Clinical significance of small-sample estimation in measuring the changes of minimal bone mineral density in vertebra body with Dual-energy X-ray bone densometer under different conditions

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Abstract

OBJECTIVE:

To explore the short-time precision of bone mineral density minimum with clinical significance after measuring bone mineral density (BMD) of aluminum model of lumbar vertebra, live lumbar vertebra, dead lumbar vertebra (with soft tissue) with DPX-MD dual-energy X-ray bone densometer, so as to provide evidence for clinical significance of small-sample estimation in measuring the changes of BMD in vertebra body with Dual-energy X-ray bone densometer under different conditions.

METHODS:

The experiment was performed at the Human Anatomy Laboratory and Bone Density Laboratory of North Sichuan Medical College from May 2004 to December 2006. ①Source of aluminum model: self-check die-block equipped by DPX-MD dual-energy X-ray bone densometer produced by American LUNAR Company; three centrums were obtained from a 38 years old healthy male, a 40 years old osteoporosis male, and a 62 years old osteopenia female. One dead vertebral body was provided by Human Anatomy Laboratory of North Sichuan Medical College. ②Measurements and evaluation: Bone density of vertebral body was measured by bone densitometer, 3 times per day for 5 successive days. Double end of aluminum model and dead vertebral body were fixed at the height of 6.5 cm with small wood block, and then put into water bath with the height of 15 cm. The operation was performed by one person to decrease operation error. Variation coefficient of each vertebral body and BMD was measured, and the smallest number of samples was evaluated.

RESULTS:

①Base on the premise that conclusion is reliable; the variation coefficient of BMD was small in the aluminum model and healthy male, which need small samples for estimation, especially in aluminum model. The variation coefficient of BMD of osteopenia female and dead vertebral body was great, which need more samples for estimation. 2Compared with the variation coefficient of vertebral body BMD, the variation coefficient of L2-4 was smaller, so base on the premise that conclusion is reliable; number of needed samples could be small. ③Extremely specific vertebral body could be estimated with more than a thousand cases.

CONCLUSION:

①The minimum number of samples for estimation is different due to different conditions of tested objects. ② Quantitative detection sample size should be estimated correctly when measuring the changes of BMD with Dual-energy X-ray bone densometer in determining the therapeutic effects of drugs. Severity of osteoporosis and different conditions, such as hyperostosis should be attracted more attention.

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