Authors of a @JAADjournals research letter describe risk factors for onychomycosis and assess adherence to the AAD guidelines that recommend confirmatory testing before oral antifungal therapy is prescribed. During 2018, among more than 21 million outpatients, onychomycosis prevalence was 1.6% overall and 12.7% among patients 65 years of age and older. Male gender and nonrural residence were associated with onychomycosis. Common underlying conditions included diabetes (23%), immunosuppressive conditions (21.8%), and non-unguium tinea (12.6%). . Across specialties, confirmatory lab testing was infrequent (15.3%); 12% of patients received a histopathology test, 2.8% a fungal culture, 2.1% direct microscopy, and 2.1% fungal polymerase chain reaction; 0.5% received antifungal susceptibility testing. Patients seen by dermatologists more frequently received confirmatory testing (31%) than those seen by podiatrists (16.9%) or general practitioners (5.2%). . Of the patients prescribed an oral antifungal drug, only 9.7% received confirmatory diagnostic testing. The authors conclude that confirming the diagnosis of onychomycosis with lab testing is important for avoiding unnecessary antifungal exposure as a global resistance to terbinafine has emerged. . Visit the link in our bio to read more in #DermWorldWeekly.