Onychomycosis Treatment in the United States

Onychomycosis is a common progressive infection of the nails caused by dermatophytes, nondermatophyte molds, and yeasts, with Trichophyton rubrum being the most common causative organism.^1-3 Onychomycosis affects approximately 2% to 26% of different populations worldwide. It represents 20% to 50% of onychopathies and approximately 30% of fungal cutaneous infections.^4-9 Less than 30% of infected persons seek medical advice or treatment even in developed areas of the world.¹⁰ Onychomycosis may be a source of more widespread fungal skin infections or give rise to complications such as cellulitis. Chronic, long-lasting infection may result in nail dystrophy and can lead to pain, absence from work, and decreased quality of life.^1,11 Because the dermatophyte can contaminate communal bathing facilities and spread to others,¹² it is important to effectively target and treat patients with onychomycosis, thus reducing the rate of related morbidities.^1,9

The primary aim of onychomycosis treatment is to cure the infection and prevent relapse. Both topical and oral agents are available for the treatment of fungal nail infections. Generally, systemic therapy for onychomycosis is more successful than topical treatment, likely due to poor penetration of topical medications into the nail plate.^1,2,9 However, newer topical drugs have shown promising results in treating some types of onychomycosis.¹³ In its guidelines for treatment of onychomycosis, the British Association of Dermatologists recommends use of topical treatment under the following conditions: (1) when there is not extensive involvement of the nail plate (eg, candidal paronychia, superficial white onychomycosis, early stages of distal and lateral subungual onychomycosis), (2) when systemic therapy is contraindicated, or (3) in combination with systemic therapy.¹ Although there are multiple treatments for fungal nail infections, there are limited reports on the ways in which physicians actually use these treatments or the frequency with which they prescribe them.

This study provides a representative portrayal of onychomycosis visits in the US outpatient setting using a large nationally sampled survey. In particular, we aimed to assess the number of visits related to onychomycosis, the demographics of patients, and the treatments being prescribed for onychomycosis.

Methods

Study Design

Data from January 1, 1993, to December 31, 2010, were collected from the National Ambulatory Medical Care Survey (NAMCS), an ongoing survey of nonfederal employed US office-based physicians who are primarily engaged in direct patient care. The NAMCS has been conducted by the National Center for Health Statistics every year since 1989 to estimate the utilization of ambulatory care services in the United States. Since 1989 including 1993 to 2010, the NAMCS sampled approximately 30,000 visits per year. For each visit sampled, a 1-page patient log including demographic data, physicians’ diagnoses, services provided, and medications was completed. In the NAMCS survey, visits were divided into 2 groups: (1) visits from established patients that have been seen in that office before for any reason, and (2) visits for new (ie, first-time) patients. The current study included all visits in which fungal nail infection (code 110.1 according to the International Classification of Diseases, Ninth Revision [ICD-9]) was listed as 1 of 3 possible diagnoses.

Statistical Analysis

Sampling weights were applied to data to produce estimates for the total US outpatient setting.¹⁴ Data were analyzed using SAS version 9.2, and SAS survey analysis procedures were used to account for the clustered sampling of the survey. The total numbers of visits for which onychomycosis was 1 of 3 possible diagnoses and for which it was the sole diagnosis were reported. Visit rates per population by demographic characteristics (ie, patient sex, age, race, and ethnicity) were calculated. Population estimates were based on the 2001 NAMCS Public Micro-Data File Documentation records of the US census estimates for noninstitutionalized civilian persons.¹⁵ Trends in proportion of visits linked with an onychomycosis diagnosis over time were evaluated using the SAS SURVEYREG procedure. Types of physicians who attended to these visits as well as leading comorbidities that had been diagnosed and documented in the medical record were characterized. Onychomycosis-related medications prescribed at these visits were reported and prescribing trends over time were evaluated. Differences in the treatment prescribed according to the type of visit (ie, first-time or return visit); physician specialty; and patients’ gender, race, and health conditions (eg, obesity, diabetes mellitus) were examined. To exclude the possibility that fluconazole and other broad-spectrum antifungals were being used for secondary diagnoses, we determined the number of visits that had an additional diagnosis of either candidiasis (ICD-9 codes 112.0–112.9) or “other specified erythematous conditions” (ICD-9 code 695.89).