Evaluation of GeneXpert MTB/RIF Assay for Detection of Pulmonary Tuberculosis on Sputum Samples

Abstract

Objective: To analyse the diagnostic performance of MTB/RIF assay for the diagnosis of pulmonary tuberculosis and detection of rifampicin resistance using sputum samples.

Study design: Observational cross-sectional study.

Place and duration of study: Provincial TB Reference Laboratory (PTRL), Hayatabad Medical Complex, Peshawar, Pakistan, from January to October 2015.

Methodology: A total of 268 participants were consecutively enrolled in the study after meeting the inclusion criteria. Their sputum samples were collected and processed by N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) method and GeneXpert MTB/RIF assay.

Results: This study determined the overall sensitivity and specificity of MTB/RIF assay, it was 92.4% (86/93) and 97.1% (138/142), respectively. The sensitivity was 98.4% (60/61) in culture proven smear positive samples, whilst sensitivity in culture proven smear negative samples was 93.7% (30/32), using culture as reference standard.

Conclusion: GeneXpert MTB/RIF assay could greatly improve early diagnosis of PTB in smear negative cases as well as multidrug resistant tuberculosis.