Detection of M. tuberculosis by LCx M. tuberculosis Assay

Kim, Myeong You; Park, Jong In; Lee, Jeong Nyeo

Abstract

BACKGROUND: Mycobacterial culture is a confirmatory test to detect the Mycobacterium tuberculosis, but it requires considerable time and the diagnosis and treatment may be delayed. The recently developed LCR (ligase chain reaction) is a more rapid and more specific test for the detection of M. tuberculosis. In this study, we compared the LCR results with those of the culture and AFB smear.
METHODS
Mycobacterial culture was performed on 3% Ogawa media for 8 weeks. For LCR, we used LCx Mycobacterium tuberculosis assay kit (Abbott Laboratories, North Chicago, Ill.). The specimens for LCR were resuspended to LCx respiratory specimen resuspension buffer, and then separated mycobacterial DNA by ultrasonicator (Abbott LCx Lysor). Then the samples were mixed in amplification vial containing DNA polymerase and DNA ligase and amplified. For the detection, we used LCx analyzer from Abbott laboratories.
RESULTS
The sensitivity, specificity, and positive and negative predictive values of the LCx M. tuberculosis assay were 95, 100, 100, 60%, respectively; 90, 100, 100, 42.9%, for culture; and 62.5, 100, 100, 16.7%, for acid-fast staining, respectively. The agreements between culture and LCx, smear and LCx, and culture and AFB smear were 86%, 65% and 60%, respectively.
CONCLUSIONS
LCx was confirmed as a more rapid and sensitive test than the culture test and AFB smear.