Eugenia Lin

Biomarkers of Irritable Bowel Syndrome

Traditionally, irritable bowel syndrome (IBS) has not been regarded as an organic disease, and the pathophysiology of IBS is heterogeneous. Currently, the diagnosis of IBS is based upon the Rome diagnostic criteria. The performance of these criteria is only modest in predicting IBS, and moreover their validation is lacking. Additionally, as functional symptoms are common in the general population, healthy controls or volunteers are difficult to define and there is currently no definition of “normal” in the Rome criteria. Due to the weaknesses of the current diagnostic criteria, patients and doctors expect new gold standard diagnostic tools. Various etiologic mechanisms result in potential biomarkers. The focus of this research has been to find non-invasive biomarkers from serum, breath gas, and fecal materials. Though biomarkers should be based on biological and pathogenic processes, most biomarkers for IBS have been developed to identify organic diseases and therefore eliminate IBS. To date, these types of biomarkers for IBS have been disappointing. The purposes of developing biomarkers include improvement of diagnosis, differentiation from other organic diseases, and discrimination of IBS subtypes. A true mechanistic biomarker would make it possible to rule in IBS, rather than to rule out other organic diseases. New serologic biomarkers for diarrhea-predominant IBS have been introduced based on the pathophysiologic findings from a rat model and validation in a large-scale clinical trial. Further investigations of abnormal organic findings from each subtype of IBS would enable the development of new, simple subtype-specific biomarkers.

Intestinal methane production is associated with decreased weight loss following bariatric surgery

To determine whether methane and hydrogen on breath test affects weight loss after bariatric surgery, 156 subjects (pre-surgery BMI ≥33) were recruited ≥4 months after surgery. Pre- and post-surgery weights and BMIs were recorded. Post-surgery methane and hydrogen levels were determined. % total weight loss and % change in BMI were prorated to six months after surgery. M+/H+ subjects (N=13) exhibited lower prorated % change in BMI vs. all other subjects (N=144) (p=0.13), and significantly lower prorated % total weight loss (p=0.036). These findings may suggest that subjects with positive breath methane and hydrogen lose less weight following bariatric surgery.

Examination of the effects of breath hydrogen and methane levels on the EC/IR II

ABSTRACT Fifty patients undergoing hydrogen and methane breath testing at Cedars-Sinai GI Motility Lab were recruited, and consented to having their breath tested for alcohol using the EC/IR II (Intoximeters, Inc., St. Louis). The subjects gave multiple breath samples for alcohol analysis during this controlled study. All subjects had hydrogen in their breath ranging from 1 to 176 parts per million (ppm). Methane was also present in some patients’ breath samples (0–107 ppm). In all cases, except for one subject that admitted to heavy drinking the night before, breath alcohol results were 0.000 g/210 L. Based on these findings, breath hydrogen and methane do not have any impact on breath alcohol results with the EC/IR II.

A definitive blood test for post-infectious irritable bowel syndrome?

Irritable bowel syndrome (IBS) is one of the most common conditions in gastroenterology [1], and is also one of the most challenging for clinicians. This is in part due to the lack of specific biological markers, as well as the lack of hallmark findings on endoscopy. In attempting to elucidate the pathophysiology of IBS, experts have investigated several avenues including the role of stress [2], alterations in the brain-gut axis [3], changes in bile acid metabolism [4], and altered intestinal motor function [5], amongst others. However, two bacterial concepts have proven to have great significance in IBS. These include the findings of altered small bowel microbiota in IBS [6], and that acute gastroenteritis can precipitate the development of IBS [7].