Comparison of plain vertebral x-ray and dunal energy x-ray absorptiometry for the identification of older women for fracture prevention in primary care

Background: Recently, the dual-energy X-ray absorptiometry (DXA) diagnostic cut-off (T-score) for Australian Pharmaceutical Benefits Scheme (PBS) supported primary fracture prevention therapy with alendronate for older women (>70 years) has been changed from -3.0 to -2.5. Aim: To examine the impact of the expanded criteria for PBS-supported fracture prevention therapy in older women on case finding and cost. Methods: One thousand, nine hundred and eighty-three women, median age 76 years, not previously known to have low bone mineral density by DXA or a vertebral fracture underwent DXA scanning and a thoracolumbar X-ray. A woman was considered eligible for fracture prevention therapy if she had a T-score -2.5 at the femoral neck and/or the lumbar vertebrae (two to four) or at least one vertebral fracture of 20 deformity. Results: Seven hundred and forty-six women (37.6 ) met the new criteria as a case for PBS-subsidised fracture prevention therapy. Four hundred and thirty-one (21.7 ) had a T-score -2.5 on DXA compared with 10.6 (n = 210) with a T-score -3.0. Four hundred and eighty-three (24.4 ) had at least one vertebral fracture. Only 8.5 (n = 168) had both a T-score -2.5 and a prevalent vertebral fracture. The cost per case found by DXA equated to 460 compared with 398 for screening by thoracolumbar X-ray. Conclusions: The use of either DXA or X-ray will identify approximately two-thirds of women aged 70 years and over who would be eligible for fracture prevention. The use of X-ray would identify a marginally larger number of women and at lower financial cost but involve substantially greater radiation exposure.