Dermatophyte test medium culture versus mycology laboratory analysis for suspected onychomycosis. A study of 100 cases in a geriatric population.

Onychomycosis is the most frequently encountered condition in podiatric practice in the United States. A variety of modalities are available to confirm the presumptive diagnosis of onychomycosis. This study was conducted to compare the results of in-office dermatophyte test medium cultures with those of mycology laboratory analysis for 100 cases of suspected onychomycosis in a geriatric population. The results demonstrated that 20% of the patients had dermatophyte involvement, 56% had saprophyte involvement, and 19% had yeast involvement. Only 50% of positive dermatophyte test medium cultures correlated with a positive microscopic fungal culture for dermatophytes. Given these results, it is questionable whether in-office dermatophyte test medium cultures should be routinely used in geriatric patients for the diagnosis of onychomycosis. The authors believe mycology laboratory testing with fluorescent potassium hydroxide preparations and microscopic fungal cultures to be superior to in-office dermatophyte test medium cultures for the diagnosis of onychomycosis in geriatric patients.