Document ID: FDA-2022-D-2424-0001
Agency: fda
Document Type: Notice
Title: Protein Efficiency Ratio Rat Bioassay Studies To Demonstrate That a New Infant Formula Supports the Quality Factor of Sufficient Biological Quality of Protein; Draft Guidance for Industry; Availability; Agency Information Collection Activities; Proposed Collection; Comment Request
Posted Date: 2023-02-10T05:00Z

[Federal Register Volume 88, Number 28 (Friday, February 10, 2023)]
[Notices]
[Pages 8868-8872]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-02836]

[[Page 8868]]

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DEPARTMENT OF HEALTH AND HUMAN SERVICES

Food and Drug Administration

[Docket No. FDA-2022-D-2424]

Protein Efficiency Ratio Rat Bioassay Studies To Demonstrate That 
a New Infant Formula Supports the Quality Factor of Sufficient 
Biological Quality of Protein; Draft Guidance for Industry; 
Availability; Agency Information Collection Activities; Proposed 
Collection; Comment Request

AGENCY: Food and Drug Administration, HHS.

ACTION: Notice of availability.

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SUMMARY: The Food and Drug Administration (FDA or we) is announcing the 
availability of a draft guidance entitled ``Protein Efficiency Ratio 
(PER) Rat Bioassay Studies To Demonstrate That a New Infant Formula 
Supports the Quality Factor of Sufficient Biological Quality of 
Protein.'' The draft guidance, when finalized, will provide information 
for manufacturers and contract laboratories that perform PER studies to 
assist in designing, conducting, evaluating, and reporting PER studies. 
The draft guidance, when finalized, will explain ``appropriate 
modifications'' of AOAC Official Method 960.48 (the AOAC Method) with 
the aim of supporting industry in successfully conducting PER studies 
that demonstrate that a new infant formula meets the quality factor of 
sufficient biological quality of protein when fed as the sole source of 
nutrition.

DATES: Submit either electronic or written comments on the draft 
guidance by May 11, 2023 to ensure that we consider your comment on the 
draft guidance before we begin work on the final version of the 
guidance. Submit electronic or written comments on the proposed 
collection of information in the draft guidance by May 11, 2023.

ADDRESSES: You may submit comments on any guidance at any time as 
follows:

Electronic Submissions

    Submit electronic comments in the following way:
     Federal eRulemaking Portal: https://www.regulations.gov. 
Follow the instructions for submitting comments. Comments submitted 
electronically, including attachments, to https://www.regulations.gov 
will be posted to the docket unchanged. Because your comment will be 
made public, you are solely responsible for ensuring that your comment 
does not include any confidential information that you or a third party 
may not wish to be posted, such as medical information, your or anyone 
else's Social Security number, or confidential business information, 
such as a manufacturing process. Please note that if you include your 
name, contact information, or other information that identifies you in 
the body of your comments, that information will be posted on https://www.regulations.gov.
     If you want to submit a comment with confidential 
information that you do not wish to be made available to the public, 
submit the comment as a written/paper submission and in the manner 
detailed (see ``Written/Paper Submissions'' and ``Instructions'').

