nature of the condition (e.g., color, area, thickness, 
texture), the number of assessors (e.g., investigator, subject, or blinded evaluator), or 
the timepoints for assessment.  When appropriate, scales should allow for worsening of 
the condition as well as improvement.  Studies may evaluate efficacy, safety, or patient 
satisfaction outcomes.  All scales used should be validated to the extent possible. 
 
7.  If efficacy is based on the number of patients responding to treatment (i.e., a responder 
analysis), then the patient success decision rule should be described.  This may 
involve meeting a single criteria or meeting all components of a composite endpoint.      
 
8.  The overall study success decision rule should be prespecified.  Study success should 
depend on both clinical significance and statistical significance.  The protocol should 
include a plan for adjusting for multiplicity in cases with more than one endpoint to 
control the type I error.  
 
9.  The follow-up schedule should be fully described.  Long-term follow-up may be 
needed to assess duration of effect (i.e., for one-time use or intermittent use products).  
Protocols should include plans to minimize loss to follow-up, especially in cases where 
subjects may not be motivated to return for follow-up after receiving treatment or 
complying with only some of the post-treatment visits. 
17 
  Contains Nonbinding Recommendations 
 
 
 
10. The length of treatment or the number and spacing of treatments should be specified.  
Data should be collected on dosing or volume of product administered. 
 
11. The statistical methods to be used for the analysis of all endpoints should be specified 
in the statistical plan, and should be appropriate for the type of data collected.  If the 
statistical method will incorporate important covariates, such as with various 
regression methods or subgroup analyses, the covariate list should be prespecified.  
How the covariates will be used should be spelled out in the statistical plan. 
 
12. The primary analysis cohort (e.g., ITT, modified ITT, per-protocol) should be pre-
specified.  If other analysis cohorts will be used, these should be prespecified as well. 
 
13. For some types of treatments administered by the investigator, the investigator 
technique may impact the results.  Studies should be designed to enroll sufficient 
numbers of subjects per center so that investigator-to-investigator variability and 
treatment-by-center interactions can be adequately assessed.  Number of 
investigational centers planned (#US and #foreign) should be carefully considered. 
 
14. If the study is a non-inferiority study, the control treatment should be shown to be 
effective at the primary analysis time point.  It would be inappropriate to evaluate non-
inferiority/equivalence to an ineffective treatment. 
 
15. Primary and secondary endpoints intended for labeling should be clinically relevant 
and supported by appropriate prespecified statistical hypotheses.  The labeling should 
only reflect what was demonstrated in the clinical trial. 
 
16. There should be a plan for handling missing data which includes the type of 
imputation that will be used for missed observations and a plan for a sensitivity 
analyses.   
 
17. Any planned subgroup analyses should be prespecified or they will be considered 
exploratory.  In some cases a multiplicity adjustment is needed. 
 
18. Any planned interim analyses (i.e., early stopping for futility or effectiveness) should 
be prespecified.  The purpose of the analysis should be clearly stated as well as the 
alpha spending function to be used to control the overall type 1 error.   
 
19. The kappa statistic, weighted kappa, or intra-class correlation coefficient (ICC) 
may be used to measure inter-rater agreement, intra-rater agreement, or reliability 
depending on the nature of the data (e.g., dichotomous, ordered categorical, 
continuous).  It is reasonable to obtain more than one opinion on the amount of clear 
nail. 
 
20. Some trials require the use of a Data Safety Monitoring Board (DSMB).  An interim 
analysis of safety may be needed if the risk of the medical device is high.  
18 
  Contains Nonbinding Recommendations 
 
 
 
 
D.  Labeling Considerations 
 
Devices which are cleared for temporary increase in clear nail in patients with onychomycosis 
should be clearly labeled for this indication.  Specifically, claims should be limited to aesthetic 
improvement.   
 
Since the IFU specifies visual improvement in fungally-infected nails, appropriate labeling 
should include language which states this clearly by conveying both components of the IFU: 
 
1)  Target nails are those whose appearance is altered due to fungal infection.  Physician 
labeling should list the species assessed, and should recommend that physicians confirm 
fungal etiology. 
2)  The physician labeling should indicate that the device has not been cleared to treat 
fungus, as discussed in the Regulatory Considerations section above. 
 
