Onychomycosis (nail fungus)
Phenotype Algorithm Pseudo Code
March 28, 2012
Ver. 03
Group Health Contacts:
David Carrell (carrell.d@ghc.org)
BACKGROUND
Onychomycosis, also known as tinea unguium and toe fungus, is a fungal infection of the nail. It
is the most common disease of the nails, affecting 6-8% of the population and constituting half
of all nail abnormalities. This condition may affect toenails or fingernails, but toenail infections
are most common.
ALGORITHM
The EMR phenotype definition below combines evidence from diagnosis codes, procedure
codes, and medication fills. These may be available from either the outpatient or inpatient
setting.
Cases
A subject may qualify as a case by meeting any one or more of the following three criteria:
1) has a history of multiple diagnosis codes for onychomycosis spanning a time period ≥
3 years (≥1,095 days), or
2) has a diagnosis code for onychomycosis and a nail debridement/excision procedure
within a 7-day period, or
3) has an oral medication fill for treating onychomycosis and either a diagnosis code for
onychomycosis or a nail debridement/excision within a 7-day period.
4) no dx for HIV “ever” (1993-2011)
Note that there is no minimum age at time of first evidence of the phenotype for cases.
The diagnosis code for onychomycosis is:
(ICD) 110.1* (Dermatophytosis of nail)
Nail debridement/excision procedure codes include:
1. CPT: 11720: DEBRIDE NAIL, 1-5
2. CPT: 11721: DEBRIDE NAIL, 6 OR MORE
3. CPT: 11730: REMOVAL OF NAIL PLATE
4. CPT: 11732: REMOVE NAIL PLATE, ADD-O
5. CPT: 11750: REMOVAL OF NAIL BED
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6. CPT: 11752: REMOVE NAIL BED/FINGER T
Medications for treating _ include:
1. TERBINAFINE (NDC: 55111025030)
2. GRISEOFULVIN V (NDC: 62021460)
3. 7E C29 GRIS-PEG (NDC: 884077304)
4. 7D GRISEOFULV V (NDC: 45021170)
5. B GRISEOFULVIN (NDC: 884076304)
Note: this mediations list is partial and will be expanded.
The index date is the date of the first diagnosis code or the first nail procedure or the first
medication, whichever appears in the patient’s record first.
Controls
A subject may qualify as a control by meeting the following criteria:
1) is ≥ 40 years of age, and
2) has a minimum history of continuous enrollment of 10 years, and
3) has no diagnosis codes for onychomycosis on record, and
4) has no evidence of nail debridement/excision procedures, and
5) has no evidence of prescriptions or fills for medications to treat fungal infections of the
nail.
6) no dx for HIV “ever” (1993-2011)
Note: For settings where care is not provided in an integrated (e.g., HMO) care
environment, the minimum enrollment criterion above will be implemented as follows:
 at least one encounter prior to 2002, and
 at least one encounter in 6 or more calendar years in the 8-year period 2002-2009,
and
 at least one encounter in 2010 or 2011
 (if deceased relax minimum encounter requirements – we’ll specify the details
when we see the data).
Matching of cases and controls by age and race will be handled analytically after genotyping
(needs discussion).
Covariates
1. Immunosuppressant rxs – all dates
2. Nursing home stays – all dates
3. Vitals (height, weight, and BMI)
- For cases, mean value in the 6 mo preceding phenotype index date
- For controls, the mean value “ever”
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Censoring
- chemotherapy tx – all dates
- soft cancer dx – all dates
Flowchart
See Validation Guidelines document
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