Relationship between local and total bone mineral in patients with rheumatoid arthritis and normal subjects.

Total body bone mineral (TBBM) measured by dual photon absorptiometry and local bone mineral (BMC) measured by single photon absorptiometry were determined in 55 patients with definite or classical rheumatoid arthritis. All of them had been on a steady dose of anti-inflammatory drugs for at least 12 months, and furthermore, 13 patients were on glucocorticoids. The results were compared with 49 normal persons matched for sex, age and menopausal state. A highly significant correlation was found between BMC and TBBM in the patients (r = 0.84, SEE = 13.0%) as well as in the controls (r = 0.77, SEE 10.5%). Moreover, the intercepts and the slopes were virtually of the same order. Subdividing the patients according to glucocorticoid treatment the same high correlations were shown in the two subgroups. As a group the patients on glucocorticoids had a highly significant generalized osteopenia (a reduction of TBBM of 26% compared to normals). The patients on other anti-inflammatory drugs had a significant, but less pronounced generalized osteopenia (a reduction of TBBM by 11% compared to normals). It is concluded, that BMC of the forearm can be used as a valid estimate of total body calcium in groups of patients with rheumatoid arthritis and in normal subjects.