Optimized 5-hour multiplex PCR test for the detection of tinea unguium: performance in a routine PCR laboratory

We recently reported the development of a 5-hour multiplex PCR test for the detection of tinea unguium and the optimization of this test by the inclusion of an inhibition control. Here we report the performance of this procedure as used in a routine clinical laboratory as compared to conventional microscopy and culture-based techniques performed in a mycology reference laboratory. We found in processing 109 samples that 22 (20.2%) yielded fungi in culture while the suspected etiologic agents were noted microscopically in 15 (13.8%) that were negative in culture. Fungi were detected by PCR in 37 (33.9%) samples, of which only three were positive in culture. Since the majority of PCR positive but culture negative samples were positive in microscopic examinations, the increased sensitivity was not due to contamination. PCR inhibitors were present in 5% of the samples, but this was overcome by re-running the samples with a 50% reduction of sample DNA. In conclusion, the PCR test performance in the routine setting was excellent and provided a markedly reduced time to diagnosis with a higher sensitivity.