The effect of intra-articular (i-a) steroid injection on ESR and C-reactive protein (CRP) in rheumatoid arthritis (RA) was investigated. One week following injection of 1 or 2 knees there was a significant fall in ESR (p less than 0.0001) and CRP (p less than 0.01) in a cohort of 20 RA patients. The mean drop for both ESR and CRP was 46%. This effect lasted over a variable period up to 6 months. A survey of 50 published drug efficacy studies in RA revealed that, while 44 used ESR and 20 CRP as efficacy measures, 37 neither excluded nor recorded i-a steroid injections during the study. Steroid injections were excluded in 8 studies and recorded in 5, being used as an outcome measure in 2 of these. It is recommended that the frequency with which i-a injections are used in drug efficacy studies is reported and that they are avoided in the 3 months preceding an outcome measurement if ESR or CRP are being used as outcome measures.

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