Ultrasonography as an additional item in the American College of Rheumatology classification of Sjögren's syndrome

Objective: In this study we evaluated US as an additional classification item in the ACR classification of SS.

Methods: Of 581 patients classified as either SS (n = 364) or non-SS (n = 217) based on the minimum requirements of the American-European Consensus Group (AECG) classification, 184 patients (102 SS and 82 non-SS) who had scored two or more positive or two or more negative results according to the ACR criteria were selected. The AECG classification was used as the gold standard. A parotid and/or submandibular gland that was assigned a score ≥G1 was designated as SS positive. We evaluated US alone or with varying combinations of the ACR classification items in the diagnosis of SS.

Results: The ACR criteria diagnosed the 184 patients with 91% sensitivity, 90% specificity and 91% accuracy. US alone diagnosed the 184 ACR patients with 79% sensitivity, 90% specificity and 83% accuracy, which was comparable to the results of US diagnosis in the AECG cohort (81%, 86% and 83%, respectively). Incorporating the US criteria as an alternative to one of the three ACR classification items achieved 89-91% sensitivity, 87-96% specificity and 89% or 92% accuracy, which was comparable to that of the original ACR classification. Furthermore, kappa analysis indicated that the results of the original ACR and US-replaced ACR classifications matched completely (κ = 0.960-0.974).

Conclusion: These results suggest that US can be used as an alternative to any of the three ACR classification items.