Introduction: According to ISCD position statement, bone mineral density (BMD) should be measured at spine and hip in all patients. In certain circumstances, BMD of non-dominant forearm should also be measured, such as in patients whose hip and/or spine cannot be measured, those with hyperparathyroidism or very obese patients. The forearm can either be scanned in supine and sitting position. However, there may be significant difference in measured BMD when forearm is scanned in different positions, hence affecting the diagnosis and management.
Objectives: The purpose of this study was to assess whether the measured non-dominant forearm BMD between scanning in supine and sitting positions are concordant.
Methods: A cohort of 30 subjects (4 males and 26 females) between 41 and 91 years of age were included. Each patient had same-day repeat DXA scans of non-dominant forearm on a Hologic fan-beam scanner (Hologic Horizon A) in both supine and sitting positions. Positioning of patients was followed according to the manufacturer operator manual. A total of 3 technologists acquired the 60 scans. All acquisitions of each patient were analyzed by the same technologist. Forearm region of interest was defined as one-third radius according to ISCD recommendation. The forearm BMD measured in the two scanning positions was compared by independent-sample t-tests. Results were considered significant when p < 0.05. A Bland-Altman plot was also constructed to determine the agreement of measured forearm BMD between the two scanning positions.
Results: Mean forearm BMD measured in supine and sitting positions were 0.578g/cm2 and 0.572 g/cm2 respectively. There was no significant difference between forearm BMD measured in the two scanning positions (p = 0.852). The Bland-Altman plot (figure 1) also showed satisfactory agreement of measured BMD of non-dominant forearm between supine and sitting scanning positions.
Conclusions: Non-dominant forearm BMD measured in supine and sitting positions are concordant.
