РЕТРОСПЕКТИВНА ЕВАЛУАЦИЈА COBAS AMPLICOR MTB ТЕСТА У ДЕТЕКЦИЈИ Mycobacterium tuberculosis ИЗ РЕСПИРАТОРНИХ УЗОРАКА

Abstract

Traditional methods for detection of mycobacteria are limited by low sensitivity and/or specificity, with the time necessary for the identification of Mycobacterium tuberculosis of several weeks. A number of molecular techniques, including different biomarkers, have been developed for rapid identification of mycobacteria. The aim of this study was to evaluate the reliability of the COBAS AMPLICOR MTB Test in detection of Mycobacterium tuberculosis in respiratory specimens. Samples were decontaminated with N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH). One drop was used for detection of acid-fast bacilli positive-smears by Ziehl-Neelsen (ZN) staining, 200 µL to inoculate Löwenstein-Jensen (LJ) medium, 500 µL for cultivation in BACTEC MGIT 960 System, and 100 µL for the COBAS AMPLICOR MTB Test, performed according to manufacturer's recommendations. Out of 100 samples, 50 samples were smear-positive and 50 smear-negative. Mycobacterium tuberculosis was isolated from 59 samples by at least one cultivation method. After the analysis of inconsistent results, the overall sensitivity, specificity, positive and negative predictive value of the COBAS AMPLICOR MTB Test were 94.93%, 100%, 100% and 91.89% compared to diagnostic cultures, with an inhibition rate 2%. The values for smear-positive and smear-negative samples were 97.87%, 100%, 100%, 50%, and 83.33%, 100%, 100% and 94.29%, respectively. The greater numbers of positive samples were detected using the COBAS AMPLICOR MTB Test than by direct microscopy. Based on the obtained results, considering the methodological simplicity and completely automatized amplification and detection, the COBAS AMPLICOR MTB Test has proven to be very reliable in the diagnosis of tuberculosis (TB).