title: Multicenter evaluation of the Abbott LCx Mycobacterium tuberculosis ligase chain reaction assay.
abstract: Four Australian hospital laboratories evaluated the performance of the Abbott LCx Mycobacterium tuberculosis assay with 2,347 specimens (2,083 respiratory and 264 nonrespiratory specimens) obtained from 1, 411 patients. A total of 152 specimens (6.5%) were culture positive for Mycobacterium tuberculosis complex (MTBC); of these, 79 (52%) were smear positive. After resolution of discrepant data, the overall sensitivity, specificity, and positive and negative predictive values for the LCx assay were 69.7, 99.9, 99.1, and 97.7% respectively. For smear-positive respiratory specimens that were culture positive for MTBC, the values were 98.5, 100, 100, and 98.4%, respectively, while the values for smear-negative respiratory specimens were 41.5, 99.9, 96.4, and 98%, respectively. Relative operating characteristic curves were constructed to demonstrate the relationship between sensitivity and specificity for a range of possible cutoff values in the LCx assay. These graphs suggested that the assay sensitivity for respiratory samples could be increased from 70.2 to 78.6%, while the specificity would be reduced from 99.9 to 99.4% by inclusion of a grey zone (i.e., LCx assay values of between 0.2 and 0.99). An algorithm is presented for the handling of specimens with LCx assay values within this grey zone.
authors.affiliation: Infectious Diseases Laboratories, Institute of Medical and Veterinary Science, Adelaide, South Australia, Australia. richard.lumb@imvs.sa.gov.au
authors.forename: R
authors.initials: R
authors.lastname: Lumb
authors.forename: K
authors.initials: K
authors.lastname: Davies
authors.forename: D
authors.initials: D
authors.lastname: Dawson
authors.forename: R
authors.initials: R
authors.lastname: Gibb
authors.forename: T
authors.initials: T
authors.lastname: Gottlieb
authors.forename: C
authors.initials: C
authors.lastname: Kershaw
authors.forename: K
authors.initials: K
authors.lastname: Kociuba
authors.forename: G
authors.initials: G
authors.lastname: Nimmo
authors.forename: N
authors.initials: N
authors.lastname: Sangster
authors.forename: M
authors.initials: M
authors.lastname: Worthington
authors.forename: I
authors.initials: I
authors.lastname: Bastian
mesh_terms: D011088:DNA Ligases; D005784:Gene Amplification; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D012680:Sensitivity and Specificity
chemical_list: D011088:DNA Ligases