Early changes in bone mineral density measured by digital X-ray radiogrammetry predict up to 20 years radiological outcome in rheumatoid arthritis

INTRODUCTION Changes in bone mineral density (BMD) in the hand as evaluated by digital X-ray radiogrammetry (DXR) of the second to fourth metacarpal bones has been suggested to predict future joint damage in patients with rheumatoid arthritis (RA). This study's objective was to investigate whether DXR-BMD loss early in the course of the disease predicts the development of joint damage in RA patients followed for up to 20 years. METHODS A total of 183 patients (115 women and 68 men) with early RA (mean disease duration, 11 months) included from 1985 to 1989 were followed prospectively (the Lund early RA cohort). Clinical and functional measures were assessed yearly. Joint damage was evaluated according to the Larsen score on radiographs of the hands and feet obtained in years 0 to 5 and years 10, 15 and 20. These radiographs were digitized, and BMD of the second to fourth metacarpal bones was evaluated by DXR. Early DXR-BMD change rate (that is, bone loss) per year calculated from the first two radiographs obtained on average 9 months apart (SD ± 4.8) were available for 135 patients. Mean values of the right and left hand were used. RESULTS Mean early DXR-BMD loss during the first year calculated was -0.023 g/cm2 (SD ± 0.025). Patients with marked bone loss, that is, early DXR-BMD loss above the median for the group, had significantly worse progression of joint damage at all examinations during the 20-year period. CONCLUSIONS Early DXR-BMD progression rate predicted the development of joint damage evaluated according to Larsen score at year 1 and for up to 20 years in this cohort of early RA patients.