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

Objectives To assess the performance of an innovative method of transporting sputum to centralised facilities for molecular detection of Mycobacterium tuberculosis: using a swab to inoculate sputum in a transport medium, PrimeStore® Molecular Transport Medium (PS‐MTM). Methods Two sputum specimens were obtained from suspected patients with tuberculosis (TB) at rural healthcare facilities in South Africa. A swab was taken from each specimen and placed into PS‐MTM, prior to it being processed by either liquid culture or Xpert MTB/RIF assay (Xpert). Results A total of 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 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). Conclusions 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 decentralised high‐tech molecular testing. Objectifs Evaluer la performance d'une méthode innovante de transport des expectorations vers des établissements centralisés pour la détection moléculaire de M. Tuberculosis, en utilisant un écouvillon pour inoculer l'expectoration dans un milieu de transport, PrimeStore® Molecular Transport Medium (PS‐MTM). Méthodes Deux échantillons de crachats ont été obtenus de patients suspectés de tuberculose (TB) dans des établissements de soins de santé en milieu rural en Afrique du Sud. Un prélèvement de chaque échantillon prélevé par écouvillon a été placé dans le PS‐MTM, avant qu'il ne soit traité pour la culture liquide ou pour le test Xpert MTB/Rif (Xpert). Résultats 141 patients (dont 47 confirmés TB au laboratoire) ont été inclus dans cette analyse. M. tuberculosis a été détectée dans 29% par la culture et 29% par Xpert, alors que 31% ont été testés positifs par la PCR IS6110 en temps réel à partir de la culture de PS‐MTM et 36% à partir de l’échantillon Xpert‐apparié. La concor