Factors influencing the incidence of infections in Felty's syndrome.

To identify clinical and laboratory risk factors for the susceptibility to infections in Felty's syndrome, 46 patients were studied prospectively during a total number of 431 periods of three months ("patient-quarters"). The incidence of infections increased significantly with polymorphonuclear leukocyte (PMN) counts below 0.1 X 10(3)/mm3 (less than 0.1 X 10(9)/L). At PMN levels over 0.1 X 10(3)/mm3 (greater than 0.1 X 10(9)/L), no association was found between PMN counts and the incidence of infections. Other factors found to be associated with an increased incidence of infections were severe disability, skin ulcers, glucocorticosteroid dose, monocyte counts, hypocomplementemia, and high levels of circulating immune complexes. The activity of the rheumatoid arthritis, erythrocyte sedimentation rate, hemoglobin concentrations, and lymphocyte counts were not associated with increased incidence of infections.