Rheumatoid arthritis is a complex inflammatory disease of unknown cause. Although various laboratory and clinical measurements are useful in managing these patients, there is a need for better tests to quantitatively assess disease activity. The purpose of this study was to investigate the association of certain immune and inflammation (I-I) parameters with four traditional disease severity measures and a functional measure in rheumatoid arthritis patients. A single set of patient blood samples was analyzed, and four traditional disease severity measures and patient functional statuses were determined from 64 consecutive outpatients with rheumatoid arthritis. Plasma tumor necrosis factor-alpha (TNF), soluble interleukin-2 receptor (sIL-2R), sCD4 and sCD8 (and the sCD4/sCD8 ratio), neopterin, and fibrin D-dimer were analyzed in relationship to Westergren erythrocyte sedimentation rate (ESR), physician assessment of disease activity, joint pain count, grip strength, and Arthritis Impact Measurement Scale (AIMS) scores. Rheumatoid arthritis patients had higher mean levels of all I-I measures (except sCD4) compared to healthy subjects. Initial significant correlations between TNF, sIL-2R, and D-dimer and several disease severity and functional measures were detected. When we controlled for the covariates age, gender, race, and medications, regression analyses indicated that, as a group, the I-I measures were significantly related to grip strength, physician disease severity rating, ESR, and total joint pain. When the predictive values of the I-I measures were tested controlling for the covariates and ESR, D-dimer was independently and significantly associated with variability in grip strength, physician disease severity, and AIMS physical disability, while TNF was associated with a significant amount of variability in total joint pain.(ABSTRACT TRUNCATED AT 250 WORDS)