Rheumatoid factor in the United Kingdom. II. Associations with certain infections

Persons having positive tests for rheumatoid serum factors in population samples in Leigh (Lancashire) and Wensleydale (Yorkshire) were investigated for evidence of infection. Comparison was made with seronegative persons and with persons having doubtful titres matched by age and sex with the seropositive groups. Routine cultures were made of throat swabs and mid-stream specimens of urine were also cultured. The blood serum was assayed for ASO in both populations but for salmonella and Brucella abortus antibodies only in Leigh. The latex fixation test (LFT) was tested in both samples on the follow up but initially only in Wensleydale. There was a significant association between the results of the sheep cell agglutination test and radiological evidence of sinusitis. Salmonella or brucella antibodies were associated significantly with a positive or doubtful sheep cell agglutination test. There was no association with the presence of haemolytic streptococci in the throat. The mean ASO titre showed some relationship to the sheep cell agglutination test in Leigh but not in Wensleydale. The latex fixation test showed no significant association with any of the infections studied but the number with positive tests was small. Higher bacterial counts were obtained in the urine of both sheep cell agglutination (SCAT) and LFT positive than in seronegative individuals but the differences were not significant. There was no significant association between arthritis and any of the infections studied. Of those with a positive SCAT at the final test, 41% had rheumatoid arthritis, 24% had evidence of salmonella or brucella infection, 15% had sinusitis, 3% tuberculosis and 3% influenza.