Reliability of three methods of radiologic assessment in patients with rheumatoid arthritis.

RATIONALE AND OBJECTIVES

To assess the intraobserver reliability of three methods used frequently to evaluate joint destruction in rheumatoid arthritis: the Sharp method, the Larsen method, and the carpo:metacarpal ratio.

METHODS

One observer analyzed twice within a 6-week interval 71 radiographs from patients with rheumatoid arthritis. Reliability was estimated by intraclass correlation coefficient (R) and by Altman-Bland graphical method. Correlations were examined by the Spearman's coefficient (r).

RESULTS

The intraobserver reliability of each method appeared satisfactory with a good result for the Sharp method (R = 0.97). The correlation was strong (r > 0.80) between the results obtained by Sharp's and Larsen's methods and weaker between the results of the two former methods and the carpo: metacarpal ratio.

CONCLUSIONS

Sharp's method should be used preferentially in studies evaluating the radiologic changes in rheumatoid arthritis over time, especially in clinical trials. The carpo:metacarpal ratio may be considered as a complementary method, when wrist destruction is of conceptual importance.