DXA scans

Please check that the persons doing DXA scans on your patients know what they are doing.

My 51-year-old patient was new in town and made an appointment for her and her family to establish relationships with a new set of doctors. As she was going through the menopause transition her first visit was to a gynecologist who had been recommended by her neighbor. The history and physical went well, they discussed the pros and cons of hormone therapy and a set of relevant lab studies was ordered.

“While you are here I think you should have a bone density study.” Fortunately he had a DXA in his office suite and she was able to get the study done during this visit.

The lowest spine T-score was –1.1 and at the femoral neck it was –0.8. “But wait, there’s more!” The T-score at Ward’s area was –2.7. She left the office with a prescription for teriparatide (Forteo, Eli Lilly) and a starter kit explaining how to give herself the daily injections.

“You have lost some bone and need this medicine to prevent further bone loss.”

Can you count the errors in this clinical encounter?

1: There are no guidelines recommending a bone density study in healthy women younger than 60 (if risk factors are present) or younger than 65 (in the absence of risk factors). My patient was a very healthy woman with no personal or family history to suggest an increased risk for fracture. The pre-visit “check box” that she shared with me did not contain any place where a history of risk factors for osteoporosis could be recorded and she did not recall being asked anything about this during the history taking.

2: It is absurd to make a dynamic statement about bone loss on the basis of a single time point measurement. A negative number for a T-score does not mean that bone loss has occurred; the value could well be the patient’s peak bone mass value.

3: Ward’s area is not an acceptable site for making a diagnosis of osteoporosis. Anatomically Ward’s triangle is that area of the femoral neck that is almost devoid of cancellous bone and has no impact on bone strength. When “measured” by DXA it represents that 1 square cm of the proximal femur when bone density is lowest and the location on the DXA scan will vary from patient to patient. If you watch the analysis you can likely see the cursor moving around the image to find that lowest BMD spot.

4: Let’s assume that my patient did indeed have a personal or family history indicating an increased risk of fracture or that the gynecologist had been” taught” to make the diagnosis on the lowest T-score on the report – the –2.7 at Ward’s area. Teriparatide is infrequently (I would like to say rarely) first-line therapy.

You wouldn’t have an ECG performed by someone who didn’t know how to properly position the leads, nor would you send your patient to a lab for blood work if they couldn’t tell the difference between hemoglobin and hematocrit. The DXA errors my patient encountered are just as egregious.

Visit this website to familiarize yourself with some of the do’s and don’ts of DXA.

Conflict statement: Dr. Kleerekoper is a member of the International Society for Clinical Densitometry and serves on the editorial board of the Journal of Clinical Densitometry.