Clinical study of Dermatophyte Test Strip, an immunochromatographic method, to detect tinea unguium dermatophytes

The Dermatophyte Test Strip visualizes mycotic antigens by immunochromatography. It allows easy and fast detection of dermatophytes. A multicenter, single-arm, comparative clinical study was designed to evaluate the capacity of Dermatophyte Test Strip to detect dermatophytes in suspected tinea unguium specimens in comparison with direct microscopy and polymerase chain reaction (PCR). Signed consent was obtained from 222 subjects and all subjects completed the study. With the Dermatophyte Test Strip, dermatophytes were detected in 201 of 222 (90.5%) specimens but not in 21 of 222 (9.5%) specimens. With direct microscopy, dermatophytes were detected in 170 of 222 (76.6%) specimens but not in 52 of 222 (23.4%). Of the 45 specimens that showed inconsistent results between the two methods, PCR gave further results for 40 specimens, of which 37 (92.5%) specimens were positive and three (7.5%) were negative for dermatophytes. The positive concordance rate, negative concordance rate and overall concordance rate between the Dermatophyte Test Strip and direct microscopy were 81.1%, 66.7% and 79.7%, respectively. When inconsistent results were corrected using the results of PCR, these rates were 97.5%, 71.4% and 95.0%, respectively. When five specimens that could not be tested by PCR because no piece for the PCR test was left were excluded from analysis, these rates were 99.0%, 78.9% and 97.2%, respectively. The present results indicate good detection capacity of the Dermatophyte Test Strip. The Dermatophyte Test Strip provides a reliable, convenient and quick method to test for tinea unguium.