Background Most studies on the presentation and progression of SLE to date have come from specialist secondary care settings which may not be representative of SLE patients in the general population.
Objectives We aimed to characterise severity at diagnosis and disease progression for up to five years after diagnosis in patients identified from a population-based, primary care setting.
Methods We identified incident cases of SLE from the CPRD between 1/1/00 and 31/12/12 using a previously described algorithm1 and classified disease severity at baseline using prescribing data within one year after diagnosis. Patients with prescriptions for NSAIDs, hydroxychloroquine and/or prednisolone ≤7.5mg/day were classified as having mild disease. Patients with at least a one month prescription for any immunosuppressant, rituximab or prednisolone >7.5mg/day were classified as having severe disease. Those with no prescriptions were classified as having unknown disease severity. We classified disease severity for each 12 month period after baseline. Patients with no prescriptions within any 12 month period after the initial baseline assessment were classified as having quiescent disease during that period. Poisson regression was used to calculate adjusted relative risks of death.
Results Of 1426 incident cases of SLE, 762 (53.4%) were classified as having mild disease, 389 (27.3%) severe disease and 275 (19.3%) had disease of unknown severity at baseline. The proportion of patients with mild, severe and apparently quiescent disease remained relatively stable throughout the follow-up period. In each year of follow-up between 8.6% and 12.6% of patients with mild disease at baseline were classified as having severe disease and between 15.8% and 33.9% of those with severe disease at baseline had mild disease at follow-up. Seventy-two patients died during the first five years of follow-up. An increased risk of death was associated with severe disease at baseline (RR 2.0 (CI95 1.2, 3.3)), age 50+ at diagnosis (RR 18.5 (CI95 2.6, 133.6)) and vasculitis prior to diagnosis (RR 2.3 (CI95 1.5, 3.5)).
Conclusions In general patients tended to persist over time in the severity group into which they were initially classified although a small number did develop more severe disease over time. Older patients and those with severe disease at baseline had the highest mortality rates. The study was limited by a lack of data on hospital prescribing which could have led to the misclassification of patients prescribed medicines only in secondary care settings as having mild or unknown disease severity.
Nightingale AL, Farmer RD, de Vries CS. Incidence of clinically diagnosed systemic lupus erythematosus 1992-1998 using the UK General Practice Research Database. Pharmacoepidemiol Drug Saf. Sep 2006;15(9):656-661.
Acknowledgements Sponsor: GlaxoSmithKline; WEUKBRE6479
Disclosure of Interest A. Nightingale Grant/research support: GlaxoSmithKline, J. Davidson Shareholder of: GlaxoSmithKline, Employee of: GlaxoSmithKline, J. Snowball Grant/research support: GlaxoSmithKline, C. Molta Shareholder of: GlaxoSmithKline, Employee of: GlaxoSmithKline, H. Kan Shareholder of: GlaxoSmithKline, Employee of: GlaxoSmithKline, N. McHugh Grant/research support: GlaxoSmithKline, Consultant for: GlaxoSmithKline