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.