Written/Paper Submissions

    Submit written/paper submissions as follows:
     Mail/Hand Delivery/Courier (for written/paper 
submissions): Dockets Management Staff (HFA-305), Food and Drug 
Administration, 5630 Fishers Lane, Rm. 1061, Rockville, MD 20852.
     For written/paper comments submitted to the Dockets 
Management Staff, FDA will post your comment, as well as any 
attachments, except for information submitted, marked and identified, 
as confidential, if submitted as detailed in ``Instructions.''
    Instructions: All submissions received must include the Docket No. 
FDA-2022-D-2424 for ``Protein Efficiency Ratio (PER) Rat Bioassay 
Studies To Demonstrate That a New Infant Formula Supports the Quality 
Factor of Sufficient Biological Quality of Protein.'' Received comments 
will be placed in the docket and, except for those submitted as 
``Confidential Submissions,'' publicly viewable at https://www.regulations.gov or at the Dockets Management Staff between 9 a.m. 
and 4 p.m., Monday through Friday, 240-402-7500.
     Confidential Submissions--To submit a comment with 
confidential information that you do not wish to be made publicly 
available, submit your comments only as a written/paper submission. You 
should submit two copies total. One copy will include the information 
you claim to be confidential with a heading or cover note that states 
``THIS DOCUMENT CONTAINS CONFIDENTIAL INFORMATION.'' We will review 
this copy, including the claimed confidential information, in our 
consideration of comments. The second copy, which will have the claimed 
confidential information redacted/blacked out, will be available for 
public viewing and posted on https://www.regulations.gov. Submit both 
copies to the Dockets Management Staff. If you do not wish your name 
and contact information to be made publicly available, you can provide 
this information on the cover sheet and not in the body of your 
comments and you must identify this information as ``confidential.'' 
Any information marked as ``confidential'' will not be disclosed except 
in accordance with 21 CFR 10.20 and other applicable disclosure law. 
For more information about FDA's posting of comments to public dockets, 
see 80 FR 56469, September 18, 2015, or access the information at: 
https://www.govinfo.gov/content/pkg/FR-2015-09-18/pdf/2015-23389.pdf.
    Docket: For access to the docket to read background documents or 
the electronic and written/paper comments received, go to https://www.regulations.gov and insert the docket number, found in brackets in 
the heading of this document, into the ``Search'' box and follow the 
prompts and/or go to the Dockets Management Staff, 5630 Fishers Lane, 
Rm. 1061, Rockville, MD 20852, 240-402-7500.
    You may submit comments on any guidance at any time (see 21 CFR 
10.115(g)(5)).
    Submit written requests for single copies of the draft guidance to 
Office of Nutrition and Food Labeling (HFS-800), Center for Food Safety 
and Applied Nutrition, Food and Drug Administration, 5001 Campus Dr., 
College Park, MD 20740. Send one self-addressed adhesive label to 
assist that office in processing your request or include a Fax number 
to which the draft guidance may be sent. See the SUPPLEMENTARY 
INFORMATION section for information on electronic access to the draft 
guidance.

FOR FURTHER INFORMATION CONTACT: 
    With regard to the draft guidance: Andrea Lotze, Center for Food 
Safety and Applied Nutrition, Office of Nutrition and Food Labeling 
(HFS-800), Food and Drug Administration, 5001 Campus Dr., College Park, 
MD 20740, 240-402-1450, email: [email protected]; or Keronica 
Richardson, Center for Food Safety and Applied Nutrition, Office of 
Regulations and Policy (HFS-024), Food and Drug Administration, 5001 
Campus Dr., College Park, MD 20740, 240-402-2378.
    With regard to the proposed collection of information: Rachel 
Showalter, Office of Operations, Food and Drug Administration, Three 
White Flint North, 10A-12M, 11601 Landsdown St., North Bethesda, MD 
20852, 240-994-7399, [email protected].

SUPPLEMENTARY INFORMATION:

I. Background

    FDA is announcing the availability of a draft guidance for industry 
entitled

[[Page 8869]]

