Objectives. To validate the ACR-EULAR classification criteria for primary SS (pSS), and compare them to the American-European Consensus Group (AECG) and ACR criteria in a Dutch prospective diagnostic cohort.
Methods. Consecutive patients (n = 129) referred for suspicion of pSS underwent a multidisciplinary evaluation, including a labial and/or parotid gland biopsy. Patients with an incomplete work-up (n= 8) or associated systemic auto-immune disease (n= 7) were excluded. The ACR-EULAR classification was compared with expert classification, AECG and ACR classification. Additionally, the accuracy of individual ACR-EULAR items in discriminating pSS from non-pSS was evaluated. The validity of criteria sets was described separately using parotid or labial gland biopsy results for classification.
Results. Of the 114 evaluated patients, the expert panel classified 34 (30%) as pSS and 80 (70%) as non-pSS. Using labial gland biopsy results, ACR-EULAR classification showed 87% absolute agreement (kappa = 0.73) with expert classification, with a sensitivity of 97% and specificity of 83%. Using the parotid gland biopsy results, the ACR-EULAR criteria performed excellently as well. Focus score, anti-SSA titre and ocular staining score showed good to excellent accuracy, whereas unstimulated whole saliva and Schirmer's test had poor accuracy. The ACR-EULAR and AECG criteria had equal validity. Compared with ACR classification, ACR-EULAR classification showed higher sensitivity but lower specificity.
Conclusion. The ACR-EULAR criteria showed good agreement with expert classification, but some patients may be misclassified as pSS. Unstimulated whole saliva and Schirmer's test showed poor discriminative value. The ACR-EULAR criteria performed equally to the AECG criteria, and had higher sensitivity but lower specificity than the ACR criteria.