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To the Editor Mikailov and colleagues1 propose that the empirical treatment of onychomycosis with terbinafine without confirmatory testing is cost-effective. While the approach may be reasonable when disease prevalence is exceedingly high, prescribing medications with known adverse effects, some serious, leads to delay in correct treatment and unnecessary therapy for patients with dystrophic nails who do not have onychomycosis. In fact, only about half of dystrophic nails are caused by fungi2,3; the other half are manifestations of psoriasis, lichen planus, and trauma, among other causes. If empirical treatment is provided for clinically suspected onychomycosis in dystrophic nails, correct treatment is delivered only half the time, the same probability as a random coin flip. The calculations of cost savings using 75% disease prevalence by Mikailov et al1 overestimate savings. Fingernail dystrophy without toenail involvement is seldom caused by a dermatophyte; therefore, empirical treatment with terbinafine should be administered with caution. Furthermore, recent meta-analyses for the prevalence of onychomycosis in Europe and North America estimate it to be only 4%, with previous reports of 7% to 14% in North America.3- 5
Wang AL, Elewski BE, Elmets CA. Confirmatory Testing for Onychomycosis. JAMA Dermatol. 2016;152(7):848. doi:10.1001/jamadermatol.2016.0786