Evaluation of GeneXpert MTB/RIF assay for detection of pulmonary tuberculosis on sputum samples

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

Comparison of GeneXpert MTB/RIF assay and LED-FM microscopy for the diagnosis of extra pulmonary tuberculosis in Khyber Pakhtunkhwa, Pakistan

ABSTRACT GeneXpert is one of the recent technological instruments used to diagnose tuberculosis in a short span of time. In this study, the performance of GeneXpert MTB/RIF assay for the diagnosis of extrapulmonary tuberculosis (EPTB) was compared with light-emitting diode Fluorescent Microscopy (LED-FM) in Khyber Pakhtunkhwa, Pakistan. A total of 737 EPTB samples were collected from tuberculosis (TB) suspected patients. Out of these samples, male to female ratio was 53% (n = 390) to 47% (n = 347) respectively. The sensitivity and specificity was 73% and 100% for GeneXpert, while 40% and 100% for LED-FM microscopy. This shows that the sensitivity of GeneXpert is 40-50%, higher than LED-FM microscopy. GeneXpert also detected low number of bacilli as compared to LED-FM microscopy.

Molecular characterization and spoligotyping analysis of multi drug resistant mycobacterium tuberculosis from a high TB endemic area of Pakistan

Background: Multidrug resistant tuberculosis caused by Mycobacterium tuberculosis is an infection that is resistant to rifampicin and isoniazid. Management of Multidrug resistant tuberculosis is a serious challenge worldwide

Objectives: To investigate hotspot mutations in rpoB, katG and inhA genes and its possible co-relation with predominant genotypes in Khyber Pakhtunkhwa, Pakistan

Study design, settings and duration: This cross sectional study was conducted after approval from research and ethics committee of Provincial TB Control Program, Khyber Pakhtunkhwa in March 2015

Materials and Methods: A total of 166 clinical isolates were analysed which were collected from programmatic management of drug-resistant tuberculosis units. All samples were characterized by phonotypical drug susceptibility test, genotypic drug resistant test [line probe assay] and spoligotyping analysis using ''TB-SPRINT' micro bead assay

Results: Out of the total 166 samples, 97 strains were resistant to rifampicin [RIF] and 106 strains were resistant to isoniazid [INH]. Most common mutation in rpoB was S531L in 75 [77%] isolates followed by D516V in 10 [10%] and H526Y in 6 [6%] samples respectively. A rare mutation in rpoB gene at codon 522 and deletion of codon 518 was also reported. In 106 INH resistant strains, 97[91%] were associated with mutation in katG gene while resistance in 9 [8.4%] strain was due to mutation in the inhA promoter region. Spoligotyping analysis revealed 55 distinct types of different patterns. Spoligotyping patterns of 146 samples matched with 15 different linage of M.tuberculosis in which 101 [60%] were identified as the predominant CAS1-Delhi linage. The pattern of 20 strains [12%] did not matched to any other pattern in the SITVIT database and were named orphan KP

Conclusion: Molecular characterization of M.tuberculosis is very helpful in the early identification of MDR-TB. As CAS1-Delhi is the predominant type in this region, its association with drug resistance, treatment failure and patient demographic profiles should be investigated