Validation and comparative evaluation of the osteoporosis self-assessment tool (OST) in a Caucasian population from Belgium

BACKGROUND: Risk indices have been developed to identify women at risk of low bone mineral density (BMD) who should undergo BMD testing. Aim: To compare the performance of four risk indices in White ambulatory women in Belgium. DESIGN: Epidemiological cross-sectional study. METHODS: Records were analysed for 4035 postmenopausal White women without Paget's disease or advanced osteoarthritis, seen at an out-patient osteoporosis centre between January 1996 and September 1999. Osteoporosis risk index scores were compared to bone density T-scores. The ability of each risk index to identify women with low BMD (T-score < -2.0) or osteoporosis (T < -2.5) was evaluated. RESULTS: Using an Osteoporosis Self-Assessment Tool (OST) score <2 to recommend DXA referral, sensitivity ranged from 85% at the lumbar spine to 97% at the total hip to detect BMD T-scores of <or= -2.5, and specificity ranged from 34% at the total hip to 37% at the femoral neck and lumbar spine. The negative predictive value was high at all skeletal sites (89-99%), demonstrating the usefulness of the OST to identify patients who have normal BMD and should not receive DXA testing. All risk indices performed similarly, although the OST had somewhat better sensitivity and somewhat lower specificity than the other indices at the cut-offs evaluated. Among the 11-12% of women who were classified as highest risk using OST or the Osteoporosis Index of Risk (OSIRIS), 81-85% had low bone mass and 68-74% had osteoporosis. DISCUSSION: The performance of these risk indices among women in Belgium was similar to that reported earlier for other samples in Asian countries, the US, and the Netherlands. The OST and other risk indices are effective and efficient tools to help target high-risk women for DXA testing.