1st August 2023

Diagnosis

The World Health Organisation (WHO) defines osteoporosis as a Dual Energy X-ray Absorptiometry (DEXA) scan T-score of less than -2.5 or a geriatric patient presenting with a low trauma fracture. DEXA scans are the only diagnostic investigation. This uses low dose x-rays to measure BMD, typically of the vertebra, pelvis, and femur. T-scores on a DEXA scan are a standard deviation of the BMD compared to that of an average healthy 30-year-old adult. The Z-score on a DEXA scan is a standard deviation of the BMD adjusted to the patient’s age and gender.

Tools can be used to predict the risk of a patient suffering from an osteoporotic fracture, such as the Fracture Risk Assessment Tool (FRAX®) or Q Risk (fracture risk) calculator. These tools consider a person’s risk factors to calculate their 10-year probability of having a major osteoporotic or hip fracture.

NICE recommends DEXA scans for those over 50 years with a history of a fragility fracture or those <40 years with a high-risk factor for osteoporosis (as the FRAX® tool is not used in those <40 years). Those >40 years with risk factors (without a fragility fracture) require a FRAX® score, for which a fracture risk of greater than 10% would indicate the need for a DEXA scan.

DEXA scan images of pelvic and L1-L4 vertebrae

Image Source: Wikimedia Commons (2011). Morbus Fabry DXA 01, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Morbus_Fabry_DXA_01.jpg (Accessed: 17 February 2022).

Due to the potential differential diagnoses and secondary causes of osteoporosis, it is important to conduct a full history, physical examination, and blood tests in addition to the above.

Blood tests would be unremarkable in osteoporosis in primary osteoporosis.