Abstract
Background: Considerable debate has occurred concerning the utility of different methods of obtaining joint counts and their usefulness in predicting outcomes in persons with rheumatoid arthritis.
Objective: The purpose of this study was to compare two methods of assessing disease activity in the joints (clinician joint count, self-reported joint count), and to compare their relative utility in predicting two methods of assessing outcomes (self-reported ratings of impairment and pain, objective performance index) with and without controlling for negative affectivity.
Method: Data for this study were obtained during home visits from 185 persons diagnosed with rheumatoid arthritis. Individuals completed a series of self-report measures including the joint count. Trained research assistants completed a 28-joint count and timed participants on a series of measured performance activities (e.g., grip strength, pinch strength, walk time).
Results: The self-report joint count was highly correlated with the clinician joint count and also accounted for as much, if not more, variance in the subjective outcome measures than did clinician assessments. Both types of indicators predicted unique variance in the objective performance index.
Conclusions: For most research purposes, measures such as self-report joint counts have sufficient validity to be used in place of more costly clinician assessment of joint counts.