Diagnostic PCR of dermatophytes--an overview

The prevalence of onychomycosis is increasing steadily, sevenfold alone in the US within the last twenty years. An important aspect in this development is the demographic development of the human population of the industrial countries like Germany. A fast and accurate laboratory diagnosis is essential for successful treatment because 50% of the cases are misdiagnosed when relying on the clinical appearance only. The current diagnosis of dermatophytosis, based on direct microscopy and culture of the clinical specimen, is problematic given the lacking specificity of the former and the length of time needed for the latter. Molecular techniques can help to solve these problems. In recent years, a number of in-house PCR assays have been developed to identify dermatophytes directly from clinical specimens. Based on the "Mikrobiologisch-infektiologischen Qualitätsstandards (MIQ) für Nukleinsäure-Amplifikationstechniken" and the MIQE guideline (Minimum Information for Publication of Quantitative Real-Time PCR Experiments) 11 studies are reviewed which were published between 2007 and 2010. The present article evaluates the quality of the PCR assays regarding false positive and false negative results due to contamination, PCR format, statistical analysis, and diagnostic performance of the studies. It shows that we are only at the beginning of providing high quality PCR diagnosis of dermatophytes.