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Determining osteoporosis risk.

The article based on Dr. Margaret Gourlay and her colleagues' findings, "Osteoporosis Screening Intervals Are Proposed," (OB.GYN. NEWS, February 2012, p. 1), points out that if a healthy woman aged 65 years or older has a normal bone mineral density (defined as a T score greater than -1.0), then about 15 years or so would be expected to pass before she would cross the threshold into the osteoporosis range (T score less than -2.5). As a fact, that is indeed true. However, utilizing those data to define clinical practice for the use of DXA in the postmenopausal population is fraught with problems.

Using the same data set, the authors have previously shown that about 55% of hip fractures (the archetypical fracture for osteoporosis) occur in women whose HMD is in the low-normal range (T score, -1.0 to -2.5). In other words, there are those who are at increased risk of fracture who do not have osteoporosis, a diagnosis made after an arbitrary cut-point is crossed.

The clinical issues are obvious. First, it is important to realize that while BMD is a determinant of fracture risk, it is not the only one. Risk-assessment tools help in evaluating the risk of fracture in those who do not have osteoporosis. (FRAX is the one most readily available in the United States.)

Second, the study participants were healthy, and many of the patients seen clinically have comorbidities that might have prohibited their participation in the study, but increase their risk of fracture.

Third, the risk of fracture is related to loss of bone mass as well as the absolute level of bone mass (determined in DXA measurements largely by height and weight at peak bone mass). Loss of mass creates abnormal architecture - think of a bridge with a few of its horizontal struts removed - and osteoporosis is largely an architectural problem.

The key is to determine the risk of fracture. Several years ago, a working group from the National Osteoporosis Foundation suggested that it would be cost effective to intervene if fracture risk over 10 years were 20% or greater and hip fracture risk greater than 3% - (based on FRAX, which uses hip BMD). While there is little argument that individuals with normal BMD (that is, a T score of better than -1.0) do not require monitoring annually or every second year, using the same data set suggests that a 3- to 5-year follow-up would catch many folks as they fall into the low bone mass category and allow risk assessment by FRAX or another tool. For those with low bone mass or who could be considered at high risk of rapid bone loss, current guidelines should be followed. It was noticeable in the study that many individuals who - by guidelines - should have had BMD testing, in fact had not, a feature of greater concern perhaps than the issue of follow-up.

Robert Lindsay, M.D. New York, N.Y
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Title Annotation:LETTERS
Author:Lindsay, Robert
Publication:OB GYN News
Article Type:Letter to the editor
Date:Mar 1, 2012
Previous Article:Who is "experienced"?
Next Article:Dr. Margaret Gourlay replied.

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