Endomicroscopy Fails to Detect Wheat Sensitivity in IBS Patients

Diagnostic accuracy of confocal laser endomicroscopy (CLE) was too low to identify wheat sensitivities in non-celiac irritable bowel syndrome (IBS) patients, according to a prospective multicenter study.

The method accurately detected wheat sensitivity in only about half of the individuals who responded to a gluten-free diet at 2 months (51.4% sensitivity, 97.5% CI 38.7-63.9%), reported Christian Bojarski, MD, of Charité–Universitätsmedizin Berlin in Germany, and colleagues.

CLE, which “generates high-resolution images of the gastrointestinal tract after intravenous injection of fluorescein during ongoing endoscopy,” was slightly better in ruling out wheat sensitivity (67.9% specificity, 97.5% CI 52.9-79.9%), the authors wrote in Gut.

Overall, CLE had a sensitivity of 83.1% (97.5% CI 69.9-91.3%) at 6 months for detecting any food sensitivity (wheat, soy, yeast, or milk) in the study sample, but a specificity of just 32% (97.5% CI 15.7-54.3%).

“Everybody has been looking for some magic intervention for IBS for years,” Mark Corkins, MD, of the University of Tennessee Health Science Center in Memphis, told MedPage Today. “One of the big theories is gluten intolerance.”

“I loved the way they designed the study, I thought it was very well done, and I trust these results!” said Corkins, who was not involved in the research. “They were trying to use this laser endomicroscopy with its ability to magnify. This is expensive, specialized — not something everybody does — and this study shows it does not work.”

Prior research had suggested that CLE could “represent a diagnostic tool to identify wheat-sensitive patients and could improve IBS therapy by offering causative treatment options,” wrote Bojarski and coauthors. But, based on the findings, they concluded that it “cannot currently be recommended as an initial diagnostic test,” and suggested that an 8-week gluten-free diet might be more beneficial.

Bojarski’s group evaluated 147 non-celiac patients who met the ROME III IBS criteria, and tested them with CLE to detect any potential wheat sensitivity by exposing them to diluted wheat (3 g; index testing), followed by soy (3 g), yeast (1 g), or milk (1.5 g). Adult patients with worse symptoms after meals, typical duodenal histology, normal colonoscopies, and more severe IBS were included.

In all, 130 patients (average age 36) completed the study, 74 with wheat sensitivity and 56 without wheat sensitivity. Most of the patients were women (77%), with 49% having IBS-mixed subtype, 41% having IBS with diarrhea, and 10% IBS with constipation.

Follow-up occurred at 6 and 12 months. An endoscope was inserted in the duodenum of the patients and changes were analyzed. Patients had weekly nutritionist visits for dietary guidance on gluten-free diet adherence.

Secondary outcomes evaluated improvement in gastrointestinal symptoms in response to the diet. Median number of days with flatulence was lower across IBS subtypes with the diet, as was the median number of days without abdominal pain. Median stool type according to the Bristol Stool Scale decreased in IBS with diarrhea, and increased in IBS with constipation.

Five patients experienced minor adverse events ranging from tonsillitis to the common cold after CLE, and two experienced “medium” adverse events, influenza and rotavirus.

The analysis had several limitations, the researchers acknowledged, including that use of CLE has not been widely proposed to identify non-celiac gluten sensitivity, and that patients’ response to the gluten-free diet may have been due to a reduction in the intake of other wheat components, such as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.