Diagnosis is based on bone density measurement, which determines the T-score. This is a statistical value that compares the measured bone density with that of young adult women and indicates the risk of fracture. Various techniques are available to measure bone density (BMD, bone mineral density):
The most widely used is dual-energy X-ray absorptiometry (DXA or DEXA). The WHO definition of osteoporosis is also based on it. Bone density measurement with DXA devices is currently the most useful method, especially as it involves little radiation. The value of DXA is well documented. DXA measurements are also best suited to monitoring osteoporosis during treatment. In five to ten minutes, the device measures how much the X-rays are weakened at the lumbar spine and thigh. From this, the computer calculates the so-called T-score and Z-score.
The Z-score compares the result with your age group and is less important for treatment decisions.
Another method is quantitative computed tomography (QCT or pQCT). Computed tomography involves higher radiation exposure. Measuring bone density by ultrasound, known as quantitative ultrasound (QUS), is highly controversial and meaningful only in very few cases.
Bone density measurement for early detection is not covered by statutory health insurance; you have to pay for it yourself unless you have already had a fracture without significant force (a so-called fragility fracture) with suspected osteoporosis.