Onychomycosis: A simpler in-office technique for sampling specimens

Background▶ In onychomycosis, proper specimen collection is essential for an accurate diagnosis and initiation of appropriate therapy. Several techniques and locations have been suggested for specimen collection. Objective▶ To investigate the optimal technique of fungal sampling in onychomycosis. Methods▶ We reexamined 106 patients with distal and lateral subungual onychomycosis (DLSO) of the toenails. (The diagnosis had previously been confirmed by a laboratory mycological examination - both potassium hydroxide [KOH] test and fungal culture - of samples obtained by the proximal sampling approach.) We collected fungal specimens from the distal nail bed first, and later from the distal underside of the nail plate. The collected specimens underwent laboratory mycological examination. Results▶ KOH testing was positive in 84 (79.2%) specimens from the distal nail bed and only in 60 (56.6%) from the distal underside of the nail plate (P=.0007); cultures were positive in 93 (87.7%) and 76 (71.7%) specimens, respectively (P=.0063). Combining results from both locations showed positive KOH test results in 92 (86.8%) of the 106 patients and positive cultures in 100 (94.3%) patients. Conclusions▶ Based on our study, we suggest that in cases of suspected DLSO, material should be obtained by scraping nail material from the distal underside of the nail and then collecting all the material from the distal part of the nail bed.