Measurement of bone density: indication of a benefit in postmenopausal women, also in those without pre-existing fractures
Osteodensitometry helps identify persons who may benefit from therapy / However, the benefit of bone density monitoring during therapy is unclear
A large decrease in bone density (osteoporosis) may promote fractures. For this reason, drugs aiming to prevent osteoporosis-related fractures by inhibiting the breaking down or supporting the building up of bone have already been on the market for decades. With the help of bone density measurement (osteodensitometry) those persons can be identified who potentially benefit from such a targeted drug therapy. This has been scientifically proven for a long time, at least in postmenopausal women who previously suffered an osteoporosis-related fracture. A final report by the German Institute for Quality and Efficiency in Health Care (IQWiG) now concludes that women without pre-existing fractures may also benefit from osteodensitometry.
To date, health insurance funds pay for measurement only after a fracture
To date, bone density measurement is reimbursed by the German statutory health insurance funds only for persons who have already suffered an osteoporosis-related fracture and show other signs of osteoporosis. However, some professional societies also recommend the measurement of bone density in men and women who have not yet suffered a fracture, but show specific risk factors in this respect. The hope is to reduce the fracture risk by preventive treatment. The Federal Joint Committee (G-BA) therefore commissioned IQWiG to specifically assess the benefit of bone density measurement in men and women who had not yet suffered the type of fracture typically related to low bone density.
Bone density decreases with age
The stability of bones depends on a number of factors; bone density is only one of several. Dual-energy X-ray absorptiometry (DXA or DEXA) is the standard method of measurement, which is applied at the lumbar spine or femoral neck. With this method the bone is screened by weak X-rays. Depending on the bone density value, the intensity of the X-rays is attenuated to a greater or lesser extent. The result of the measurement is compared to the average value of a healthy young adult.
It is a normal ageing process that bone density slowly decreases from the age of about 20. However, this decrease varies greatly between individuals, and depends not only on age, gender, and genetic disposition, but also on such factors as low body weight, low dietary calcium intake, a lack of physical exercise, and smoking. Certain chronic illnesses and the related intake of medications can also promote a decrease in bone density.
This decrease often has no consequences for a person's health, but if the bone density is greatly reduced (osteoporosis), there is a greater risk of fracture even for the slightest reason. The vertebral bodies, femoral neck and lower arm are particularly vulnerable. These fractures occur mostly in women older than 65.
The therapy studies considered included nearly 25,000 women
IQWiG initially searched for studies with participants who had been randomly allocated to 2 groups. Persons in the test group had undergone bone density measurement and, depending on the result, treatment had been initiated. In contrast, no such measurement had been performed in the comparator group. However, from the studies IQWiG identified that covered the whole diagnostic and therapeutic chain, no robust conclusions could be inferred on the benefit or harm of health care strategies including or excluding bone density measurement.
Nevertheless, what IQWiG and its external experts did find were therapy studies in which low bone density had been a criterion for inclusion in the study. In part, these therapy studies had also investigated from which decrease in bone density patients would benefit from treatment with certain medications. IQWiG was able to include 15 such therapy studies in the assessment. Overall nearly 25,000 women (and only a few men) had participated; they had been followed up for a period of at least 2 years after measurement.
Therapy may prevent fractures
In all therapy studies, the women's bone density had been measured by means of DXA at the start of the study. The studies provided an indication that treatment with certain medications may effectively prevent hip, vertebral body and other types of fractures. However, this benefit of treatment is largely restricted to women with very low bone density (following the definition of the World Health Organization, WHO).
According to the study findings, DXA can help to distinguish between women for whom treatment is meaningful and those for whom a benefit from treatment is not to be expected. This distinction is advantageous, as the available preventive medications are not free of risks and adverse effects. The report did not identify any diagnostic procedure representing an equivalent alternative to DXA.
One of the research questions of the project was to test whether measurement within the framework of therapy monitoring is potentially beneficial, namely, if such a measurement enables better decision-making as to whether a therapy should be continued, adapted or discontinued. However, due to a lack of suitable studies no conclusion is possible in this regard.
Low bone density also increases fracture risk in men
The relationship between low bone density and an increased fracture risk in postmenopausal women has been repeatedly demonstrated since the mid-nineties. This relationship has been less clear in men. As the IQWiG report shows, studies also provide proof of a statistical relationship between low bone density and an increased hip fracture risk in men if bone density was measured with the DXA test at the site of the femoral neck. In contrast, this relationship cannot be inferred from the available studies in men and women with very low bone density caused by a different underlying condition (secondary osteoporosis). However, this is primarily due to the fact that data for this patient group are scarce.
Procedure of report production
IQWiG published the preliminary results, the preliminary report, at the beginning of July 2009 and interested persons and parties were invited to submit comments. When the commenting procedure ended, the preliminary report was revised and sent as a final report to the contracting agency, the Federal Joint Committee, at the end of 2010. Documentation of the written comments and the minutes of the oral debate are published in a separate document simultaneously with the final report. The report was produced in collaboration with external experts.
An overview of the background, methods and further results of the final report is provided in the following executive summary.
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