# Reclassification of ICD-9 Codes into Meaningful Categories for Oncology Survivorship Research

Authors: S. R. Rassekh; M. Lorenzi; L. Lee; S. Devji; M. McBride; K. Goddard
Journal: Journal of Cancer Epidemiology
 (2010)

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## Abstract

Background. The International Classification of Disease, ninth revision (ICD-9) is designed to code disease into categories which are placed into administrative databases. These databases have been used for epidemiological studies. However, the categories used in the ICD9-codes are not always the most effective for evaluating specific diseases or their outcomes, such as the outcomes of cancer treatment. Therefore a re-classification of the ICD-9 codes into new categories specific to cancer outcomes is needed. Methods. An expert panel comprised of two physicians created broad categories that would be most useful to researchers investigating outcomes and morbidities associated with the treatment of cancer. A Senior Data Coordinator with expertise in ICD-9 coding, then joined this panel and each code was re-classified into the new categories. Results. Consensus was achieved for the categories to go from the 17 categories in ICD-9 to 39 categories. The ICD-9 Codes were placed into new categories, and subcategories were also created for more specific outcomes. The results of this re-classification is available in tabular form. Conclusions. ICD-9 codes were re-classified by group consensus into categories that are designed for oncology survivorship research. The novel re-classification system can be used by those involved in cancer survivorship research.


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## Body

## 1. Background

The importance of a classification system for the grouping of causes of morbidity or mortality has long been known to be crucial for the study of disease. The first attempt to classify disease systematically has been attributed to Francois Bossier de Lacroix, (1706–1777), better known as Sauvages [1] in his treatise Nosologia Methodica, written in the 18th century. Subsequently, many groups have made attempts to create their own classification systems to compile quantitative data about various diseases within different population groups. In these systems, individual code categories are assigned to conditions that occur frequently and are associated with significant morbidity; others are grouped together, often by anatomical site or physiologic system [2]. Since the early 1900’s, international collaborations have attempted to revise and update these classification systems and this has led to the development of the International Classification of Diseases, which is now under the direction of the World Health Organization. The first version of the International Classification of Diseases was adopted in 1900. The ninth version, known as ICD-9, was published in 1975 and uses a five-digit coding system where the categories are meaningful at the 3-digit level [3].The ICD-9 has become a useful tool for health researchers, as the use of administrative databases in the study of diseases has flourished over the last decade. Administrative databases provide a quick and efficient method of eliciting clinical information regarding hospitalization, as compared to the historically used gold standard of chart review. These administrative databases were not intended for research but rather to collect information regarding resource utilization. However, studies have shown that clinical data extracted from hospital databases in Canada provide reliable data when compared to manual chart review [4]. There are limitations to these databases; it has been suggested that comorbidities in these databases may be underreported for certain codes [5].A reorganization of ICD-9 codes has been completed for four major chronic conditions (coronary artery disease, congestive heart failure, asthma, and chronic obstructive pulmonary disease) by a group of researchers for the purpose of creating a consistent research tool for the study of these health problems [6]. These researchers used the consensus of experts in the field and followed the recommendations made by Fink et al. [7]. Their recommendations stated that a group consensus should focus on a carefully defined problem that could be investigated in a timely and economical way, that consensus panel members should be representative of their profession, and that decisions on important issues should be justified by available empirically derived data as well as by judgments and experience.The Childhood/Adolescent/Young Adult Cancer Survivor Program (CAYACS) is a research program investigating late outcomes in survivors of pediatric and young adult cancer through the linkage of administrative databases. One of the major aims of this program was to analyze hospitalizations in survivors of childhood and adolescent cancer occurring 5 years after the date of diagnosis. ICD-9 codes reported on the hospital separation forms of 5-year cancer survivors can be linked and compared with controls who did not have childhood cancer. In reviewing the ICD-9 coding book, it became clear that the categories used in this book were not ideally suited for research into cancer survivorship. Therefore, a reclassification of ICD-9 coding was needed that was specific for all cancer survivorship issues. The purpose of this paper is to develop this reclassification of the ICD-9 codes that can be used by all researchers in cancer survivorship. Specifically, this reclassification system can be used by researchers interested in iatrogenic late effects due to therapies given to patients with cancer. It can also be used to study the association of cancer with other diseases that may share etiologic determinants. Finally, it can also be used in Health Services research investigating the rates of hospitalizations or medical services use in those who had previously treated cancer.


