Doctors can use a patient's abdominal CT scans to also check
for signs of the bone-weakening disease osteoporosis, according to a new study.
The researchers, who published their findings in the Annals
of Internal Medicine compared patients' CT scans to their
dual-energy X-ray absorptiometry (DXA), which is traditionally used to diagnose
osteoporosis.
Doctors used the CT
scans for signs of osteoporosis
"What we found is that there is pretty good
correlation," said the study's lead author Dr Perry Pickhardt, professor
of radiology at the University of Wisconsin School of Medicine and Public
Health in Madison. The idea, say the researchers, is doctors can use patients'
CT scans that are ordered for another reason - such as looking for tumors - to
also check for signs of osteoporosis.
That may spare the
patients from additional testing and additional costs. In an editorial
accompanying the study, however, experts wrote that using CT scans to gauge
bone density could lead to some people being incorrectly diagnosed,
particularly if people at low risk are tested.
In this study, the average age was about 59 years old - six
years younger than the age at which the US Preventive Services Task Force, a
government-backed panel, recommends all women begin being screened for
osteoporosis. The disease affects over 12 million Americans over 50.The panel
also suggests younger women at an increased risk for bone fractures should be
screened, but there's no recommendation for men of any age.
Despite DXA scans being safe and cost effective, Pickhardt and
his colleagues say the test is underused. CT scans, however, are considered
overused - with more than 80 million performed in the US during 2011.
‘Incidentaloporosis’
For the new study, the researchers analysed test results
from 1 867 patients, who had both types of scans performed within six months of
each other over a 10-year period, to see if their CT scans showed osteoporosis
as well as the DXAs.
Overall, about 23% of the people were diagnosed with
osteoporosis, about 45% were diagnosed with some bone-weakening and about 32%
were healthy based on their DXAs. The researchers then found that their ability
to accurately diagnose those same patients with osteoporosis from a CT scan
depended on what threshold for bone density they used.
Dr Sumit Majumdar, who wrote an editorial accompanying the
new study, said a lower threshold for bone density would catch most cases of
osteoporosis and limit "incidentaloporosis" - incorrect osteoporosis
diagnoses "discovered" while doctors were looking for something else.
At the lower threshold, the researchers found 9% of those
diagnosed with osteoporosis were misdiagnosed. Pickhardt said the screenings
would have to target the right groups of people to prevent
overdiagnosis."Obviously it's something we need to worry about, but if you
apply it to a population that's suitable for diagnosis you wouldn't run that
risk," he said.
Costs involved tests
and scans
CT v. DXAMajumdar, a
professor of medicine at the University of Alberta in Canada, said CT scans are
better tests, but stomach scans don't include the hip - like a DXA would. A DXA
can cost a couple hundred dollars, while a CT scan can cost about $500 (R4600).
Both involve radiation.
Dr Beatrice Hull, from the Center for Osteoporosis and Bone
Health at the Medical University of South Carolina in Charleston, told Reuters
Health that she'd want her patients to have a DXA scan even with a diagnosis
from a CT scan."I don't think at this point this one test is going to
prevent further testing. I think it will identify patients who are at a higher
risk and need more testing," said Hull, who wasn't involved with the new
research.
