Bioelectrical Impedance Analysis (BIA) and AIDS Survival
by Nelson R. Vergel
Most medical doctors do not know about the use of a powerful, simple, and inexpensive tool to help assess their HIV+ patients' health. As an HIV+ patient, I have always been amazed about how doctors are only concerned about total body weight to assess whether a person is wasting or not. It is well known that although total body weight may not change for years after HIV infection, body composition changes even at asymptomatic stages. Lean Body Mass (LBM) tends to decrease while fat and water weight tend to compensate for that decrease. Once that LBM decreases to values close to 54% of normal, death occurs regardless of the cause.1 A person could be showing signs of wasting even if his/her body weight is unchanged. I remember how some of my friends who are now dead used to argue that their weight had not changed at all, even though I could easily notice their deterioration.
A simple technique called Bioelectrical Impedance Analysis (BIA) can answer questions which can not be answered with the common practice of getting a patient on a weight scale as soon as his/her name is called into a doctor's office.
A study2 showed that BIA indeed may be more useful for early detection of occult wasting in persons with HIV/AIDS in comparison to the normally used weight-for-height methods.
BIA takes only a few minutes to determine a patient's body composition. It is accepted as a means for measuring nutritional status and body cell mass, and has been validated for this purpose in AIDS patients.2,3,4 It is also reimbursable by insurance companies. Four self-adhering electrodes are attached to the subjects hands and feet. A painless AC current of 800 micro amps at 50 kiloherts is then introduced. Electric current conductance is greater in lean tissue, as it contains most of the water, conducting electrolytes and cell mass in the body. Fat tissue, because of its lower water content, is less conductive.
Once the impedance measurements of resistance and reactance are made, a third number, the phase angle, can be calculated. From these three numbers, plus the patient's height, weight, sex, and age, it is also possible to estimate body cell mass, fat-free mass, and other body parameters.
An interesting German study5 of 75 patients found that the phase angle predicted three-year survival better than CD4 (T-helper cell) count or any of several other measurements tested. Also, body cell mass, serum cholesterol, CD4 cell count, and serum albumin were predictive to a lesser degree, while age, weight, serum protein, and serum triglycerides were not statistically significant in predicting survival.
The study analysis showed that patients with median phase angle of 5.46º had a somewhat greater than a 50% survival during the 1000 days (The mean - 1 Standard Deviation phase angle for 340 healthy control subjects was 5.6º). Those at the 25th percentile (phase angle 4.87º) - (which means that 25% of the patients in the study had a lower phase angle and 75% had a higher phase angle) had about 15% survival. For those at the 75% (phase angle 5.96º), survival was better than 80%.
As can be inferred, until there is more definitive information, it may be reasonable to accept improvement in the phase angle obtained from BIA as an indicator of improved health.
BIA is one of the main tools used in research protocols designed by PoWeR to assess the effectiveness of anabolic steroid therapy, nutritional intervention and resistance weight training in increasing LBM and, thus, survival.
After reading all the references cited and talking to several nutritionists, it seems that one of the most commonly used BIA machines used in studies and clinical practice is manufactured by RJL Systems (33955 Harper Ave, Clinton Twp., MI 48035; Phone 800-528-4513). They have a hand held analyzer, a desktop model and a fully computerized version. A comprehensive weight, diet and exercise software program is included with each system. All of their BIA machines and their corresponding software cost under $6,000.
1. Kotler et al, "Magnitude of body cell mass depletion and timing of death from wasting in AIDS". Am. J. Clin. Nutr. 1989;50:444-7.
2. Muurahainen N et al. Detection of occult wasting by BIA technology. Graduate Hosp. of Philadelphia. Int. Conf. AIDS 1994 Aug 7-12;10(2):220 (abstract no. PB0895).
3. Sluys T. et al. Body Composition in patients with acquired immunodeficiency syndrome: a validation study of biolectric impedance analysis. Journal of Parenteral and Enteral Nutrition 1993; volume 17, number 5, pages 404-406.
4. Wang J; Kotler D., et al. Body-fat measurement in patients with acquired immunodeficiency syndrome: which method should be used?. Am. J. Clin. Nutr. 1992 Dec;56(6):963-7.
5. Jacobs, D.O. Biolectric Impedance analysis: A way to assess changes in body cell mass in patients with AIDS?. Journal of Parenteral and Enteral Nutrition 1993;volume 17, number 5, pages 401-402.