## 2. Methods

The first step was to review the categories used in the ICD-9 and then to decide what categories would be useful for oncology outcome research. Two investigators (SRR and KG) decided which major categories should be included. These categories included both main categories and a few subcategories as required. It was decided to use a category called “other” to group together all codes which were not easily identifiable or did not seem as important for oncology research.The second step was then to create an expert panel which included a radiation oncologist, a pediatric oncologist, and a data coordinator with extensive knowledge in ICD-9 coding (KG, SRR, LL). All 3 members of the panel had experience in survivorship research and were involved in a study using administrative databases to look at long-term outcomes in children treated for cancer (the CAYACS program). This panel then systematically reviewed each code in the ICD-9 coding book and placed each code into its new category in an Excel database.The final step was the transformation of this spreadsheet (performed by ML) into a program that reads ICD-9 codes from a data file and assigns the correct category using R code (reference), so that this new database could be easily used in future studies.


## 3. Results

The categories decided upon by the panel are shown in Table1. This changed the number of major categories from the 17 found in ICD-9 to 39 categories. The categories first used the ICD-9 categories served as a backbone and then new categories were created to encompass groups of conditions that would be of interest to those involved in survivorship research. After long discussion, the 2 clinicians involved in the study determined that these were the categories of choice.Table 1
Categories created by the panel.
Infectious disordersInfertility disordersNeoplasmsPerinatal conditionsEndocrine disordersSkin and subcutaneous disordersNutritional disordersMusculoskeletal and connective tissue disordersFluid and electrolyte disordersCongenital anomaliesInherited metabolic, and immune disordersNonspecific abnormal findingsHematologic disordersOther and unspecified mortality and morbidityPsychiatric disordersInjuriesSubstance abusePoisonings by drugs, medicaments, and biologicalNeurological disorderssubstancesENT and eye disordersEffects of foreign body entering through orificeCardiovascular disordersToxic effects of substancesVaricose veins, haemorrhoids, and lymphaticOther and unspecified effects of external causesDisordersCertain adverse effects not elsewhere classifiedRespiratory disordersComplications from a Procedure or DeviceDental disordersComplications of Medical CareDigestive system disordersLate EffectsGenitourinary disordersExternal Causes (E Codes)Gynecological disordersFactors Influencing Health Status and Contact withBreast disordersHealth Services (V Codes)Pregnancy, childbirth, and puerperiumMorphology of Neoplasms (M Codes)The reclassification of the ICD-9 codes into the new categories is shown in Table2. All the codes from the ICD-9 book were able to be incorporated into the new classification groups. The group was able to achieve full consensus for all codes. The majority of codes were easy to place into the new categories, but there were many codes that did not fit easily into a specific category. However, group consensus was achieved for all the reclassification choices.Table 2
Full categorization of ICD-9 codes.
