Molecular Diagnosis of Chlamydia trachomatis Infections by Probe Hybridization, PCR, LCR, TMA, and Q-β Replicase
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The use of cell cultures for the laboratory diagnosis of Chlamydia trachomatis infections was popularized during the 1970s and 80s (1-4). The techniques required live organisms and were restricted to specialized laboratories. During the 1980s the detection of chlamydia-specific antigens was extensively used and compared to cell culture, provided a less stringent transportation of clinical specimens. Both direct fluorescent antibodies (DFA) and enzyme immunoassay (EIA) systems were commercialized (5-7) and algorithms for confirming false positives were popularized (8,9). The first nucleic acid detection assay for C.trachomatis was evaluated during this time frame with comparisons to culture and antigen detection (10-14). In the early 1990s, the following amplified nucleic acid assays detecting C. trachomatis gene fragments were developed: polymerase chain reaction (PCR), ligase-chain reaction (LCR), Q-β replicase-amplified hybridization (QBRAH), transcription-mediated amplification (TMA), and nucleic acid sequence-based amplification (NASBA). Extensive evaluations of PCR and LCR have shown, through discordant analysis and expansion of the reference standard for positives, that these amplified assays are 20-30% more sensitive than culture, antigen, or nonamplified nucleic-acid detection methods (15-29). This range in sensitivity (for PCR and/or LCR) is influenced by the rate of inhibitors of amplification found in clinical specimens.
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