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Bio-electrical Impedance Analysis

by David Pieribone

Summer 1998

Bio-electrical Impedance Analysis (BIA) is a simple painless procedure which enables a doctor or healthcare provider to analyze the amounts of fat, muscle and water in the body. Not all healthcare providers perform BIA tests, but more and more are becoming aware of its importance. It costs around $35-$65 and is sometimes reimbursable through standard insurance.

If you have HIV disease your worst enemy can be the loss of weight specifically of lean body mass (LBM), which is also known as fat free mass (FFM). FFM is muscle as well as the metabolically active tissue in your organs. The loss of LBM may be an indication of wasting. Weight measurements alone may not detect the presence of wasting. Without the proper amount of LBM, the body does not function properly, and with the loss of 1/3 or more, death can occur. If the loss of lean body mass is significant, measures to reverse the loss may be necessary. Using anabolic agents like steroid hormones, and human growth hormone, in conjunction with resistance exercise and good nutrition can be benificial. In addition to telling how much LBM an individual has, BIA can also give information about hydration status. Hydration, or how much water is in the body, is very important for overall health. Someone with diarrhea or vomiting who is not getting enough liquids runs the risk of becoming dehydrated.

BIA is a test which can be given in a doctor's office and takes only a few minutes. The test is preformed lying down. Electrodes are placed on the wrist and the ankle on one side of the body. Then a small electrical current is passed through the body and measurements are made. The electrical current is so small that it can not be felt at all. After the information is collected, it is put into a computer which calculates the percentages of fat, muscle and water in the body according to height, weight, sex and age. A single BIA measurement is not as important as tracking BIA over time which can show trends in a person's body composition.

The BIA analysis is accurate to within 5%, and is considered to be as good as any test to measure body composition. Most experts prefer the RJL BIA machine which uses equations validated by wasting expert and CRIA Vice President, Donald Kotler, MD .

Dr. Norma Muurahainen, a well known expert on wasting and HIV infection, recommends that persons with T-cell counts above 300 should have a BIA every four to six months. Individuals with under 300 T-cells should have measurements every three months.

There are some considerations you should keep in mind when having a BIA done. Firstly, be careful of alcohol and caffeine intake 24 to 48 hours prior to the test since they can cause dehydration and alter tests results to show an increase of body fat. Second, try and have the BIA done first thing in the morning before you eat, exercise or have your morning coffee or tea. This will give you more accurate test results.


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