Prevalence of metacarpal osteopenia in young rheumatoid arthritis patients.

The aim of this study was to assess the prevalence of and diagnostic role of metacarpal osteopenia in rheumatoid arthritis (RA) and to evaluate its detectability using receiver operating characteristic (ROC) analysis. Metacarpal bone mineral density was measured in 98 patients with classical RA using a computer-assisted measure of 6 metacarpal diameters (radiogrammetry) in patients aged less than 50 years. Sensitivity and specificity of the technique in discriminating the RA patients from 85 normal controls and osteopenic RA subjects from their normopenic counterparts, was determined by standard statistical techniques. Clinical, laboratory and radiological variables were compared in their ability to explain the variance of metacarpal bone density. The prevalence of metacarpal osteopenia in RA was 55%. Prolonged disease and reduced function significantly differentiated osteopenic from non-osteopenic RA patients. Discriminant analysis of RA and control groups showed that measurement of 6 metacarpals was more accurate than the 2nd metacarpal measurement alone in predicting the RA patients. The sum of 6 metacarpal combined cortical width (CCW) had a sensitivity of 61% and specificity of 68% in discriminating the RA patients from the controls. Receiver operating characteristics curves showed, not surprisingly, that objective measurement of bone diameters was superior to clinical or laboratory measures of disease activity in correctly classifying a randomly chosen RA patient as osteopenic or not. Metacarpal osteopenia is common in RA and it may be a useful measure of the disease in young patients.