Patch Test–Directed Dietary Avoidance in the Management of Irritable Bowel Syndrome
This study investigated the utility of skin patch testing to identify delayed-type food hypersensitivities that trigger irritable bowel syndrome (IBS) symptoms. Using an extensive panel of type IV food allergens, patch testing was performed on individuals with IBS symptoms, after which patch test–directed avoidance diets were implemented in those patients with patch test reactions. All patients placed on avoidance diets were invited to participate in a questionnaire-based study assessing IBS symptom response to the diet. Primary end points included average abdominal pain during the more than 3-month food avoidance period and degree of improvement in overall IBS symptoms 3 or more months after initiation of the avoidance period. The results from this study add to the expanding body of evidence of a role for delayed-type food hypersensitivities in the pathogenesis of some cases of IBS. Skin patch testing to type IV food allergens offers a new approach to evaluating and managing these patients.
Practice Points
- Recent observations of inflammation in irritable bowel syndrome (IBS) challenge its traditional classification as a functional disorder.
- Delayed-type food hypersensitivities, as detectable by skin patch testing, to type IV food allergens are one plausible cause for intestinal inflammation.
- Patch test–directed food avoidance improves IBS symptoms in some patients and offers a new approach to the evaluation and management of this condition.
- Dermatologists and other health care practitioners with expertise in patch testing are uniquely positioned to utilize these skills to help patients with IBS.
Following patch test application on day 1, two follow-up visits occurred on day 3 and either day 4 or day 5. On day 3, patches were removed, and the initial results were read by a board-certified dermatologist according to a standard grading system.14 Interpretation of patch tests included no reaction, questionable reaction consisting of macular erythema, weak reaction consisting of erythema and slight edema, or strong reaction consisting of erythema and marked edema. On day 4 or day 5, the final patch test reading was performed, and patients were informed of their results. Patients were advised to avoid ingestion of all foods that elicited a questionable or positive patch test response for at least 3 months, and information about the foods and their avoidance also was distributed and reviewed.
Food Avoidance Questionnaire
Patients with questionable or positive patch tests at 72 or 96 hours were advised of their eligibility to participate in an institutional review board–approved food avoidance questionnaire study investigating the utility of patch test–guided food avoidance on IBS symptoms. The questionnaire assessed the following: (1) baseline average abdominal pain prior to patch test–guided avoidance diet (0=no symptoms; 10=very severe); (2) average abdominal pain since initiation of patch test–guided avoidance diet (0=no symptoms; 10=very severe); (3) degree of improvement in overall IBS symptoms by the end of the food avoidance period (0=no improvement; 10=great improvement); (4) compliance with the avoidance diet for the duration of the avoidance period (completely, partially, not at all, or not sure).
Questionnaires and informed consent were mailed to patients via the US Postal Service 3 months after completing the patch testing. The questionnaire and consent were to be completed and returned after dietary avoidance of the identified allergens for at least 3 months. Patients were not compensated for participation in the study.
Statistical Analysis
Statistical analysis of data collected from study questionnaires was performed with Microsoft Excel. Mean abdominal pain and mean global improvement scores were reported along with 1 SD of the mean. For comparison of mean abdominal pain and improvement in global IBS symptoms from baseline to after 3 months of identified allergen avoidance, a Mann-Whitney U test was performed, with P<.05 being considered statistically significant.
Results
Thirty-seven consecutive patients underwent the testing and were eligible for the study. Nineteen patients were included in the study by virtue of completing and returning their posttest food avoidance questionnaire and informed consent. Eighteen patients were White and 1 was Asian. Subcategories of IBS were diarrhea predominant (9 [47.4%]), constipation predominant (3 [15.8%]), mixed type (5 [26.3%]), and undetermined type (2 [10.5%]). Questionnaire answers were reported after a mean (SD) duration of patch test–directed food avoidance of 4.5 (3.0) months (Table 1).
Overall Improvement
Fifteen (78.9%) patients reported at least slight to great improvement in their global IBS symptoms, and 4 (21.1%) reported no improvement (Table 2), with a mean (SD) improvement score of 5.1 (3.3)(P<.00001).
Abdominal Pain
All 19 patients reported mild to marked abdominal pain at baseline. The mean (SD) baseline pain score was 6.6 (1.9). The mean (SD) pain score was 3.4 (1.8)(P<.00001) after an average patch test–guided dietary avoidance of 4.5 (3.0) months (Table 3).
