Gene Xpert Testing Of Stool Samples for the Diagnosis of Pulmonary Tuberculosis in Children Less Than 15 Years in Hospitals In and Around Nairobi

Abstract

Globally Tuberculosis (TB) is a major infectious disease. In 2011, there were an estimated 8.7 million new cases with 6% childhood tuberculosis. The majority of the cases occurring in high TB burden countries like Kenya. Accurate pediatric pulmonary tuberculosis (PTB) diagnosis is a challenge. Symptoms are nonspecific, young children are unable to expectorate sputum samples and the procedures for obtaining respiratory samples are invasive. Thus Mycobacterium tuberculosis (M.tuberculosis) cultures and smears are often not performed. This study was done to assess stool samples as an alternative to respiratory samples for the diagnosis of pediatric PTB using stool Xpert MTB/RIF assay test and, to determine its sensitivity for detecting the DNA of MTB in stool. The study was a laboratory based cross- sectional prospective design. Children less than 15 years of age, who attended Gertrude’s Children’s Hospital Nairobi and Kiambu District Hospital and were suspected to have pulmonary tuberculosis on clinical grounds from September 2013 to April 2014 were included. Stool specimens were collected after consent was obtained, from their parents or legal guardians. Data of the clinical features and the results of the routinely done tests by the hospitals were obtained from the filed medical records. A total of 91 stool samples were collected from pediatric cases where the median age was 3. Stool for Xpert was processed in two ways, direct and prior extraction of DNA using QIAGEN stool DNA extraction kit. Out of this, 53(58.2%) had sputum ZN smear microscopy. Six (11.3%) of them were confirmed smear positive for PTB. Stool Gene Xpert tested positive in all the six smear positive children as well as four (7.5%) smear negative patients. Stool Gene Xpert with 100% sensitivity and 89.36% specificity had significant association (P value = 0.000). Thus this study reports that M. tuberculosis DNA can be detected in stool using Xpert testing with a higher sensitivity than sputum smear microscopy. Therefore stool which can easily be obtained are an appropriate alternative sample for the diagnosis of PTB using Xpert assay for children unable to give respiratory samples. Furthermore Xpert turn round time is less than two hours.