Infectious Disorders001–136, 320–326, 370.1, 370.3–370.5, 372.0-372.1, 373.4–373.6, 377.3, 380.1, 382, 383.0–383.2, 420–422, 447.7, 460-466, 480-487, 511.1, 513, 540.1, 567.0-567.2, 573.1-573.2, 577.0-577.1, 581.8, 583.8, 590, 595.4–595.8, 597, 598.0, 601.2, 601.4, 603.1, 604, 614.2–614.4, 616.0-616.1, 616.3-616.5, 681–686, 711, 727.0, 727.3, 728.0, 730, 785.4, 790.7-790.8Central Nervous System Infections013, 036.0-036.1, 046–049, 053.0-053.1, 054.3, 054.7, 055.0, 056.0, 062–064, 072.1-072.2, 320–326, 331.5-331.6Bacteremia Infections036.2, 038, 790.7Endocarditis and Pericarditis Infections036.4, 420, 421Hepatitis Infections070, 573.1-573.2Gastrointestinal Infections007–009, 014, 054.2, 072.3, 120.1, 127, 129, 540.1, 567.0–567.2, 577.0-577.1Genitourinary Infections016, 054.1, 072.0, 078.6, 110.3, 112.1-112.2, 131, 581.8, 583.8, 590, 595.4–595.8, 597, 598.0, 601.2, 601.4, 603.1, 604, 614.2–614.4, 616.0-616.1, 616.3–616.5Sexually Transmitted Infections090–099, 447.7Other Infections001–006, 010–012, 015, 017-018, 020–027, 030–035, 037, 039–041, 045, 050–052, 053.2–053.9, 054.0, 054.4–054.9, 055, 056.7–056.9, 057, 060-061, 065-066, 071, 072.7–072.9, 073–077, 078.0–078.5, 078.7-078.8, 079–088, 100–104, 110.0–110.2, 110.4–110.9, 111, 112.0, 112.3–112.9, 114–118, 120.0, 120.2–120.9, 121–126, 128, 130, 132–136, 370.1, 370.3–370.5, 372.0-372.1, 373.4–373.6, 377.3, 380.1, 382, 383.0–383.2, 422, 460–466, 480-487, 511.1, 513, 681–686, 711, 727.0, 727.3, 728.0, 730, 785.4, 790.8Neoplasms140–239Malignant Neoplasm of Breast174-175Malignant Neoplasm of CNS191-192Malignant Neoplasm of Thyroid Gland193Leukemia204–208Malignant Cancers of soft tissue, connective tissue and bone170-171Malignant Cancers of Skin172-173Endometrial Cancer182Other Malignant Neoplasms140–169, 176–181, 183–190, 194–208Benign Neoplasms210–224, 225.0-225.1, 225.8-225.9, 226–229Meningiomas225.2–225.4Carcinoma In Situ Tumours230–234Neoplasm of Uncertain Behavior235–238Neoplasm of Unspecified Nature239Endocrine Disorders240–259Thyroid Gland Disorders240–246Diabetes Mellitus250Hypothalamus/Pituitary Disorders253Adrenal Gland Disorders255Ovarian/Testicular Dysfunction Disorders256-257Other Endocrine Disorders251-252, 254, 258-259Nutritional Disorders260–275, 278, 783Malnutritional/Anorexic Disorders260–263, 783.0, 783.2Obesity Disorders278.0-278.1, 783.1Vitamin Deficiency Disorders264–269Other Nutritional Disorders270–275, 278.2–278.8, 783.3–783.9Fluid And Electrolyte Disorders276Inherited Metabolic and Immune Disorders277, 279Hematologic Disorders280, 281, 282–289, 325, 415.1, 444, 451–453, 790.0Anaemias280, 281, 282–285Coagulation Defects286-287, 325, 415.1, 444, 451–453White Blood Cell Defects288Other Hematologic Disorders289, 790.0Psychiatric Disorders293-298, 300-302, 306-309, 311-313, 314, 316Depression Disorders300.4, 309.0-309.1, 311, 313.1Psychosis Disorders293–298Anxiety Disorders300.0–300.3, 300.5–300.9, 308, 309.2, 313.0Personality Disorders301, 312Eating Disorders307.1–307.5Hyperkinetic Syndrome (Attention Deficit Hyperactivity Disorders)314Other Psychiatric Disorders302, 306, 307.0, 307.2–307.4, 307.6–307.9, 309.3–309.9, 313.2–313.9, 316Substance Abuse291-292, 303–305Alcohol Abuse291, 303Drug Abuse292, 304-305Neurological Disorders290, 299, 310, 315, 317–319, 327, 330, 331.0–331.5, 331.7–331.9, 332–337, 340-359, 430–437, 780-781, 784.0, 797Cognitive Disorders290, 299, 310, 315, 317–319, 797Cerebral Degeneration Disorders330, 331.0-331.2, 331.7–331.9Hydrocephalus Disorders331.3–331.5Seizure Disorders345, 780.3Coma780Migraine and Headaches346Cerebrovascular Disorders430–437Spinal Cord Disorders336, 344Other Neurological Disorders327, 784Ent and Eye Disorders360–369, 370.0, 370.2, 370.6–370.9, 371, 372.3–372.9, 373.0–373.3, 373.8-373.9, 374–376, 377.0–377.2, 377.4–377.9, 378-379, 380.0, 380.2–380.9, 381, 383.3–383.9, 384–389, 470–478, 526–529, 784.1–784.9Eye and Adnexa Disorders360–369, 370.0, 370.2, 370.6–370.9, 371, 372.3–372.9, 373.0–373.3, 373.8-373.9, 374–376, 377.0–377.2, 377.4–377.9, 378-379Ear Disorders380.0, 380.2–380.9, 381, 383.3–383.9, 384–387Hearing Loss Disorders388-389Nasal