As discussed in the Regulatory Considerations section above, due to the potentially increased 
risk of these treatments in patients with diabetes, peripheral vascular disease, immune 
suppression, and other compromised medical states, the labeling should include a warning in 
both the physician and patient labeling stating that these devices are to be used with caution in 
these populations. 
 
The labeling for devices cleared for a clear nail indication should contain details regarding the 
clinical study data, including: 
 
Physician labeling: 
 
  Representative before and after photos of nail with various severities prior to treatment 
  Description of the treatment protocol used, including any adjunctive interventions such as 
topical antifungal products or debridement 
  Potential and observed adverse events, and frequency as available 
  A table summarizing the percent complete responders, partial responders (which may be 
further stratified), and non-responders. 
  Fungal species assessed, and response rates for each species. 
  Clinical presentations of onychomycosis assessed (e.g., DSO). 
  If a controlled study, results should be reported for both treated and control data with p-
values for any statistical comparison tests performed. 
  Caveat that the results represent the US population, and that these data may not be 
extrapolatable to other strains or other geographic areas. 
 
Patient labeling: 
 
  Representative before and after photos of nail with various severities prior to treatment. 
19 
  Contains Nonbinding Recommendations 
 
 
  Description of the treatment protocol used, including any adjunctive interventions such as 
topical antifungal products or debridement. 
  A table summarizing the percent complete responders, partial responders (which may be 
further stratified), and non-responders. 
  Potential and observed adverse events and frequency as available. 
  If a controlled study, results should be reported for the untreated group (p-values need not 
be included here). 
 
IV. TREATMENT OF ONYCHOMYCOSIS 
 
A.  Regulatory considerations 
 
1.  Defining treatment of onychomycosis 
 
In contrast to the indication of temporary increase in clear nails in patients with 
onychomycosis, which provides support only for aesthetic improvement, the IFU of treatment 
of onychomycosis is a medical indication, based on reduction or elimination of fungal 
organisms as assessed by mycological testing.  As discussed in section III.A.1 (Defining 
temporary increase in clear nail), stains may be used to assess the presence or absence of 
fungal organisms, while culture is needed to assess whether the organisms are viable and to 
identify the species.  Mycological cure is therefore defined as simultaneous occurrence of 
negative stain and negative culture.  However, in slow-growing nails, there may be residual 
fungal forms detectable by staining which are not viable.  In such cases, two serial negative 
cultures from the same nail may provide evidence of mycological cure. 
 
Mycological cure may be assessed in parallel to clear nail.  Antifungal drug studies have also 
assessed overall response rate using an endpoint of effective treatment which was defined as 
mycological cure plus 0% nail involvement or a pre-defined minimum distance of unaffected 
nail growth, to allow inclusion of nails which are mycologically cured but whose slow growth 
precludes complete nail replacement within the anticipated timeframe. 
 
As discussed above, nails which are structurally abnormal can only clear by outgrowth of the 
dystrophic component and replacement by newly-created normal-appearing nail.  Based on the 
mean growth rate for nails in healthy U.S. adults, the ideal effective treatment would be expected 
to yield a fully clear fingernail after approximately 6 months and a fully clear great toenail 
approximately 12 months after the initiation of treatment.12  In contrast to the IFU of temporary 
increase in clear nail, it is anticipated that effective treatment of the fungus underlying 
onychomycosis will lead to durable changes in the nail after 6 and 12 months, respectively.  Any 
regression could indicate incomplete or unsuccessful elimination of the fungus or recurrent 
fungal infection. 
                                                           
12Yaemsiri S, Hou N, Slining MM, He K.  Growth rate of human fingernails and toenails in healthy American young 
adults.  Journal of the European Academy of Dermatology & Venereology, 2010; 24(4): 420-23. 
20 
  Contains Nonbinding Recommendations 
 
 
 
2.  Combining treatment with antifungal drugs or debridement 
 
Due to the nature of the indication, the use of antifungal drug therapy of any kind in studies 
performed in support of treatment of onychomycosis could compromise assessment of device 
effectiveness and are therefore not recommended.  Debridement may be offered for functional 
improvement, but such interventions should be used uniformly across study subjects with given 
severities and should be disclosed in labeling.   
 
