A few words in defense of bioimpedance

    Bioimpedance is a controversial and contested, discussed and tested method of assessing an organism that has both supporters and critics.



    In clinical medicine, however, it is used, and not only for analysis of body composition. We decided that it would not be out of place to make a few comments about this technique.

    Historically,

    as noted in several publications, the starting point for bioimpedance is the end of the 18th century. Since then, its value has been equally exalted by some and disputed by others. At the same time, both “camps of protesters” behave quite correctly, and the evidence base of the former can sometimes be read in favor of the latter and vice versa. In other words, there is no direct sharp distortion of the facts - no.

    The method is based on the electrical resistance of tissues, so there are a lot of formulas, physics, mathematics, in other words, exact sciences, far from medicine, where there are many random factors. This, in fact, is the key argument of the antagonists: it is impossible to calculate and sort out the human body.

    Indeed, there are observations that bioimpedansometry on patients with fair skin works differently than on patients with dark skin. And if we take factors such as height, weight, the presence of any chronic diseases ...

    But, in fairness, I must say that not only this diagnosis has such problems: not so long ago there was a case when Polar optical heart rate monitors refused exactly measure the pulse of black athletes.

    Studied or not?

    In Russia, the book published by Science in 2009 is devoted to this technique , which, of course, is more like a physics textbook. There is also a large-scale article explaining the principles of bioimpedance measurement: Theory and principles of bioimpedance in clinical diagnosis.

    In the last article there are also quite “radical” comparisons: they say that analysis with the help of current is not necessary and there is no particular need to prove it: there are ECGs and EEGs that do not raise doubts; but they are not the only ones. Moreover, bioimpedance is divided into several "subspecies".

    Why is it important? The most controversial "bioimpedanceometer" is called modern smart scales. The fact is that many dubbed them as a “truncated”, “truncated”, “inferior” method. While in the above material the classification is given: bioimpedanceometry can be carried out in three ways of applying electrodes: “hand to hand”, “hand to foot”, “foot to foot”. In other words, based on this text, scales are one of the ways that should also be recognized as complete.



    We can not add that the applicability of bioimpedance is wider than the task that manufacturers of modern gadgets entrust to it: clinical tests are known where bioimpedance acts as a method for diagnosing cervical cancer. Also in one ofStudies have argued that bioimpedance shows adequate results in the analysis of fat mass in HIV-positive patients. This is by the way that there are too many exceptions that complicate the diagnosis.

    Body analysis

    To date, bioimpedansometry is most popular as a method for diagnosing body composition, where parameters such as fat level, bone mineral composition, muscle mass, hydration, and some others are considered.

    Almost any material on this topic begins with a general quote that it is a method that has no alternative in terms of accuracy, speed, and availability compared to others. What is true is true: faster and cheaper - only by eye or with a caliper.

    Accuracy is a debatable issue. There are a number of supporting materials in whichthe accuracy of bioimpedance according to one of the indicators (important, of course) is stated - the level of fat in the body. The error - where without it - of bioimpedance is estimated as 3 - 6%, which is considered acceptable.

    Reproducibility - a critical component for science - is also confirmed in studies with a larger sample, subject to a significant number of additional factors, such as race, age, gender.



    Bioimpedance is compared with a DEXA body composition benchmark study (DXA, densitometry). Simply put, this is an x-ray of body composition. At the moment, it is argued that bioimpedansometry gives comparable results for some indicators, especially fat mass. Even in the article, where this method seems to “swear”, the same permissible error and deviation of up to 6% is given.

    At the same time, DEXA analysis costs incomparable money, and if bio-impedance at home using weights will cost on average 2-3 thousand rubles forever, in a clinic - from 1000 rubles, then DEXA on average costs about 10 thousand. Often it is also not recommended to do it: no, but irradiation.

    According to the analysis of fat mass, the scales we tested coincided with DEXA and the clinical apparatus-bioimpedanceometer "MEDASS".

    DataMEDASSMgbDexa
    Fat mass in%19.521,419.7
    Fat mass in kg12.513.611.9
    Muscle mass27,228.5Muscle mass + connective tissue + fluids - 48.6
    Metabolism1555 Kcal / day1348 kcal / day1427 kcal / day
    Mineral composition2,652 kg2.5 kg2,773 kg

    Correlation of other results.

    Controversial, it is true. In words, then the doctors who conduct the DEXA analysis are openly negative about bioimpedance. Those who make bioimpedance, on the contrary, consider that it is permissible to rely on the results obtained in diagnostics.

    The main reason why the method is distrusting is a high degree of dependence on additional factors: for example, ceteris paribus, two people may have different results because one of them drank a glass of water five minutes before the study.

    At the same time, it is believed that the assessment of hydration is quite within the power of the bioimpedance meter: at low sensitivity with a single measurement, the reproducibility of serial trends was convincing.

    Thus, it must be said that most studies, articles and tests are devoted to the problem of obesity, and here bioimpedance shows good results, according to the authors. Even where it is difficult to identify additional factors: pharmacology at the time of the examination, medical history, situational (dehydration or vice versa), we can talk about the exact results.

    Some results

    Face-to-face DEXA and bio-impedance are acceptable in some respects if certain conditions are met. For example, two hours before bioimpedance analysis, you can’t drink liquid, and drink alcohol a day, this will increase the accuracy of calculations.

    Bioimpedance has its advantages, some of which are outside of medicine: it's fast, it's affordable, it's cheap. At the same time, the data is reproducible and repeatable, but this method does not demonstrate ultra-high sensitivity, therefore, it is more suitable for identifying trends in some metabolic processes. DEXA - on the contrary: it’s often impossible to do it, it’s expensive, without the doctor’s comments some parameters cannot be deciphered.

    Today, many scientific publications are devoted to bioimpedance analysis, since they see it as a cheap and accurate diagnostic alternative, however, the method should still be recognized as “medical-physical-mathematical”, which is not always suitable for “spontaneous” processes that occur in organism. We also did both studies: bioimpedance lies here, DEXA - here . The table is above.

    In other words, we must nevertheless recognize that bio-impedance - exists, is a clinically proven diagnostic method with a declared margin of error. The method is assessed as accurate for detecting fat mass, and also coincides in a number of other parameters.

    Home bio-impedance meters, or smart scales, are also part of “this system”, belong to the class of “foot-to-foot” bio-impedance meters and show high accuracy of the results with proper weighing and calibration. The test we passed was carried out on a DEXA apparatus from General Electric, a MEDASS apparatus and the MGB Body Fat Scale Bluetooth scales .

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