Population-Based Incidence and Time to Classification of Systemic Lupus Erythematosus by Three Different Classification Criteria

Abstract Objective To estimate the incidence and time-to-classification of systemic lupus erythematosus (SLE) by the 1997 American College of Rheumatology (ACR97) criteria, the Systemic Lupus International Collaborating Clinics (SLICC) criteria, and the European Alliance of Associations for Rheumatology/American College of Rheumatology (EULAR/ACR) criteria. Methods We identified all incident SLE cases from 2000–2018 in the well-defined Olmsted County population. Clinical data included in the ACR97, SLICC and EULAR/ACR criteria were manually abstracted from medical records. All incident cases met at least one of the 3 classification criteria. Time-to-classification was estimated from the first documented lupus-attributable disease manifestation to the time of criteria fulfillment by each of the three definitions. Annual incidence rates were age or age/sex adjusted to the 2000 US population. Results Of 139 incident cases there were 126 cases by the EULAR/ACR criteria, corresponding to an age/sex-adjusted incidence of 4.5 per 100 000 population (95% CI, 3.7–5.2). The age/sex-incidence was higher than that of the SLICC criteria (113 cases; 4.0 per 100 000 [95%CI, 3.3 – 4.7], p= 0.020) and the ACR97 (92 cases; 3.3 per 100 000 [95%CI 2.6–3.9], p< 0.001). The median time from first disease manifestation to criteria fulfillment was shorter for the EULAR/ACR criteria (29.4 months) than the ACR97 criteria (47.0 months, p< 0.001) and similar to the SLICC criteria (30.6 months, p= 0.83). Conclusion The incidence of SLE was higher by the EULAR/ACR criteria compared with the ACR97 and the SLICC criteria, and the EULAR/ACR criteria classified patients earlier that the ACR97 criteria but similar to the SLICC criteria.