Comparison of real-time PCR with conventional methods to detect dermatophytes in samples from patients with suspected dermatophytosis

Abstract

A PCR detecting dermatophytes within a short turnaround time would significantly enhance the management of patients with suspected dermatophytosis. This study aimed at comparing the results of a real-time PCR assay with those of the conventional diagnostic (direct microscopy and culture) performed by a dermatologist working in a medical mycology laboratory for the detection of dermatophytes in nail and skin samples. A total of 112 specimens (54 nail and 58 skin) were collected from 52 patients with one to four suspected dermatophytosis lesions. The PCR diagnostic indices were calculated for either sample- or patient-based dermatophytosis diagnosis. The sample-based diagnostic efficacy yielded 79% sensitivity and 73% specificity. The patient-based diagnostic efficacy was higher with 100% sensitivity and 82% specificity. Interestingly, PCR yielded significantly (p < 0.004) lesser false negative results and performed overall better (diagnostic odds ratio = 24.0 vs. 5.5) in nail than in skin samples. In conclusion, this real-time PCR assay performance was consistent with those of the conventional methods in the hands of a skilled expert and particularly efficacious in diagnosing dermatophyte onychomycosis. This PCR is suited to high throughput batch processing; if used instead of direct microscopy, it could reduce hands-on time in the routine clinical laboratory workflow.

Keywords: Dermatophytes; Dermatophytosis; Diagnosis; Real-time PCR.