An evaluation of the association between C-reactive protein, the change in C-reactive protein over one year, and all-cause mortality in chronic immune-mediated inflammatory disease managed in UK general practice

Abstract

To evaluate the association between systemic inflammation, as measured by CRP, and all-cause mortality. To also evaluate the association between change in CRP status (sub-acute, < or =10 mg/l and acute >10 mg/l) and all-cause mortality. A cohort of patients was selected from The Health Improvement Network (THIN) data set of anonymized patient-level data from UK general practice. Patients were selected if they had a diagnosis of RA, psoriasis, AS or PsA. Survival was evaluated using Cox proportional hazards regression models (CPHMs). A total of 11 362 cases had at least one CRP measurement. Analysis grouped by each additional unit increase in log-CRP (range 1-6) across the observed range was associated with a 21% increase in the hazard ratio (HR) of death, after controlling for cardiovascular risk factors (P < 0.001). This observation was consistent in separate analysis of cases with either RA or psoriasis. Repeated CRP observations around 1 yr apart were recorded in 2802 subjects. After controlling for confounding factors, in cases whose CRP changed from sub-acute (< or =10 mg/l) to acute (>10 mg/l), the HR for death increased 2-fold (P < 0.001) relative to cases whose CRP remained sub-acute. In comparison, among those subjects whose CRP was reduced from acute to sub-acute, the HR was virtually identical to those who stayed sub-acute (P = 0.571). CRP level predicted all-cause mortality after standardization for traditional risk factors, as did change in CRP status from sub-acute to acute observed over 1 yr.