Test and diagnosis of Osteoporosis

Bone density scanning is the benchmark technique used to diagnose osteoporosis and assess the risk of suffering a fracture. Bone mass is analysed through dual-energy X-ray absorptiometry (DXA). Patients receive a very low dose of radiation during densitometry tests. The International Society for Clinical Densitometry (ISCD) has established the two areas of the body to be assessed as the lumbar region of the spine and the hips. Under certain circumstances, bone density can also be scanned at the wrist.

It is a straightforward, rapid and painless test. There is no need to fast or perform any specific prior preparation. Patients do not need to be accompanied for the test. Bone density scans are not recommended for pregnant women, however, as they involve the use of X-rays. 

Bone density values are expressed in g/cm² and comparison scales are used to evaluate results with respect to normal values. In adults aged 50 or over and/or post-menopausal women, bone mineral density (BMD) values are compared with those of a healthy young adult population, which is when humans theoretically have their highest levels of bone mass. In the case of young adults, particularly those under the age of 50, BMD test results are compared with a healthy population of the same age and gender.

Densitometry analyses:

• Bone mineral content in grams.
• Bone mineral density (BMD), which is an analysis of bone mass and is expressed in grams per square centimetre.
• T-score, the number of standard deviations (SD) away from the average value for a population of 20–39 year olds of the same sex as the patient. As patients become older their BMD decreases and this alters the T-score.
• Z-score, the number of standard deviations (SD) away from the average value for a population with the same age and sex as the patient. 

The World Health Organization (WHO) has established some densiometric criteria that use the T-score as a primary parameter to evaluate the risk of future fractures. These criteria are commonly used today. A T-score of between -1.0 and -2.5 is defined as osteopenia, while a T-score of less than -2.5 is classified as osteoporosis.