Global prevalence of onychomycosis in general and special populations: An updated perspective

Abstract

Background: Onychomycosis is a chronic nail disorder commonly seen by healthcare providers; toenail involvement in particular presents a treatment challenge. Objective: To provide an updated estimate on the prevalence of toenail onychomycosis. Methods: We conducted a literature search using PubMed, Embase and Web of Science. Studies reporting mycology-confirmed diagnoses were included and stratified into (a) populations-based studies, and studies that included (b) clinically un-suspected and (c) clinically suspected patients. Results: A total of 108 studies were included. Based on studies that examined clinically un-suspected patients (i.e., with or without clinical features suggestive of onychomycosis), the pooled prevalence rate of toenail onychomycosis caused by dermatophytes was 4% (95% CI: 3–5) among the general population; special populations with a heightened risk include knee osteoarthritis patients (RR: 14.6 [95% CI: 13.0–16.5]), chronic venous disease patients (RR: 5.6 [95% CI: 3.7–8.1]), renal transplant patients (RR: 4.7 [95% CI: 3.3–6.5]), geriatric patients (RR: 4.7 [95% CI: 4.4–4.9]), HIV-positive patients (RR: 3.7 [95% CI: 2.9–4.7]), lupus erythematosus patients (RR: 3.1 [95% CI: 1.2–6.3]), diabetic patients (RR: 2.8 [95% CI: 2.4–3.3]) and hemodialysis patients (RR: 2.8 [95% CI: 1.9–4.0]). The prevalence of onychomycosis in clinically suspected patients was significantly higher likely due to sampling bias. A high degree of variability was found in a limited number of population-based studies indicating that certain pockets of the population may be more predisposed to onychomycosis. The diagnosis of non-dermatophyte mould onychomycosis requires repeat sampling to rule out contaminants or commensal organisms; a significant difference was found between studies that performed single sampling versus repeat sampling. The advent of PCR diagnosis results in improved detection rates for dermatophytes compared to culture. Conclusion: Onychomycosis is an underrecognized healthcare burden. Further population-based studies using standardized PCR methods are warranted.