Performance of the Systemic Lupus Erythematosus Risk Probability Index in a Cohort of Undifferentiated Connective Tissue Disease

Objectives: We sought to evaluate the performance of the SLE Risk Probability Index (SLERPI) for identification of SLE in a large cohort of patients with UCTD.

Methods: The SLERPI was applied in a cohort of patients who met classification criteria for UCTD and did not fulfil any classification criteria for other defined CTD including SLE. Patients with a SLERPI score of >7 were 'diagnosed' as SLE. Patients diagnosed with SLE and those not were compared in terms of disease characteristics and index parameters.

Results: A total of 422 patients with UCTD were included in the study. Median (interquartile range) SLERPI was 4.25 (2.5) points, while 39 (9.2%) patients had a SLERPI score >7 and were diagnosed as SLE. Patients with younger age (P = 0.026) and presence of malar rash (P < 0.0001), mucosal ulcer (P < 0.0001), alopecia (P < 0.0001), ANA positivity (P < 0.0001), low C3 and C4 (P = 0.002), proteinuria >500 mg/24 h (P = 0.001), thrombocytopenia (P = 0.009) or autoimmune haemolytic anaemia (P < 0.0001) were more likely to fulfil criteria for SLE by the SLERPI.

Conclusion: SLERPI enabled a significant proportion of patients to be identified as SLE in our UCTD cohort. This new probability index may be useful for early identification of SLE among patients with signs of CTD without fulfilling any definite criteria set.