Observation Period Effects on Estimation of Systemic Lupus Erythematosus Incidence and Prevalence in Quebec

Abstract

Objective. To determine how duration of observation affects estimation of incidence and prevalence of systemic lupus erythematosus (SLE). Methods. SLE incidence and prevalence estimates from data periods as brief as 3 years (2001–2003) were compared to estimates from a 15-year period (1989–2003). Results. The 15-year period incidence was 5.6/100,000 (95% CI 5.0–6.1) and the prevalence was 59.1/100,000 (95% CI 57.4–60.8). When a 3-year period was used, incidence was overestimated by 238.1% and prevalence underestimated by 66.0%. Conclusion. SLE incidence and prevalence estimates vary considerably according to the observation period; more than 5 years of data is likely required.