Collection of fungi samples from nails: comparative study of curettage and drilling techniques

Onychomycosis is a common problem. Obtaining a positive laboratory test before treatment is important in clinical practice because the treatment of onychomycosis requires expensive oral antifungal therapy with potentially serious side-effects.

The purpose of this study was to compare curettage and subungual drilling techniques of nail sampling in the diagnosis of onychomycosis.

We evaluated 194 patients suffering from distal and lateral subungual onychomycosis and lateral subungual onychomycosis using curettage and subungual drilling sampling techniques. Nail samples were obtained in each case from proximal, medial and distal parts of the nail. KOH examination and fungal culture were used for detection and identification of fungal infection.

With each technique, the culture sensitivity improved as the location of the sample was more proximal (drilling proximal vs. distal, chi(2) = 5.15, P = 0.023; curettage proximal vs. distal, chi(2) = 4.2, P = 0.041). In each sample location, the drilling technique has a better culture sensitivity (drilling vs. curettage proximal, chi(2) = 11.9, P = 0.001; drill vs. curettage distal, chi(2) = 13.7, P < 0.0001). Trichophyton rubrum was by far the most common pathogen detected by both techniques from all sampling sites.

The drilling technique was found to be statistically better than curettage at each site of sampling. With each technique, we found that the culture sensitivity improved as the location of the sample was more proximal. More types of pathogens were detected in samples taken by both methods from proximal parts of the affected nails.