SKIN PRICK TEST (SPT) VERSUS ATOPY PATCH (APT) TEST IN THE DIAGNOSIS OF FOOD ALLERGY IN PATIENTS WITH IRRITABLE BOWEL SYNDROME

Abstract

SUMMARY I rritable bowel syndrome affects a large proportion of the general population and it can have a significant effect on quality of life. It carries a huge financial burden, both in terms of utilization of health resources and time lost at work. The inherent diagnostic uncertainty based on symptom criteria alone, the chronicity of the condition and an individual’s illness perception pressurizes the clinician to undertake extensive and often negative investigations. Recently, food hypersensitivity has re-surfaced as a possible approach in the diagnosis and management of many chronic disorders, including irritable bowel syndrome. Data from dietary elimination and food challenge studies support the role of diet in the pathogenesis of a sub-group of irritable bowel syndrome patients. For the first time, a pathophysiological basis for irritable bowel syndrome is beginning to emerge, but further work is needed to advance current understanding of the exact mechanisms by which gastrointestinal immune system handles food and microbial antigens in health and disease. The present study was undertaken to identify the prevalence of food allergy in the adolescent and adult population with IBS and the diagnostic accuracy of atopy patch test in those patients. Forty IBS patients were enrolled in this study (recruited from our clinics at Ain shams university hospitals) at the period from June 2012 to April 2014, and another 20 healthy individuals as control group. All patients completed symptom questionnaire. Atopy patch test (APT), skin pricks test (SPT), and serum total IgE were performed for all participants. Diet elimination was applied for those with positive APT and SPT results. We found that11/40 of IBS patients (27.5%) were suspected to have food allergy to common food allergens, 12.5% of them diagnosed by positive APT to certain food (s) and positive elimination diet to the same food, 2.5% of them diagnosed by SPT and elimination diet,12.5% of them diagnosed by positive APT, SPT and elimination diet. On the other hand negative APT results were obtained in the entire control group. Sensitivity and specificity of APT were 75% and 78.6% respectively, PPV and NPV were 60% and 88% respectively. These values were almost comparable to values previously obtained in different studies. We concluded that APT seems to be valuable additional tool in the diagnostic work up of food allergy suspected in patients with food-related gastrointestinal symptoms like IBS patients. Positive both APT and SPT in the same patients indicates coincidence of IgE-mediated and non- IgE-mediated hypersensitivity to foods and this suggests more the allergic background of IBS in some patients.