Intra-observer reliability of commonly used outcome measures in rheumatoid arthritis.
OBJECTIVE
To determine the reliability of some commonly used outcome measures in patients with rheumatoid arthritis.


METHODS
We studied 22 consecutive patients with rheumatoid arthritis enrolled in a clinical trial in a tertiary care center. The study design consisted of a test-retest, in which the same rheumatologist evaluated all of the patients twice, with an interval between evaluations of 90 to 120 minutes. Statistical analysis of the data consisted of calculation of the weighted Kappa (kw) and the intraclass correlation coefficient (ICC).


RESULTS
For the Ritchie articular index, kappa w = 0.83, ICC = 0.49, p < 0.0001; tender joint count, kappa w = 0.82, ICC = 0.49, p < 0.0001; physician's global assessment, kappa w = 0.79, ICC = 0.48, p < 0.0001; disease activity score, kappa w = 0.79, ICC = 0.49, p < 0.0001; utilities, kappa w = 0.71, ICC = 0.48, p < 0.0001; swollen joint count, kappa w = 0.7, ICC = 0.47, p < 0.0001; patient's global assessment, kappa w = 0.58, ICC = 0.44, p < 0.0001; pain kappa w = 0.45, ICC = 0.41, p < 0.0001.


CONCLUSIONS
The reliability of most of the outcome measures was good. It was higher for those measurements evaluated by a rheumatologist and for the composite indexes. Those requiring patient participation need to be improved.
Hernández-Cruz
B
B
Department of Immunology and Rheumatology, Instituto Nacional de la Nutrición Salvador Zubirán, México City, México.
Cardiel
M H
MH
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D017063:Outcome Assessment, Health Care; D010146:Pain / Q000503:physiopathology; D011897:Random Allocation; D015203:Reproducibility of Results; D012720:Severity of Illness Index