Breath Testing in Pediatric Gastroenterology

By Elizabeth Collyer, MD, and Naim Alkhouri, MD

Noninvasive screening tests are becoming increasingly important in pediatrics. A test that could distinguish between various disease states with minimal invasiveness and good specificity would be ideal. We are in the preliminary stages of working to develop such a test in Cleveland Clinic Children’s Department of Pediatric Gastroenterology.

Need for discrimination between disease states

Many of the diseases that pediatric gastroenterologists encounter have similar presenting symptoms, such as abdominal pain and diarrhea. Wouldn’t it be helpful to be able to distinguish among these illnesses without subjecting children to painful blood draws and even more invasive tests like endoscopy? Enter the breath test.

Why breath testing?

The human body emits a wide array of volatile organic compounds (VOCs) in the breath; each individual’s distinctive mixture of these compounds can be considered his or her characteristic “breath print.” Various disease states can lead to the production of new VOCs or a change in VOCs — and thus can have distinctive breath prints as well. Advances in mass spectrometry have made it possible to identify hundreds of VOCs in the breath. Use of this technology has made breath testing a noninvasive, quick, painless procedure that can help in characterizing and distinguishing various disease states.

Methods in brief

After our group’s initial work demonstrating the potential of breath VOC analysis as a noninvasive tool for detecting pediatric nonalcoholic fatty liver disease1 (as reported in this publication two years ago), we were motivated to assess this method’s diagnostic utility for other pediatric gastrointestinal conditions.

Patients with three commonly encountered diseases — irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and celiac disease — were recruited from Cleveland Clinic Children’s pediatric gastroenterology clinics, and comparable healthy controls were recruited from our institution’s general pediatric clinics. Breath testing was performed on both groups of children using selective ion flow tube mass spectrometry. The children completed a mouth rinse with water prior to exhaled breath collection to eliminate sources of mouth VOCs. Next they were asked to inhale to total lung capacity and then exhale into a collection bag against 10 cm of water pressure at a constant flow (Figure). The bag was taken to the laboratory, and analysis for a wide array of VOCs was completed using the mass spectrometry machine.

Results: IBS, IBD and celiac disease have unique breath prints

We found distinctive breath prints among the children with IBS and IBD, and results are promising in patients with celiac disease as well.

Among our patients with IBS, significant differences were noted relative to controls in levels of benzene, dimethyl sulfide, 1-octene and 3-methylhexane. Discriminant analysis of five mass scanning ion peaks was able to accurately distinguish IBS patients from healthy controls with an excellent area under the curve (AUROC) of 0.99.2

In our analysis of IBD, 21 VOCs were found to correctly classify patients as having IBD or as healthy controls (P < .0001). Additionally, three known compounds — 1-octene, 1-decene and (E)-2-nonene — were shown by multivariable analysis to be able to correctly classify subjects as IBD patients or as healthy controls with an AUROC of 0.96.3

In preliminary analyses of patients with celiac disease, multiple unknown compounds were found to differ significantly between the existing-diagnosis patients and new-diagnosis patients. Discriminant analysis was performed and was able to correctly classify all but three of 40 patients.4

Next steps

Now that we have established on a small scale the possibility of a unique breath print for each of these diseases, we will be working toward comparing the various groups to one another and expanding our sample sizes. Cleveland Clinic Children’s is one of few centers across the country with the capability of performing exhaled breath analysis at this time, and we will be looking to expand and externally validate many of our findings.

The overall goal: Reliable noninvasive testing

Exhaled breath analysis shows promise as a noninvasive and painless method for detecting various gastrointestinal diseases encountered in the gastroenterology clinic. We hope our findings will ultimately enable children to be evaluated for these diseases without the need for invasive testing.

Figure. Dr. Alkhouri assists as a patient exhales into the collection bag used for breath analysis via selective ion flow tube mass spectrometry. Cleveland Clinic Children’s is studying the technology as a promising noninvasive means of detecting a growing number of gastrointestinal diseases in children.

References

1. Alkhouri N, Cikach F, Eng K, Moses J, Patel N, Yan C, Hanouneh I, Grove
D, Lopez R, Dweik R. Analysis of breath volatile organic compounds as a noninvasive tool to diagnose nonalcoholic fatty liver disease in children. Eur J Gastroenterol Hepatol. 2014;26:82-87.
2. Patel S, Patel N, Okwu V, Matloob A, Grove D, Rome E, Dweik R, Alkhouri N. Analysis of exhaled volatile organic compounds reveals new biomarkers for irritable bowel syndrome. Am J Gastroenterol. 2014;109(suppl 2):S540. Abstract 1827.
3. Patel N, Alkhouri N, Eng K, Cikach F, Mahajan L, Yan C, Grove D, Rome ES, Lopez R, Dweik R. Metabolomic analysis of breath volatile organic compounds reveals unique breathprints in children with inflammatory bowel disease: a pilot study. Aliment Pharmacol Ther. 2014;40:498-507.
4. Collyer E, Patel S, Anani A, Lappe S, Grove D, Dweik R, Alkhouri N. Analysis of volatile organic compounds in the exhaled breath of patients with celiac disease. J Pediatr Gastroenterol Nutr. 2015;61(suppl 2):115.

Dr. Collyer (collyee@ccf.org) is a pediatric gastroenterology fellow in the Department of Pediatric Gastroenterology.

Dr. Alkhouri is Director of Research in the Department of Pediatric Gastroenterology.