How reliable is a radiological report in osteoporosis in diagnosing low bone density?

Patients are often referred to osteoporosis clinics with a radiological diagnosis of osteoporosis. Previous studies attempting to ascertain risk of osteoporosis from radiographs have been conflicting. The aim of our study was to determine how reliable spinal radiographs were at detecting low bone density compared with Dual Energy X ray Absorptiometry (DXA). We retrospectively measured the Bone Mineral Density (BMD) at the spine in 130 patients with a radiological diagnosis of osteopenia or osteoporosis in the absence of vertebral fractures. They were compared with a group of 119 age and sex matched patients with one or more low trauma vertebral fractures. There was a statistically significant difference in the mean BMD between these two groups. 12.7%, of the x-ray group with osteopenia reported, had a normal bone density, 49.2% had osteopenia (T-score -1 to -2.5) and 38.1% had osteoporosis (T-score <-2.5). Of those with a radiological report of osteoporosis, 12.8% had a normal bone density, 44.7% had osteopenia and 42.6% had osteoporosis. We conclude that a radiological report of low bone density is a strong predictor of osteopenia or osteoporosis by BMD measurement.