and Oral Disorders470–478, 526–529, 784.1–784.9Cardiovascular Disorders390–398, 401–414, 416-417, 423–429, 440–443, 446–448, 458-459, 785.0–785.3, 785.5, 785.9, 794.3Cardiomyopathy and Heart Failure Disorders425, 428Arryhthmia Disorders426-427, 785.0-785.1, 794.3Hypertensive Disorders401–405Atherosclerotic Disorders440Ischaemic Heart Disorders410–414Hypotensive Disorders458, 785.5Other Cardiovascular Disorders390–398, 416-417, 423-424, 429, 441–443, 446–448, 459, 785.2-785.3, 785.9Varicose Veins, Haemorrhoids, and Lymphatic Disorders454–457, 785.6Varicose Veins and Hemorrhoids Disorders454–456Lymphatic Disorders457, 785.6Respiratory Disorders415.0, 490–496, 500–508, 510–512, 514–519Radiation Manifestations508.0-508.1Dental Disorders520–525Digestive System Disorders530–537, 540.0, 540.9, 541–543, 550–553, 555–558, 560, 562, 564–566, 567.8–567.9, 568–572, 573.0, 573.3–573.9, 574–576, 577.2–577.9, 578-579, 787, 789Irritable Bowel Disorders555-556, 558Liver Disorders570–572, 573.0, 573.3–573.9Biliary Tract and Gallbladder Disorders574–576Stomatitis528Esophagitis530Other Digestive System Disorders530–537, 540.0, 540.9, 541–543, 550–553, 557, 560, 562, 564–566, 567.8-567.9, 568-569, 577.2–577.9, 578-579, 787, 789Genitourinary Disorders580, 581.0–581.3, 581.9, 582, 583.0–583.7, 583.9, 584–589, 591–594, 595.0–595.3, 595.9, 596, 598.1–598.9, 599-600, 601.0-601.1, 601.3, 601.8-601.9, 602, 603.0, 603.8-603.9, 605, 607-608, 788Renal Disorders580, 581.0–581.3, 581.9, 582, 583.0–583.7, 583.9, 584–589, 591Calculus Disorders592, 594Bladder Disorders595.0–595.3, 595.9, 596Urethral Disorders598.1–598.9, 599Other Genitourinary Disorders600, 601.0-601.1, 601.3, 601.8-601.9, 602, 603.0, 603.8-603.9, 605, 607-608, 788Gynecological Disorders614.0-614.1, 614.5–614.9, 615, 616.2, 616.8-616.9, 617–627, 629Menstrual Disorders626Menopausal Disorders627Other Gynecological Disorders614.0-614.1, 614.5–614.9, 615, 616.2, 616.8-616.9, 617–625, 629Breast Disorders611Pregnancy, Childbirth, and Puerperium630–648, 650–676, V22–V24, V27Spontaneous Abortions630–632, 634Therapeutic Abortions635–638Ectopic Pregnancy633Complications Following Abortion, Ectopic, and Molar Pregnancies639Complications Related to Pregnancy640–648Indication for Care in Pregnancy, Labour and Delivery650–659Complications Occurring in Labour and Delivery660–669Complications of the Puerperium670–676Supervision and Pregnancy StateV22–V24Delivery OutcomeV27Infertility Disorders606, 628, 792.2Male Infertility606, 792.2Female Infertility628Perinatal Conditions760–779, V30–V39Perinatal Conditions760–799Birth OutcomeV30–V39Skin and Subcutaneous Disorders680, 690–698, 700–709, 782Hair and Hair Follicles Disorders704Other Skin and Subcutaneous Disorders680, 690–698, 700–703, 705–709, 782Musculoskeletal and Connective Tissue Disorders710, 712–726, 727.1–727.2, 727.4–727.9, 728.1-728.2, 729, 731–739Rheumatological Disorders710, 712–716, 725-726Joint Disorders717–719Spine Disorders720–724, 737Other Musculoskeletal and Connective Tissue Disorders727.1-727.2, 727.4–727.9, 728.1–728.8, 729, 731–736, 738-739Congenital Anomalies740–759Nonspecific Abnormal Findings790.1–790.6, 790.9, 790.9, 791, 792.0-792.1, 792.3–792.9, 793, 794.0–794.2, 794.4–794.9, 795-796Other and Unspecified Morbidity and Mortality798-799Injuries800–848, 850–854, 860–887, 890–897, 900–904, 910–929, 940–959Fractures (Excluding Skull and Spinal Fractures)807–829Head Injuries (Including Skull Fractures)800–804, 850–854, 870–873, 900, 910, 918, 920-921, 925, 950-951Spinal Injuries (Including Spinal Fractures)805-806, 839–839.5, 846-847, 952–954Burns940–949Other Injuries (Excluding Fractures)830–838, 839.6–839.9, 840–845, 848, 860–869, 874–887, 890–897, 901–904, 911–917, 919, 922–924, 926–929, 955–959Poisonings by Drugs, Medicaments, and