PAS and GMS utility in dermatopathology: Review of the current medical literature

Abstract

The American Society of Dermatopathology has established an Appropriate Use Criteria (AUC) Committee with the intention of establishing evidence-based recommendations regarding the appropriateness of various ancillary tests commonly utilized by dermatopathologists. Periodic acid Schiff (PAS) and Grocott (or Gomori) methenamine silver (GMS) stains represent some of the most commonly employed ancillary tests in dermatopathology. The utility of these tests was targeted for evaluation by the AUC. This literature review represents a comprehensive evaluation of available evidence for the utility of PAS and/or GMS staining of skin and nail biopsies. In concert with expert opinion, these data will be incorporated into future recommendations by the AUC for PAS and GMS staining in routine dermatopathology practice.

Appropriate use criteria for ancillary diagnostic testing in dermatopathology: New recommendations for 11 tests and 220 clinical scenarios from the American Society of Dermatopathology Appropriate Use Criteria Committee

“…Our results support pre‐ordering PAS or GMS for onychomycosis in nail clippings, which is not surprising given the superior sensitivity of the stains over H&E in nail clippings submitted to rule out onychomycosis. One difference between these stains is that GMS highlights living and dead organisms, whereas only viable organisms are highlighted by PAS 10,28 ; our results did not indicate an attributable difference between these stains, likely because of limitations in the methodology employed to develop the AUC where tests are considered independently. Although one might favor the superior absolute sensitivity of GMS, detecting only viable organisms (ie, by using PAS) might be more clinically relevant.…”

“…The other subgroup selected Gömöri methenamine silver (GMS; Grocott‐Gömöri) and periodic acid‐Schiff (PAS) stains for AUC development. Review and analysis of the literature (from 1957 to May 2019) was reported by Shalin et al 10 Twenty‐eight clinical scenarios were rated with 16 of these rated for PAS and GMS (44 total ratings). Consensus by panel raters was reached in 31 of 44 clinical scenarios (70%) scenarios, with over 50% rated “usually appropriate” or “majority usually appropriate.” The ratings for GMS and PAS stains in identical scenarios were largely the same.…”

“…Although one might favor the superior absolute sensitivity of GMS, detecting only viable organisms (ie, by using PAS) might be more clinically relevant. Nail clippings represent a unique scenario in which the differential diagnosis is highly focused and the sensitivity of the stains when applied to nail specimens for the detection of onychomycosis is greater than that reported for cultures 10 . The rigid, brittle nature of the nail plate also creates unique technical challenges.…”

“…Literature reviews included primary studies published in English from as early as 1940 through early 2019. Case series of n > 3 could be included if better evidence was lacking 8‐11 . Prior AUC literature review served as the basis for an updated literature review 12‐16 …”

Diagnosis and Treatment of Invasive Candidiasis

“…Special stainings, such as the periodic acid–Schiff stain, are capable of detecting polysaccarides and glycoproteins of the fungal cell wall; the Grocott–Gomori methenamine silver stain that targets carbohydrates is also used in histopathology [ 64 , 75 , 76 , 77 , 78 , 79 ]. The use of stains with fluorescent brighteners can increase sensitivity [ 27 ].…”