Prevalence and epidemiology of onychomycosis in patients visiting physicians' offices: A multicenter Canadian survey of 15,000 patients

A prospective, multicenter study to determine the epidemiology of onychomyc osis was performed in the offices of 3 dermatologists and 1 family physicia n in Ontario, Canada. In the sample of 15,000 patients, abnormal-appearing nails were observed in 2505 persons (16.7%). There were 1199 patients (8%) with toenail or fingernail onychomycosis confirmed on mycologic examination , with 1137 patients (7.6%) who had only pedal onychomycosis, 40 patients w ith toenail and fingernail onychomycosis (0.27%), and 22 patients (0.15%) w ith only fingernail onychomycosis. The condition was more common in male pa tients (P<.0001) and older persons (P<.0001). The ratio of onychomycosis in toenails/fingernails was 19:1. When onychomycosis was present in toenails, the ratio of distal/lateral subungual onychomycosis (DLSO) to white superf icial onychomycosis to proximal subungual onychomycosis was 360:59:1, The e xtent of DLSO in toenails was mild (less than or equal to 25% nail involvem ent), moderate (26%-74%; disease), and severe (greater than or equal to 75% nail involvement) in 27.6%, 39.9%, and 32.5% of patients, respectively. Af ter adjusting for the age and sex distribution of the general population, t he projected rate of onychomycosis in Canada is 6.5% (95% confidence interv al [CI], 6.1%-6.9%). The organisms causing toenail onychomycosis were 90.5% ; dermatophyte, 7.8% nondermatophyte molds, and 1.7% Candida spp. The corre sponding organisms causing fingernail onychomycosis were 70.8%, 0%, and 29. 2%, respectively In a large sample of 15,000 patients, abnormal-appearing n ails were present in 17% of the sample with mycologic evidence of toenail o r fingernail onychomycosis in 8%. The projected prevalence of onychomycosis in Canada is 6.5% (95% CI, 6.1%-6.9%).