Identifying patients at risk of developing an osteoporosis-related fracture will continue to be a challenge. The "gold standard" for osteoporosis diagnosis is bone densitometry. However, economic issues or availability of the technology may prevent its use under a mass screening scenario. A risk assessment instrument, the "simple calculated osteoporosis risk estimation" (SCORE), has been reported to appropriately identify women likely to have low (t score < or = -2 SD) bone mineral density (BMD) and who should be referred for bone densitometry. The aim of our study is to evaluate the discriminatory performance of SCORE in a random sample of postmenopausal white women from Belgium. For this purpose, we gathered medical data on 4035 consecutive patients aged > or = 45 years, either consulting spontaneously or referred for a BMD measurement to an outpatient osteoporosis center located at the University of Liège, Belgium. BMD measurements, using dual-energy X-ray absorptiometry (DXA) technology, were taken at the hip (total and neck) and lumbar spine (L2-4). At the recommended cutoff point of 6, SCORE had a sensitivity of 91.5% to detect low BMD at any of the measured sites, a specificity of 26.5%, a positive predictive value of 52.8%, and a negative predictive value of 77.7%. According to SCORE, 18% of the patients would not be recommended for densitometry. Among these, 10.9% were misclassified as they had osteoporosis (t score < or = -2.5 SD) at one or more of the sites investigated. The negative predictive errors of SCORE, when failing to detect osteoporosis, were only 1% for the total hip, 3.2% for the femoral neck, and 8.8% for the lumbar spine. We conclude that, notwithstanding the high values of sensitivity, SCORE specificity is too low to be useful as a diagnostic tool for screening patients at high risk to later develop osteoporosis. Nevertheless, from a resource allocation perspective, this instrument can be used with relative confidence to exclude patients who do not need a BMD measurement, and would therefore provide an opportunity to realize substantial cost savings in comparison to a mass screening strategy.