A simple method for determining the optimum intervals for re-testing bone mineral density in women with osteopenia has been developed by New Zealand clinicians.
Their finding that fracture risk increases at a consistent rate across a range of osteopenic BMDs will help reduce unnecessary re-testing by predicting when the threshold for treatment is likely to occur, they said.
Using the FRAX fracture prediction algorithm, Professor Ian Reid and colleagues at Auckland University modelled fracture risk at five-year intervals in three different clinical scenarios based on a 65 year-old woman without other risk factors and with baseline BMD T-score levels of either -1.0, -1.5, or -2.0.
Fracture risk depended mainly on age and BMD and bone loss in older women was relatively constant at around 1% annually, they noted in the Journal of Bone and Mineral Research.
The study found that hip fracture risk would rise progressively over a 15 year period and doubling times were similar across osteopenic BMD levels at 4.8, 5.1, and 5.6 years for T-scores of -1.0, -1.5, and -2.0, respectively.
The “remarkable consistency” meant that a in doubling times period of five-six years could be used in clinical practice when determining the appropriate interval for follow-up BMD measurements, the researchers suggested.
Thus a woman with a 1% risk of fracture at baseline would be expected to reach a 2% risk at four years and hit the 3% threshold for preventive treatment at about six years, they said. In contrast, a women with a baseline risk of 0.6% would only reach the 3% threshold after a decade, and re-testing could be timed to anticipate that, they said.
“This knowledge can avert the waste associated with too frequent BMD testing during follow up and allow patients to have clear expectations of when intervention is likely to be needed,” they concluded.