P238 The use of a faecal bile acid test for diagnosing patients with bile acid diarrhoea

Abstract

<h3>Introduction</h3> BAD is a common cause of chronic diarrhoea, affecting 1% of the general population. Type 1 is secondary to ileal resection or inflammation; type 2 is idiopathic; and type 3 is a result of other intestinal conditions such as cholecystectomy. Although the UK gold standard diagnostic test for BAD is the ⁷⁵selenium-homotaurocholic acid (SeHCAT) scan, this is not widely available. This study examines the validity of measuring faecal bile acids (FBA) in a single stool sample as a diagnostic tool for bile acid diarrhoea (BAD) by direct comparison to the SeHCAT. <h3>Methods</h3> Patients with chronic diarrhoea investigated for BAD with a SeHCAT scan were prospectively recruited to the study. Patients provided random stool samples to measure FBA, using an enzyme-linked immunosorbent assay. Patients were characterised into four groups: SeHCAT negative control group (CG), post-cholecystectomy (PC), idiopathic BAD and post-terminal ileal resection Crohn’s disease (CD). SeHCAT retention of &lt;5%, 5-10%, 10-15% and &gt;15% were considered to be severe BAD, moderate, mild and normal, respectively. <h3>Results</h3> 108 patients had a stool with a comparative SeHCAT result. FBA concentrations (umol/g) and interquartile ranges in patients in CG (2.6; 1.6-4.1), PC (4.0; 2.4-6.6) and BAD (3.6; 1.9-7.2) were similar, but all were significantly lower (p&lt;0.001) compared to patients with CD (12.5; 10.2-16.1). FBA concentrations in patients with SeHCAT retention of &lt;5% (8.6; 4.3-15.4) were significantly higher (p&lt;0.005) than those with a SeHCAT retention &gt;15% (2.6; 1.5-4.2). Using ≤15% SeHCAT retention as diagnostic for BAD, the sensitivity and specificity with FBA cut-off of 1.6umol/g were 89% and 26% respectively. <h3>Conclusion</h3> This pilot study demonstrated that a single random stool sample may have potential use in diagnosing severe BAD or BAD in CD patients. Larger studies are needed to confirm the potential efficacy of a single, random FBA test to accurately diagnose BAD in the absence of SeHCAT testing.