Diagnostic Accuracy of Xpert Mtb/Rif Assay in Stool Samples in Intrathoracic Childhood Tuberculosis Saba Samad Memon 1 , Sanjeev Sinha 1* , SK Sharma 1 , SK Kabra 2 , Rakesh Lodha 2 and Manish Soneja 1 1 Department of Medicine, AIIMS, Delhi, India 2 Department of Pediatrics, AIIMS, Delhi, India * Corresponding author: Sanjeev Sinha, Department of Medicine, AIIMS, New Delhi, P.O. Box 110029, India, Tel: +919810164416, 011-26594440; Fax: 011-26588918; E-mail: drsanjeevsinha@gmail.com Received Date: February 08, 2018; Accepted Date: March 06, 2018; Published Date: March 13, 2018 Copyright: © 2018 Memon SS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Background: The study aims at finding out usefulness of Xpert in stool samples in children, as they usually swallow their sputum. It also simultaneously compares the results of stool Xpert with Xpert, smear and culture in gastric lavage and sputum samples. Materials and methods: A diagnostic accuracy study included children (<15 years) with probable tuberculosis. Induced sputum, gastric aspirate and stool samples each were subjected to Xpert, AFB stain and culture. Diagnostic utility of stool Xpert was calculated with reference to liquid culture in sputum or gastric aspirate as gold standard. Results: The study included 100 children. Stool Xpert was positive in 4 cases (4%). Overall cultures positivity was 26%. The total yield including culture and Xpert (sputum or gastric aspirate) was 45%. The sensitivity of stool Xpert was 11.54% and specificity 98.65% as compared to culture. There was association of stool Xpert positivity with sputum AFB (p 0.024), sputum Xpert (p 0.004) and gastric aspirate Xpert (p 0.039), while there was no significant association with X-ray pattern or malnutrition. Conclusion: Stool sample for Xpert cannot replace gastric aspirate and induced sputum for diagnosis, and hence should not be used as a first line test. Keywords: Childhood tuberculosis; Xpert Mtb/Rif assay; Stool samples Introduction Childhood tuberculosis presents unique challenges in diagnosis. he paucibacillary nature of the disease makes bacterial isolation diicult; hence diagnosis oten relies on clinical and epidemiological characteristics, positive tuberculin skin test and radiological indings [1]. However, these are rather imperfect tools as radiology is subject to inter-observer variability and tuberculin test serves as a marker of infection rather than disease [2]. For microbiological tests to be efective, the sample must be representative of lower respiratory tract. hese are also diicult in paediatric population as they are unable to produce deep cough for adequate sputum [3]. Gastric aspirate as a sample has the drawbacks that it is minimally invasive and necessitates fasting state [4]. Stool as a sample for intrathoracic tuberculosis has been explored on the premise that children usually swallow their sputum [5]. It is a convenient to obtain, non-invasive sample compared to sputum or gastric aspirate. Smear microscopy gives quick results, but has a low sensitivity [6] whereas culture has a good sensitivity albeit requires long time [7]. Xpert Mtb/Rif (Xpert) test is a molecular method which has revolutionised the diagnosis of tuberculosis. In children with suspected drug resistant tuberculosis or cases with HIV and tuberculosis, Xpert has been recommended as the irst line test by WHO [6]. However there are only a handful of studies regarding the same in stool samples in intrathoracic childhood tuberculosis with each of them giving discrepant results [3,7-9]. he detection of paediatric tuberculosis in a timely, eicient and efective manner through improvement in existing diagnostic Methods are a priority for global research. Stool molecular studies aim to ind a rapid method of diagnosis, in a population where the paucibacillary nature of conventional samples does not allow immediate detection of the bacillus. his study thus explores the utility of stool Xpert in Indian patients with childhood intrathoracic tuberculosis. It further adds to the literature by providing a simultaneous comparison of stool Xpert with sputum and gastric aspirate Xpert, smear and culture as well. Our study includes ambulatory patients, rather than hospitalized ones; thus making it more relevant to community based setting. Materials and Methods he study was conducted at a tertiary care centre (All India Institute of Medical Sciences, New Delhi, India) on consecutive children (6 months to 15 years age) attending the paediatric tuberculosis clinic (outpatient department) between December 2014 and July 2016. A sample size of 100 was derived assuming the likely yield of stool Xpert as 70% with precision of 15%, conidence interval of 95% and possibility of culture conirmed tuberculosis as 40% among probable tuberculosis. he consensus deinition by Graham et al. [10] was used in deining probable tuberculosis. A case was excluded if consent was not given, patient had received anti-tubercular therapy or Isoniazid prophylaxis for more than 4 weeks, had signs of upper airway J o u r n a l o f T u b e r c u l os i s a n d T h e r a p e u t i c s Journal of Tuberculosis and Therapeutics Memon et al., J Tuberc Ther 2018, 3:2 Research Article Open Access J Tuberc her, an open access journal Volume 3 • Issue 2 • 1000115