Evaluation of finger ultrasound in the assessment of bone status with application of rheumatoid arthritis.

Abstract

Osteoporosis associated with active rheumatoid arthritis (RA) has been demonstrated in both the axial and peripheral skeleton, especially the periarticular regions more directly affected by the disease. Quantitative ultrasound (QUS) is a recently accepted tool for the assessment of bone status, and therefore could be used to monitor bone changes in RA patients. In a cross-sectional study we measured ultrasound velocity (Ad-SOS) through the proximal phalanges in three groups of female subjects. These included: 51 patients with rheumatoid arthritis (group 1), 44 general practitioner (GP)-referred patients for osteopenia (group 2) and 52 young healthy volunteers (group 3). For groups 1 and 2 bone mineral density (BMD) of the lumbar spine and proximal femur were also measured. For the RA patients BMD of the hand, measurement of hand function (HAQ and grip strength) and disease activity (ESR and CRP) were also assessed. The precision of long-term Ad-SOS measurements on volunteers gave a root mean square coefficient of variation (CV) of 0.7% and standardized CV of 3.6%. No statistically significant effect of dominance was observed in the measured Ad-SOS between the dominant and non-dominant hand (r = 0.96, p < 0.001). Ad-SOS was found to be significantly different in the three groups (p < 0.0001). Ad-SOS was highly dependent on age (r = -0.67), with a gradual reduction (-5.2 m/s per year) after the age of 30 years for female patients in both group 1 and group 2. Ad-SOS was significantly correlated with lumbar spine, femoral neck and hand BMD, with correlation coefficients of 0.49, 0.51 and 0.72 respectively for RA patients. Finger ultrasound was moderately correlated with measures of hand function, with coefficients of 0.37 and 0.39 for HAQ and grip strength respectively. Hand BMD also correlated to the same power with these parameters. Neither finger ultrasound nor BMD was significantly correlated with ESR and CRP (measures of disease activity). We have demonstrated that bone status can be assessed quickly and cheaply using a portable QUS device. Ad-SOS relates to the measure of hand function in RA patients. Longitudinal studies are required to determine the usefulness of finger ultrasound for monitoring disease progression or the effect of treatment in RA.