CRP and rheumatoid arthritis: In 20 OA patients, the serum CRP level was 0.08 ± 0.02 mg/dL (range: 0.01 to 0.3 mg/dL) and the SF CRP level was 0.04 ± 0.01 mg/dL (range: 0.02 to 0.09 mg/dL); these values were significantly lower than those in RA patients (P <0.005, data not shown).