``Protein Efficiency Ratio (PER) Rat Bioassay Studies To Demonstrate 
That a New Infant Formula Supports the Quality Factor of Sufficient 
Biological Quality of Protein.'' Our regulations, at 21 CFR 106.96, 
establish requirements for quality factors for infant formulas, 
including the quality factor of sufficient biological quality of 
protein. Subject to a limited exception (see Sec.  106.96(g)), each 
manufacturer of an infant formula that is not an eligible infant 
formula must demonstrate that the formula meets the quality factor of 
sufficient biological quality of protein by establishing the biological 
quality of the protein in the infant formula when fed as the sole 
source of nutrition using an appropriate modification of the AOAC 
Official Method 960.48 (the AOAC Method) Protein Efficiency Ratio (PER) 
Rat Bioassay (Sec.  106.96(f)).\1\
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    \1\ We support the principles of the ``3Rs'' to reduce, refine, 
and replace animal use in testing when feasible. We encourage 
sponsors to consult with us if they wish to use a non-animal testing 
method they believe is suitable, adequate, and validated to 
demonstrate that the formula supports the quality factor for the 
biological quality of the protein as described in 21 CFR 
106.96(g)(3). We support alternative methods by exemption in 21 CFR 
106.96(f) which allows the manufacturer to request an exemption and 
provide certain required assurances described in 21 CFR 106.96(g). 
The applicability of this exemption is not the subject of this 
guidance.
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    The AOAC Method provides a procedure by which the quality of a 
protein in food can be evaluated and compared with those of other 
proteins. Protein ``quality'' can be defined as the ability of a 
protein to meet the essential amino acid needs of an animal. The AOAC 
Method is a standardized bioassay with published collaborative study 
data. The AOAC Method permits the calculation of a PER as the ratio of 
the average animal body weight gain per gram of protein consumed of a 
test protein versus casein after a 28-day feeding period. Typically, 
the protein concentration of both the test and casein reference diet is 
set at about 10 percent, a level that is below the estimated 
requirement for growth of rats of 15 percent, to improve the 
sensitivity of the method. While growth is slower at 10 percent protein 
than at 15 percent protein, the lower protein level assures that 
available protein is efficiently utilized.
    In the PER study described in the AOAC Method, a protein ingredient 
was assayed at 10 percent and other potential variables were 
standardized so that their numbers and potential effects were 
minimized. Vitamin composition, moisture, ash, carbohydrates, fat, and 
fiber were adjusted between the casein reference diet and the test 
diet. Use of a test diet that contains an infant formula in its 
entirety introduces matrices of high fat content and additional 
vitamins, minerals, and other ingredients, as well as the low protein 
source. A major challenge in analyzing infant formulas by the AOAC 
Method is matching the casein reference diet and test diet to achieve 
dietary groups with as few confounding variables as possible.
    Since we promulgated Sec.  106.96, we have found that industry is 
experiencing difficulties in consistently meeting its requirements. 
Therefore, we are announcing the availability of a draft guidance for 
industry entitled ``Protein Efficiency Ratio (PER) Rat Bioassay Studies 
To Demonstrate That a New Infant Formula Supports the Quality Factor of 
Sufficient Biological Quality of Protein.'' This draft guidance, when 
finalized, will help infant formula manufacturers and contract 
laboratories that perform PER studies in designing, conducting, 
evaluating, and reporting PER studies. The draft guidance, when 
finalized, will explain ``appropriate modifications'' of the AOAC 
Method to help manufacturers and contract laboratories conduct PER 
studies that demonstrate to FDA that a new infant formula meets the 
quality factor of sufficient biological quality of protein.
    FDA's work on this draft guidance document began prior to 
significant infant formula supply chain concerns that arose in early 
2022. Although this guidance was not prepared specifically to alleviate 
supply chain concerns, this guidance will help ensure that infant 
formula products meet FDA's regulatory requirements and will contribute 
to ensuring a more resilient infant formula supply. We are issuing the 
draft guidance consistent with our good guidance practices regulation 
(21 CFR 10.115). The draft guidance, when finalized, will represent the 
current thinking of FDA 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 
alternate approach to make ``appropriate modifications'' if it 
satisfies the requirements of the applicable statutes and regulations. 
Topics discussed in the draft guidance include:
     Purpose of the AOAC Method;
     Overview of the AOAC Method as originally described;
     Need for ``appropriate modifications'' to update the AOAC 
Method and for use of infant formulas in PER bioassays;
     Conduct and analysis of a PER study with ``appropriate 
modifications'' (matching the reference and test diets);
     Protocols and reports;
     Reference guidelines; and
     Appendices: AOAC Official Method 960.48, composition of 
vitamin and mineral mixtures, compositions of diets, and examples of an 
approach for matching vitamin, mineral, and (methionine + cystine) 
compositions of PER study diets.

