Frequently Asked Questions about Bio-Impedance Analysis

How does bio-impedance (BIA) work?

Each two adhesive skin electrodes are placed on the hand and foot on one side, typically the right side of the body and connected to the instrument by an electrode cable set. A non-susceptible current is entered into the body through the first pair of hand-foot electrodes. The second electrode pair is used to determine the voltage drop caused by the body water dependent impedance or total resistance. Simultaneously the phase shift of the “injected” alternating current is measured, indicating primarily the cell mass dependent capacitive resistance or reactance. For analysis of test data and interpretation of body composition an evaluation program is used. The software is a part of the delivered package comprising all necessary items to perform a test and properly store or transport the BIA device.
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How long will a test take?

The test itself takes only a few seconds. Preparing the test and performing the evaluation with take a total of three to five minutes.
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What is the difference between BIA and fat scale testing?

In fat testing fat mass is assessed by use of a so-called “fat scale”. The test, depending on a variety of uncertain factors and assumptions, is known to be error prone. Therapy guidance based on weight and even well estimated fat mass only often leads to false interpretations (and frustrations in the trainer/therapist as well as in the trainee/client). Although the term “fat” receives high levels of attention in the public, cell mass and extracellular water ratio in combination with phase angle carry substantially more physiological and clinical importance and deserve more professional emphasis. Only if the before mentioned bio-impedance parameters can be modified and improved, therapy can be successful. In a cook-book manner, our BIA webseminars give a detailed guide to the most relevant BIA parameters, offering a BIA interpretation which can easily applied in the daily routine work.
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What is needed to perform a BIA test?

Besides the instrument and the patient cable set four electrodes are needed to perform a single BIA test. For the evaluation of test results a software program is required which is part of the delivery. Also part of the delivery is a set of accessories needed for proper operation, such as the electrode cable set, electrode pack, charger, transport case, program CD, and a life-time software license. The included electrode pack is good for 25 BIA tests
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How precise is BIA based body composition analysis?

In countless scientific studies bio-impedance testing was validated against reference methods. The current scientific literature documents a high validity (accuracy, repeatability, and operator independence) for essential body composition parameters, such as total body water, fat free mass, fat mass, cell mass, extracellular water, relative to so-called gold standards. Also the BiaVector analysis was extensively validated. Nevertheless, critical clinical situations, substantial changes in body weight, body fluids, cell mass or shifts in the water compartments require special interpretation techniques which are thoroughly discussed in our BIA seminars.
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Why is testing in supine position preferable?

A diagnostic, clinically relevant BIA test should be performed with the test person in supine position, aiming at a more uniform distribution of body fluids. We recommend a laying time of 5 minutes, in adipose subjects of 10 minutes before the test. In principle the bio-impedance test can be carried out in any body position, also sitting. To avoid erroneous tests due to skin contact between extremities and trunk, arms and legs should be slightly abducted, in particular in obese individuals.
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What determines the proper placement of electrodes?

Each two electrodes are placed on the hand and foot of the right side of the body. Should the right side not be available for testing due to an amputation, metal implants, or for any other valid reason, the left side can be used. Repeat tests should always be applied to the same side of the body. In the area where the electrode is to be attached, the skin surface should be cleaned using an alcoholic swap or spray, removing fatty substances, such as body lotion, and skin residue. The exact, repeatable position of the proximal electrode, oriented on anatomical landmarks, determines test precision and comparability. Small difference in electrode positioning can lead to substantial differences in test result. The electrode placement will be practices during our BIA seminars.
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How often are live BIA Webseminars offered by SMT?

Our life BIA Webseminars take place several times per month and can be booked according to the schedule. Individually seminars, through the web, at our office, or onsite can also be arranged.
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How much is a BIA Seminar participation?

With each purchase of a BIA instrument you will obtain a seminar voucher, valid for a free participation of you and your staff in a life BIA Webseminar, providing a multiple access to one session. Each additional seminar fee will be € 190. For onsite seminars we will provide an individual quotation.
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Can the BIA test also be performed in children?

