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Patients with irritable bowel syndrome (IBS) have chromic symptoms and have usually been fully investigated with negative findings on endoscopy and barium studies. The patients may be variously described as neurotic or suffering from a functional disability. Consequently, an attempt is made to suppress their symptoms with a variety of anti-cholinergic and anti-inflammatory agents usually with partial success, but symptoms are often not eliminated completely.
If one accepts an hypothesis that food might be implicated, and this is being more generally recognized then currently the only course of action to establish such a link is an exacting programme of dietary elimination followed by selective food challenges based on experience or more usually guesswork. In either event the process of identification is laborious and difficult for the patient and clinician, often with poor compliance by both!
The advantages of a reliable in vitro test for adverse reactions to food would be to short-circuit this lengthy process. We describe the results of a cellular test which goes some way to fulfilling this objective.
PATIENTS, MATERIALS AND METHODS
Twenty patients (16 female, four male, mean age 53 years, range 23-81), were selected who had a longer than three year history of IBS often associated with arthralgia, headaches and lethargy. They had all been fully investigated by endoscopy and barium enema and no major pathology demonstrated. Skin tests were performed on all patients and only one subject was positive (grass, peanut, potato, tomato, and cheese), the positives in this patient being confirmed by RAST.
Alcat Food Intolerance Test
Citrated blood is diluted 1 in 5 with buffer and 500 ul added to each freeze-dried food extract on nylon discs in Coulter-type cuvettes. The solution is buffered as a physiological fluid to pH 7.4 with sodium bicarbonate. The nylon discs contain dialyzed and freeze-dried skin test extracts of foods (Dohme Hollister Steer) taken from a solution of 50% glycerol and 50% water with a 1 in 10 dilution of the antigen. Following an incubation at 37 ° C with constant agitation, the cuvettes are incubated for a further an at room temperature. Red cells are lysed by adding 16 ml Isoton II containing 0.5% Alcalyse to each cuvette. Each sample is then analyzed in sequence in a modified Coulter counter with one control for every 10 food tests.
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The basis of the food intolerance test is the accurate measurement of changes in cell size/volume following incubation with food extracts using the modified Coulter ZF linked to a computer. There are many publications indicating that contact between allergens and cells (lymphocytes and polymorphs) will cause autolysis, a phenomenon known as allergic autocytotoxicity (ACT). There are three mechanisms which cause this phenomenon, and one does not require the priming of cells in vitro by either antibody or antigen.
It was on this basis that an automated method was sought which would not only be reproducible and objective but would directly correlate with in vivo food challenge. The computer is programmed to compare cultures incubated in the presence and absence of food extracts giving a percentage shift in cell volumes related to exposure to the extract, 13% and above being positive, 9% below being negative with the intervening per cent equivocal. Previous studies of healthy controls, as well as food sensitive patients, were used to determine the percentage levels. The University of Miami football team on a balanced nutritional plan, with no food sensitivity, aged 18-25 were compared with patients matched for age but suffering a variety of food sensitivity problems.
Study Design
The study was double-blind with respect to food challenge in that those foods deemed by the tests be negative and positive were randomly assigned to the challenge periods. The technician performing the test randomly selected three positive foods on F.I.Test and three negative foods. These were mixed and allocated to the patient’s number. The patients, physician and nurses monitoring the study were not involved in the randomization.
A two week initial elimination diet based on Food Intolerance Test results was followed by six single one week food challenges, (three positive and three negative) with randomly assigned foods. After this was a six week exclusion diet based on the original F.I.Test prediction with inclusion of any negative foods from the challenge period.
It is accepted that the ideal method would be to blind each food in some carrier agent but the design of the study is such that it was thought necessary that the patients freely consumed the foods and were unaware as to whether there had been identified by the Food Intolerance Test as positive or negative. They were not aware that the elimination diet contained only negative foods.
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