II. Paperwork Reduction Act of 1995

    Under the Paperwork Reduction Act of 1995 (PRA) (44 U.S.C. 3501-
3521), Federal Agencies must obtain approval from the Office of 
Management and Budget (OMB) for each collection of information they 
conduct or sponsor. ``Collection of information'' is defined in 44 
U.S.C. 3502(3) and 5 CFR 1320.3(c) and includes Agency requests or 
requirements that members of the public submit reports, keep records, 
or provide information to a third party. Section 3506(c)(2)(A) of the 
PRA (44 U.S.C. 3506(c)(2)(A)) requires Federal Agencies to provide a 
60-day notice in the Federal Register concerning each proposed 
collection of information before submitting the collection to OMB for 
approval. To comply with this requirement, FDA is publishing notice of 
the proposed collection of information set forth in this document.
    With respect to the following collection of information, FDA 
invites comments on these topics: (1) whether the proposed collection 
of information is necessary for the proper performance of FDA's 
functions, including whether the information will have practical 
utility; (2) the accuracy of FDA's estimate of the burden of the 
proposed collection of information, including the validity of the 
methodology and assumptions used; (3) ways to enhance the quality, 
utility, and clarity of the information to be collected; and (4) ways 
to minimize the burden of the collection of information on respondents, 
including through the use of automated collection techniques, when 
appropriate, and other forms of information technology.

Protein Efficiency Ratio (PER) Rat Bioassay Studies To Demonstrate That 
a New Infant Formula Supports the Quality Factor of Sufficient 
Biological Quality of Protein

OMB Control Number 0910-0256--Revision

    Under Sec.  106.96(e), an infant formula must meet the quality 
factor of sufficient biological quality of protein, and Sec.  106.96(f) 
provides how an infant formula manufacturer must demonstrate that a 
formula meets this quality factor. PER studies are used to demonstrate 
to FDA that a new infant formula meets

[[Page 8870]]

the quality factor of sufficient biological quality of protein when fed 
as the sole source of nutrition. This draft guidance, when finalized, 
would help manufacturers and laboratories performing PER studies in the 
design, conduct, evaluation, and reporting of such studies. When 
finalized, the draft guidance would provide recommendations for 
additional recordkeeping and reporting of protocols and PER studies 
related to the composition of test and control diets, as well as 
conditions, adverse effects, and attrition in rats. The draft guidance, 
when finalized, also will explain ``appropriate modifications'' of the 
AOAC Method to help manufacturers and contract laboratories conduct PER 
studies that demonstrate to FDA that a new infant formula meets the 
quality factor of sufficient biological quality of protein.
    Description of Respondents: Respondents to the information 
collection are manufacturers of infant formula. Respondents are from 
the private sector (for-profit businesses).
    We estimate the burden of this collection of information as 
follows:

                                                   Table 1--Estimated Annual Recordkeeping Burden \1\
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                                               Number of      Number of records     Total annual
   Activity; guidance document section       recordkeepers    per  recordkeeper       records       Average burden per  recordkeeping     Total hours
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Records for composition of the test and                   15                  2                 30  1................................                 30
 control diets during PER studies;
 Section IV.
Records for conditions, adverse effects,                  15                140              2,100  0.083 (5 minutes)................                174
 and attrition in rats during PER
 studies; Section IV.
                                          --------------------------------------------------------------------------------------------------------------
    Total................................  .................  .................  .................  .................................                204
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\1\ There are no capital costs or operating and maintenance costs associated with this collection of information.

