Tailoring IBS Dietary Therapy Based on Proprietary IgG-Based Blood Test –Does It Work?

Posted on by

Background (from editorial): “Biomarkers that correspond with the distinct pathophysiological disturbances that underlie food sensitivity, and that can be used to monitor and guide management or predict response to food elimination are lacking…Previous studies have suggested a role for IgG-mediated food sensitivities in driving IBS symptoms.12 However, the role of IgG testing and subsequent dietary elimination for the management of IBS symptoms remains a subject of debate. Elevated IgG levels have been observed in healthy individuals, indicating that these antibodies may reflect a physiological response to dietary exposure rather than intolerance or sensitivity to a specific food.”

In this study, the researchers used a proprietary IgG-based sensitivity testing (“inFoods IBS” ELISA) from the company sponsor, Biomerica.  This was a randomized, double-blind, sham-controlled trial enrolling subjects with IBS from 8 centers. Subjects positive for ≥1 food on an 18-food IgG assay. 223 were included in the modified intention-to-treat analysis. The primary outcome was a ≥30% decrease in abdominal pain intensity for ≥2 of the last 4 weeks of the treatment period.

Key findings:

  • A significantly greater proportion of subjects in the experimental diet group met the primary outcome than those in the sham diet group (59.6% vs 42.1%, P = .02).
  • Subgroup analysis revealed that a higher proportion of subjects with constipation-predominant IBS and IBS with mixed bowel habits in the experimental diet group met the primary endpoint vs the sham group (67.1% vs 35.8% and 66% vs 29.5%, respectively).

Discussion Points:

The authors claim the following: “Because IgG-based antibodies to foods can be elevated in healthy controls, it is important to develop disease-specific assays. The assay used in our study was developed specifically for patients with IBS and uses cutoff values derived from healthy controls.”

Limitations:

  1. “Adherence was poor. Of those who filled out the dietary diary as instructed, 35% were nonadherent in the intervention group and 42% nonadherent based on a yes to an adherence question on ≥80% of days over the 12-week trial.” Adherence was higher in the sham control.
  2.  “Second, in a per-protocol analysis that included only the adherent participants, the clinical outcomes are much less impressive for the IgG-based elimination diet, raising critical questions as to whether other factors were responsible for the improvement in symptoms in the full dataset.”
  3. Possible confounding bias: “2 of the 3 most commonly eliminated foods in the IgG-based elimination diet were high in FODMAPs (eg, milk, wheat), whereas all 3 most commonly eliminated foods in the sham diet were low in FODMAPs (poultry, rice, and goat cheese).”
  4. The authors noted that it was unexpected that the response was more robust in the IBS-C and IBS-M groups rather than the IBS-D groups.

The company sponsor has had good success in publicizing their results on ABC, CBS and NBC. Here is a link from their website direct to YouTube. It highlights a specific young woman reporting success with this approach and commentary by one of the lead authors: inFoods IBS Finding Trigger Foods Faster.

My take: While most patients are eager to pinpoint trigger foods, I remain skeptical about this “precision testing for IBS.” There is no data indicating that this IgG-based diet outperforms patients who limit dairy and wheat, two common triggers. I agree with the associated editorial: “The clinical efficacy of IgG-based elimination diets will need further evaluation before they are implemented in routine clinical practice.”

Related blog posts:

Andaman Sea (Thailand)