How are QCT results interpreted?
QCT, like any bone density measurement, is used to compare a patient to normal control data or to an absolute reference value, and to measure the change in bone density with time in a given patient. Researchers have established a “fracture threshold” level for all bone density methods; patients with bone density above this level are rarely seen with osteoporotic fractures, while below it the prevalence of patients with fractures rises. This level is about 100–110 mg/cm3 for QCT. As the value decreases below this threshold, the fracture prevalence increases, so that below 50 mg/cm3 most patients seen already have spinal fractures. The QCT value for a patient, when added to other diagnostic information, can be helpful in deciding an approach to treatment. Serial QCT measurements can establish the rate of change of bone mineral density in both treated and untreated patients, but the sensitivity of the method depends on how well the technique is done at a given hospital. In most cases, a c
