Background: The successful diagnosis of dermatomycosis depends on specimen collection. Dermatomycosis is sampled mainly for scales, but there is a lack of research on specimens of blister fluid.
Objectives: To explore whether blister fluid can diagnose dermatomycosis and compare blister fluid and scale specimens for dermatomycosis diagnosis.
Methods: From April to July 2021, we prospectively gathered 34 patients who needed to meet all inclusion criteria simultaneously and collected their blister fluid and scales as specimens. The two samples were tested by fluorescent stain microscopy, fungal culture and PCR, and the diagnosis results were compared.
Results: The blister fluid sample's sensitivity, specificity and accuracy were 90%, 100% and 94.1%, respectively, whereas the scales sample were 60%, 100% and 76.5%, respectively. The positive likelihood ratios were >10 for both blister fluid and scales specimen, and the negative likelihood ratios were not <0.1. On the Youden's index, the blister fluid specimen was 90%, and the scales specimen was 60%. As for the diagnostic odds ratio, both of them were >1. By fungal culture, we detected 14 cases of fungi in blister fluid and eight in scales. On PCR, 22 cases of fungi in blister fluid and ten in scales were identified.
Conclusions: This study demonstrated that a sample of blister fluid had better sensitivity, accuracy and Youden's index in diagnosing dermatomycosis with blister fluid. Collection of blister fluid might compensate for the inadequacy of collecting only scales specimens for mycological testing.
Keywords: blister fluid; dermatomycosis; diagnosis; scale.
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