Radiological changes in rheumatoid arthritis: measurement of area of juxta-articular bone as outcome event in clinical therapeutic trials of antirheumatic drugs.

A high degree of intra - and inter - rater reproducibility was obtained in measurement of a standardized area of the head of the first right metacarpal using a precision digitizer. This instrument had an accuracy for every point digitized of 0.127 mm. Intra-rater difference between readings at approximately a month's interval showed no significant differences. The method is reasonably simple to perform and is applicable to small joints such as the proximal interphalangeal joints. The method may prove useful in following progression of joint damage in rheumatoid arthritis.