Answer: The readings the BIA takes includes how the body resists electrical current (resistance) and reacts to electrical current (reactance).  The relationship of the body to electrical current is complex.  Most tissues in the body resist electricity while some tissues react, such as body water. The cell membranes even “hold” the electrical charge for a short time.  For example, healthy cell membranes can contribute to a higher reactance reading while fat tissues are much less conductive.  Long, thin fibers of muscle tissues in arms and legs are more resistive than wider and shorter muscle tissues in the torso area.
 

Question: How is phase angle computed, and is it important? Answer: The actual calculation used for determining the “phase angle” as an electrical property of the body is: a-phase angle = arctangent (reactance/resistance) x (180/P) Because it is a ratio (resistance and reactance), it cannot be looked at as an independent value to base judgment about the body’s health. The phase angle will change as BCM, extracellular tissue and fat levels change. Studies have shown that when the phase angle is less than 4, there is a higher risk of morbidity and mortality. Conversely, high levels may indicate problems and would suggest a closer view of body composition values.  Whether the phase angle is up or down, you will still have to look at each of the body compartments before making a decision about what it might mean. Question: What factors should clinicians consider when making treatment recommendations? Answer: Factors to consider when making a treatment recommendation include the extent of BCM or fat wasting and hydration and the body compartment responses to therapy in follow-up monitoring. Other factors typically used in a nutrition assessment such as: past and recent medical history, medication adherence, biochemistry, dietary history, and drug and alcohol use should be considered as well. Question: How can clinicians learn more about the use of BIA. Answer: ANSA offers free on site, one-on-one BIA training to its members. To see if you or your agency might qualify to receive this service, please contact John Buckely, Technical Assistance Coordinator via email or telephone 847/228-5200.  In addition, two online courses are available.  A short course is offered by  Serono  and a more comprehensive course is offered at  Hi-R-Ed.org. References 1. Lazin B. Bioelectrical Impedance Analysis Basics. Workshop, 8th Annual AIDS Meal and Nutrition Providers' Conference, Philadelphia, PA. Sept 2001.  2. Fields-Gardner C. Bioelectrical Impedance Analysis Advanced Concepts and Interpretation. Workshop, 8th Annual AIDS Meal and Nutrition Providers' Conference, Philadelphia, PA. Sept 2001.   (Forward to page 15)