Low bone mineral density in the hand is a valid predictor of overall mortality in patients with rheumatoid arthritis (RA) and indicates long-term prognosis, according to a new study presented today at EULAR 2008, the Annual Congress of the European League Against Rheumatism in Paris, France. Digital X-ray radiogrammetry (DXR) demonstrated bone mineral density to be as effective predicting mortality as well-established means of assessment such as radiographic damage and functional disability.
During the study, different standard measures of disease activity were investigated in order to assess their capacity to predict all-cause mortality. Over a period of 27 years (1978 -- 2005), age-sex adjusted proportional hazards models for 84 RA patients, found the following to be significant predictors of mortality:
Bone mineral density in the hand (RR=0.55/1SD, 95% CI 0.35-0.87)
Steinbrocker functional classification (RR=1.86/1SD, 95% CI 1.35-2.56)
The physician's global assessment (RR=1.37/1SD, 95% CI 1.02-1.82)
Erythrocyte sedimentation rate (RR=1.86/1SD, 95% CI 1.41-2.46)
Conversely, during this study, certain measures of rheumatic disease activity, including rheumatoid factor, Larsen index, Ritchie index and the patient's global assessment, were not found to be significant predictors of mortality in RA.
The study's lead researcher, Dr Christina Book of Malmö University Hospital, Sweden, said: "This long-term study establishes that measurement of bone mineral density in the hand may be an important physical gauge in anticipating the course of rheumatoid arthritis. It offers physicians an effective tool for assessing a patient's disease and so developing the most appropriate individual management plan."
In the study, 152 consecutive patients (119 women, 33 men) with a mean disease duration of 13 years were enrolled. X-rays of the hands at inclusion were available in 108 patients, and in 84 of these, bone mineral density was evaluated by DXR on the same digitised hand X-rays used for scoring radiographic joint damage. Placement of joint prostheses or severe malalignment prevented DXR evaluation in the other 24 patients. Manual measurements, such as dividing the combined cortical thickness by the width of metacarpal II (CCTr) were performed in all 108 patients with X-rays at inclusion. Measures of disease activity and damage at inclusion in the 84 subjects were used to predict mortality by Cox regression models. Furthermore, standardised mortality ratios were computed using the general Swedish population as a benchmark, to assess the overall increased mortality in the group, which was three-folded increased.
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