Validation of the new classification criteria for systemic lupus erythematosus on a patient cohort from a national referral center: a retrospective study.

Aim: To validate Systemic Lupus International Collaborating Clinics (SLICC)-12 and American College of Rheumatology (ACR)-97 classification criteria on a patient cohort from the University Hospital Center Zagreb.

Methods: This retrospective study, conducted from 2014 to 2016, involved 308 patients with systemic lupus erythematosus (SLE) (n=146) and SLE-allied conditions (n=162). Patients' medical charts were evaluated by an expert rheumatologist to confirm the clinical diagnosis, regardless of the number of the ACR-97 criteria met. Overall sensitivity and specificity, as well as the sensitivity and specificity according to disease duration, were compared between ACR-97 and SLICC-12 classifications. Predictive value for SLE for both classifications was assessed using logistic regression and receiver operating characteristic (ROC) curves.

Results: The SLICC-12 criteria had significantly higher sensitivity in early disase, which increased with disease duration. The ACR-97 criteria had higher specificity. The specificity of the SLICC-12 criteria was low and decreased with disease duration. Regression analysis demonstrated the superiority of the SLICC-12 classification criteria over the ACR-97 criteria, with areas under the ROC curve of 0.801 and 0.780, respectively.

Conclusion: Although the SLICC-12 criteria were superior to the ACR-97 and were more sensitive for diagnosing early SLE, their specificity in our population was too low. The sensitivity of the SLICC-12 classification is increased by better defined clinical features within each criterion. Our results contribute to the current initiative for developing new criteria for SLE.