Prevalence of systemic lupus erythematosus in New Zealand primary care: A retrospective descriptive study

Background Systemic lupus erythematosus (SLE) is a complex autoimmune condition with a high level of morbidity, mortality and healthcare costs. In New Zealand prevalence of the condition has been increasing over time, although studies to date are based on national administrative datasets or hospital records. Objective We aimed to estimate the prevalence of SLE based on primary care medical records in New Zealand and to evaluate the differences in age, gender and ethnicity. Methods Potential SLE cases were identified through electronic primary care records from 1 January 2000 to 20 March 2024. All records were manually reviewed to identify the diagnosis based on 2019 European League Against Rheumatism/American College of Rheumatology classification criteria. Prevalence was based on definite and probable cases. Results Sixty-eight SLE cases were identified (55 definite, 6 probable, 7 possible) from a total practice population of 96,348. The crude prevalence of SLE estimated using primary care records was 63.3 per 100,000 people in 2024. The World Health Organization age-standardised prevalence was 52.9 per 100,000 people in 2024. SLE prevalence generally increased with advancing age. Women were five times more likely than men to have SLE (RR 5.36, 95% CI 2.63 – 10.93. Pacific people had the highest age-standardised prevalence of SLE (94.1), followed by Asian (58.7), European/Others (48.3) and Māori (42.9 per 100,000). Conclusion The use of primary care medical records builds on national studies based primarily on administrative databases. Prevalence of SLE is highest in the elderly (>85 years), females and Pacific people based on primary care data in New Zealand.