Value of C reactive protein in the assessment of erosive osteoarthritis of the hand.

OBJECTIVE To investigate the value of serum C reactive protein (CRP) as a marker of erosive osteoarthritis (EOA) of the hand. METHODS Ninety eight patients, 67 with EOA and 31 with non-EOA of the hand, were included in the study and analysed for radiographic score (RS), number of erosions, and joint count (JC) at clinical observation and at bone scintigraphy. CRP was assayed in a serum sample by a highly sensitive immunonephelometric method. RESULTS The median (interquartile range) CRP level was 4.7 (2.4-6.9) mg/l in the EOA and 2.1 (0.5-4.9) mg/l in the non-EOA group (p = 0.001). In all patients, CRP correlated with RS (r(s) = 0.43, p<0.001), and mainly with JC at clinical observation (r(s) = 0.72, p<0.001) and at bone scintigraphy (r(s) = 0.47, p<0.001). The correlation of CRP with RS and JC was confirmed at clinical observation and at bone scintigraphy in the EOA subgroup, but only with JC at clinical observation in the non-EOA subgroup. CONCLUSIONS CRP levels are higher in EOA than in non-EOA patients. These levels probably reflect the disease activity of EOA, as suggested by correlations between CRP and JC at clinical observation and at bone scintigraphy.