Increased serum C reactive protein may reflect events that precede radiographic progression in osteoarthritis of the knee

Objective-Raised serum C reactive protein (CRP) and hyaluronate (HA) concen trations predict the progression of knee osteoarthritis (OA) in the long te rm but the consistency of these relations with time is unknown. The purpose of this work was therefore to determine if raise CRP and HA at entry and t hree years before entry (-3 years) predict radiological progression of knee OA in a group of patients between entry and five years. Methods-Knee radiographs from 90 patients with knee OA at entry and five ye ars follow up were assessed for progression of disease over five years. The concentrations of serum CRP and HA were measured at entry (n=90) and also in 40 serum samples available from -3 years. Odds ratios (OR) for predictin g progression were calculated by logistic regression. Results-Serum CRP at entry was not predictive of progression between entry and five years (OR 1.12, 95% CI 0.81, 1.55) but serum CRP at -3 years was p redictive of progression (OR 1.90, 95% CI 1.01, 3.28). Serum HA concentrati on at entry predicted progression between entry and five years (OR 2.32, 95 % CI 1.16, 4.66). Conclusion-These results are consistent with previous reports relating to H A, and suggest that raised serum CRP reflects events that precede a period of later radiographic progression in knee OA. However, because of the large overlap between groups, the serum CRP of HA concentration are not good pre dictors of individual patient progression and have a poor sensitivity and s pecificity.