Comparison of Ziehl Neelsen microscopy and geneXpert for the diagnosis of pulmonary tuberculosis among pulmonary tuberculosis-suspected patients in northwest Ethiopia

Abstract

In low-income countries, the diagnosis of pulmonary tuberculosis (PTB) is most frequently achieved using Ziehl Neelsen (ZN) microscopy rather than the GeneXpert system. The performance of the former has not been evaluated against the latter in Ethiopia. A total of 180 PTB-suspected patients were enrolled in our study. Sputum specimens were tested both by ZN microscopy and geneXpert. The sensitivity, specificity, positive predictive value, and negative predictive value of ZN microscopy were 75%, 99.4%, 92.3%, and 97.6%, respectively. The Kappa value of agreement between the two diagnosis methods was 0.80. We concluded that there was a good agreement between ZN microscopy and the reference Xpert assay, which suggests that ZN microscopy is still a good diagnostic method in health care facilities that do not have the latter test.