Background: A hospitalized-based cohort study suggested that elevated C-reactive protein (CRP) levels are associated with radiographic sacroiliitis progression in ankylosing spondylitis (AS) patients. However, data from community-based populations are limited.
Objective: We sought to determine the association between elevated CRP levels and AS diagnosis in a prospective community-based study of 129,681 Chinese adults over a follow-up period of 8 years.
Methods: We measured the plasma CRP concentration at baseline and every 2 years thereafter with the high-sensitivity (hs)-CRP test. Incident AS cases were confirmed on the basis of modified New York diagnostic criteria after review of medical records. We used Cox proportional-hazard models to calculate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for AS on the basis of hs-CRP concentrations, adjusting for age, sex, education, income, cigarette smoking, alcohol intake, physical activity, body mass index, blood-pressure status, blood glucose status, total cholesterol, history of cardiovascular disease, and use of antihypertensives, lipid-lowering agents, and aspirin.
Results: During 1,033,609 person-years (average 7.97 ± 1.36 years per person) of follow-up, we identified 55 incident AS cases. Baseline hs-CRP was positively associated with the risk of future AS. Compared with hs-CRP <1 mg/L, the HR was 1.28 (95% CI 0.54-3.08) for hs-CRP of 1.00-2.99 mg/L, 4.71 (95% CI 2.26-9.81) for hs-CRP of 3.00-9.99 mg/L, and 19.8 (95% CI 9.6-40.9) for hs-CRP ≥10.00 mg/L (P-trend <0.001) after adjustment for potential confounders. We found similar results after excluding AS cases that occurred in the first 2 years of follow-up, and using the cumulative average hs-CRP concentration as a predictor.
Conclusion: This is the first study in a community-based cohort to demonstrate that CRP plasma concentrations predict the risk of future AS, thus providing a test that is easy to routinely perform in the clinic to assess for AS risk.