Circulating antinuclear antibody and rheumatoid factor in coal pneumoconiosis.

Circulating antinuclear antibody and rheumatoid factor have been measured in 109 coal miners with pneumoconiosis whose chest radiograph showed a range of abnormalities varying from simple pneumoconiosis of mild degree to advanced progressive massive fibrosis.At a screening dilution of 1/10 the overall incidence of antinuclear antibody was 17%. In almost half of the positive cases the titre was 1/40 or greater.The prevalence of antinuclear antibody was lowest in those with simple pneumoconiosis (9%) and highest in those with category C progressive massive fibrosis (27%). A similar but less striking trend was seen with rheumatoid factor, ranging from 6% in simple pneumoconiosis to 18% in category C progressive massive fibrosis. The trend of increasing frequency of autoantibodies with advancing radiographic category was most marked when the frequencies of antinuclear antibody and rheumatoid factor were combined. These autoantibodies were found in 13% of the miners with simple pneumoconiosis and 45% of those with category C progressive massive fibrosis (P for the trend=0.01).