Yes, BIA tests can also be applied to children and infants. The Bodygram software contains pediatric predicted norms. The electrode placement differs from that of adults and will be taught in our BIA seminars.
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Can electrodes be reused?

No, BIA electrodes are intended for single use only. The electrodes contain a gel, supposed to diffuse into the skin, providing stable skin impedance. If electrodes are reused substantial differences in test results may occur.
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Can normal ECG electrodes be used in BIA tests?

Most ECG electrodes are unsuited for BIA testing. Precise and reproducible BIA test results can only be achieved by applying suitable BIA electrodes.
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Do the electrodes carry an expiration date?

Yes, BIA electrodes are medical products and therefore carry an expiration date printed on the packaging.
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What is the best place of storage for electrodes?

Any opened electrode pack should be placed inside the zipper bag provided in the delivery and protected against heat. Best place to store electrodes over a longer period of time is the fridge. Contain a gel electrodes may dry out in case of unsuited storage. A dry electrode will influence skin impedance and may lead to erroneous test results. Please observe that the test accuracy is dependent on the use of specially suited and validated BIA electrodes. When used in a medical environment only medically approved electrodes are allowed.
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Which type of electrodes should be used?

We recommend the utilization of CE certified electrodes which need to be specially suited and validated for bio-impedance testing. If case you change your electrode supplier you should perform comparative tests to ensure not only test accuracy but also compatibility with previous results.
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Are the SMT medical supplied BIA instruments medically certified?

All BIA instruments supplied by SMT medical are medically certified according the CE class 2A (Directive 2007/47/CEE).
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How long does a battery charge of the BIA device last?

The operational time of a fully charged BIA instrument varies depending on the model: In BIA101 (current 2012 version) the uninterrupted testing time is up to 12 hours, in BIA101 Anniversary up to 6 hours, and in the Bodycomp MF+ up to 4 hours. As a single test only takes a few seconds, many tests in as many subjects can be performed before recharging needs to take place. We recommend charging the battery at max. once a week, overnight. BIA101 and BIA101 Anniversary include an automatic switch off feature which will turn of the instrument after a few minutes.
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What is a test circuit („Dummy”)?

Each of our BIA instruments is supplied with a test circuit („Dummy“) serving as a simple tool in assuring the proper function and accuracy of the instrument and the electrode cable set. The electronic components of the circuit simulate the bio-electrical properties of the human body. Although the circuit cannot be used to calibrate the instrument, it can be applied in assuring testing quality.
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Can the BodyGram PRO software be used in combination with other BIA devices?

No, the Akern software programs were developed for exclusive use with the Akern BIA instruments. The implemented proprietary algorithms and exclusive formulae were developed with and for Akern BIA instruments and validated in numerous studies. BIA instruments of other manufacturers may be calibrated differently and may therefore lead to differing results. This is particularly relevant for the BiaVector nomogram, validated and published by Prof. Antonio Piccoli using a Akern BIA101.
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Have the Akern BIA instruments ever been applied in animals?

Yes in cats, cows, ice bears, brown bears, pigs, sheep, apes, horses, and other animals. Testing of animals requires techniques and methodology different from that of humans.
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Are there any contraindications or limitations of BIA testing in humans?

For the application of bio-electrical impedance testing only a limited number of contraindications exists.
The following persons should not be tested:

  • Persons with implanted cardio-verter-defillibrator (ICD)
  • Persons with high fever
  • Pregnant women (only out of ethical reasons)

While the following persons can be tested:

  • Persons with prostheses or metal implants
  • Persons with amputations
  • Persons with pace makers

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From which age can BIA testing be applied?

In general, there is no age limitation in BIA testing. Nevertheless normative data for pediatric populations below the age of 2 years do not exist. Norms for persons above 2 years of age are contained in our BIA software programs.
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Do bracelets, wrist watches, and jewellery need to be removed before testing?

Only metal items need to be removed when in close proximity to the area where electrodes are placed.
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Is a test person allowed to drink or eat before BIA testing?

Test subjects may moderately consume drinks or food before testing. As long as the fluid or food remains within the stomach, not absorbed by body tissue, test results will not be influenced.
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