Screening Post-menopausal Women for Bone Mineral Level by Bioelectrical Impedance Spectroscopy of Dominant Arm

Comparison of whole body bone mineral density measurements between dual energy X-ray absorptiometry and novel bioelectrical impedance analysis

Bone mineral density (BMD) is a crucial indicator of osteoporosis. Bioelectrical impedance analysis (BIA) introduces a new method for assessing body composition, specifically BMD measurement. Compared with existing ultrasound and dual-energy X-ray absorptiometry for BMD screening and diagnosis, BIA has the advantages of safety, convenience and speed. However, the accuracy of BIA for BMD measurement needs to be explored. This study aimed to evaluate the accuracy of the novel BIA technique in conducting whole-body BMD assessments in the general population of Taiwan. Overall, 318 healthy adults in Taiwan (37.67 ± 19.44 years of age; 145 male and 173 female patients) were included. Whole-body BMD was measured via foot-to-foot BIA-StarBIA-201 (StarBIA Meditek Co. LTD, Taichung, Taiwan) and the dual-energy X-ray absorptiometry (DXA) Lunar Prodigy technology (GE Medical Systems, Madison, WI, USA). Linear regression analysis, Pearson's correlation coefficient, the Bland-Altman plot, and paired t tests were used. The whole-body BMDs measured by BIA and DXA were 1.139 ± 0.124 g/cm2 and 1.202 ± 0.168 g/cm2, respectively. The regression equation was y = 1.057x + 0.063. The Pearson correlation coefficient, mean difference, and limits of agreement were r = 0.737, - 0.053 g/cm2, and - 0.290-0.165 g/cm2, respectively. The regression equation was y = 1.057x + 0.063. The Pearson correlation coefficient, mean difference, and limits of agreement were r = 0.737 (p < 0.001), - 0.053 g/cm2, and - 0.290-0.165 g/cm2, respectively. Standing BIA was correlated with the DXA gold standard for estimating whole-body BMD in adults; however, its interchangeability remains limited. The potential bias in the measurement results of this study represents a current challenge with BIA compared with that of DXA, and there is still room for improvement. The convenient BIA method for measuring whole-body BMD may be useful in the application of primary screening and future development of BMD assessment methods. BIA is widely used to measure body composition, but its application to the measurement of BMD represents a novel technological breakthrough.

Impedance Analysis to Evaluate Nutritional Status in Physiological and Pathological Conditions

A thorough knowledge of body composition assessment techniques is the cornerstone for initiating a customized nutritional program. The second step is to consider the potential of their application in different physiological and pathological conditions and their effectiveness in the management of a monitoring pathway during dietary interventions. To date, bioimpedance analysis is the most effective and reliable method for assessing body composition due to its advantages in terms of speed of execution, non-invasiveness and low cost. Therefore, this review article aims to analyze the main concepts and application areas of bioimpedance measurement techniques, in particular vector frequency-based analysis (BIVA) systems, in order to assess their validity in both physiological and pathological conditions.

2D-ROC: a receiver operating surface and its illustrative application in clinical diagnostics

OBJECTIVE

When there are multiple tests, the receiver operating characteristic (ROC) curve analysis does not answer the question of how the individual tests can be combined in medicine.

APPROACH

In this study, 2D-ROC analysis is considered to calculate the correct classification rate (CCR) by using two independent test results. To obtain the best combination of paired tests, results were combined as 'BOTH', 'ANY' or 'AVERAGE' for the final 2D-ROC decision.

MAIN RESULTS

When the combined model was 'AVERAGE', the CCR was better than individual test results. At every correlation level, the 2D-ROC was shown to have a better CCR compared to individual tests, and when the correlations were lower, the CCR of 2D-ROC was even better. For uncorrelated test pairs (r  =  0, p   <  0.0001), in healthy and diseased populations with normal distributions, the improvement in CCR compared to individual tests were from 2.6% to 6.5%, and leptokurtic distribution of diseased population (k  =  2, p   <  0.0001) was better by 1.3% to 5.3%. As a clinical application, multifrequency bioelectric impedance (BI) spectroscopy characteristic frequency (f _c) and body mass index (BMI) measurements from 53 post-menopausal women were used in finding the 2D-ROC decision matrix to determine the hip area bone mineral deficiency. Using the 'AVERAGE' combination model, the CCR of 2D-ROC was 1.6% better than BMI and 14.8% better than fc alone. In the second clinical application of prediction of metabolic syndrome (MeS), parameters such as BMI, waist circumference, abnormal fasting blood sugar, triglyceride and high-density lipoprotein cholesterol were measured from 5533 subjects and combined to assess individual and paired success rates. Using the 'AVERAGE' combination model, the CCR of pairs were up to 6.1% better compared to using each parameter alone.

SIGNIFICANCE

Although the use of a simple 'AVERAGE' function was promising, the formulation for combining paired test results could be extended to include the deviations from ideal by weighted averaging of individual tests or by adding other parameters like their kurtosis or disease prevalence into the formulation.