Osteoporosis - Diagnosis 

Diagnosing osteoporosis 

The FRAX tool

The World Health Organization (WHO) has developed a 10-year Fracture Risk Assessment Tool to help predict a person's risk of fracture between the ages of 40 and 90.

The tool is based on bone mineral density and other relevant risk factors, such as age and sex.

The algorithms used give a 10-year probability of hip fracture and a 10-year probability of a major fracture in the spine, hip, shoulder or forearm.

Osteoporosis is often diagnosed after weakened bones have led to a fracture.

If you're at risk of developing osteoporosis, your GP may refer you for a bone mineral density scan, known as a dual energy X-ray absorptiometry (DEXA, or DXA) scan.

Normal X-rays are a useful way of identifying fractures, but they aren't a reliable method of measuring bone density.

DEXA (DXA) scan

DEXA scan can be used to help diagnose osteoporosis. It's a quick, safe and painless procedure that usually takes about five minutes, depending on the part of the body being scanned.

The scan measures your bone mineral density and compares it to the bone mineral density of a healthy young adult and someone who's the same age and sex as you.

The difference between the density of your bones and that of a healthy young adult is calculated as a standard deviation (SD) and is called a T score.

Standard deviation is a measure of variability based on an average or expected value. A T score of:

  • above -1 SD is normal 
  • between -1 and -2.5 SD is defined as decreased bone mineral density compared with peak bone mass
  • below -2.5 is defined as osteoporosis

Although a bone density scan can help diagnose osteoporosis, your bone mineral density result isn't the only factor that determines your risk of fracturing a bone.

Your age, sex and any previous injuries will need to be taken into consideration before deciding whether you need treatment for osteoporosis.

Your doctor can help you take positive steps to improve your bone health. If you need treatment, they can also suggest the safest and most effective treatment plan for you. 

Page last reviewed: 23/04/2014

Next review due: 23/04/2016


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The 2 comments posted are personal views. Any information they give has not been checked and may not be accurate.

User609324 said on 24 October 2011

A point well made by nh7kk about the T score inaccuracy. It may be helpful to point out the T score is simply the standard deviation measure compared to a young adult population and therefore the score values are simply a variation rather than some sort of absolute figure. In this way the definiaitons are also somewhat arbitrary and set by academics and clinicians rather than linked to fracture risk for example.

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nh7kk said on 20 October 2011

The information on T score appears different to what I have seen elsewhere. There is no definition for a T Score between -1 and 0. No wonder NHS choices is not the first choice of many NHS patients who want accurate health information.

The text reads
" If your T score is between 0 and 1, you're considered to be within the normal range.
A T score between -1 and -2.5 is classed as osteopenia, which is the name for the category of bone density between normal and osteoporosis.
If your T score is below -2.5, you will be classed as having osteoporosis. "

The World Health Organsiation have the following ACCURATE definitions
Normal is a T-score of -1.0 or higher
Osteopenia is defined as between -1.0 and -2.5
Osteoporosis is defined as -2.5 or lower

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