Preordering Periodic Acid-Schiff Staining: A Quality Improvement Study

Periodic acid-Schiff (PAS) stain is a commonly used ancillary test for inflammatory and infectious dermatoses, yet infrequently changes the diagnosis. Previous studies have shown that clinical suspicion and histopathologic features are poor predictors of PAS positivity. Current appropriate use criteria from the American Society of Dermatopathology supports PAS staining when histopathologic features could be consistent with a dermatophyte infection. At the authors' institution, PAS stains are preordered on biopsies of inflammatory and infectious diagnoses to aid in a timelier sign out. Our aim was to reduce the percentage of PAS stains preordered on all dermatology specimens over a 6-month period without reducing the percentage of fungal infections identified. Review of a 12-month preintervention period found that our laboratory received 6104 biopsies for which PAS stain was preordered on 616 (10.1%). Based on a review of the preintervention period, preordering PAS on cases with clinical suspicion for cutaneous T-cell lymphoma was stopped unless there was clinical suspicion for eczematous dermatitis, vesiculobullous disorders, or fungal infection. The proposed intervention resulted in a 3.7% reduction in the number of PAS stains ordered while PAS-positivity rate remained unchanged. The described quality improvement process may be used as a model for other laboratories.