Monitoring Osteoporosis Therapy with Bone Densitometry: Misleading Changes and Regression to the Mean
Clinical Briefs
By Louis Kuritzky, MD
Monitoring Osteoporosis Therapy with Bone Densitometry: Misleading Changes and Regression to the Mean
Bone mineral density (bmd) is often used as a surrogate marker of efficacy for osteoporosis treatments. Cummings and colleagues evaluated whether the small number of women who are reported to lose BMD during treatment with an active agent (alendronate or raloxifene, in this case) are indeed losing BMD, which should be consistent and continuous over time, or whether, with continued monitoring, these women would tend to regain bone mass, indicative of a regression to the mean (RTM) type effect.
Study subjects (n = 6588) were composed of participants in the Fracture Intervention Trial and Multiple Outcome of Raloxifene Evaluation trial. Subjects had to have completed two years of treatment in the trials. Outcomes measured were hip and spine BMD at baseline, 12, and 24 months.
On average, treatment resulted in an increase of 2.2% in the hip and 4.5% in the spine BMD at the end of year 1. Of women who lost BMD during year 1, those with the greatest loss showed the steepest slope of increase BMD during year 2. Cummings et al comment that indeed individuals who have measurements disparate from the mean tend to demonstrate RTM effect when followed for longer time periods. One conclusion to be drawn is that treatment of osteoporosis with pharmacotherapy may still be continued even in persons who initially lose BMD, as most will reverse this trend with continued therapy.
Cummings SR, et al. JAMA 2000;283: 1318-1321.
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