Disease activity in rheumatoid arthritis : Studies in interleukin-6, tumour necrosis factor alpha, monocyte activity, acute phase markers, glucocorticoids, and disability
Abstract: In the present studies, aspects of some disease activity measures in rheumatoid arthritis (RA) have been investigated, including the effect of glucocorticoids on this activity. In RA, serum interleukin(IL)-6 levels were elevated and were shown to have a circadian rhythm, with peak levels in the morning, declining towards low or normal levels in the afternoon and evening. In contrast, serum levels of tumour necrosis factor(TNF) alpha were low and stable. In other connective tissue diseases, serum TNF alpha levels were elevated but without circadian variation, while IL-6 levels were low and stable. Nocturnal administration (at 2:00 a.m.) of low-dose prednisolone a few hours before the early morning peak of IL-6 was shown to be significantly more effective in reducing clinical symptoms of disease activity and serum IL-6 levels than the traditional morning administration (at 7:30 a.m.) of the same dose of prednisolone. Circulating monocytes are activated in RA, expressing receptors related to adhesion and phagocytosis. Treatment with glucocorticoids suppressed the expression of these receptors on monocytes, and this may be one mechanism of the beneficial effect of glucocorticoids in RA. Endogenous levels of cortisol seem to play a minor role in expression of monocyte receptors. The different acute phase markers used to assess disease activity in RA showed good corrrelations with each other and with serum IL-6 levels. There were especially strong corrrelations between C-reactive protein (CRP) and Serum amyloid protein A (SAA), and between fibrinogen and erythrocyte sedimentation rate (ESR). Fibrinogen and CRP showed stronger correlation than ESR with the Modified Health Assessment Questionnaire (MHAQ) score and with the neutrophil count. Four simple objective function tests were each compared with the HAQ score a with a radiological joint damage score (Larsen score). The objective function tests correlated with the MHAQ score, and each of these two methods of assessing physical disability correlated with pain, CRP and ESR. In addition, most of the objective function tests correlated significantly with radiological joint damage, while the MHAQ score did not.
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