Utilization of DXA Bone Mineral Densitometry in Ontario: An Evidence-Based Analysis

Systematic reviews and analyses of administrative data were performed to determine the appropriate use of bone mineral density (BMD) assessments using dual energy x-ray absorptiometry (DXA), and the associated trends in wrist and hip fractures in Ontario.

DUAL ENERGY X-RAY ABSORPTIOMETRY BONE MINERAL DENSITY ASSESSMENT: Dual energy x-ray absorptiometry bone densitometers measure bone density based on differential absorption of 2 x-ray beams by bone and soft tissues. It is the gold standard for detecting and diagnosing osteoporosis, a systemic disease characterized by low bone density and altered bone structure, resulting in low bone strength and increased risk of fractures. The test is fast (approximately 10 minutes) and accurate (exceeds 90% at the hip), with low radiation (1/3 to 1/5 of that from a chest x-ray). DXA densitometers are licensed as Class 3 medical devices in Canada. The World Health Organization has established criteria for osteoporosis and osteopenia based on DXA BMD measurements: osteoporosis is defined as a BMD that is >2.5 standard deviations below the mean BMD for normal young adults (i.e. T-score <-2.5), while osteopenia is defined as BMD that is more than 1 standard deviation but less than 2.5 standard deviation below the mean for normal young adults (i.e. T-score< -1 & ≥-2.5). DXA densitometry is presently an insured health service in Ontario.

BURDEN OF DISEASE: The Canadian Multicenter Osteoporosis Study (CaMos) found that 16% of Canadian women and 6.6% of Canadian men have osteoporosis based on the WHO criteria, with prevalence increasing with age. Osteopenia was found in 49.6% of Canadian women and 39% of Canadian men. In Ontario, it is estimated that nearly 530,000 Ontarians have some degrees of osteoporosis. Osteoporosis-related fragility fractures occur most often in the wrist, femur and pelvis. These fractures, particularly those in the hip, are associated with increased mortality, and decreased functional capacity and quality of life. A Canadian study showed that at 1 year after a hip fracture, the mortality rate was 20%. Another 20% required institutional care, 40% were unable to walk independently, and there was lower health-related quality of life due to attributes such as pain, decreased mobility and decreased ability to self-care. The cost of osteoporosis and osteoporotic fractures in Canada was estimated to be $1.3 billion in 1993.

With 2 exceptions, almost all guidelines address only women. None of the guidelines recommend blanket population-based BMD testing. Instead, all guidelines recommend BMD testing in people at risk of osteoporosis, predominantly women aged 65 years or older. For women under 65 years of age, BMD testing is recommended only if one major or two minor risk factors for osteoporosis exist. Osteoporosis Canada did not restrict its recommendations to women, and thus their guidelines apply to both sexes. Major risk factors are age greater than or equal to 65 years, a history of previous fractures, family history (especially parental history) of fracture, and medication or disease conditions that affect bone metabolism (such as long-term glucocorticoid therapy). Minor risk factors include low body mass index, low calcium intake, alcohol consumption, and smoking.

The Ontario Health Insurance Program (OHIP) Schedule presently reimburses DXA BMD at the hip and spine. Measurements at both sites are required if feasible. Patients at low risk of accelerated bone loss are limited to one BMD test within any 24-month period, but there are no restrictions on people at high risk. The total fee including the professional and technical components for a test involving 2 or more sites is $106.00 (Cdn).

This review consisted of 2 parts. The first part was an analysis of Ontario administrative data relating to DXA BMD, wrist and hip fractures, and use of antiresorptive drugs in people aged 65 years and older. The Institute for Clinical Evaluative Sciences extracted data from the OHIP claims database, the Canadian Institute for Health Information hospital discharge abstract database, the National Ambulatory Care Reporting System, and the Ontario Drug Benefit database using OHIP and ICD-10 codes. The data was analyzed to examine the trends in DXA BMD use from 1992 to 2005, and to identify areas requiring improvement. The second part included systematic reviews and analyses of evidence relating to issues identified in the analyses of utilization data. Altogether, 8 reviews and qualitative syntheses were performed, consisting of 28 published systematic reviews and/or meta-analyses, 34 randomized controlled trials, and 63 observational studies.

