Histochemistry Testing for Cutaneous Fungal Infections: A Meta-Analysis

Background

Specialized histochemistry testing for cutaneous fungal infection is common, but the comparative diagnostic accuracy of different test modalities such as periodic acid-Schiff (PAS) and Grocott methenamine silver (GMS) remains uncertain.

Methods

We performed a meta-analysis of 23 studies involving 4404 patients who underwent histochemical testing for onychomycosis and seven studies involving 1221 patients who underwent histochemical testing for deep fungal infection.

Results

The analysis revealed a sensitivity of 0.84 (95% CI: 0.78–0.88) for PAS detection of onychomycosis vs. 0.73 (95% CI: 0.67–0.78) for GMS detection of onychomycosis. Studies on onychomycosis did not include a separate reference standard, and specificity could not be calculated. PAS showed higher estimated sensitivity (0.73) for diagnosis of deep fungal infection than GMS (0.49), but results were associated with broad, overlapping confidence intervals. Methodological issues prevented reliable conclusions on their accuracy in this setting.

Conclusions

While the choice of test for onychomycosis depends on user preference, if all factors are equal, PAS should be selected over GMS. The existing literature on histochemistry testing for deep fungal infection does not allow for reliable conclusions on its accuracy, and there is a compelling need for well-designed diagnostic accuracy studies in this area.