NEW DELHI: A simple stool test could soon help doctors identify a commonly missed cause of chronic diarrhoea, potentially ending years of uncertainty for many patients.A new study by researchers from AIIMS and other leading centres, led by Dr Govind K. Makharia, has been published in the Indian Journal of Gastroenterology. The study finds that measuring bile acids in a single stool sample may offer a practical way to diagnose bile acid malabsorption (BAM)—a condition often missed because existing tests are complex and not widely available.Chronic diarrhoea is frequently attributed to conditions such as irritable bowel syndrome, but experts say a significant number of these patients may actually have BAM, which requires a different line of treatment.“Chronic diarrhoea is quite common in India, affecting nearly 8–10% of people, and about 80% of these cases are due to functional bowel disorders like IBS. However, a small but important subset of patients may have bile acid malabsorption, which often goes undiagnosed because existing tests are complex and not widely available. With newer spot stool tests, it is now possible to identify these cases more easily and tailor treatment accordingly,” said Dr Makharia, department of Gastroenterology and human nutrition, AIIMS.The study tested a method that estimates fecal bile acids (FBA) using a simple assay and identified a clear diagnostic cut-off. An FBA level of 2.8 µg/g was found to accurately detect the condition, with high sensitivity (89.5%) and specificity (92%), indicating strong diagnostic performance.Researchers compared healthy individuals and patients suffering from intestinal diseases, found markedly higher bile acid levels in those affected. When applied to real-world patient groups, the results were striking.Around 21% of patients with IBS-related diarrhoea or functional diarrhoea were found to have BAM. The proportion was even higher in other groups—57% among those who had undergone gallbladder removal and over 54% of patients with intestinal tuberculosis.These findings suggest that a substantial number of patients currently being treated for other causes of chronic diarrhoea may have an underlying, treatable condition that is being missed.Doctors say this has direct implications for care. Without correct diagnosis, patients often continue to suffer symptoms despite treatment, leading to repeated consultations and reduced quality of life.The biggest advantage of the new approach is its simplicity. Unlike existing diagnostic methods that are technically demanding and limited to specialised centres, this test can be performed on a single stool sample, making it far more accessible for routine use.Experts believe that wider adoption of such testing could help identify hidden cases earlier and enable more targeted treatment.