The prevalence of unsuspected onychomycosis and its causative organisms in a multicentre Canadian sample of 30 000 patients visiting physicians’ offices

[[[ Background: ]]] Onychomycosis is difficult to treat and a concern for many patients. Prevalence estimates of onychomycosis in North American clinic samples have been higher than what has been reported for general populations. [[[ Objective: ]]] A large, multicentre study was conducted to estimate the prevalence of toenail onychomycosis in the Canadian population. [[[ Methods: ]]] Patients were recruited from the offices of three dermatologists and one family physician in Ontario, Canada. Nail samples for mycological testing were obtained from normal and abnormal-looking nails. This sample of 32 193 patients includes our previous published study of 15 000 patients. [[[ Results: ]]] Abnormal nails were observed in 4350 patients. Of these, the prevalence of culture-confirmed toenail onychomycosis was estimated to be 6.7% (95% CI, 6.41-6.96%). Following sex and age adjustments for the general population, the estimated prevalence of toenail onychomycosis in Canada was 6.4% (95% CI, 6.12%-6.65%). The distribution of fungal organisms in culture-confirmed onychomycosis was 71.9% dermatophytes, 20.4% non-dermatophyte moulds and 7.6% yeasts. Toenail onychomycosis was four times more prevalent in those over the age of 60 years than below the age of 60 years. [[[ Conclusion: ]]] The present data highlights that onychomycosis may be a growing medical concern among ageing patients.