    The estimates in tables 1 and 2 are based on experience with our 
infant formula safety and nutrition programs. We estimate that fifteen 
manufacturers annually will each create and maintain two records for 
the composition of test and control diets of PER studies. We estimate 
the recordkeeping burden to be 1 hour per record for an annual burden 
of 30 hours (15 manufacturers x 2 records). These estimates are based 
on numerous PER study protocols, reports, and laboratory experiences.
    We estimate that fifteen manufacturers annually will each create 
and maintain 140 records to account for conditions, adverse effects, 
and attrition in rats during PER studies. We estimate these records 
will take 5 minutes per record for an annual burden of 174.3 hours, 
rounded to 174 (15 manufacturers x 140 records x 0.083/hours). We 
calculate the total recordkeeping burden will be 204 hours annually.

                                 Table 2--Estimated Annual Reporting Burden \1\
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                                                     Number of                        Average
   Activity; guidance document       Number of     responses per   Total annual     burden per      Total hours
             section                respondents     respondent       responses       response
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Development and submission of a               15               1              15              70           1,050
 PER study protocol; Section V..
Development and submission of a               15               1              15              40             600
 PER study final report; Section
 V..............................
                                 -------------------------------------------------------------------------------
    Total.......................  ..............  ..............  ..............  ..............           1,650
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\1\ There are no capital costs or operating and maintenance costs associated with this collection of
  information.

    We estimate that fifteen manufacturers will prepare and submit to 
FDA a protocol to ensure that the specifications of the AOAC Method and 
FDA's ``appropriate modifications'' are met. A protocol is a detailed 
plan for the conduct of the PER study that helps the manufacturer meet 
the requirements of Sec.  106.96. In Table 1 in Appendix 6 of the draft 
guidance, we offer an illustration of how the values can be recorded as 
part of a protocol. An interested manufacturer will call FDA to discuss 
the manner in which a protocol will be submitted. We estimate each 
protocol will take 70 hours for an annual burden of 1,050 hours (15 
protocols x 70 hours).
    In addition, we estimate that fifteen manufacturers will submit a 
final report on all aspects of the PER study, including Certificates of 
Analyses (i.e., a full specification of results) for relevant 
ingredients to FDA. A final report is submitted in the same manner as a 
protocol. We estimate each final report will take 40 hours for an 
annual burden of 600 hours (15 final reports x 40 hours). We calculate 
the total reporting burden will be 1,650 hours annually.
    This draft guidance also refers to previously approved FDA 
collections of information. The collections of information in 21 CFR 
part 106 have been approved under OMB control number 0910-0256.

III. Electronic Access

    Persons with access to the internet may obtain an electronic 
version of the draft guidance at https://www.fda.gov/RegulatoryInformation/Guidances/default.html, https://www.fda.gov/regulatory-information/search-fda-guidance-documents, or https://www.regulations.gov.

IV. Other Issues for Consideration

    Although FDA welcomes comments on any aspect of the draft guidance, 
we particularly invite comments on the following sections, issues, and 
questions related to the compositions of PER study test (infant 
formula) and reference (casein control) diets. We ask that your

[[Page 8871]]

comments explain how suggestions will meet the overall requirement of 
demonstrating that the quality factor has been met using an 
``appropriate modification.'' When commenting on a particular question, 
please use the question numbers below as this will make it easier for 
us to determine how a specific comment relates to a particular question 
or topic.

