Application of the SLERPI scoring system as a classification tool in systemic lupus erythematosus and its performance...

The SLE Risk Probability Index (SLERPI) was developed as diagnostic aid in early disease. Previous studies applied it as a classification tool in established SLE, even when analyzing its performance in early disease. We assessed the performance of SLERPI as a classification tool but also at initial assessment, in antinuclear antibody positive patients. In a cross-sectional setting, we enrolled 104 consecutive SLE patients and 104 ANA-positive controls with inflammatory rheumatic conditions. The performance of SLERPI and the EULAR/ACR-2019 criteria was analyzed cumulatively and at initial assessment. Different SLERPI positivity thresholds were evaluated. The cumulative SLERPI score was higher in the SLE group (14.5; IQR 12.0-18.6) compared to controls (7.0; IQR 5.0-8.3). It exhibited a sensitivity of 98.1%, slightly higher compared to EULAR/ACR-2019 (97.1%), and a low specificity (54.8%), lower compared to EULAR/ACR-2019 (56.7%). At initial assessment, SLERPI was higher among SLE patients (median 10.0; IQR 8.5-12.6) compared to controls (median 5.0, IQR 4.5-7.0). Its sensitivity was 83.7% and specificity 76.0%, both higher compared to the EULAR/ACR-2019 (80.8 and 75.0%). Areas under the curve (AUC) for both criteria were 0.898 initially. Cumulatively, the AUC of SLERPI was 0.961, and the AUC of EULAR/ACR-2019 0.956. SLERPI misclassified 20.2% (cumulatively) and 5.8% (initially) of controls as "definite SLE". Higher thresholds of SLERPI (8 initially, 8.5 cumulatively) were associated with the highest Youden index. SLERPI retained a high sensitivity for early recognition and classification purposes, even in ANA-positive patients, with higher cut-off values of its positivity performing somewhat better.