Alpha 1-antichymotrypsin, C-reactive protein and erythrocyte sedimentation rate in polymyalgia rheumatica and giant cell arteritis.

Forty-four patients with polymyalgia rheumatica and/or giant cell arteritis (PMR/GCA) were followed from presentation, through remissions and relapses for a median duration of 36 months. Clinical disease activity, ESR, CRP and alpha 1-antichymotrypsin (alpha 1-ACT) were measured. Before treatment ESR, CRP and alpha 1-ACT were all significantly raised, compared with age- and sex-matched controls. On clinical remission with prednisolone treatment, ESR and CRP fell to control levels but alpha 1-ACT behaved quite differently, remaining raised for 18 months or until prednisolone treatment could be withdrawn. At 18 month follow-up of PMR/GCA, and alpha 1-ACT level of < or = 0.7 g/l was associated with a reduced risk of subsequent relapse (P = 0.006). At clinical relapse during treatment, ESR was not raised compared with controls, and CRP, although significantly higher than controls (P = 0.015), remained less than 6 mg/l in the majority of patients. The three laboratory investigations were, therefore, of limited value in confirming relapses of PMR/GCA during prednisolone treatment, but alpha 1-ACT may be useful as an indicator of underlying disease activity and hence as a guide to the speed that the prednisolone dosage should be reduced.