Update on techniques in the diagnosis of Chlamydia trachomatis infections.
There are two major advances in the laboratory diagnosis of Chlamydia trachomatis, one lies in the use of nucleic acid amplification techniques and the second in the evaluation of urine as an alternative to invasive sampling of urethral and cervical specimens. There is however, the problem of inhibitors in urine that needs to be addressed, in order for this method to achieve 100% sensitivity. The Q-beta (Q beta) replicase test, Gen-Probe transcription-mediated amplification (TMA) test and the nucleic acid sequence-based amplification (NASBA) test are some of the newer nucleic acid amplification methods being evaluated for the detection of C. trachomatis. These are RNA-based amplification techniques that can potentially achieve very high levels of sensitivity because of the presence of multiple RNA copies in microorganisms and may also be useful for detecting active infection. Q-beta has been found to be less subjected to inhibitory substances in urine than polymerase chain reaction (PCR). Cell culture remains the gold standard for the legal diagnosis of C. trachomatis infections and is the method of choice for the detection of infection at uncommon sites. It forms part of the expanded gold standard for the evaluation of nonculture methods that do not involve nucleic acid amplification, and is also a confirmatory test for such techniques. Notwithstanding, clinicians must remember the basic tenet of laboratory tests, that is, good specimen collection and handling, for any laboratory test to yield accurate information to guide their management of patients.
Ngan
C C
CC
Department of Pathology, Singapore General Hospital, Singapore.
D002478:Cells, Cultured; D002690:Chlamydia Infections / Q000175:diagnosis*; D002692:Chlamydia trachomatis / Q000302:isolation & purification; D005821:Genetic Techniques; D006801:Humans; D007159:Immunologic Tests