Serum Amyloid a Immunostaining of Granulomatous Tissue as a Novel Diagnostic Test for Sarcoidosis

SESSION TITLE: Lung Pathology SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, October 26, 2016 at 01:30 PM - 02:30 PM PURPOSE: To determine the sensitivity and specificity of Serum Amyloid A (SAA) staining in diagnosing sarcoidosis. METHODS: Histological specimens from patients with granulomatous diseases were retrospectively identified from January 2004 to December 2013. Medical records were reviewed to ensure that a specific granulomatous diagnosis could be determined. SAA staining was performed using standardized algorithms on an initial group of 5 sarcoidosis and 5 non-sarcoidosis histological specimens. The SAA stain was modified to maximize specificity for the diagnosis of sarcoidosis. The modified SAA immunostaining technique was subsequently used to stain the remaining specimens. Two pathologists independently reviewed the specimens, while remaining blinded to the diagnosis. Specimens with conflicting reads were reevaluated blindly by the two pathologists simultaneously and a consensus decision was reached. RESULTS: One hundred and six specimens from 100 patients were included. Mean age was 45 years (SD 18), 56% was female, and 76% white. Sarcoidosis was the diagnosis in 30 patients while the remaining 70 had other granulomatous processes. The most common organs biopsied were: lung (31%), skin or soft tissue (21%), and lymph nodes (18%). The overall specificity of SAA staining for sarcoidosis was 81.9%, the sensitivity 41.2%, positive predictive value 51.9%, and negative predictive value 74.7%. When only lung tissue specimens were evaluated (n=33), the specificity was 83.3% and sensitivity 33.3% for sarcoidosis. In a sub-analysis where the 4 World Trade Center related sarcoid-like reactions were classified as sarcoidosis, the SSA staining specificity was 86.4% and sensitivity 45% for sarcoidosis. In another sub-analysis including only the specimens that the two pathologists agreed upon after their independent read (n=86), the SAA staining had a specificity of 91.4% and a sensitivity of 42.9% for sarcoidosis. CONCLUSIONS: SAA staining is fairly specific for the diagnosis of sarcoidosis but not specific enough to be used in isolation as a diagnostic test. It is not highly sensitive and has a high false negative rate as well. CLINICAL IMPLICATIONS: SAA staining can be a useful adjunctive test in diagnosing sarcoidosis. DISCLOSURE: The following authors have nothing to disclose: Efstratios Koutroumpakis, Albert Huho, Siddhartha Dalvi, Timothy Jennings, Amit Chopra, Aakash Modi, Neha Rane, David Prezant, Christine Sheehan, Mehul Patel, Llewellyn Foulke, Marc Judson No Product/Research Disclosure Information