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This is a sidebar to an investigation on the growing use of QCT to screen for osteoporosis.

Which test should the doctor and patient believe?

This journalist can corroborate concerns about the accuracy -- or at least the confusing summary interpretation -- of the quantitative computed tomography (QCT) technique for measuring bone mineral density.

During my annual checkup, I asked my doctor to order a bone density scan for me, which at age 73, would be my first. But for reasons that aren't clear, the order was for a QCT rather than the dual-energy x-ray absorptiometry (DXA), which has been the gold standard screening strategy for decades. I am neither petite nor obese, have not fallen or fractured a bone, and do not have degenerative disease or any other red flags that are said to justify the higher radiation dose of the QCT.

The -- delivered to my email inbox a few hours after I left the scanner -- was alarming. It gave my lumbar spine T-score, which compares the patient's bone to that of a young adult, at -2.87. At first, that seemed to categorize me as having osteoporosis, severe bone loss, since elsewhere on the summary milder bone loss or osteopenia was defined as minus -1.0 to -2.5. My Z-score, which compared me to age-matched controls, was given as +0.46, meaning my bone health was better than others my age. But still, not good.

Visions of falling and not being able to get up ran through my head. What if I couldn't call for help? I exercise regularly -- fast-walking on a treadmill at an incline or pedaling a bike several times a week -- and consider myself healthy. This was scary.

The QCT said my left neck proximal femur hip wasn't as bad, with a -1.71, and my Z-score +0.1, meaning just one click better than others my age.

I wanted to know: What could I do to restore my bone health. Exercise? Diet? Calcium supplements? Doctors I asked didn't know, or gave conflicting answers. They said yes, keep walking or running or lifting weights because they help -- or they said no, they don't. You need to go on drugs.

My own doctor said the treadmill would do nothing for my bone health, but that walking on hard pavement (he stomped his foot) was shown to help. He suggested a serious conversation about going on bisphosphonates or denosumab (Prolia).

Drug Side Effects

But the side effects are scary. Pain, flu-like symptoms, upset stomach, erosion of the esophagus. Paradoxically, they even make some patients more susceptible to fracture.

Most doctors I talked with acknowledged that clinicians have a lot to learn about what to tell women like me about restoring bone density. I thought I had enough to pitch a story about what doctors don't know about exercise and skeletal health.

That theme led me to Bart Clarke, MD, an endocrinologist and bone metabolism expert at the Mayo Clinic in Rochester, Minnesota, who set my story on a different trajectory.

He said something astonishing: "The QCT over-reads the severity of the bone loss in the spine." He sees it all the time. Patients from Iowa just to the south, who for some reason get a lot of QCT studies for their BMD evaluations instead of DXA scans, are told they have osteoporosis of the lumbar spine and must go on medication. So they come to the Mayo for a second opinion, get a DXA. Almost every time, they don't have osteoporosis, he said.

"So in your case, maybe you've got normal bone density if you did it by a DXA."

I told my doctor, also an endocrinologist, about Clarke's comment about QCT's inaccuracy of the spine T-score, and asked him to refer me for a DXA. The imaging center that performed my QCT could not give me an appointment for several months, so the DXA was scheduled in a Scripps outpatient department in La Jolla, California, on March 26. I abided by the instruction not to take any medications that could contain calcium 24 hours before the exam as it could skew the results.

Spine and Hip Reversed

The were in exact reverse. My spine was fine, with a T-score of -1.8 and a Z-score of +0.2. My hips, however, interpreted by the QCT as "osteopenic," were in much worse shape. The DXA report also said I had a history of "age-related osteoporosis without current pathological fracture," though I had never been diagnosed with osteoporosis before.

Though my left total hip T-score was okay, with a -1.4 and Z-score +0.5, my left hip femoral neck was on the line, with a T-score of -2.5 and a Z-score of -0.5. My right hip femoral neck T-score was -2.6 with a Z-score of -0.5. My right total hip was fine, with a T-score of -1.6 and a Z-score of +0.3.

My hip FRAX score, which predicts risk of fracture within 10 years, was 5%, suggesting that medical therapies should be considered.

Clarke said my scan results, at least for the spine, validated what he sees at the Mayo Clinic all the time.

What might cause this variation in test results? What can you believe? If QCTs are unreliable, why are they done and are they followed by DXAs? As I chose to do?

I asked my doctor.

"This is confusing," he replied. "How can they both be right?"

For patients like me who get conflicting results from confusing summaries, the treatment decisions are complex and difficult, with important consequences for a healthy future.

According to the , 1.5 million people in the nation suffer a fragility fracture each year -- including one in two women and one in five men older than 50 during their lifetime -- with dire from fracture-related falls including brain injury and death.

My two cents: we need to be clearer about how to measure and treat loss of bone mineral density, and make the summaries, which are now promptly read by patients before the physician can see them, a lot more understandable.

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