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Objectives SLERPI (Systemic Lupus Erythematosus Risk Probability Index) is a scoring system developed to assist in the diagnosis of SLE. However, its use has primarily been tested in prevalent disease (as a classification tool), whereas data on its performance at initial presentation are scarce. We aimed to evaluate the performance of SLERPI as a classification tool and its value for early SLE recognition, in patients with a positive ANA finding.Methods We conducted a cross-sectional study involving 104 patients with a clinical diagnosis of SLE and 104 ANA-positive patients (controls) with other inflammatory rheumatic diseases. The performance of SLERPI and the 2019 ACR/EULAR criteria were analysed at initial examination and cumulatively (up to the last visit).Results The proportion of females was similar in both groups (94/104 SLE vs. 90/104 controls), whereas SLE patients were cumulatively younger (46, IQR 37-55 years vs. 53, IQR 39-66 years, p=0.013). The SLE group exhibited a higher proportion of malar/maculopapular rash, alopecia, arthritis, proteinuria, leukopenia, thrombocytopenia/AIHA, decreased C3 and C4, and immunologic disorder. Cumulatively, serositis was also more frequent. SLERPI demonstrated comparable performance to the ACR/EULAR criteria: its sensitivity was 83.7% (95% CI 75.4-89.5%) at initial presentation and 98.1% (95% CI 93.3-99.5%) cumulatively, compared to the sensitivity of the ACR/EULAR criteria of 80.8% (95% CI 72.2-87.2%) initially and 97.1% (95% CI 91.9-99.0%) cumulatively. The specificity of SLERPI was 76.0% (95% CI 66.9-83.2%) at initial presentation and 54.8 (95% CI 45.2-64.0%) cumulatively, compared to the specificity of the ACR/EULAR criteria of 75.0% (95% CI 65.9-82.3%) initially and 56.7% (95% CI 47.1-65.8%) cumulatively.The SLERPI had the same area under the curve (AUC) as the ACR/EULAR criteria at initial presentation (0.898) (SLERPI initially: green ROC curve); ACR/EULAR initially: red ROC curve). On the other hand, the SLERPI exhibited a slightly higher numerical value of the AUC cumulatively (0.961, orange ROC curve) compared to the ACR/EULAR criteria (0.956, blue curve).Abstract PO:06:154 Table 1Abstract PO:06:154 Figure 1Conclusions SLERPI demonstrated a solid diagnostic performance, especially at initial examination, with somewhat higher sensitivity and lower specificity compared to the ACR/EULAR criteria. It may serve as a useful tool for early SLE identification, even when the control patients are ANA-positive.