3.  Species-dependent outcomes 
 
Clinical studies may reveal that different organisms respond differently to the procedure, or may 
require varying doses or treatment protocols.  However, the Indication for Use of treatment of 
onychomycosis is worded broadly.  A sponsor may choose to specify within the IFU what 
species can be treated effectively, or may provide this information in the labeling.  The goal in 
either case is to ensure that the device be used to treat only nails which are likely to respond to 
the treatment protocol. 
 
4.  Special populations 
 
As discussed in section III.A.4 (Special populations), effective treatment of a fungal infection is 
of particular clinical relevance for vulnerable populations, who may remain at ongoing medical 
risk with partially-treated or unsuccessfully-treated onychomycosis.  Furthermore, in these 
populations, trauma to the nail due to potential adverse events during the procedure may result in 
delayed wound healing or may predispose to severe or life-threatening infections.  To protect 
these populations, the labeling should include the following statement:  
 
Warning: These devices should be used with caution in patients with diabetes, 
peripheral vascular disease, or immune-suppression, or with any other medical 
state that renders the foot at risk of infection or delayed wound healing. 
 
A device whose labeling includes an Intended Use or Indication for Use for treating 
onychomycosis and which has not been studied in such vulnerable populations should be labeled 
with a similar warning.   
 
B.  Clinical trial considerations 
 
1.  Special populations 
 
As discussed above (section III.B.1 (Special populations)), risk to special populations should be 
minimized.  Special populations may be considered particularly vulnerable and may not be 
appropriate subjects for clinical studies assessing treatment of onychomycosis in lieu of 
definitive therapy, until such procedures are demonstrated safe and effective.  It is recommended 
that subjects with diabetes mellitus, peripheral vascular disease, recurrent cellulitis, lymphatic 
insufficiency, or immune compromise (whether due to underlying medical disorders or to 
21 
  Contains Nonbinding Recommendations 
 
 
immunosuppressive treatments), or other compromised states of health be excluded from 
participating in clinical trials intended to treat onychomycosis. 
 
Investigators are urged to design clinical studies which enroll a cross-section of subjects that 
reflects the U.S. population by including subjects with varying age, gender, race, and Fitzpatrick 
skin type, if applicable, in which it is anticipated the device will be used.   
 
2.  Inclusion/exclusion criteria: recommendations 
 
Clinical involvement 
The recommendations discussed above (section III.B.2 (Clinical involvement) will also apply to 
studies performed in support of the treatment of onychomycosis.   
 
Clinical presentations of onychomycosis 
The different clinical forms of onychomycosis, which are differentiated by their appearance, are 
discussed in section III.B.2 (Clinical presentations of onychomycosis).  Certain clinical forms are 
associated with particular species of fungus.  As such, some clinical forms may be more resistant 
to treatment, both due to anatomical factors and due to variably sensitive organisms.  It may 
therefore be of value to evaluate various clinical forms separately, or to analyze and report the 
outcomes obtained in the treatment of different clinical forms of onychomycosis separately. 
 
Confirmation of fungal infection  
As described section III.B.2 (Confirmation of fungal infection underlying nail appearance), a 
small number of fungal strains are the predominant causes of toenail and fingernail 
onychomycosis.  To maximize the clinical relevance of trial results, and to provide data that is 
most predictive of treatment response in the population of patients with onychomycosis, it is 
recommended that studies include only subjects whose nails have been demonstrated to harbor 
the common causative organisms and exclude subjects whose nails are infected by rare fungal 
species or non-fungal organisms such as mold or bacteria. 
 
To support an IFU of treatment of onychomycosis, it is appropriate that all enrolled subjects 
have confirmed nail infection by one of these fungal organisms prior to treatment and that the 
nails be definitively assessed for cure of the fungal organism at the relevant timepoint after 
treatment.  Mycological cure is defined as negative stain (e.g. periodic acid Schiff (PAS); silver 
stains; potassium hydroxide (KOH)) concurrent with negative fungal culture.  The concurrence 
of a negative stain and a negative culture from the same nail may be considered definitive.  In the 
event that the stain and the culture provide conflicting results, i.e., one is positive and the other 
negative, resolution may be obtained by several approaches.  A nail which shows fungal 
organisms by staining may yield a negative culture.  It is known that cultures may yield false 
negative results in up to 30% of cases due to partially-treated organisms, fastidious organisms, 
nuances in laboratory methodology, or recent contact with a topical microbicidal agent 
(including alcohol or acetone applied to the nail prior to collecting the specimen).13  Conversely, 
                                                           
13Fletcher CL, Hay RJ, and Smeeton NC. Onychomycosis: the development of a clinical diagnostic aid for toenail 
disease. Part I. Establishing discriminating historical and clinical features. Br J Dermatol. 2004 Apr;150(4):701-5. 
 
