Programmatic Impact of Implementing GeneXpert MTB/ RIF Assay for the Detection of Mycobacterium Tuberculosis in Respiratory Specimens from Pulmonary Tuberculosis Suspected Patients in Resource Limited Laboratory Settings of Eastern Nepal

Abstract

Background:In Nepal, introduction of GeneXpert MTB/RIF assay (Xpert assay) as an initial confirmation test for tuberculosis (TB) has been considered to have impact as a significant decrease in number of clinically diagnosed pulmonary tuberculosis (PTB) cases than previous years. This study aims to find out the distribution profile of suspected tuberculosis cases according to patients age, gender, treatment history and HIV status as well as to evaluate the utility of the Xpert assay over conventional acid-fast bacilli (AFB) staining method for the proper diagnosis of M. Tuberculosis in respiratory specimens from the tuberculosis (TB) suspected patient samples. Methods:The prospective cross-sectional analytical study was conducted in National Anti-Tuberculosis Center (NATA) center- Biratnagar and Primary Healthcare Center (PHC) - Manglabare, Morang District, of eastern Nepal from January 2014 to August 2014. Laboratory investigation was done by conventional AFB staining followed by Xpert assay. Results:A total of 1549 sputum samples were initially analyzed. AFB staining resulted in 1441 AFB smear negative samples and 88 AFB smear positive samples, whereas 20 samples were directly processed for Xpert assay. The male: female smear positive ratio was 2.8:1 and was higher among age groups (21-40) years. Tuberculosis among HIV patients was found 22.22%. Xpert assay demonstrates that out of 1441 smear negative AFB cases, 258 were found to have TB positive, whereas out of 88 smears positive AFB cases 12 were found to have TB negative. The sensitivity of the Xpert assay in patients classified as AFB smear positive was found 85.4% and the specificity in smear negative patients was 81%. Conclusion:The study concluded that implementation of Gene Xpert MTB/RIF assay is a helpful tool for early and rapid detection of tuberculosis with greater sensitivity and specificity over traditional AFB staining techniques.

Diagnostic Performance of Xpert MTB/RIF Assay Versus Ziehl-Neelsen Method for the Diagnosis of Pulmonary Tuberculosis in Addis Ababa, Ethiopia

“…The specificity of Xpert MTB/RIF assay in the present study was much lower compared to study in Pakistan showing specificity of 98.3% [13] and 90% specificity from India [12]. This study includes both smear positive and negative sputum while the study of Thailand was on smears negative PTB [19].…”

Comparison of Ziehl-Neelsen Microscopy Technique and Genexpert in the Diagnosis of Tuberculosis in Sudanese Patients

“…One sample detected positive for the AFB by ZN smear, but it was shown negative by GeneXpert. It has been reported that ZN smear microscopy has less accuracy and provides false results compared with GeneXpert and culture (26,27).…”

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“…This study has few limitations: first, it is a prospective study based on only pulmonary samples, which includes sputum, BAL, and gastric aspirate; further studies with more varieties of samples need to be done especially among extrapulmonary cases. Second, the cost of the cartridge was too high, and the number of test failures due to power cut-off needs to be reprocessed again, which created an overburden and increase in expenditure 28 . Third, WHO recommends CBNAAT for diagnosis of pulmonary tuberculosis and detection of RIF's resistance simultaneously, especially in those clients who were already suffering with HIV and re-treatment cases who are at risk of development of MDR-TB.…”