Biological Substances960–979Effects of Foreign Body Entering Through Orifice930–939Toxic Effects of Substances980–989Other and Unspecified Effects of External Causes990–994Certain Adverse Effects Not Elsewhere Classified995Adverse Effects Due to Drug, Medicament, or Biological Substance995.0, 995.2, 995.4Other Adverse Effects995.1, 995.3, 995.5, 995.8Complications from a Procedure or Device996–998Complications of Medical Care999Late Effects137–139, 268.1, 326, 438, 905-909, E929, E959, E969, E977, E989, E999Late Effects of Infectious and Parasitic Diseases137–139Late Effects of Ricketts268.1Late Effects of Intracranial Abscess or Pyogenic Infection326Late Effects of Cerebrovascular Disease438Late Effect of Poisoning Due to Drug, Medicament, or Biological Substance909.0Late Effect of Toxic Effects of Nonmedical Substances909.1Late Effects of Radiation909.2Late Effects of Complications of Surgical and Medical Care909.3Late Effects of Other and Unspecified Causes909.4–909.9Late Effects of Injuries905–908Late Effects of Accidental InjuryE929Late Effects of Self-Inflicted InjuryE959Late Effects of Injury Purposely Inflicted by Other PersonE969Late Effects of Injuries Due to Legal InterventionE977Late Effects of Injury, Undetermined Whether Accidentally or Purposely InflictedE989Late Effects of Injury Due to War OperationsE999External Causes (E Code) (Supplementary Codes)External Causes of InjuryE800–E807, E810–E838, E840–E848, E880–E888, E890–E928, E970–E976, E978, E980–E988, E990–E998Railway AccidentsE800–E807Motor Vehicle Accidents-Traffic and NontrafficE810–E825Pedal Cycle AccidentsE826Other Transport AccidentsE827–E838, E840–E848All Accidental FallsE880–E888All Accidents Caused by Fire and FlamesE890–E899All Other AccidentsE900–E928All Injuries Caused by Legal InterventionE970–E976, E978Injury Undetermined Whether Accidentally or Purposely InflictedE980–E988Injury Resulting From Operations of WarE990–E998External Causes Of Poisoning By Drugs, Medicaments, And BiologicalsE850–E858External Causes Of Poisoning By Solid And Liquids, Gases And VapoursE860–E869Accidental Poisoning by Alcohol, Not Elsewhere ClassifiedE860Other Accidental PoisoningsE861–E869Misadventures To Patients During Surgical And Medical CareE870–E876Abnormal Reaction Or Complication To Patient After Surgical Or Medical CareE878-E879Adverse Effects In Therapeutic Use Of Drugs, Medicaments, And BiologicalsE930–E949Chemotherapy Adverse EffectsE930.7–E933.1Other Adverse EffectsE930.0–E930.6, E930.8-E930.9, E931-E932, E933.0, E933.2–E933.9, E934–E949Suicides And Self-Inflicted InjuryE950–E958Homicide And Injury Purposely Inflicted By Other PersonsE960–E968Factors Influencing Health Status And Contact With Health Services (V Code)V01–V21, V25-V26, V28, V40–V82Personal History of Malignant NeoplasmV10Family History of Malignant NeoplasmV16Personal History of Mental DisorderV11Mental and Behavioral ProblemsV40Health Supervision of Infant or ChildV20Constitutional States In DevelopmentV21Problems With SightV41.0-V41.1Problems With HearingV41.2-V41.3Elective Surgery for Purposes Other Than Remedying Health StatesV50, V51Fitting and Adjustment of Hearing AidV53.2Fitting and Adjustment of Cardiac PacemakerV53.3Radiotherapy SessionV58.0Maintenance ChemotherapyV58.1Housing, Household, and Economic CircumstancesV60.0-V60.2Other Family CircumstancesV61UnemploymentV62.0Observation For Suspected Malignant NeoplasmV71.1Special Screening For Malignant NeoplasmsV76Other Factors Influencing Health Status and Contact With Health ServicesV01–V09, V12–V15, V17–V19, V25-V26, V28, V41.4–V41.9, V42–V49, V52, V53.0-V53.1, V53.4–V53.9, V54–V57, V58.2–V58.9, V59, V60.3–V60.9, V62.1–V62.9, V63–V70, V71.0, V71.2–V71.9, V72–V75, V77–V82Morphology Of Neoplasms (M Codes)M8000-M9970


