Utility of MTB/RIF Assay in Diagnosing Smear Negative Pulmonary Tuberculosis in   Low Income Countries

Shumaila Ambreen; Syeda Lyba Onaiz; Syed Onaiz  Anwar; Mahwash Bizenjo; Shahneela Tabbassum; Luqman Satti; Rabiya Zaib

doi:10.51253/pafmj.v76iSUPPL-3.12307

Authors

Shumaila Ambreen Department of Pulmonology, PNS Shifa Hospital, Karachi Pakistan
Syeda Lyba Onaiz Department of Medicine, PNS Shifa Hospital, Karachi Pakistan
Syed Onaiz Anwar Department of Medicine, PNS Shifa Hospital, Karachi Pakistan
Mahwash Bizenjo Department of Medicine, PNS Shifa Hospital, Karachi Pakistan
Shahneela Tabbassum Department of Neurology, PNS Shifa Hospital, Karachi Pakistan
Luqman Satti Department of Pathology, PNS Shifa Hospital, Karachi Pakistan
Rabiya Zaib Department of Pathology, PNS Shifa Hospital, Karachi Pakistan

DOI:

https://doi.org/10.51253/pafmj.v76iSUPPL-3.12307

Keywords:

Acid-Fast Bacillus, GeneXpert Assay, Mycobacterium tuberculosis (MTB), Resistance to Rifampicin (RIF) Ziehl Neelsen Staining.

Abstract

Objective: To determine the effectiveness of the GeneXpert MTB/RIF assay in diagnosing smear-negative pulmonary tuberculosis and to assess its diagnostic yield in comparison with Ziehl–Neelsen smear microscopy in a low-resource setting

Study Design: Cross sectional study.

Place and Duration of Study: Pulmonology Department, PNS Shifa Hospital Karachi, Pakistan from Jan to Dec 2023.

Methodology: We examined the efficacy of GeneXpert in pulmonary (n=210) pulmonary specimens with Ziehl Neelsen (ZN) staining. Patients older than 12 with suspected TB were included in our study. Samples were sent for routine AFB smear and GeneXpert MTB/RIF by convenient sampling method. The individuals’ demographic information and clinical history were obtained from their hospital records.

Results: A total of 210 patients suspected of pulmonary tuberculosis were included in the study. Among them, 153 (72.9%) were males and 57 (27.1%) were females. Median age was 36.0 (32.5) year range from 12 to 83 years. Smear microscopy for AFB/Ziehl Neelsen was positive in 13 (6.1%) sputum samples and GeneXpert MTB/RIF was positive in 121 (57.61%) samples. Two of the samples came positive for RIF resistance.

Conclusions: GeneXpert is the most eﬀective quick diagnostic tool available since it can identify MTB and rifampicin resistance genes at the same time. GeneXpert's reliability and accuracy were shown to be superior to AFB staining. As a result, a negative GeneXpert test can rule out tuberculosis.

When compared to smear microscopy, GeneXpert is costly and requires advanced apparatus.

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