Bone Density Testing

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    Bone Density Testing

    Before you agree to take medication,  I suggest you read:  "The Myth of Osteoporosis"  by Gillian Sanson
     
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    Re: Bone Density Testing

    High bone density does not necessarily equate with good bone structure.  Bisphosphonates increase bone density.  Do they improve structure?  I don't think so. 
     
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    Overtreated: our risk, our expense

    With the development of high-resolution DEXA, introduced in 1987 by the Hologic QXR, and with the 1996 FDA clearance for Fosamax from Merck, bone-density measurements and therapies began to provide leverage for yet another episode of medical cost inflation. As a previous comment suggested, the missing element has been strong evidence for durable health benefits over health risks, as contrasted with mere laboratory results--a situation that has a close parallel in blood lipid measurements and statin therapies.

    [ Margaret L. Gourlay, MD, et al., Bone-density testing interval and transition to osteoporosis in older women, New England Journal of Medicine 366(3):225-233, 2012, abstract at http://www.nejm.org/doi/full/10.1056/NEJMoa1107142 ]
    [ Gina Kolata, Osteoporosis patients advised to delay bone density retests, New York Times, January 19, 2012, at http://www.nytimes.com/2012/01/19/health/bone-density-tests-for-osteoporosis-can-wait-study-says.html ]
    [ Angelo Licata, MD, Bone density vs. bone quality: what's a clinician to do?, Cleveland Clinic Journal of Medicine 76(6):331-336, 2009, at http://www.ccjm.org/content/76/6/331.long ]
    [ John Abramson, MD, Overdosed America, 2004, Harper-Collins]
    [ Shannon Brownlee, Overtreated, 2007, Bloomsbury ]

     
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    Bone strength: unmeasured

    Readers venturing into Dr. Licata's interesting article will benefit from a comfort-level with quantitative information to take away his understated conclusion. Despite about 180 years of research, there is still no reliable, non-invasive and non-destructive measurement for bone quality.

    [ Angelo Licata, MD, Bone density vs. bone quality: what's a clinician to do?, Cleveland Clinic Journal of Medicine 76(6):331-336, 2009, at http://www.ccjm.org/content/76/6/331.long ]

    Treatments that can be less risky than alendronate and other bisphosphonates are available, but no reliable and direct way has been found to measure treatment effects. Bone density and modulus ("stiffness") are all that is now measured. Alone or in combination, they are only weakly correlated with bone strength.

    Engineers won't find that surprising, since practical measurements of strength for all ordinary materials rely on actually fracturing samples of them.

     
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    Fracture risk estimation

    A key element encouraging bone-density screening is increasing primary-care physician earnings by providing more care. In the slow-moving field of osteoporosis diagnosis and treatment, the latest gadget is a "risk assessment" survey known as the Fracture Risk Assessment Tool (FRAX), produced at Sheffield University (UK) by Prof. Eugene McCloskey and colleagues. [ J.A. Kanis, O. Johnell, A. Oden, H. Johansson and E. McCloskey, FRAX and the assessment of fracture probability in men and women from the UK, Osteoporosis International 19(4):385–397, 2008, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267485/ ]

    The tool is a questionnaire, an atttempt to improve on the older Garvan nomogram. It does not require the intervention of a physician or result of a medical test. The topics of questions involve population group, sex, weight, height, arthritis diagnosis, history of fractures, family history of osteoporosis, tobacco use, heavy alcohol use and glucocorticoid hormone use.

    An on-line version of the tool is available free from Sheffield. [at http://www.sheffield.ac.uk/FRAX/ under the heading "Calculation Tool"] It does require a media player, preferably Flash. When there is no bone-mineral test result available, for the question Femoral neck BMD, choose "T-score" and enter a zero. By trying out different answers to questions, one can explore ranges of factor weights and estimates.

    Research shows predictions of FRAX as only qualitative, applied to individuals. Such a tool may be a small assist to a physician but has not been cleared by FDA for use in diagnosis or therapy. A physician advertising such a tool might instead be engaged in mystification. [ M.J. Bolland, et al., Evaluation of the FRAX and Garvan fracture risk calculators in older women, Bone Mineral Research 26(2):420-427, 2011, at http://www.ncbi.nlm.nih.gov/pubmed/20721930 ]

     
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    Loose correlation between clinical lab test and fracture risk

    Writing recently in the NY Times, Nicholas Bakalar reported on a finding from the long-term, ongoing project called Study of Women's Health Across the Nation (SWAN). NTX testing of urine samples was correlated with risks of bone fracture. [ Urine test may predict women's bone risk, New York Times, August 6, 2012, at http://well.blogs.nytimes.com/2012/08/06/urine-test-may-predict-womens-bone-risk/ ]

    Unfortunately, Mr. Bakalar, who is sometimes a more careful reporter, did not describe the clinical test accurately. It is hardly a surprise that NTX levels (cross-linked N-telopeptide of Type 1 collagen, measured with an enzyme-linked antibody) will correlate with bone fractures, since the test was designed to measure an osteoporosis marker. FDA-approved home testing kits for urine samples have been available since 2001, under the Osteomark brand.

    The recent results found NTX levels measured for women who reported bone fractures over about 8 years averaged about 10 percent higher than those measured for women who did not report bone fractures. [ Jane A. Cauley, et al., Bone resorption and fracture across the menopausal transition, Menopause, preprint July 30, 2012, abstract available at http://www.ncbi.nlm.nih.gov/pubmed/22850443 ]

    While that finding may be scientifically interesting, it is not particularly useful for clinical medicine because of the well known, high variability in NTX levels, particularly when measured in urine samples. Measured levels can vary by 20 percent or more from day to day. A systematic study several years ago reported, "to be 90% confident that a decrease in NTX after initiation of antiresorptive therapy in an individual patient is not caused by variability alone, a 31% decrease in urine NTX...is required." [ Richard Eastell, et al., Biological variability of serum and urinary N-telopeptides of type I collagen in postmenopausal women, Journal of Bone Mineral Research 15(3):594-598, 2000, abstract available at http://www.ncbi.nlm.nih.gov/pubmed/10750575 ]

    Neither the authors of the SWAN report nor Mr. Bakalar of the NY Times cautioned their readers that NTX testing of urine samples is not reliable enough to be used for screening individual patients without other, confirming tests.

     
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    Re: Bone Density Testing

    Teriparatide
    Forteo (teriparatide), an injectable form of human parathyroid hormone, is approved for postmenopausal women and men with osteoporosis who are at high risk for having a fracture.

    Unlike the other drugs used in osteoporosis, Forteo acts by stimulating new bone formation in both the spine and the hip. Given as a daily injection for up to 24 months, it increases bone tissue and bone strength, and has been shown to reduce the risk of spine and other fractures.

    Side effects include nausea, dizziness and leg cramps.

    Forteo also has a black box warning from the FDA because of the small possibility that Forteo may increase your risk of developing osteosarcoma, a rare but serious cancer. Because of this risk, you should not use Forteo unless you have osteoporosis and at least one of the following conditions is met: You have already had at least one bone fracture; your doctor has determined that you are at high risk of fractures; or you cannot take or do not respond to other medications for osteoporosis.

    Thanks, but,  No Thanks!
    (regarding suggested osteoporosis meds)

     

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