Title: 'Alternative tests for food allergy'

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Type: Article

Author: Dr M Draper

'Alternative tests for food allergy'

Introduction

Controversy surrounds the topic, due to practitioners incorrectly labelling food intolerance (non-immunological) as an allergy (immune mediated hypersensitivity). The classical, rapid Type 1 allergic reaction, which is IgE mediated can be tested for conventionally with the Skin Patch test and Skin Prick test (1), Radioallergoabsorbant (RAST) Test. IgG mediated tests (FAST & ELIZA) are unreliable due to false negative and positive reactions (2); positive tests may not be clinically relevant and hence the increased popularity of "alternate" methods as patients find their own way.

(A) Skin Tests

Intradermal Provocative Skin Test (Miller technique) Similiar to a Patch Test (3) except intradermal injections of progressively highly diluted extracts (potential allergens) are used to elucidate delayed-onset food reactions (4) and treat by neutralistion. It is safe, without any recorded anaphylaxis, however, unpleasant, time consuming, unreliable, and saline is equally effective (5).

(B) Laboratory Tests

Cytotoxic Tests Blood samples (Bryan's leukocytotoxic technique) are exposed to food and morphological changes in neutrophils (Neutron) and lymphocytes (ALCAT)(6) are assessed. These tests are expensive and do not correlate with patient's symptom severity (7), however they have 65% reliability (6), good reproducibility (8) and comparability (9).

The Food Allergen Cellular Test (FACT) measures leukotrine release from white blood cells following exposure to 154 food samples and is 80% accurate.

Hair Analysis Blinded duplicate hair samples from subjects with established fish allergies (skin prick test) were sent to 5 commmercial labs which tested negative for both samples (10) and were, as expected, unreliable.

(C) Practitioner Dependent Techniques

Applied Kinesiology Food samples are either held or placed below the umbilicus of the subject, the observer tests muscle tone and strength, usually of the arm. The test is observer dependent, under critical analysis results equal that expected by chance (11).

Auriculo-cardiac Reflex Method Application of foods on filter paper to the skin of the forearm is followed by testing for a rising pulse and shining a light on the earlobe. Slow, laborious and lacks validation.

Dowsing (Radionics) Subject or observer use a pendulum to detect food intolerance. Patients often avoid foods on the basis of 'self-detected' positive results which is difficult to analyse.

Electrodermal (VEGA) Test Explained by Schimmel (12) & Voll, bioelectrical potentials are measured via a galvonometer and skin resistance probes on specific acupuncture points to allergens placed in a metallic grid. A drop in resistance may indicate allergy or intolerance (13). Accuracy 96%(14). Elimination of detected allergens gives 90% improvement of symptoms with recurrence on re-exposure. It is cheap, relatively quick, comprehensive, non-invasive but not supported by proper trials (15).

Conclusion Vega testing appears to be one of the most popular and objective indirect methods of food allergy testing. However the concensus among various experts is that 'dietary elimination and food challenge '(16) with oral provocation test remains the best method (17).

References

(1) Fitzgibbon, J.(1998) 'Could it be allergy?' Newleaf, Dublin.

(2) Botley, J. et al. (1991) 'Immunoallergic techniques for the diagnosis of food allergy '.in Food Allergy in Infancy: Proceedings of the International Symposium, Palma deMallorca, Spain.

(3) Isolauri, E & Turijanmaa, K. (1996) 'Combined skin prick and patch tests enhances identification of food allergy in infants with atopic dermatitis 'J Allergy Clin Immunol 97: 9-15.

(4) Brosstroff, J. & Gamlin, L. (1998) 'The Complete Guide to Food Allergy and Intolerance'. Bloomsbury Publishing Ltd, London.

(5) Jewett, D.L. et al. (1990) 'A Double-blind study of symptom provocation to determine food sensitivity' N.Engl. J Med 323: 429-433.

(6) Fell, P.J. et al. (1991) 'Cellular responses of food in Irritable Bowel Syndrome - an investigation of the ALCAT test ' J Nutr Med 2:

(7) Anthony, H et al. (1997) 'Environmental Medicine in Clinical Practice'. BSNAEM Publications, Southampton.

(8) Holopainen, E. (1980) 'Cytotoxic leucocyte reaction 'Acta Otolarngol 89: 222-226.

(9) Eaton, K.K. (1990) 'Laboratory tests of food intolerance: ALCAT and Cytotoxic compared with elimination and challenge. Food and Environment Factors in the Human Disease. BSNAEM Buxton.Abstract 29

(10) Sethi, T.J. (1987) 'How reliable are commercial allergy tests?'

Lancet 1987; i :92-94.

(11) Garrow, J.S. (1998) 'Kinesiology and food allergy ' BMJ (Clin Res Ed) 296: 6636, 1573-1574.

(12) Schimmel, H.W. et al (1981) 'Short Manual of the Vega test method 'Vega Grieshaber Gmbh &Co. D-7622. Schitach/Scharzwald, West Germany.

(13) Fox, A.D. (1991) 'Milk Intolerance and Vegatest Diagnosis'.

Biol Ther Vol 9, 2: 127-130.

(14) Krop, J et al. (1997). 'A Double Blind Randomised, Controlled Investigation of Electrodermal Testing in the Diagnosis of Allergies'. J Altern Compl Med 3: 241-248.

(15) Katelans, C.H. et al. (1991) 'Vega testing in the diagnosis of allergic conditions'. Med J Aust 1555: 2, 113-114.

(16) Hunter, J.O. (1997) 'Food allergy and intolerance ' Presc J 37, 4: 193-198.

(17) Joneja, J.V. (1998) 'Dietary management of Food Allergies & Intolerances ' J.H. Hall Publications Ltd, Vancouver.