Sensitivity of classification criteria from time of diagnosis in an incident systemic lupus erythematosus cohort: a population-based study from Norway.

OBJECTIVES: To compare the sensitivity of 2019 European Alliance of Associations for Rheumatology/American College of Rheumatology (EULAR/ACR) classification criteria against 1997 ACR criteria for systemic lupus erythematosus (SLE), for incident SLE cases in the presumably complete population-based Nor-SLE cohort from Southeast Norway (2.9 million inhabitants). METHODS: All cases International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) coded as SLE during 2000-2017 were individually reviewed. Those with a confirmed SLE diagnosis by expert clinical assessment were included in the Nor-SLE cohort. Core clinical data were recorded, and the cases were classified according to 2019 EULAR/ACR and 1997 ACR criteria. Juvenile SLE was defined as <16 years at diagnosis and adult SLE was defined as ≥16 years at diagnosis. RESULTS: We included 737 incident SLE cases (701 adults, 36 juveniles). At diagnosis, 2019 EULAR/ACR criteria were more sensitive than 1997 ACR criteria for adults (91.6% vs 77.3%; p<0.001), but not for juveniles (97.2% vs 88.9%). The 2019 EULAR/ACR counts at diagnosis differed by age group and ethnicity, being higher in young cases and those originating from Asia. From time of diagnosis to study end the fulfilment rate of 2019 EULAR/ACR criteria for the adult cohort increased from 92.5% and 86.5% to 94.6% and 91.0%, respectively, for females and males (mean disease duration of 7.5 years). CONCLUSION: Showing 92% criteria fulfilment already at time of SLE diagnosis by 2019 EULAR/ACR criteria versus 77% by 1997 ACR criteria, the results from this population-based study suggest that the 2019 EULAR/ACR criteria will achieve its goal of capturing more early-SLE cases for clinical trials.

Persisting mortality gap in systemic lupus erythematosus; a population-based study on juvenile- and adult-onset SLE in Norway 1999-2022.

OBJECTIVE: To estimate mortality and survival rates of systemic lupus erythematosus (SLE) in a contemporary, population-based setting and assess potential influences by time, sex, ethnicity, classification criteria and age at diagnosis. METHODS: We assessed mortality and survival in the Nor-SLE cohort, which includes all chart-review confirmed SLE cases resident in Southeast Norway (population 2.9 million) 1999-2017. Study end was at death, emigration, or 1 October 2022. We defined juvenile SLE by age <16 years at diagnosis. For standardized mortality rate (SMR) estimates, we applied 15 population controls per case, all matched for age, sex, residency, and ethnicity. We analyzed survival by Kaplan-Meier and risk factors by cox regression. RESULTS: The Nor-SLE cohort included 1558 SLE cases, of whom 749 were incident and met the 2019 European Alliance of Associations for Rheumatology and American College of Rheumatology (2019-EA) classification criteria. SMR was increased to 1.8 (95% CI 1.6-2.2) in incident adult-onset SLE but did not differ between females and males. Survival rates at 5-, 10-, 15 and 20-years were lower in incident adult-onset SLE than in matched controls. In multivariable analysis, lupus nephritis associated with decreased survival, while sex did not. Separate, long-term mortality analyses in the total Nor-SLE cohort showed that SMR peaked at 7.2 (95% CI 3.3-14) in juvenile-onset SLE (n = 93) and fell gradually by increasing age at SLE diagnosis. CONCLUSION: This study shows persistence of a mortality gap between adult-onset SLE and controls at population level and provides indications of worryingly high mortality in juvenile-onset SLE.