## 4. Discussion

The development of the ICD-9 codes has enabled health administrators and policy makers to investigate the frequency and causes for hospitalizations across jurisdictions. This coding system categorizes headings into 17 major groupings. There has been recent interest in the use of these hospital administrative databases to help answer epidemiological hypotheses. However, as the coding system is generalized to the entire spectrum of health conditions, it is not ideal for specific groups of interest. This became evident to our CAYACS program when we were attempting to use ICD-9 codes to analyze causes of hospitalizations in cancer survivors. The existing numerical groupings were not ideal for survivorship research. For instance, causes of infections were scattered throughout the ICD-9 coding groupings despite having infection as a major grouping. The hospital’s data coordinator could code an infection based on the pathogen (codes 001-139.8) or could code based on the system affected by the infection (codes scattered throughout the range). For a clinical researcher who is interested in all infections in a group of individuals with a specific health condition, the ICD-9 code groupings are not suited for this type of research. This becomes even more important when considering a very specific area of research, such as the treatment of cancer and its late outcomes. The purpose of this study was to reclassify the ICD-9 codes into practical groupings that can be used by a health researcher specifically for cancer follow-up outcomes.This study has therefore reclassified the ICD-9 codes into categories which are useful to those involved in oncology research using administrative databases. This reclassification system can be used by all groups looking at causes of hospitalization in those diagnosed with cancer, whether these patients are on active treatment or are in posttherapy surveillance as long-term survivors. All the codes in ICD-9 are accounted for and have been placed into specific categories. Subcategories were created that would help distinguish areas of interest within larger groups. For instance, within the cardiovascular system it is important to distinguish hypertension, myocardial infarction, arrhythmias, valvular disease and cardiomyopathy from each other, as each subcategory would likely have differing attributable factors and risks. By separating out these different conditions, we can study the the long-term risk of hospitalization associated with different initial childhood cancer diagnoses and therapies. We can for example, measure the risk of hospitalization for different cardiac conditions in long-term survivors treated for childhood Hodgkin lymphoma treated with mantle radiotherapy.A strength of this study is that consensus was easily achieved for all ICD-9 codes between the 3 members of the panel. The inclusion of a senior data coordinator who has extensive experience and expertise in coding in hospital discharges gave insight into the practicality of coding. As all 3 members of the panel are involved in survivorship research, the new classification scheme was based on experience with data derived from ICD9-coding.The main limitation of this study is that it represents the opinion of only one group of clinicians. Certainly others may have a few subtle changes they would suggest to the classifications or the categories in general.


## 5. Conclusions

By our accounts this is the first reclassification of the ICD-9 codes into new diagnostic groupings that are more useful for the clinical researcher. Moreover, this new classification system is ideal for oncology-specific outcomes and can therefore be used by all researchers in the study of cancer treatment and survivorship.


## Conflict of Interests

The authors declare that they have no conflict or-interests.


## Authors Contributions

S. R. Rassekh  conceived the study, participated in the design, was on the expert panel that performed the reclassification, and drafted the manuscript. M. Lorenzi helped design the study, created all the tables, and helped draft the manuscript. L. Lee helped design the study and was on the expert panel that performed the reclassification and helped draft the manuscript. S. Devji helped in the design of the study and in drafting the manuscript. M. McBride helped design the study, is the primary investigator of the CAYACS project which helped fund this study, and helped draft the manuscript. K. Goddard helped to conceive the study, participated in the design, was on the expert panel that performed the reclassification, and helped draft the manuscript. All authors read and approved the final manuscript.



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