Evaluation of stool with sputum DNA on FTA card, microscope slide and TB-Lamp for Mycobacterium Tuberculosis detection using Xpert MTB/Rif (Xpert) as Gold standard among Pulmonary Tuberculosis patients

Abstract

The Xpert MTB/RIF (Xpert) and TB-Lamp assay technology allows rapid and sensitive diagnosis of pulmonary tuberculosis (PTB) from sputum specimens. The conventional plastic sputum containers allow transportation of sputum specimens from lower health facilities to centralized laboratories through the hub system for PTB testing using XpertMTB/RIF (Xpert). However, transportation of sputum in plastic container is not convenient, risky in case of any sputum leakage and diagnosis of PTB using sputum is difficult for patients who cannot produce sputum. The objective of this study was to evaluate stool with sputum DNA on FTA card, Microscope slide and TB-Lamp for Mycobacterium tuberculosis detection using Xpert MTB/RIF (Xpert) as gold standard among pulmonary tuberculosis patients. Both stool and sputum samples from known Xpert positive PTB patients were collected from Mpigi HCV, Maddu HCV and Gombe Hospital. Sputum smeared on the FTA card and Slide to airy dry. As a control Sputum and Stool samples were collected from Xpert MTB/RIF (Xpert) negative individuals who were reporting in the respective health units. Samples prepared, aseptically smeared on FTA card, slide and the remainder used for Xpert and TB-Lamp for Sputum. An overall of 160 sputum and stool samples were collected from 127 PTB patients and another 33 non-PTB patients by Xpert MTB/RIF. The different results for sensitivity, Specificity, PPV, NPV of the following; Stool Xpert, Xpert FTA card, Xpert slide and TB-Lamp assay were 96.9%,100%, 100%,88.5% (95%, Cl, 0.96948-0.99951), 94%,100%, 100%,81.5% (95% Cl,0.953-0.992),48.84%,100%,100%,31.9% (95%, Cl, 0.70089- 0.7874). 96.12%, 96.7%, 99.2%, 85% (95%Cl, 0.000- 0.0712) respectively. Besides, stool Xpert, FTA card Xpert and Slide Xpert established agreeable results with the sputum Xpert for detection of rifampicin susceptibility except FTA card Xpert 13 samples with trace MTB detection were unable to detect rifampicin resistance. The FTA card, stool, TB-Lamp assay would be beneficial for sample transportation, patients who cannot expectorate sputum like children, can be installed in lower facilities to replace microscopy since it’s very sensitive. Slide needs further studies on its applicability