Field evaluation of a novel preservation medium to transport sputum specimens for molecular detection of Mycobacterium tuberculosis in a rural African setting

Abstract

To assess the performance of an innovative method of transporting sputum to centralized facilities for molecular detection of M. tuberculosis: using a swab to inoculate sputum in a transport medium, PrimeStore(®) Molecular Transport Medium (PS-MTM).Two sputum specimens were obtained from suspected tuberculosis (TB) patients at rural healthcare facilities in South Africa. A swab taken from each specimen and placed into PS-MTM, prior to it being processed by either liquid culture or Xpert MTB/Rif assay (Xpert).141 patients (including 47 with laboratory-confirmed TB) were included in this analysis. M. tuberculosis was detected at 29% by culture and 29% by Xpert, whereas 31% tested positive by IS6110 real-time PCR of PS-MTM from the culture and and 36% from the Xpert-paired specimen. Concordance between the method under evaluation with culture was 82% (McNemar, p=0.55) and 84% (McNemar, p=0.05) for Xpert. Stratified by culture result, the detection rate by IS6110 real-time PCR of PS-MTM was similar to Xpert for patients with positive culture (p=0.32), but significantly higher if culture was negative (p=0.008).These results suggest that swab collection of sputum into PS-MTM for transport is a promising method for diagnosis of TB in rural healthcare settings thereby potentially improving the options available for molecular diagnosis of TB in countries incapable of applying decentralized high-tech molecular testing. This article is protected by copyright. All rights reserved.