Osteoporosis related fractures result in a significant individual and societal burden. This diagnosis is usually based on finding low bone mineral density (BMD) using dual energy x-ray absorptiometry (DXA). This study assessed the effectiveness of repeated BMD testing in routine clinical practice as a predictor of treatment related fracture risk.
METHODSSince 1997, routine DXA baseline screening has been completed for women in Manitoba, Canada, at the age of 65 years, as well as younger women with additional risk factors. This program′s recommended interval for follow-up is three years for most patients and at least five years for those reported as low risk. From this database, women 40 years or older were identified, each of whom had undergone at least one follow-up examination. Using a linkage witha province-wide retail pharmacy network, women were identified who had not been receiving osteoporosis treatment during the year before baseline testing, who had then initiated. The DXA Scans were reviewed to determine whether subsequent scans revealed stable, decreased or increased BMD. Incident fractures were recorded and compared to the DXA data.
The final sample were 6629 women, with an average age of 64.3 years at baseline. Of these. 57.2% met the BMD criteria for osteoporosis at one or more sites. Biphosphonates were prescribed in 84.9% of the women. The mean interval between the first and second BMD tests was 4.5 years. For the total hip, a detectable increase was seen in 30.4% of the women and a detectable decrease in 18.8%.
RESULTSAs compared with stable total hip BMD, a decrease in total hip BMD was associated with a greater risk of fracture (P<0.001). while an increase was associated with lower risk of fracture (P＝0.004). A one standsrd devistion increase in total hip BMD was associated with 19% relative reduction in the fracture hazard rate.
CONCLUSIONThis Canadian study found that treatment related increases in total hip BMD are associated with a reduction of fracture risk, while decreases in BMD are associsted with an increased risk of fracture.