22 
  Contains Nonbinding Recommendations 
 
 
in slow-growing nails the distal nail margin may contain non-viable organisms, leading to a true 
negative culture and a positive stain.  In this case also, two serial negative cultures from the same 
nail may provide evidence of mycological cure.   
  
Co-morbidities 
Many non-fungal conditions can affect nail appearance, including psoriasis, lichen planus, 
trauma from ill-fitting shoes, running, or overly-aggressive nail care.  These conditions may be 
the primary cause of nail dystrophy but may also predispose a subject to secondary fungal 
infection.  While these subjects may benefit from procedures which can treat the secondary 
onychomycosis, it is recommended that they not be included in clinical studies, as the nail 
appearance may remain abnormal despite successful eradication of the fungus. 
 
Prior or ongoing antifungal drug therapy 
Because systemic antifungal drugs are deposited in the nail substance and remain in the nail until 
the nail grows and is trimmed, enrollment of subjects who have been exposed to antifungal drugs 
in the 12 months prior (in the case of toenails) or 6 months prior (in the case of fingernails) could 
confound interpretation of the study data and is not recommended. 
 
While topical antifungal drugs are less effective in providing clinical clearance of 
onychomycosis, their application can interfere with fungal cultures, even if applied only to the 
skin.  It is therefore recommended that such treatments be discontinued prior to screening and 
enrollment and for the duration of the clinical trial and follow-up period.   
 
3.  Adjunctive therapies 
 
Adjunctive medical therapies may mask the true performance of the device.  The use of a topical 
or systemic antifungal therapy would preclude the ability to assess true safety and effectiveness 
of a device in treating onychomycosis and are therefore not recommended.  If a sponsor or 
investigator wishes to assess the ability of a second intervention to work in synergy with a 
device, for example, a topical product that would increase the absorption of laser light, 
appropriate study design could be established in support of the combination, by providing 
properly-controlled comparative data of the product alone, the device alone, and the 
combination.  Sponsors are urged to discuss such study designed with the Agency in advance, 
and to address whether such combinations would be drug-device combination products.14 
 
4.  Endpoints 
 
Based on the average nail growth rates discussed above, and to provide a fair and informative 
guideline for assessment of the success of a treatment, FDA recommends the following 
effectiveness endpoints for treatment of onychomycosis, based on achieving endpoints of both 
clear nail and mycology.   
 
                                                           
14 See 21 CFR 3.2(e).   
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Clear nail: The specifications for clear nail are described below.  The 95% one-sided confidence 
interval (i.e., lower bound only) around the observed response rate as described below should be 
50%.   
 
Mycology: Among toenails and fingernails which are deemed responders based on the clear 
nail criteria, at least 80% should demonstrate negative mycology (negative stain with 
concurrent negative culture, or two negative cultures from the same nail).   
 
Toenails: (based on assessment in the first toe) 
  Measurement of clear nail increase: 
 
  at least 12 mm increase in clear nail, with evidence of distal growth of the 
o
affected area, 12 months after the first treatment; 
or 
  an additional 120 mm2 of clear nail (based on mean width of the first 
o
toenail), with evidence of distal growth of the affected area, 12 months 
after the first treatment; 
or 
  complete clearance 12 months after the first treatment if less than 12 mm 
o
distal nail was involved prior to treatment.   
 
  The response should be progressive in at least 2 sequential timepoints that are at 
least 3 months apart, with projected increase of at least 1 mm per month. 
 
