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We were very interested to read Professor Croft’s article1 about pain in the rheumatic diseases because we are interested in studying the relation between patients’ perception of disease and objective signs.2 In the daily management of a cohort of approximately 600 patients with inflammatory arthritis at Poole Hospital we noticed a dissociation between reported pain and objective measures of disease activity in a number of patients.
To further study this phenomenon we randomly selected a sample of 100 patients with rheumatoid arthritis (mean (SD) age = 63 (12) years, 73% rheumatoid factor positive). We looked at the pattern of change of reported pain (10 cm visual analog scale (VAS)), number of swollen joints (EULAR 28 articular index), and serum C reactive protein (CRP, normal <10 mg/l) in the previous two years.
We identified a close linear relation in 72 patients. In 18 patients pain was repeatedly reported at not less than 20 mms VAS despite no evidence of disease activity (CRP <10 mg/l and swollen joint count = 0) at any point during their follow up. In 10 patients pain was repeatedly scored as absent despite disease activity markers reflecting joint inflammation (CRP >15 mg/l, with or without >2 swollen joints). Fifteen of 18 patients showing pain but no disease activity were rheumatoid factor positive and there was no obvious difference in the degree of joint deformity clinically although detailed assessment of joint damage radiologically was not made.
These preliminary data support our contention that, in about one third of patients followed up in a district general hospital, there is a dissociation between reported pain and objective signs of joint inflammation. These differences may be related to joint damage in the patients with pain but no disease activity but cannot be so explained in those patients with disease activity but no pain. A more detailed analysis of these patients may reveal the reasons for this dissociation. In the meantime we suggest that rheumatologists might consider managing pain separately from disease activity in some of their patients. We also urge caution in interpreting summated disease activity indices that include pain and joint tenderness as major parts of their score.
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