An unconventional device called the Vega-test machine is promoted by some alternative medicine practitioners for diagnosing illnesses and determining appropriate treatments. Other names for this approach include electrodermal testing (EDT) and electroacupuncture according to Voll (EAV). The method, which has many variations, generally involves measuring the body's electrical resistance at acupuncture points. Possible allergens or toxins, or prospective treatments, are placed within a device called a honeycomb that is said to test the effects of that substance on the body. More recent devices use a computer that supposedly simulates the presence of test substances.
There is no obvious commonly accepted scientific basis for the use of this method. To the limited extent that it has been tested, it has not proven itself a valid diagnostic technique.
Four Vega-test practitioners, each with at least 10 years experience, agreed to participate in a study conducted by a proponent of EDT testing.1 Thirty people volunteered to participate as patients. Half the volunteers had known allergies to house dust mites or cat dander (as determined by skin testing), while the others were not allergic to these allergens. Each participant was tested with six items in three separate sessions by each of three different operators of the Vega machine, resulting in a total of more than 1,500 separate allergy tests over the course of the study. The results showed that the Vega-test practitioners were unable to distinguish between allergic and non-allergic participants. In addition, no individual operator of the machine was more accurate than any other.
In another study, the Vega test failed to distinguish between people with respiratory allergies to a defined set of substances and those without them.2
One smaller double-blind study did find the Vega test capable of distinguishing between allergens and non-allergens.3 However, one of the authors of this study felt that it suffered from significant flaws, and went on to conduct the first trial discussed above.
On the basis of this information, the only fair assessment at present is that the Vega test has not been shown to be a meaningful method of identifying allergies to dust mites or cat dander. Proponents of the Vega device and other EDT techniques object that identifying respiratory allergens is not the device's primary use. However, at present there is no reliable evidence that the method has validity for any use.
1. Lewith GT, Kenyon JN, Broomfield J, et al. Is electrodermal testing as effective as skin prick tests for diagnosing allergies? A double blind, randomised block design study. BMJ. 2001;322:131-134.
2. Semizzi M, Senna G, Crivellaro M, et al. A double-blind, placebo-controlled study on the diagnostic accuracy of an electrodermal test in allergic subjects. Clin Exp Allergy. 2002;32:928-932.
3. Krop J, Lewith GT, Gziut W, A double blind, randomized, controlled investigation of electrodermal testing in the diagnosis of allergies. J Altern Complement Med. 1997;3:241-248.
Last reviewed September 2014 by EBSCO CAM Review Board