Background Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with heterogeneous clinical phenotypes. Various classification criteria have been developed to identify patients with SLE for research studies.
Objectives We used the 1982 American College of Rheumatology (ACR), revised 1997 ACR and the 2012 Systemic Lupus International Collaborating Clinics (SLICC) criteria to estimate incidence of SLE in our predominantly white, population based cohort, from 1993-2005.
Methods An incident SLE case was defined as an individual who fulfilled either 4 out of 11, 1982 or revised 1997 ACR SLE classification criteria or who met ≥4 SLICC criteria (with at least 1 clinical and 1 laboratory) or had biopsy proven lupus nephritis with positive ANA or anti-dsDNA (SLICC) and who had been a resident of the county for at least 1 year prior to first physician diagnosis of SLE. The incidence date was the date of fulfillment of the fourth criterion. Cases with isolated cutaneous lupus, drug- induced lupus and overlap diseases were excluded. Overall incidence and prevalence was age- and sex-adjusted to the 2000 US white population.
Results There were 45 incident cases who met ACR (1982 and 1997) and SLICC criteria, 11 who met SLICC criteria only and one patient who met both SLICC and 1997 ACR but not 1982 ACR criteria. The age and sex adjusted incidence of SLE was higher at 3.6 per 100 000 by SLICC criteria than 2.9 per 100 000 by 1982 or 1997 ACR criteria, however this difference was not statistically significant (p=0.05, respectively). The incidence per 100000 in females was 5.8 by SLICC, 5.0 by 1982 ACR and 5.1 by 1997 ACR criteria (p=0.06); in men it was 1.02 per 100000 using SLICC and 0.5 by ACR 1982 and 1997 criteria (p=0.11). The average age of 42±17.6 years was not different in the SLICC cohort compared to 41±17.9 years in the 1982 and 1997 ACR cohort (p=0.24). The female to male ratio was 6:1 in patients fulfilling SLICC criteria and 10: 1 in those fulfilling ACR (1982 or 1997) however this did not reach statistical significance (p=0.06). The mean number of SLE criteria in the SLICC cohort were 5.3 (range 2-8) and 4.7 (range 4-7) in the ACR cohorts respectively.
Conclusions The 2012 SLICC criteria may be more sensitive than 1982 and revised 1997 ACR criteria in identifying patients with SLE however larger studies in diverse populations are needed to validate these findings.
Disclosure of Interest None declared