The interpretation of test results

Dermatoepidemiology

Dermatoepidemiology is an important emerging discipline in dermatology. This article reviews clinical and analytic epidemiology pertinent to reading, interpreting, and critically examining the literature, and presents an overview of evidence-based dermatology as a starting point for further study.

Intraepidermal neutrophils--a clue to dermatophytosis?

BACKGROUND

Dermatophyte infections are occasionally diagnosed by histopathology. Spongiotic or psoriasiform features are typical but non-specific, and neutrophils may be present within the stratum corneum. Traditionally, this latter finding has been felt to be a diagnostic clue for dermatophytosis, and usually precipitates a periodic acid Schiff (PAS-D) stain to confirm the presence of hyphae in the stratum corneum. Our objective was to evaluate whether the presence of neutrophils within the stratum corneum is a sensitive or specific test for dermatophytosis.

METHODS

We performed a retrospective case-control study on 303 cases of spongiotic or psoriasiform dermatitides over a 35-month period. Hematoxylin and eosin (H&E) and PAS-D stains were utilized to identify intraepidermal neutrophils and fungi.

RESULTS

The sensitivity and specificity for diagnosing dermatophyte infection based upon neutrophils within the stratum corneum were 62 and 59%, respectively. The positive and negative predictive values in our population were 4 and 98%, respectively.

CONCLUSION

The histologic feature of neutrophils within the stratum corneum is neither sensitive nor specific in the diagnosis of dermatophytosis.