Fingernails: (based on assessment in the thumb) 
 
  Measurement of clear nail increase: 
 
  at least 12 mm increase in clear nail measured from the cuticle to the most 
o
proximal area of nail dystrophy, with evidence of distal growth of the 
affected area, 6 months after the first treatment; 
or 
  an additional 90 mm2 of clear nail (based on mean width of the thumb 
o
nail), with evidence of distal growth of the affected area, 6 months after 
the first treatment; 
or 
  complete clearance 6 months after the first treatment if less than 12 mm 
o
distal nail was involved prior to treatment.   
 
  The response should be progressive in at least 2 sequential timepoints that are at 
least 3 months apart, with projected increase of at least 2 mm per month. 
 
Studies performed on fingernails only should only be used to support an IFU in the fingernails.  
Studies which include the toenails can be used to support an IFU for all nails. 
 
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As stated earlier, these recommended endpoints arise from the combined consideration of the 
expected response to an effective treatment (in which the majority of nails would respond) with 
the known slower nail growth rate in older individuals and in certain disease states.  It is 
anticipated that at least half the treated nails would show a response within the designated time 
frame for assessment, while slower-growing nails would achieve the response later.  FDA may 
consider alternate endpoints and/or response rates for devices which pose very high or very low 
risk.  If alternate endpoints are being considered, FDA recommends that you contact the Agency 
through the pre-submission process to discuss these endpoints.   
 
The indication of treating onychomycosis should include demonstration of mycological cure, 
defined by the concurrence of a negative stain and a negative culture.  Sponsors and investigators 
may choose to apply a nested study design, in which early endpoints are applied and discussed 
for the clear nail indication (section III.A.1 (Defining temporary increase in clear nail)) in the 
first phase, and to pursue a subsequent IFU of treatment of onychomycosis with the data 
generated in a second phase of the study, in accordance with the recommended endpoints 
(section III.B.4 (Endpoints)).  If such a study design is used, pre-specified statistical 
considerations should be included in the study design to account for the interim data analysis and 
unblinding.   
 
To evaluate the overall response rates, it is recommended that the study report be written in a 
tiered fashion, citing the success rate for the subjects exhibiting mycological cure concurrent 
with clear nail, with separate presentation of the data for subjects exhibiting mycological cure 
with residual nail dystrophy. 
 
5.  Follow-up 
 
The goal of treatments for onychomycosis is complete elimination of the fungal organism and 
full clearance of the nail.  Follow-up for this indication should be based on the anticipated time 
for complete nail regrowth, which is approximately 6 months for fingernails and 12 months for 
toenails as discussed above.  Longer follow-up times will be helpful for assessing recurrence 
rates.  To control for loss of subjects who do not exhibit the desired visual outcome, it is 
recommended that subjects who drop out or are lost to follow-up be considered as treatment 
failures for this indication.  This restriction should be incorporated into the statistical analysis 
plan. 
 
6.  Controls 
 
The controls discussed in the clear nail section above (section III.B.6 (Controls) are relevant 
and can be applied to studies in support of the treatment of onychomycosis.  These controls may 
be complemented with mycological studies from the control nails. 
 
7.  Blinding 
 
The blinding considerations discussed in the clear nail section above (section III.B.7 
(Blinding)) are relevant and can be applied to studies in support of the treatment of 
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onychomycosis.  Blinding should be applied to mycological specimen assessment in addition to 
clinical assessments. 
 
8.  Dose considerations 
 
The dosimetry of energy for different toes and for toenails versus fingernails is addressed in 
section III.B.8 (Dose considerations).  It is not known whether elimination of fungal organisms 
to support the IFU of treatment of onychomycosis would require similar or higher doses of 
energy than those used for temporary increase in clear nail, nor whether a higher dose would 
be tolerated if needed.  Clinical trials and labeling should address dose considerations if a device 
is used to treat both the temporary increase in clear nail and treatment of onychomycosis 
IFU, and if it is to be used on different nails, so as to assess and ensure adequate safety and 
effectiveness in these different body sites. 
 
9.  Data analysis 
 
General considerations for data analysis are discussed in section III.B.9 (Data analysis).  Given 
the antifungal nature of the IFU of treatment of onychomycosis, there is particular importance 
in identifying dose-response relationships and species-specific response rates.  Sponsors and 
investigators may utilize bench testing to identify target parameters prior to human studies.  
However, the ability of an energy source to penetrate a living nail overlying complex structures 
will in most circumstances necessitate clinical studies.  Such studies would also provide 
information about the ability of the nail to resume normal growth after treatment. 
 
