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ARS Home » Plains Area » Grand Forks, North Dakota » Grand Forks Human Nutrition Research Center » Dietary Prevention of Obesity-related Disease Research » Research » Publications at this Location » Publication #71455
Title: AN EXAMINATION OF BIO-ELECTRICAL IMPEDANCE ERRORS USING GENERALIZABILITY THEORY

Author
item TURNER, A - U ALASKA
item BOUFFARD, MARCEL - U ALBERTA
item Lukaski, Henry

Submitted to: Sports Medicine Training and Rehabilitation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The use of bioelectrical impedance measurements of the body to assess the fat and fat-free components of an individual is increasing. Before this method can gain widespread application, it is necessary to evaluate the variability of the measurements. A group of 80 men and 83 women was measured in three separate trials of two times per day for two nonconsecutive days. Statistical analyses indicated that determination of a representative value for an individual can be achieved if measurements are made on two days rather than on one day. This finding indicates that the influence of uncontrolled factors, including skin-electrode interactions and body water distribution, impact the measured impedance variables. Knowledge of the need for duplicate measurements to assure representative impedance measurements will assist epidemiologists who seek to use the impedance method for national nutritional surveys and researchers who use this method for monitoring nutritional status of patients.

Technical Abstract: Generalizability theory, an extension of classical true-score reliability theory, was used to investigate the relative and absolute generalizability of the measurements of total body bioelectrical impedance (resistance, reactance and phase angle) for men and women. Eighty Alaskan military men (19 to 56 yr) and 83 women (19 to 54 yr) volunteered as subjects from Elmendorf Air Force Base, Anchorage, Alaska. The design was a four- faceted cross: person-by-day-by-occasion-by trial. All facets were treated as random. Each subject was measured by one tester on two d, 2 occasions and 3 trials. Data were analyzed independently for each impedance measurement and each gender group. The person-by-day interaction contributed a significant percentage of total variance on all impedance measurements for both men and women. The G-study coefficient for both relative and absolute decision ranged from 0.86 to 0.96. The alternative D-study coefficient for relative decision ranged from 0.73 to 0.98; the coefficient for absolute decision ranged from 0.72 to 0.98. The data indicate that a more precise measurement can be achieved by increasing the number of test days, while no significant enhancement may be obtained by increasing the number of trials.