Biopsy proven polymyositis in Victoria 1982-1987: analysis of prognostic factors.

Prognostic factors were analysed in 77 patients with idiopathic inflammatory myopathy identified over a 5 year period. Formal statistical tests did not differentiate useful prognostic indices and a polymyositis disability score was devised in an attempt to gain some prognostic information. Partial (47%) or full (31%) recovery were seen in most cases with no recovery of strength (9%) and death (11%) being less common outcomes. Onset before the age of 50 and duration of symptoms of less than 12 months prior to presentation were favourable prognostic features, and treatment with regimes other than steroid therapy alone a probable favourable indicator. Level of creatine kinase (CK) at presentation and histopathological separation of dermatomyositis or polymyositis failed to alter prognosis. Most patients who died did so within the initial 6 months of treatment. Four of five patients < 50 years old with either a fatal outcome or no improvement were treated with steroids alone. Large multi-centre studies are required to provide reliable data about prognostic factors in idiopathic inflammatory myopathies and the methodology used in this study can only be regarded as providing pointers towards possible prognostic factors rather than being definitive.