Introduction A third of diarrhoea predominant irritable bowel syndrome (D-IBS) results from bile acid malabsorption (BAM); diagnosed by 75SeHCAT retention test. We have previously demonstrated the ability of using an E-nose and FAIMS to detect inflammatory bowel disease (IBD) by shifts in the patterns of volatile organic compounds (VOCs) in the gases and vapours that emanate from urine samples. Here, we have extended our work to detect BAM from urine odours alone.
Methods Technology Principles - E-nose This uses an array of gas phase chemical sensors which are broadly tuned to different chemical groups. When a urine sample is presented to the sensor array, a unique response is produced. By taking all of the sensor responses together, a bio-odorant fingerprint is created. FAIMS operates on similar principles, but produces its fingerprint by measuring the differences in mobility of ionised chemicals in high electric fields.
Subjects and patients BAM (7 day retention value of < 15%): n = 15. Controls: ulcerative colitis in remission (SCAI score of < 4): n = 20; healthy subjects: n = 7. Urine was collected in 10 ml aliquots and stored frozen in universal containers. For assay, the containers were first heated to 60 ± 0.1oC. The headspace (the air above the sample) was then pumped from the containers and analysed by an AlphaMOS FOX 4000 E-nose and FAIMS instrument. Discriminant Function Analysis and Fisher Discriminant Analysis (FDA) were used for statistical evaluation, respectively.
Results The FOX 4000 E-nose plot (Figure 1) shows separate and distinct groupings of patients with BAM, UC, and healthy controls. FAIMS analysis gave a broadly similar pattern (not shown).
Conclusion D-IBS related to BAM is a common condition and treatment with BA sequestrants is effective in the majority. The SeHCAT retention test makes diagnosis easy but is not available in all centres: our pilot data offers an alternative diagnostic approach with high potential.
Disclosure of Interest None Declared.
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