Osteoporosis screening in postmenopausal women
DEXA, used to measure bone mineral density, is useful in detecting osteoporosis.
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At a glance
- Approximately 50% of white women will have a fracture attributable to osteoporosis at some point in their lives.
- Data show that more women with diabetes than without suffer osteoporotic fractures.
- Any test designed to check bone mineral content at only one site will not be as accurate as a composite evaluation.
- The advantages of densitometry are its low cost, portability, and ease of use.
Many can remember an older female family member who had the classic dowager's hump in her upper spine and seemed to literally shrink between gatherings. Unfortunately, osteoporosis that was considered a common consequence of aging in that generation often still goes undetected in spite of widespread availability of screening methods. Even with these tools, many women every year learn of their osteoporosis only after suffering an osteoporosis-related fracture.
The North American Menopause Society's 2010 position statement for the management of osteoporosis emphasizes some significant changes with regard to the way this condition is treated in primary-care practice.1 These changes illustrate the increasing focus now placed on prevention in health care in the United States.
Prevalence and significance
In the United States, there are nearly eight million women with osteoporosis, and an estimated 34 million with osteopenia.2,3 While postural body changes are the most obvious consequence of osteoporosis, the immense increase in fracture risk is the most significant. Approximately 50% of white women with osteoporosis will have a fracture attributable to the disease at some point in their lives.2,3 Sadly, many of these will be hip fractures that have a resultant mortality of nearly 20% at one year and a 25% incidence of need for long-term skilled nursing facility care.2-4
When injury and pain fail to convey real significance, dollars usually tell the rest of the story. According to the U.S. Department of Health & Human Services, the typical cost of a hip fracture in 2002 was between $34,000 and $43,000, with osteoporotic fractures costing our health systems nearly $18 billion in just one year.5,6 If statistics and money still do not depict the impact of this disease, consider the immeasurable but significant secondary decline in mental and psychosocial quality of life after a hip fracture.7
Types of osteoporosis screening
Clinical assessment. In this age of high-technology medical instrumentation, it is easy to overlook some of the simplest screening methods. Basic health histories, nutrition, and clinical assessments are still the most accurate forms of primary osteoporosis screening.3,4,8 The Simple Calculated Osteoporosis Risk Estimation (SCORE) tool is a six-item instrument that has a sensitivity of 91% and a specificity of 40%.3 SCORE is a calculator model that can be used to determine whether a woman would benefit from further, more formal screening.9 Another aid that patients may utilize prior to seeking health-care assistance is the Osteoporosis Self-assessment Tool (OST).10,11 This instrument is particularly useful in patient education arenas as a means to encourage women who score in the at-risk zones to seek professional intervention.
Other assessment options include the Osteoporosis Index of Risk (OSIRIS); the Osteoporosis Risk Assessment Instrument (ORAI); and the age, body size, no-estrogen (ABONE) decision tools.11 Each of these is useful in determining the need for further risk assessment.
The U.S. Preventive Services Task Force's (USPSTF) review of the sensitivity of these assessment tools revealed that while the factors of race, age, body weight, estrogen-replacement use, previous fracture, family history, falls, and physical activity were generally associated with positive predictive values of osteoporosis, multiple studies found a wide variation in the accuracy of this prediction.2 Screening results varied and were dependent on the makeup of the groups studied when each tool was tested and validated. The SCORE and the ORAI had the best sensitivity and specificity, at 99.6%/17.9% and 97.5%/27.8%, respectively.11
In addition to screening for pure risk factors for osteoporosis, recent investigations have shown associations between certain comorbidities that are very common in postmenopausal women. The Journal of the American Medical Association reported the results of two large studies connecting cardiovascular disease with osteoporosis attributable to genetic associations.12,13 Investigators correlated the genome that facilitates LDL-receptor activity with a higher incidence of osteoporosis in white populations.13
Researchers reported new findings associated with an enzyme level to generalized oxidative stress, cardiovascular disease, and osteoporosis. This multi-site study found that the activity of paraoxonase 1 was directly proportionate to the degree of oxidative damage in the tissues systems evaluated. This was yet another study linking osteoporosis to another major illness associated with aging.12
Types 1 and 2 diabetes have also been associated with osteoporosis.14,15 There are multiple theories as to the direct mechanisms of influence, but the data are clear that more women with diabetes than without this diagnosis suffer osteoporotic fractures.16 The literature suggests that the bone density may be influenced directly and indirectly by the disease. The well-known microvascular damage caused by diabetes is associated with bone-loss changes.17 Fracture rates are definitely higher in women with poorly controlled diabetes than those with well-controlled disease.16
The indirect correlation of diabetes and osteoporosis is reflected in the high incidence of obesity, peripheral neuropathy, and sedentary lifestyle of many diabetic patients.18,19 Many researchers believe diabetes characteristics are highly contributory to low bone mass and high fall frequency.
Finally, a postmenopausal women presenting with a low-trauma fracture would virtually scream osteoporosis to the educated practitioner. However, according to Health Employer Data Information System (HEDIS) reports from 2004, only 19% of these women were actually screened and/or treated for osteoporosis.20,21 Even without primary preventive assessment and screening, a fracture should be an automatic red flag that signals the practitioner to conduct further evaluations for osteoporosis.
Bone densitometry. Bone density can be measured by any of several different methods.22 Dual-energy x-ray absorptiometry (DEXA) quantitatively calculates the photon absorption of the minerals in bone tissue and is clinically considered the gold standard in osteoporosis screening.2,23 DEXA can measure the bone density of the whole body or selected regions (known as peripheral scanning). The typical DEXA scan consists of selected regions of the spine, hips, and wrist because these are the areas first and most often affected by osteoporotic fracture.2,7,11
Ultrasound can also be used to measure bone density. Quantitative ultrasound (QUS) uses the speed at which sound travels through the bone to indicate density.2,24 QUS and DEXA results correlate poorly, and this has lead many investigators to deem bone density measured by ultrasound inaccurate.7,25 Investigators conducting more in-depth studies have shown that it is not a question of accuracy as much as staging of the disease. Physiologically, bone tissue in the calcaneous (the site used in ultrasound techniques) undergoes remodeling much more slowly than central bone, such as that found in the spine and hip.7 In addition, since bone mineral content changes at different rates in different sites of the body, any test designed to check only one site will not be as accurate as a composite evaluation. Consequently, osteoporotic changes may not be seen in QUS as early in the disease as they are seen with a DEXA scan. Women who were diagnosed by QUS were found to be four times more likely to have a fracture in the following year than women screened with DEXA.2
Combined technology. In 2008, the National Osteoporosis Foundation, in conjunction with the International Society for Clinical Densitometry, the International Osteoporosis Foundation (IOF), and the American Society for Bone and Mineral Research, used the World Health Organization's (WHO) diagnostic criteria and other known risk factors to form the Fracture Risk Assessment Tool (FRAX).26,27 The FRAX is a Web-based calculation instrument that uses such office-assessment information as family history and personal health history as well as measured bone mineral density (BMD).27 The health-care provider enters the requested information into the calculator, and the result is a percentage probability of sustaining an osteoporotic fracture within the next 10 years.27 Ideal for use in primary-care settings, FRAX makes use of independent risk factors not often accounted for in other measures.26 The performance of FRAX has been validated in 11 independent population groups from Europe, North America, Australia, and Japan.26 In our technologically advanced era, most medical offices have access to the internet, so this tool could lead to improved risk assessment and prevention.