Validation of a PCR/Microarray-Based Dermatophyte Detection System for the Identification of Trycophyton rubrum

Abstract

The gold standard for dermatophytes identification is fungal culture, which has a turnaround time of up to six weeks. Here, we evaluate whether a qualitative PCR/microarray-based test can provide high accuracy of organism identification with a shorter turnaround time. A total of 42 residual nail specimens were tested with the EUROArray Dermatomycosis; 25 with positive culture results for Trichophyton rubrum and 17 culture-negative. Percent agreement and Cohen kappa coefficient calculation was used to determine trueness. Analytical sensitivity was determined with serial dilutions of controls and a probit regression analysis. The calculated diagnostic sensitivity and specificity of the microarray compared to culture was 88% and 76.5%, respectively. The percent positive and negative agreement were 84.61% and 81.25%, respectively. Total percent agreement was 83.3%. Cohen kappa coefficient (0.651) showed substantial inter-assay reliability. The limit of detection was four copies. Overall, this qualitative PCR/microarray-based test has a short turnaround time and is comparable to culture for the detection and identification of T. rubrum.