10. Adverse event monitoring 
 
As discussed in section III.B.10 (Adverse event monitoring) post-market monitoring of devices 
cleared for temporary increase in clear nail has identified several adverse events which may be 
device-related.  In the absence of dose-response data about such adverse events, sponsors, 
investigators, and practitioners are urged to monitor and report all adverse events in order to 
develop an accurate understanding of the risks and benefits of these procedures.  FDA will 
review adverse events and provide a benefit-risk analysis. 
 
C.  Statistical Considerations   
 
These are the same as those discussed in III.C (Statistical Considerations) above. 
 
D.  Labeling considerations 
 
Devices which are cleared for treatment of onychomycosis should be clearly labeled for this 
indication, provided they have demonstrated effectiveness in eliminating nail fungus.  No 
devices have been cleared or approved for this indication as of the publication of this guidance.  
Therefore, much is not yet known, including potential response rates, adverse events, etc. for 
these studies, and FDA cannot make specific recommendations for labeling at this time.  
However, general labeling considerations will follow best practices and provide transparency to 
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the provider and patient.  It is anticipated that the recommendations will be similar to those 
detailed in section III.D (Labeling Considerations) above.    
 
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Appendix: Light Sources for Nail Indications 
 
FDA recommends that the following information be included in marketing submissions for 
devices incorporating a light source intended for a nail indication, with specific attention to the 
parameters applicable to the IFU.  This example may serve as a paradigm for other energy-based 
devices, in which comparable relevant parameters will be evaluated. 
 
For 510(k) submissions, this information will be taken into consideration along with any 
performance data (non-clinical or clinical) when comparing the proposed device to a predicate 
device for purposes of determining substantial equivalence.  For devices that differ significantly 
from those already on the market, additional information may be necessary to evaluate those 
differences.   
 
 
I.  Wavelength: The submission should identify the individual wavelength(s) or the 
range of wavelengths of light that will be delivered to the nail by the proposed 
device. 
 
II.  Laser or Light Generation: If the device is a laser, the details of the laser 
generation method should be submitted.  This description may include the gain 
medium, pumping source, and the method used for pulsing (q-switch or other).  If 
the laser is generated without a gain medium, e.g., by laser diodes, detailed 
specifications and engineering drawings of the diodes or other laser source(s) may 
be requested.  If the device is an intense pulsed light or any other kind of light 
source, a description of the light source and the method of light generation will be 
requested.  
 
III.  Fluence: The submission should identify the total fluence (energy per area), 
delivered at each spot.  If the clinical procedure for the nail includes multiple 
steps, the submission should identify the energy delivered to a spot at each step as 
well as the total energy delivered to a spot.  
 
IV.  Spot Size: The submission should include the spot size(s) that will be used for the 
procedure.  
 
V.  Output mode: The submission should detail whether the light output is pulsed or 
continuous wave (CW).  
 
VI.  Power:  Submissions should identify the power that will be delivered during the 
procedure.  For pulsed light, the average power should be provided.  
 
VII.  Pulsed laser and light sources: The following parameters should be submitted for 
pulsed lasers and light sources.  
 
  Pulse duration   
  Energy per pulse 
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  Fluence per pulse 
  Duty cycle 
  Repetition rate (pulses per second) 
 
VIII.  Directions for use:  The directions for use should include the following 
information: 
 
  The size and the shape of the area on the nail that will be illuminated by light 
during the clinical procedure 
 
  The spatial distribution and number of spots per unit area, if the light is to be 
delivered at discrete spots 
 
  The dwell time at each spot and the time interval between spots, as well as the 
direction of movement to complete the spot pattern, if the light is delivered in 
discrete spots, or in a stacked or paintbrush fashion 
 
  The movement velocity and the direction(s) of the movement, if a 
paintbrush fashion is employed 
 
  The number of procedures per session, number of sessions per week, and the 
total number of sessions 
 
  Nail that will be treated per procedure and per session 
 
  Patient preparation, pre- and post-operative evaluation and post-operative care 
instructions 
 
  Warnings or contraindications for the proposed device 
 
29