Hydrogen and methane breath testing has become an increasingly common investigative tool for assessing carbohydrate mal-absorption, small intestinal bacterial overgrowth and gut dysbiosis. Despite hundreds of hospitals and several commercial laboratories offering breath testing services in the UK, there is little consensus as to how to perform and interpret these tests.

This situation is not peculiar to the UK. A recent review of 13 clinical trials showed that 13 different methodologies were used to acquire and interpret breath test data. In science, one needs to develop models that can be tested by experiment in order to control for known variables with as much certainty as is possible. To develop a model, parameters need to be agreed upon as a starting point so that new discoveries can be made disease understanding improved and more effective treatments developed.

In order to address this in the US, an expert panel of clinicians and scientists with experience in the use of breath testing was recently assembled to review existing practices and to try to construct and initial consensus document for the use of breath testing in gastrointestinal disease. The group developed a series of 28 questions based on existing data and voted independently on whether they agreed or not with the statements. The domains covered were clinical indications, preparation, performance, interpretation of results, and knowledge gaps.

The consensus findings were first presented at DDW in 2016 and the subsequent paper has just been accepted for publication in the American Journal of Gastroenterology. I was recently lucky enough to spend a few days at the GI Motility laboratory of two of the main authors of the document. Dr Mark Pimentel and Dr Ali Rezaie at the Cedar Sinai Hospital in Los Angeles have published extensively on breath testing in recent years and made several leaps in our understanding of its utility. The lab has performed over 50,000 breath tests and this was a great opportunity discuss some of the nuances and scientific reasoning around generation of consensus document, assess the impact on how my own service at The Functional Gut Clinic is delivered and look to disseminate these finding to the UK community.

Breath testing can be an evocative subject with investigators at different ends of the spectrum both extoling and refuting its usefulness. Two of the main controversies exist around the type of substrate that should be used and the relationship between the timing of peaks in breath gases and location of the substrate within the bowel. There are few 100% accurate tests available to physiologists and thus a pragmatic approach has to be taken which incorporates knowledge of the physiological processes and clinical conditions under which a test is performed in order to both maximise and restrain interpretation.

Implications for the UK

The UK currently finds itself between a rock and a hard place in terms of breath testing and in particular with regard to SIBO. On the one hand it is great that we may be able to improve the technical quality and scientific understanding of breath testing methodology and interpretation for UK patients but, on the other hand we don’t have ready access to treatments such as Rifaxamin when a positive SIBO test is identified.

Without larger scale trials of rifaxamin in the UK it is going to be difficult to convince the medical community and regulatory bodies that this can be an effective treatment. Anecdotally, a secondary care US physician told me that their IBS-D referrals had declined by 60-70% since rifaxamin was licensed and being used in primary care which could have potentially huge savings in healthcare cost in terms of inpatient, outpatient and colonscopy costs which total over £250-million in the UK at present.

So for now, what we will do is to continue to acquire high quality data, look to perform some comparative analysis looking at different time points and thresholds, look to develop outcome studies with our clinical partners and contribute to the scientific literature through our clinical trials data. Next steps should be a review of existing UK breath testing and establishment of a consensus group of our own would be beneficial so that we can begin to close the gap that exists between ourselves and the US.