Utility of stool samples for the diagnosis of Tuberculosis using GeneXpert MTB/RIF Ultra
Vishal Sharma1, Mohita Gaur1, Anoop Singh1, Anjali1, Chanchal Kumar2, Mandira Varma-Basil2, Anil Chaudhry3, Richa Misra1,4*, Yogendra Singh1*
1Department of Zoology, University of Delhi, Delhi-110007, India.
2Vallabhbhai Patel Chest Institute, University of Delhi, Delhi-110007, India.
3 Rajan Babu Institute of Pulmonary Medicine and Tuberculosis, Kingsway Camp, Delhi, India.
4Sri Venkateswara College, University of Delhi, Delhi-110021, India.
Tuberculosis (TB) is a bacterial disease caused by Mycobacterium tuberculosis (Mtb). This disease is still the cause of 1.2 to 1.4 million deaths each year around the world and infects roughly ten million people each year. It is the leading disease burden in developing countries impacting their economy. Diagnosis of TB mainly relies on sputum smear microscopy of Mtb and radiological tests. Nonetheless, in absence of sputum expectoration such as in children/HIV/drug-resistant TB patients, the diagnostic challenge is very much evident. In such cases, unavailability to obtain sample delays starts of anti-tubercular treatment. Relying on microbial culture methods for Mtb detection requires weeks for adequate diagnosis and is often unsuccessful, further adding to diagnostic challenges. Therefore, the use of rapid diagnostic methods still remains an urgent need. The advent of Xpert MTB/RIF and Xpert MTB/RIF Ultra assays proved to be a cornerstone in rapid diagnosis of Mtb as well as rifampicin resistance. It mostly utilizes sputum and other body fluids as the choice of specimen for suspected TB cases. However, under the paucibacillary conditions, induced sputum or gastric aspirate and other invasive specimens are opted for Mtb detection. Our study explores the usefulness of stool as an alternate, non-invasive specimen for Mtb detection that may aid in easy sample procurement and hence encourage rapid and early confirmation of the disease. We evaluated the compatibility and consistency of the Xpert Ultra system with stool for the detection of Mtb in pulmonary tuberculosis (PTB) and extra-pulmonary tuberculosis (EPTB) cases. Our results highlight the potential sensitivity for PTB and moderate sensitivity for EPTB in Xpert Ultra stool assays with a specificity of 100% for both PTB and EPTB cases. This strongly indicates that stool Xpert Ultra testing can provide a rapid, non-invasive, and bio-secure diagnosis for TB.