Weighting for joint surface area improves the information provided by a reduced 28-joint articular index of swollen joints.

The objective of our study was to examine whether weighting for joint surface area or recording of simultaneously tender and swollen joints increases the association of a reduced 28-joint articular index with clinical and outcome parameters. In a cross-sectional study we examined 61 consecutive outpatients with RA fulfilling the American Rheumatism Association 1987 revised criteria. Tender, swollen, and simultaneously tender and swollen joints were recorded. The association of 28- and 68-joint articular indices with clinical and outcome parameters were estimated with nonparametric correlation analyses. Weighting for joint surface yielded consistently increased correlation of clinical and outcome parameters with swollen and tender and swollen but not with tender joint counts. The correlation of the 28-joint articular and 68-articular indices with these parameters were similar. In conclusion, weighting for joint surface notably improves the information provided by swollen joint counts, whereas it does not appear to improve the information provided by tender joint counts.