The aim of this study was to evaluate the feasibility and performance of the American-European Consensus Group (AECG) and ACR Classification Criteria for SS in patients with systemic autoimmune diseases.
Three hundred and fifty patients with primary SS, SLE, RA or scleroderma were randomly selected from our patient registry. Each patient was clinically diagnosed as probable/definitive SS or non-SS following a standardized evaluation including clinical symptoms and manifestations, confirmatory tests, fluorescein staining test, autoantibodies, lip biopsy and medical chart review. Using the clinical diagnosis as the gold standard, the degree of agreement with each criteria set and between the criteria sets was estimated.
One hundred fifty-four (44%) patients were diagnosed with SS. The AECG criteria were incomplete in 36 patients (10.3%) and the ACR criteria in 96 (27.4%; P < 0.001). Nevertheless, their ability to classify patients was almost identical, with a sensitivity of 61.6 vs 62.3 and a specificity of 94.3 vs 91.3, respectively. Either set of criteria was met by 123 patients (80%); 95 (61.7%) met the AECG criteria and 96 (62.3%) met the ACR criteria, but only 68 (44.2%) patients met both sets. The concordance rate between clinical diagnosis and AECG or ACR criteria was moderate (k statistic 0.58 and 0.55, respectively). Among 99 patients with definitive SS sensitivity was 83.3 vs 77.7 and specificity was 90.8 vs 85.6, respectively. A discrepancy between clinical diagnosis and criteria was seen in 59 patients (17%).
The feasibility of the SS AECG criteria is superior to that of the ACR criteria, however, their performance was similar among patients with systemic autoimmune diseases. A subset of SS patients is still missed by both criteria sets.