Diagnostic Accuracy of Ziehl-Neelsen Smear Microscopy in Comparison with GeneXpert in Pulmonary Tuberculosis: A Multi-Center Study in Kandahar Province, Afghanistan
Mujeeb Ahmad
Public Health Program, Kandahar University, Afghanistan.
Muhammad Haroon Stanikzai
*
Department of Public Health, Faculty of Medicine, Kandahar University, Afghanistan.
Najeeb Rahimy
Department of Para Clinic, Faculty of Medicine, Kandahar University, Afghanistan.
Abdul Wahed Wasiq
Department of Internal Medicine, Faculty of Medicine, Kandahar University, Afghanistan.
Hadia Sayam
Department of Para Clinic, Faculty of Medicine, Malalay Institute of Higher Education, Afghanistan.
*Author to whom correspondence should be addressed.
Abstract
Background: Tuberculosis (TB) is a major global health problem. The early and accurate diagnosis is crucial for disease management and to control disease transmission and the emergence of drug resistance TB.
Objectives: This study was carried out to determine the diagnostic accuracy of Ziehl Neelsen (ZN) smear microscopy in comparison with GeneXpert MTB/RIF in pulmonary tuberculosis in Kandahar province, Afghanistan.
Methods: This was a facility-based cross-sectional study. We scrutinized TB registers of three health facilities to include patients who had their sputum tested by both ZN smear microscopy and GeneXpert MTB/RIF. We extracted 734 patients’ data registered during January 2019 - June 2020 in a structured form. Kappa value was analyzed using SPSS version 19 software at 95% Confidence Interval (CI). We calculated sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of ZN smear microscopy against GeneXpert MTB/RIF.
Results: In comparison with GeneXpert as a reference test, ZN smear microscopy has 67.7% (95% CI:63.44%-70.74%) sensitivity and 100% (95% CI:98.74%-100.00%) specificity. The positive predictive value (PPV) and negative predictive value (NPV) were 100% and 99.89% (95% CI:99.88%-99.90%), respectively. The agreement between ZN smear microscopy and GeneXpert MTB/RIF results was moderate (70.4%) and the Kappa value was 0.45 (95% CI:0.38-0.59).
Conclusion: This study has found high specificity but moderate sensitivity for the diagnosis of pulmonary TB using sputum ZN smear microscopy test. Hence, GeneXpert MTB/RIF test is more accurate and reliable for the diagnosis of pulmonary TB.
Keywords: Tuberculosis, GeneXpert MTB/RIF, ZN smear microscopy, Afghanistan.