A. Questions for Section IV.B.1.c. Fats and Carbohydrates

1. Fats
    Question 1. Companies have expressed difficulties in qualitative 
matching of fat in test and reference diets (e.g., problems with 
physical consistency of reference diets when qualitative matching is 
attempted) and difficulties in quantitative matching because of the 
much lower fat requirement of rats. We invite comments on whether the 
fat compositions of the test and reference diets should be matched: (a) 
on a quantitative basis only; or (b) on both a quantitative and 
qualitative basis. Please explain your reasoning. If your answer is 
(b), please describe what additional flexibilities might be needed to 
reduce problems with formulation and palatability of the reference 
diets (e.g., use of more saturated fat in place of the unsaturated 
(liquid) fats in infant formulas; partial substitution of the 
unsaturated fat in the infant formula with saturated fat in the 
reference diet). Please describe your experience with use of fat 
compositions in the reference diets that differ from that of the infant 
formula.
    Question 2. Would reducing the fat content of the reference diet to 
about 80 percent that of the infant formula test diet (e.g., to about 
17-20 percent fat in the reference diet versus about 22-25 percent fat 
in the test diet) help to avoid issues (e.g., problems with physical 
consistency of reference diets when qualitative matching is attempted) 
reported with high-fat reference diets? If your answer is ``yes,'' 
please describe other compositional changes that might be needed to 
keep the test and reference diets isocaloric. If your answer is ``no,'' 
please explain your reasoning.
    Question 3. The need for vitamin E increases with an increase in 
dietary polyunsaturated fatty acids (PUFA) and with the degree of 
unsaturation of PUFA. We are proposing the use of a minimum ratio value 
for vitamin E:PUFA of 0.48  0.28 milligrams (mg) of d-
[alpha]-tocopherol to grams (g) of PUFAs in the PER study diets. We 
suggest that the total PUFA content of the test and reference diets be 
estimated from the Certificates of Analysis or other information and 
used with dietary concentrations of vitamin E to calculate the ratio of 
vitamin E:PUFA for both diets. The minimum ratio value of 0.48 can be 
used as a guideline for adjusting the concentration of vitamin E in the 
reference diet. Is this adjustment for using vitamin E needed? If you 
think the adjustment for vitamin E is needed, please explain your 
reasoning. If your answer is ``no,'' please explain why not. Is the 
mean ratio of 0.48 mg d-[alpha]-tocopherol per gram of PUFA reasonable 
or is there a more appropriate value? Please explain your reasoning.
2. Carbohydrates
    Question 4. In explaining appropriate modifications to the AOAC 
Method, the IFR states that, among other things, if an infant formula 
contains a carbohydrate source other than lactose, the source(s) of 
carbohydrate in the formula should be added in the reference diet as 
well (see FDA's interim final rule, Current Good Manufacturing 
Practices, Quality Control Procedures, Quality Factors, Notification 
Requirements, and Records and Reports, for Infant Formula, 79 FR 7933 
at 8024, Feb. 10, 2014)).
    The simultaneous qualitative matching of fat and carbohydrate 
composition has proven difficult during formulation of PER study 
reference diets (e.g., problems from adding sugars such as sucrose; 
hardening of mixture and compromised oil absorption when water is added 
to liquid oils). Our current thinking is that use of the same oil blend 
in the infant formula and reference diet may be one approach if there 
is not a need to qualitatively match all the carbohydrates. We invite 
comments on potential solutions to these difficulties. For example, 
would altering the type of fat used in the reference diet while 
retaining quantitative matching of the fat contents of the test and 
reference diets be sufficient to overcome these problems? Would the use 
of corn starch as a carbohydrate source in the reference diet allow the 
reference diet to be formulated with the same oil blends used in the 
infant formula? Please explain your reasoning.

B. Questions for Section IV.B.1.d. Removal of Water From Liquid Infant 
Formulas and Determination of Moisture in PER Study Diets

    Question 5. The AOAC Method specifies a moisture content of 5 
percent in the PER study test and reference diets. Some laboratories 
have had difficulty preparing diets to match fat and water contents, 
leading to physical consistencies in diets that makes it difficult to 
accurately record food consumption. We invite comments on specific 
problems that have arisen when attempting to match dietary contents of 
fat and water, as well as solutions that have been identified to help 
limit the occurrence of such problems. Should flexibility be provided 
in matching the water and fat contents of the diets? If your answer is 
``yes,'' please describe an approach (i.e., explain the types of 
flexibilities) that might be needed to reduce problems with the 
physical consistencies of the reference diets. If your answer is 
``no,'' please explain your reasoning.

