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.
(First Release June 15 2013; J Rheumatol 2013;40:1334–6; doi:10.3899/jrheum.121215)