Title: Evaluation of faecal volatile organic compounds in the diagnosis of paediatric inflammatory bowel disease
Funder: Department of Health and Social Care

Abstract: The frequency of paediatric inflammatory bowel disease (pIBD) has risen considerably in recent years such that it is now a not uncommon presentation in paediatric gastroenterology clinics. Invasive and expensive investigations (endoscopy with biopsy usually under general anaesthetic, imaging of the GI tract, serum inflammatory markers) are required both for initial diagnosis and monitoring the response to treatment. Faecal calprotectin is a useful biomarker of intestinal inflammation, but has low specificity for IBD (0.68; 95% CI 0.50&ndash; 0.86). We need affordable, rapid and non-invasive tests that either diagnose pIBD reliably so that no further tests are needed or better identify children that do and, importantly, do not require further investigation. Faecal volatile organic compounds (VOCs), responsible for stool odour, consist of many low molecular mass carbon-based molecules including organic acids, alcohols, esters, heterocyclic compounds, aldehydes, ketones and alkanes. They result from the metabolism of the intestinal mucosa and the gut microbiota and their abundance changes according to the specific effects of intestinal diseases. Faecal VOCs distinguish adults with diarrhoea-predominant irritable bowel syndrome from active CD and UC (sensitivity 94% and 96%; specificity of 82% and 80%, respectively). They may also differentiate Crohn s disease (CD) from ulcerative colitis (UC), Crohn s colitis from UC and between active and inactive CD and UC in adult patients. We aim to evaluate whether the measurement of faecal VOCs has a role in the diagnosis of pIBD and also in monitoring response to treatment. This may be as a stand-alone test or alongside other routine, non-invasive investigations such as faecal calprotectin. Our study will address two main questions: firstly, whether the measurement of faecal VOCs distinguishes children at initial presentation with IBD from those with other common gastrointestinal disorders and, secondly, whether the measurement of faecal VOCs distinguishes children with IBD in clinical remission from those with on-going active disease. We will conduct a prospective, observational study of 286 children attending clinics in 3 leading paediatric gastroenterology referral centres in the UK in whom clinical assessment indicates that IBD is a possibility. We estimate that of these children, approximately 93 will have CD, 50 UC and 143 other gastrointestinal disorders. We will measure faecal VOCs by two methods: i) headspace SPME-Combipal GCMS and ii) GC-sensor. The first method uses equipment that is readily available in NHS clinical laboratories. The second method uses equipment that is designed for point-of-care diagnosis in the clinic (GC-sensor (Odoreader&copy;); IP established with development of a commercial instrument underway). Consistent with our findings in adults, we will determine whether the presence of a small number of VOCs can be used to diagnose pIBD and distinguish it from other common pathologies. We will also determine whether the faecal VOCS profile differs between CD and UC and repeat faecal VOCs analysis 3 months after pIBD diagnosis to determine whether they distinguish between active disease and clinical remission. Finally, we will explore the profile of VOCs in pIBD using existing compound libraries to gain insights into possible underlying disease mechanisms. If the findings in children are similar to those in adults, the measurement of faecal VOCs may provide a reliable and affordable point-of-care diagnostic test for pIBD and also for the assessment of response to treatment. This would allow treatment to be started earlier both at initial presentation and during relapse. It would also avoid expensive and invasive investigations thereby significantly reducing stress on children and their families and also NHS costs.

Lay abstract: Inflammatory bowel disease (IBD) results in serious, lifelong gastrointestinal morbidity and poor quality of life. It has become much more common in children in recent years such that 25% of all new cases now occur in young people. Gastrointestinal endoscopy and imaging are required to confirm a diagnosis in children with suspected IBD. These investigations are highly distressing for children and their families, delay diagnosis and the start of treatment and are costly to the NHS. These tests need repeating at regular intervals further impairing quality of life. Children and families who have undergone these procedures voice a strong desire for tests that are non-invasive and give a rapid result. Parents of children with IBD are members of our research team and have helped to design the study. The measurement of a marker of intestinal inflammation called &ldquo;calprotectin&rdquo; in a stool sample is helpful but does not differentiate IBD from other conditions such as gut infections. Stool volatile organic compounds (VOCs), responsible for stool odour, can be measured rapidly in the clinic at low cost. Research in adults by our group has shown that stool VOCs differentiated IBD from irritable bowel syndrome and also Crohn s colitis from ulcerative colitis. However, early-onset IBD differs greatly from adult-onset disease; therefore, this new technology needs to be tested in children. Although stool VOCs have been shown to differentiate children with IBD from healthy controls, we plan to see if they can differentiate IBD from other common gut problems seen in paediatric clinics. We will also test whether VOCs can differentiate Crohn s disease from ulcerative colitis in children and whether they are useful in monitoring response to treatment. Our ultimate goal is to see whether stool VOCs can replace endoscopy and imaging. This would greatly improve our patients experience and markedly reduce healthcare costs.

Research activity codes: 4.2 EVALUATION OF MARKERS AND TECHNOLOGIES
Health categories: ORAL AND GASTROINTESTINAL