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Updated: Nov 12, 2025

Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
Molecular detection of Mycobacterium tuberculosis in blood stained sputum samples using GeneXpert PCR assay
Enoch Aninagyei1, Reuben Ayivor-Djanie1, Juliana Attoh2
1Department of Biomedical Sciences, School of Basic and Biomedical Sciences, University of Health and Allied Sciences, Ho, Volta Region, Ghana.
Abstract:
This study investigated the possibility of detecting Mycobacterium tuberculosis (MTB) in blood-stained sputa with GeneXpert assay (Xpert MTB/Rif G4 v.5) using appropriate blood lysing (distilled water and distilled water/carbon tetrachloride) and protein denaturing (guanidinium chloride and heat) agents. Blood free sputa were collected from individuals infected with MTB. Various levels of blood-spiked sputa (0%-50%) were prepared and subsequently assayed with GeneXpert analyzer. GeneXpert was found to be reproducible at less than 2% blood contamination. However, beyond 5% blood contamination, GeneXpert was unreliable with absolute PCR inhibition at 20% of blood contamination. Boiling at 95°C for 5 minutes was able to recover MTB DNA in previously undetectable levels as well as in 57% of patients' sputa with blood stains with previous negative GeneXpert results.

