This study was undertaken to compare trabecular bone mineral density (BMD) in premenopausal rheumatoid arthritis (RA) patients and normal age-matched controls.
A protocol was designed to record age, duration of disease, use of corticosteroids (CS) and/or slow-acting antirheumatic drug (SAARD) therapy together with duration of such therapy. BMD was measured using the Hologic QDR 1,000 dual energy X-ray absorptiometer. The first four lumbar vertebrae and the left femur were measured in 56 RA patients and 165 controls. Height and weight were measured. Comparisons were made between RA patients and controls, as well as between subgroups of RA patients based on CS therapy.
Patients with RA had significantly lower BMD (P < 0.05) at all the sites than the normal controls. The mean duration of RA at the time of study was 60 months (standard deviation 58 months). Thirteen RA patients had used CS in doses less than 10 mg daily for 6 months or longer (mean 19 months), while 25 patients had been on SAARD for an excess of 6 months (mean 23 months). The CS-treated patients had significantly lower BMD than untreated subjects at the femoral neck and inter-trochanteric region (P < 0.05), but not at the lumbar spine. However, when compared with normal controls, the CS-treated subgroups had significantly lower BMD at the lumbar spine and all femoral areas. Trochanteric BMD was the best determinant of the RA group, with a sensitivity of 65% and specificity of 77%. The positive predictive value was 16%, while the negative predictive value was 10%. Using Bayes' theorem, the prevalence of osteopenia in RA was found to be 6%.
We conclude that generalised bone loss is a systemic feature of RA and that loss at the spine and femur may be aggravated by CS therapy.