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For many conditions, screening is conducted at arbitrary intervals — and bone-mineral density (BMD) testing is no exception. In a prospective study, researchers sought to determine reasonable intervals for BMD screening. They identified 5000 women (age, ≥67) without osteoporosis at baseline BMD testing and followed them for up to 15 years. Baseline BMD levels were classified as normal (femoral neck or total-hip T scores, –1.00 or higher) or as indicative of mild osteopenia (T-score range, –1.01 to –1.49), moderate osteopenia (range, –1.50 to –1.99), or advanced osteopenia (range, –2.00 to –2.49).
The interval during which at least 10% of women developed osteoporosis (T score –2.5 or lower) was longer than 15 years for those whose baseline BMDs were normal or only mildly osteopenic and was 5 years for those with baseline moderate osteopenia and 1 year for those with baseline advanced osteopenia. These estimates changed very little after adjustment for age, body-mass index, and several other relevant variables. The estimated time for 2% of women to experience hip or vertebral fractures was at least 15 years for those with normal BMD or mild osteopenia and 5 years for those with moderate-to-advanced osteopenia.
Gourlay ML et al. Bone-density testing interval and transition to osteoporosis in older women. N Engl J Med 2012 Jan 19; 366:225. (http://dx.doi.org/10.1056/NEJMoa1107142)
Comment
This analysis challenges the practice of repeating bone-mineral density tests routinely every few years. Very few older women with normal BMD developed osteoporosis within 15 years after a normal test result. For women whose baseline BMDs fell within the lower portion of the osteopenic range, screening intervals required to avoid missing the development of osteoporosis were progressively shorter. Future updates of screening guidelines should incorporate these findings. However, keep in mind that factors other than BMD affect fracture risk, and that this study did not address who might benefit from treatment.