Differences in
Bone Densitometry
Scanning Methods
As you all know, Norland is the Walmart of bone
densitometry. The company has a finger scanner, a small ultrasound device,
heel scanner, forearm scanner, a 6 ft. table, an 8 ft. table and a
peripheral CT unit. Below is a very brief description of each system and
its application.
The Paris Ultrasound System is similar to
Hologic's Sahara ultrasound system. Ultrasound reports more on the
structure of the bone than it does on actual density. They use a Rube
Goldberg kind of calculation to determine a T-score based on an impedance
and ultrasound attenuation. Again, since most patients who have low
density have also lost bone structure, a low T-Score with the ultrasound
units is generally accurate. However, there are many patients with low
bone densities that don't have fractures because they still have good
structure and there are other patients who still have fractures even if
they have good density because they have lost the structure. This is why
many experts believe the ultrasound complements, it does not compete with
DEXA. Again, all the luminaries feel the gold standard in DEXA is the hip
and spine scan.
There is currently no reimbursement code for the
ultrasound systems, so they will probably not be fully embraced by the
marketplace until physicians using them can get paid for the studies
performed with them.
Further research needs to be done to determine the
percentage of false negatives produced with ultrasound systems which may
tell patients they have a good T-score when in fact they have low bone
mineral density. This is a work in progress and again is another screening
tool being endorsed and being pushed mainly by the drug companies who are
frustrated, especially in rural America where space limitations and
capital equipment costs are limiting the number of tables available.
Again, some type of testing for low bone mineral density is better than no
testing whatsoever. There are still serious concerns about giving patients
a false sense of security and telling them they are normal within normal
ranges with the ultrasound studies, when in fact, a hip scan may show that
they have osteopenia or osteoporosis. The issue here is like the digital
system; accessibility.
Merck's Score Sheet - Merck has created a little
survey which has numerous questions about patients' high risk factors
which has been shown through some studies to identify as much as 86% of
the patients who will have an abnormal bone density scan if they lowered
the threshold to four in the score survey questionnaire. The reason why
these patients still need the bone density scans is so we can have a
baseline to track how they respond to the drug therapy and so that
patients will comply with the drug therapy and not be in denial that they
even have a problem. Once they have a T-Score, there is no denial.
Research has shown that patients are ten times more likely to take the
drug and keep taking the drug if they have a T-score in front of them.
OsteoAnalyzer SXA Heel Scanner - Norland's heel
scanner uses single ' energy x-ray absorptiometry and was used on the
Apollo astronauts. This unit has been shown to do an excellent job of
catching anybody who is going to be abnormal but yet has a high level of
false positives. That means when confirmed on tables, many of the patients
who are shown to be abnormal on the heel scanner turn out to be within
normal parameters with the hip scan. Certainly false positives are better
than false negatives since we don't want to miss any patients at risk.
Some experts actually believe these weren't really false positives since
the patient may have had low bone density at the heel but it just didn't
show up at the hip where most of the fractures occur. Studies have shown
heel scans have y= high false positive abnormals and need to be confirmed
with a hip and spine scan. The experts agree that the hip and the spine
are the areas we are most concerned about, as these are the fracture areas
with the highest morbidity by far.
Norland's heel scanner OsteoAnalyzer is currently being
modified to change it from SXA to DEXA. it will be marketed as the Apollo
DEXA heel scanner system. Again, many experts confirm abnormal heel scans
on tables and most all experts monitor drug therapy with tables.
Norland's P-DEXA Forearm Scanner - This scans two
types of bone in one scan. The proximal more dense radius and ulna site is
mostly cortical bone and the distal radius and ulna site (towards the end
of the wrist) is mostly trabecular bone. The distal radius and ulna site
correlates much better with the hip than the proximal radius and ulna
site. We have scanned many patients with the P-DEXA that have been scanned
with the finger scanner and found that the finger correlates best with the
proximal radius and ulna site because of the fingers' higher level of
cortical bone. Unfortunately, we find that the proximal radius and ulna
site does not correlate well with the hip studies. The distal radius and
ulna higher trabecular site at the end of the wrist correlates much better
with hip studies. Many patients that appear to have abnormal bone density
at the finger in the proximal radius and ulna have abnormally low bone
density at the distal site and at the hip. In fact, the distal site of the
forearm correlates better with the hip than the AP or lateral spine
studies do.
Some states pay for all of the above mentioned
peripheral scanners except ultrasound and other states don't pay for any
peripheral bone density scanning. Some project that all of these systems
with the exception of ultrasound will be reimbursed starting in July when
the federal mandate kicks in. Some physicians are actually planning on
billing for ultrasound using the DEXA codes for peripheral scanning. We
think this is a grave error and will set them up for up-coding penalties
and should never be done.
XCT 2000 Peripheral Forearm CT Scanner is a
system with stunning capabilities to separate out the dense cortical shell
from the porous trabecular bone. Since trabecular bone changes out eight
to ten times faster than cortical bone, this allows the T-score to be
based on trabecular bone only, spotting non-responders to drugs in one to
two months instead of one to two years that DEXA tables can take. One year
on Fosamax can increase many patients' bone density by only 3%. If a DEXA
table has a plus or minus I% inaccuracy, this means that it may take the
patient somewhere around 18 months of drug therapy before the changes are
picked up by the gold standard DEXA hip or spine scan. This unit is used
mainly for luminary centers and centers that scan pediatrics where the
bones are growing and standard DEXA studies are not valid. This unit is
also used by all the drug companies to massage their drugs with earlier
reports on the micro-architectural changes caused by the drugs. Again,
this unit complements the gold standard hip and spine central scanning
tables.
Norland's six foot Eclipse table comes with
capabilities to do gold standard DEXA studies of the hip, AT spine, femur
neck, Ward's triangle, lateral spine, and forearm as well as custom
software for dealing with implants and scoliosis. Again, these studies are
the gold standard in bone densitometry. They are reimbursed under the
central DEXA code which was recently increased by 8% by HCFA nationwide to
an average of $131 per patient study, whether that study was hip, spine or
both.
Finally, Norland's XR-36 eight foot table has
just recently added body composition, body fat calculations to its whole
body scanning capabilities. The XR-36 does everything the Eclipse does, in
addition, it also has body composition and whole body DEXA scanning. It is
reimbursed under the same central code as the Eclipse system, code 76075. Comment: The drug companies are desperate to
create more accessibility to help reach out and identify patients at risk
for fractures before they have the fractures. This is why they are
endorsing and encouraging the use of other types of bone density
assessment testing to find patients at risk. In northern California, 4,000
patients were scanned at Lounge's Drugs using Norland peripheral units.
94% of the abnormals followed up with table scans. We believe this
strategy will continue for abnormals found with peripheral units. This is
why we endorse the use of peripheral units in outlying areas where the
abnormals will be sent to the tables. We think that this will increase
rather than decrease the utilization of tables.
Summary: We also agree that doing something is better
than doing nothing since most women are diagnosed with osteoporosis with
their fractured hip on a radiologist's light stand. The gold standard is
and will remain for many years to come, the DEXA hip and spine scan in
bone densitometry. |
Message from the MEC/OBD
president: