Regular BMD monitoring may be unnecessary in some postmenopausal women

Routine bone mineral density testing of postmenopausal women within the first three years following initiation of potent bisphosphonate therapy may be misleading and unnecessary, according to data from the Fracture Intervention Trial.

"Nearly all women in the study (97.5%) had at least a modest increase in BMD over time," Katy J. Bell, research fellow in the Screening and Test Evaluation Program in the School of Public Health at the University of Sydney in Australia, told Endocrine Today. "Random background within-person variation in BMD was several times greater than the between-person variation in treatment effects, so that observations in individuals often showed apparent decreases of BMD."

In a secondary analysis of Fracture Intervention Trial data, the researchers compared the effects of alendronate with placebo in 2,027 postmenopausal women with vertebral fractures and 4,432 postmenopausal women without vertebral fractures.

Researchers randomly assigned patients to alendronate 5 mg daily or placebo for two years; at the second annual visit, alendronate was increased to 10 mg daily. Women with dietary calcium intake <1,000 mg per day at baseline were assigned to 500 mg of calcium daily and 250 IU of vitamin D.

After one year of treatment, there was an increase of 0.013 g/cm² (P<.001) compared with a decrease of 0.004 g/cm² per year in the placebo group (P<.001). In addition, the researchers observed an increase in BMD of 0.0085 g/cm² per year in the treatment group (P<.001).

Women in the treatment group had a significantly lower within-person variation (SD=0.012 g/cm²) compared with women in the placebo group (SD=0.014 g/cm²). The effect of alendronate on hip BMD (P=.008) remained strong even after allowing for the statistically significant random effects of background sources of variation.

"On the basis of this information, physicians may choose to not monitor their patients' BMD in the first few years after starting therapy," said Bell. "What is more important is for physicians to correctly identify those patients at high risk for fragility fractures before starting treatment, which can be done using clinical prediction tools that use demographic data and medical history as well as baseline BMD measurements. Once a decision to start a patient on therapy is made, clinic review may be used to discuss adherence and possible side effects of therapy, without any need to re-measure BMD." - by Jennifer Southall

Bell KJ. BMJ. 2009; 338:b2266.