Evaluating the Threshold Score for Classification of Systemic Lupus Erythematosus Using the EULAR/ACR Criteria

Objective: To evaluate whether a change in the European Alliance of Associations for Rheumatology (EULAR)/American College of Rheumatology (ACR) systemic lupus erythematosus (SLE) classification criteria threshold score affects accurate classification of SLE cases compared to disease-based control subjects. We evaluated a range of threshold scores to determine the score that maximizes the accurate classification of early SLE.

Methods: We conducted a cross-sectional study comparing SLE cases and control patients. A EULAR/ACR criteria score was calculated using baseline information. Sensitivity, specificity, positive likelihood ratios (+LRs), and negative likelihood ratios (-LRs) with 95% CIs were used to evaluate operating characteristics. Threshold scores of 6 to 12 were evaluated in subjects with early disease (ie, disease duration of ≤ 5 years). +LRs > 10 and -LRs < 0.1 provide evidence to rule in or rule out SLE.

Results: A total of 2764 patients were included: 1980 SLE cases who fulfilled either the ACR or Systemic Lupus International Collaborating Clinics criteria and 784 control subjects. The EULAR/ACR SLE criteria had a sensitivity of 98% (95% CI 97-98), a specificity of 99% (95% CI 98-100), a +LR of 95.5 (95% CI 48.0-190), and a -LR 0.03 (95% CI 0.02-0.03). The criteria operated well in those with early disease, in women, in men, and in White, Black, Chinese, and Filipino people. A score of 10 maximized the accurate classification of patients with early disease (+LR 174.4, 95% CI 43.8-694.6; -LR 0.03, 95% CI 0.02-0.04). An increase in the threshold score from 10 to 11 resulted in significant worsening in the -LR (threshold score 10: -LR 0.03, 95% CI 0.02-0.03 vs threshold score 11: -LR 0.05, 95% CI 0.04-0.06).

Conclusion: The EULAR/ACR SLE classification criteria threshold score of 10 performs well, particularly among those with early disease and across sexes and ethnicities.