title: Assessment of the quantitative ability of AdvanSure TB/NTM real-time PCR in respiratory specimens by comparison with phenotypic methods.
abstract: Accurate quantification of mycobacterial load is important to evaluate disease severity and to monitor the course of treatment in tuberculosis (TB). We evaluated the quantitative capability of the AdvanSure TB/NTM real-time PCR kit (LG Life Science, Korea) to determine the cycle threshold (Ct) for mycobacterial burden. We retrospectively analyzed data from 108 patients whose respiratory specimens (sputums and bronchoalveolar lavage fluids) were positive for Mycobacterium tuberculosis complex (85 culture-positive and 23 culture-negative specimens). We compared Ct values with grades of acid-fast bacilli (AFB) staining, semi-quantitative colony count on solid medium, and time to positivity (TTP) in liquid and solid media. We also investigated the cutoff Ct value for predicting stain-positive status. Ct value showed significant reverse correlation with AFB staining grade (r s=-0.635, P<0.01). Ct value significantly decreased as the semi-quantitative counts on the solid medium increased (P<0.001), and the mean Ct value of each of the groups 1+, 2+, 3+, and 4+ were 29.0, 30.0, 27.1, and 25.5, respectively. A weak correlation between Ct value and TTP in liquid and solid media was observed (r s=0.468 and 0.365, respectively). A cutoff Ct value of <33.2 best predicted stain positivity, with a sensitivity of 95.0% and a specificity of 32.0%. Our findings suggest the potential use of AdvanSure TB/NTM real-time PCR kit for quantitatively determining bacterial burden, albeit with some enhancements.
authors.affiliation: Department of Laboratory Medicine, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hyeyoung
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Kang Gyun
authors.initials: KG
authors.lastname: Park
authors.affiliation: Department of Laboratory Medicine, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Gundong
authors.initials: G
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Joonhong
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Biostatistics, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Yong-Gyu
authors.initials: YG
authors.lastname: Park
authors.affiliation: Department of Laboratory Medicine, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Yeon-Joon
authors.initials: YJ
authors.lastname: Park
mesh_terms: D019540:Area Under Curve; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis*; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D010641:Phenotype; D012372:ROC Curve; D011933:Reagent Kits, Diagnostic; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D014376:Tuberculosis / Q000175:diagnosis / Q000382:microbiology
chemical_list: D004269:DNA, Bacterial; D011933:Reagent Kits, Diagnostic
keywords: Cycle threshold; Mycobacterium tuberculosis; Quantification