Precision and Accuracy of DXA and pQCT for Densitometry of the Rat Femur

Measurements of bone mineral density and bone mineral content are key data in the study of osteoporosis and pathologic skeletal disease. Dual-energy X-ray absorptiometry and peripheral quantitative computed tomography are used in human and small animal studies. The purpose of this study was to evaluate the precision, accuracy, and systematic bias of measurement of the rat femur. Comparing machine-measured parameters with standard, nonradiographic measurements, we assessed validation of relative and absolute accuracy. Regression analysis and calculations of percent difference from standard values were used to determine the accuracy of each densitometry technique. Machine-specific and subject-specific precision was evaluated for each densitometer using repeated scans to calculate coefficients of variation. Each of the methods of densitometry examined in this study produced comparable results and was sensitive to small changes following experimental stimuli. Further, our assessment of the precision and accuracy observed between methods of scanning excised rat femurs validates our data acquisition method and serves as a foundation for future densitometry studies.