Tinea Gladiatorum Detection With a Dermatophyte Test Strip

Abstract

Objective: Determine sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and concordance of diafactory hs-TP (DTS) to detect tinea gladiatorum using direct potassium hydroxide (KOH) microscopy as the reference standard.

Design: Prospective, comparative study.

Setting: Seventeen Minnesota high schools during the winter wrestling season.

Patients: Seventy-one consecutive high school wrestlers identified with a suspicious rash during skin inspection.

Interventions: Samples were obtained from each rash for both DTS and direct KOH microscopy.

Main outcome measures: Readings were recorded as positive or negative.

Results: Direct KOH microscopy identified tinea gladiatorum in 35 of the 71 samples (46%). DTS sensitivity was 80% (95% confidence interval 63%-92%), and specificity was 82% (66%-92%). PPV was 85% (68%-95%), and NPV was 86% (72 %-91%). The DTS result was 83% concordant (72%-91%) with direct KOH microscopy.

Conclusions: Similar to rapid Covid antigen tests, DTS required brief, basic training to perform and gave onsite results in 5 to 30 minutes. Although DTS is not approved for use in the United States by the FDA, concordance compared with direct KOH microscopy in diagnosing tinea gladiatorum was similar to results reported for DTS-TU in tinea unguium and tinea pedis. Further study comparing DTS to a reference standard using PCR plus direct microscopy is warranted.