C. Questions for Section IV.B.1.e. Mineral Content

    Question 6. FDA's regulations require that the infant formula be 
studied in a PER assay (Sec.  106.96(f)). Further, the AOAC Method 
specifies that both the PER study test and reference diets contain 
similar contents of minerals based on matched ash contents. We invite 
comments on how this matching could be achieved while meeting the 
requirement that the infant formula be tested. Is ash content alone an 
adequate surrogate when matching minerals in test and reference diets? 
If your answer is ``no,'' please described why not and discuss another 
approach that might be used to achieve the matching of minerals in test 
and reference diets.
    Question 7. Multielement analysis (e.g., ICP-AES (inductively 
coupled plasma-atomic emission spectroscopy), ICP-MS (inductively 
coupled plasma-mass spectrometry)) is currently used for the 
simultaneous analysis of many minerals. We invite comments on whether 
use of multielement analysis for the quantitation and subsequent 
matching of all minerals would be preferable to continued use of ash as 
a surrogate for mineral content. If your answer is ``yes,'' please 
describe reasonable expectations regarding how such analyses can be 
used.
    Question 8. In Appendix 6 of the draft guidance, FDA has suggested 
a process by which mineral compositions of the test and reference diets 
can be matched to within 20 percent. We invite comments on 
whether this is a reasonable approach. If your answer is ``no,'' please 
explain your reasoning and suggest an alternate approach.

D. Questions for Section IV.B.1.f. Vitamin Content

    Question 9. The AOAC Method specifies that both the PER study test 
and reference diets contain the same vitamin composition. For the 
purpose of studying infant formula, we understand this to mean that the 
vitamin

[[Page 8872]]

composition of the test and reference diets in a PER study should be 
comparable. We invite comments on how such comparability should be 
defined and how it might be achieved.
    Question 10. In Appendix 6 of the draft guidance, FDA has suggested 
a process by which vitamin compositions of the test and reference diets 
can be matched to within 20 percent. We invite comments on 
whether this approach is reasonable and ask you to explain your 
thinking. If you do not believe the approach is reasonable, please 
explain your reasoning and suggest an alternative approach.
    Question 11. We invite comments on whether the matching of the 
vitamin compositions between the test and reference diets should be 
eliminated because, for example, vitamins such as vitamin K and vitamin 
B12, among others, do not impact the growth of rats during the 28-day 
PER study. If your answer is ``yes, the matching of vitamin 
compositions between test and reference diets should be eliminated,'' 
what do you propose as the vitamin composition for the reference diet? 
Please explain your reasoning. If your answer is ``no,'' please explain 
your reasoning.

E. Question for Section IV.B.1.g. Fiber

    Question 12. We invite comment on whether fiber should be added to 
the PER study test and matched casein reference diets under all 
conditions, under specified conditions, or not added at all. If your 
answer is ``yes, under all conditions,'' what is your proposed level of 
addition (e.g., to match the concentrations of non-digestible fiber in 
the infant formula at its rate of addition)? If your answer is ``yes, 
under specified conditions,'' what are the specific conditions under 
which fiber should be added and at what concentration? If your answer 
is ``no, fiber should not be added,'' please explain your reasoning.

F. Question for Section IV.B.1.h. Sulfur Amino Acids (Methionine, 
Cystine)

    Question 13. In the draft guidance, we recommend that the 
concentration of inorganic sulfur (e.g., as sulfate salts) in the PER 
study casein reference control diet be adjusted to 0.964 g/kilograms 
diet, the content calculated from the mineral composition set forth in 
the AOAC Method as originally described. We also provide a procedure 
for matching the (methionine + cystine) concentrations in the casein 
reference control and test diets, and for use of this sulfur amino 
acid-matched group as a second casein reference control group in PER 
studies. This approach will reduce the risk of a failure of the PER 
study control group. If you think the approach is needed, please 
explain your reasoning. If you think that such an approach is not 
necessary, please explain why not. If you think that other approaches 
might be more helpful in reducing the risk of a failure of the 
reference control group, please describe such approaches and explain 
their advantages.

    Dated: February 6, 2023.
Lauren K. Roth,
Associate Commissioner for Policy.
[FR Doc. 2023-02836 Filed 2-9-23; 8:45 am]
BILLING CODE 4164-01-P