Serum protein fractions in rheumatoid pneumoconiosis without arthritis.

Fractionation of the serum proteins by filter-paper electrophoresis in 14 coal-miners who had the characteristic radiological opacities of rheumatoid pneumoconiosis but no evidence of rheumatoid arthritis showed a reduction in the mean level of albumin and increases in the alpha-2 and gamma-globulins compared with the values in non-arthritic miners with simple coal-workers' pneumoconiosis and in normal subjects. The changes were smaller than those found in miners with both rheumatoid arthritis and the radiological appearances of rheumatoid pneumoconiosis (Caplan's syndrome) and the mean levels did not differ significantly from those found in non-arthritic miners with progressive massive fibrosis. It is concluded that estimation of the serum protein fractions, unlike tests for rheumatoid factors, is unlikely to help in the differential diagnosis of unusual opacities seen on chest radiographs of miners without arthritis.