Analysis of administrative data showed a 10-fold increase in the number of BMD tests in Ontario between 1993 and 2005.OHIP claims for BMD tests are presently increasing at a rate of 6 to 7% per year. Approximately 500,000 tests were performed in 2005/06 with an age-adjusted rate of 8,600 tests per 100,000 population.Women accounted for 90 % of all BMD tests performed in the province.In 2005/06, there was a 2-fold variation in the rate of DXA BMD tests across local integrated health networks, but a 10-fold variation between the county with the highest rate (Toronto) and that with the lowest rate (Kenora). The analysis also showed that:With the increased use of BMD, there was a concomitant increase in the use of antiresorptive drugs (as shown in people 65 years and older) and a decrease in the rate of hip fractures in people age 50 years and older.Repeat BMD made up approximately 41% of all tests. Most of the people (>90%) who had annual BMD tests in a 2-year or 3-year period were coded as being at high risk for osteoporosis.18% (20,865) of the people who had a repeat BMD within a 24-month period and 34% (98,058) of the people who had one BMD test in a 3-year period were under 65 years, had no fracture in the year, and coded as low-risk.Only 19% of people age greater than 65 years underwent BMD testing and 41% received osteoporosis treatment during the year following a fracture.Men accounted for 24% of all hip fractures and 21 % of all wrist fractures, but only 10% of BMD tests. The rates of BMD tests and treatment in men after a fracture were only half of those in women.In both men and women, the rate of hip and wrist fractures mainly increased after age 65 with the sharpest increase occurring after age 80 years.

SERIAL BONE MINERAL DENSITY TESTING FOR PEOPLE NOT RECEIVING OSTEOPOROSIS TREATMENT: A systematic review showed that the mean rate of bone loss in people not receiving osteoporosis treatment (including postmenopausal women) is generally less than 1% per year. Higher rates of bone loss were reported for people with disease conditions or on medications that affect bone metabolism. In order to be considered a genuine biological change, the change in BMD between serial measurements must exceed the least significant change (variability) of the testing, ranging from 2.77% to 8% for precisions ranging from 1% to 3% respectively. Progression in BMD was analyzed, using different rates of baseline BMD values, rates of bone loss, precision, and BMD value for initiating treatment. The analyses showed that serial BMD measurements every 24 months (as per OHIP policy for low-risk individuals) is not necessary for people with no major risk factors for osteoporosis, provided that the baseline BMD is normal (T-score ≥ -1), and the rate of bone loss is less than or equal to 1% per year. The analyses showed that for someone with a normal baseline BMD and a rate of bone loss of less than 1% per year, the change in BMD is not likely to exceed least significant change (even for a 1% precision) in less than 3 years after the baseline test, and is not likely to drop to a BMD level that requires initiation of treatment in less than 16 years after the baseline test.

Seven published meta-analysis of randomized controlled trials (RCTs) and 2 recent RCTs on BMD monitoring during osteoporosis therapy showed that although higher increases in BMD were generally associated with reduced risk of fracture, the change in BMD only explained a small percentage of the fracture risk reduction.Studies showed that some people with small or no increase in BMD during treatment experienced significant fracture risk reduction, indicating that other factors such as improved bone microarchitecture might have contributed to fracture risk reduction.There is conflicting evidence relating to the role of BMD testing in improving patient compliance with osteoporosis therapy.Even though BMD may not be a perfect surrogate for reduction in fracture risk when monitoring responses to osteoporosis therapy, experts advised that it is still the only reliable test available for this purpose.A systematic review conducted by the Medical Advisory Secretariat showed that the magnitude of increases in BMD during osteoporosis drug therapy varied among medications. Although most of the studies yielded mean percentage increases in BMD from baseline that did not exceed the least significant change for a 2% precision after 1 year of treatment, there were some exceptions.

A review of 3 published pooled analyses of observational studies and 12 prospective population-based observational studies showed that the presence of any prevalent fracture increases the relative risk for future fractures by approximately 2-fold or more. (ABSTRACT TRUNCATED)