Four experts answer your questions about DXA T-scores, risk calculation, secondary causes and more…

When can you diagnose osteoporosis without a bone density scan?

Osteoporosis can be diagnosed clinically in any patient aged over 50 years who sustains a minimal trauma fracture (fracture involving a fall from a standing height). This is true regardless of DXA T-score results, says Dr Sonia Davison, lead endocrinologist at Jean Hailes for Women’s Health and Past President of the Australasian Menopause Society.

“If you have lifted up a basket of washing from the floor and you fracture in the vertebral or hip region, by definition, you have osteoporosis—regardless of what the T-score has said,” she explains.

Dr Jane Elliott AM, a GP and Clinical Senior Lecturer in Obstetrics and Gynaecology at the University of Adelaide, notes that in this scenario, most GPs would order a DXA for their workup and monitoring anyway, but you can proceed directly to treatment.

A DXA T-score of ≤ –2.5, even without a fracture, is also diagnostic of osteoporosis, Dr Elliott adds.

What if a patient with a minimal-trauma fracture only shows osteopenia on DXA?

Rheumatologist Professor Peter Wong, Medical Director and Chair of the Healthy Bones Australia Medical & Scientific Advisory Committee and Chair of the Guidelines Review Committee, explains patients with a minimal trauma fracture may not meet the densitometry definition of osteoporosis on DXA testing because DXA results fall on a normal distribution curve—with fewer people having T-scores at either extreme.

“The chances are when you do the DXA after a low trauma fracture, they’re going to have a T-score of between minus one and minus 2.5, just because there’s a whole lot more people in the world who are osteopenic than osteoporotic by DXA. But they’ve still got osteoporosis because they’ve had a low trauma fracture.”

Dr Davison says this apparent mismatch can also reflect limitations of bone density testing, noting results are influenced by anatomy, positioning, ethnicity and individual variation.

What if the fracture was not in the hip or vertebra?

Minimal trauma fractures at other sites (such as the wrist) should prompt a DXA scan. If the T-score is less than or equal to –1.5, the guidelines advise initiating treatment. If it’s greater than –1.5, the guidelines recommend looking for other causes of fracture.

Professor Wong says this is because a T-score greater than –1.5 means “their bones are actually not that thin.”

“So why did they fracture? Is there something else going on? Look for coeliac disease, look for thyroid disease, why did they fall? It’s just to get you thinking about other things.”

It can also be worth considering whether the trauma that led to the fracture really was minimal, or if the average person would also have fractured in a similar situation, adds Professor Bronwyn Stuckey, Consultant Endocrinologist at Sir Charles Gardner Hospital, Medical Director of the Keogh Institute for Medical Research and Clinical Professor in the University of Western Australia’s Medical School.

“If somebody’s fallen off a bike, is that minimal trauma?”

If you’re uncertain, she recommends doing a DXA and checking bone turnover markers.

What other causes should you consider?

There are three main secondary causes of osteoporosis to look out for, Professor Stuckey says.

Coeliac disease – which can be “surprisingly silent” in adults, she says. “I’ve had patients who’ve had coeliac disease where the only symptom they have is a little bit of dyspepsia.”

Primary hyperparathyroidism – which is marked by high calcium. “There does not have to be a high PTH. You can have a sort of normal PTH and a high calcium, and that’s parathyroid hormone dependent hypercalcemia. So ionised calcium is best, but total calcium is okay.”

Paraproteins in the blood – which can be a silent cause of bone loss.

Dr Elliott notes you can often customise your practice software to include a drop-down list of secondary osteoporosis causes and which blood tests to run.

Is it ever worth measuring forearm bone density?

Professor Stuckey says this does not usually add much value, unless you’re monitoring conditions associated with appendicular bone loss—such as hyperparathyroidism and malabsorption.

It can also be used for patients with osteoarthritis causing artefactually increased spine bone density and who’ve had both hips replaced.

How can you identify at-risk patients before the first fracture?

This firstly involves identifying diseases, conditions and medications that could raise fracture risk, and referring patients with these risk factors for spine and proximal femur bone mineral density testing.

It’s also essential to consider non-modifiable and lifestyle risk factors, and fracture risk calculators are key tools here. Dr Davison explains the updated guidelines favour FRAX®, which incorporates a broader range of risk factors than the Garvan Bone Fracture Risk Calculator —including ethnicity, excessive alcohol intake, glucocorticoids, current smoking, and rheumatoid arthritis.

“You can put a femoral neck T-score in both of them,” she says. “But for FRAX, you actually don’t need it,” she adds.

Professor Wong says the FRAX gives you a 10-year absolute risk of major osteoporotic fracture (hip, vertebra, forearm, and humerus), and a 10-year risk of hip fracture.

“And the usual thresholds to treat are 20% at 10 years for major osteoporotic fracture, or 3% for hip,” he says.

“The Garvan risk factor calculator is still very useful. It’s got five input criteria, so much simpler. The one criteria that it has which FRAX doesn’t have is falls. So if you’ve got someone that’s falling a lot, Garvan is very useful.”

“The reason we’ve come down on FRAX is because FRAX has probably been validated in more worldwide populations than Garvan. Also, it’s incorporated into a lot of the DXA software. So you’ll get a FRAX reading when you order your DXA.”

Professor Stuckey and Dr Elliott recommend running an audit at a menopause consult to help women make informed choices about menopausal hormone therapy.

“Sometimes you get a surprise that women have very low bone density right at the beginning of menopause, and you have to make a decision about what you’re going to do to stop the inexorable loss of bone density with the lack of oestrogen,” Professor Stuckey says.

Menopausal hormone therapy, in the right dose, is very effective for preserving bone and preventing fractures, she adds.

Professor Wong notes menopause is a great time to advise women about bone-protective lifestyle strategies like moderating alcohol intake, smoking cessation, adequate calcium and vitamin D intake, and weight-bearing activity—noting some physiotherapists offer an exercise program called Onero™ that has been specifically designed to build bone density and reduce fracture risk.

You can find a risk assessment, diagnosis and management flow chart on page 13 of the guidelines, also available at Healthy Bones Australia.

In what circumstances will Medicare fund a DXA scan?

Under current regulations, scans are funded after a first fracture, in patients over 50 with certain risk factors, and once patients turn 70, Dr Elliott explains.

However, after about the age of 50, “we are all on the slippery dip of losing bone,” she says. “And personally, I want my bone density picked up—if it’s low—nearer the top of that slope.”

Medicare funding criteria do not cover all clinically relevant scenarios, including women with breast cancer on aromatase inhibitors and women who could benefit from testing at menopause, she says.

Women can choose to pay for testing themselves, she notes. “I understand that some people can’t afford it, but nevertheless, I think we should at least be bringing it up with patients.”

Healthy Bones Australia has a list of Medicare item numbers for DXA scans.

Who falls into the new ‘very high risk’ category?

Postmenopausal women and men aged over 50 years fall into the ‘very high risk’ category if:

• Their T-score is less than or equal to –3.0, and
• They have had a fracture within that past 2 years and/or a history of 2 or more fragility fractures, and/or
• They have multiple clinical risk factors (corticosteroids, recurrent falls, low BMI), and/or
• Their FRAX score indicates a major osteoporotic fracture risk of ≥ 30%, or a hip fracture risk of ≥ 4.5%.

These patients may be eligible for anabolic therapy to build bone. Professor Wong suggests referring them to a bone health specialist such as an endocrinologist, a rheumatologist, or a geriatrician.