Diagnosis of urogenital Chlamydia trachomatis infection by use of DNA amplification

Abstract

Numerous studies on DNA amplification and diagnosis of C. trachomatis infections have been performed since the first PCR for detection of C. trachomatis in clinical samples was described in 1990, but optimal sample preparation procedures are still lacking. The major problem in evaluating the diagnostic performance of the DNA amplification methods is that there is no clinical or microbiological reference standard for C. trachomatis infection. The evaluated diagnostic performance will therefore always be a reflection of of the chosen comparator(s). Despite this, it seems that the DNA amplification methods are more sensitive than the cell culture techniques and the techniques based on immunology. Compared with the tests based on immunology the specificity is also improved, which makes the DNA amplification methods useful for sample types contaminated with organisms cross-reacting in the immunologically based methods, i.e. pharyngeal and rectal swab samples. However, the specificity and thereby the predictive value of a positive test is not optimal. Since the predictive value of a positive test is highly influenced by the prevalence in the tested population, evaluation of applied tests is constantly needed, especially since the prevalence may be expected to decrease with intensified test activity and due to changes in safe sex practices after the advent of AIDS. The improved sensitivity of the DNA amplification methods allows the use of sample material in which the content of Chlamydia organisms is lower than in conventional swab samples, i.e. urine, semen, and vaginal secretions can be used as sample material. these samples can be obtained by the individuals themselves, and since transport conditions seem less critical for the test performance, samples can also be taken in the privacy of the home and subsequently mailed by the individual directly to the diagnostic laboratory. Such strategy for testing has led to improved partner tracing and universal screening, compared with traditional swab examinations at physicians' offices. Tests with an optimal diagnostic performance have not yet been reached, and several sample categories have not been studied sufficiently. The societal implications of the use of self-collected samples and universal screening have not been studied in full, but a milestone for new strategies in detection and preventing urogenital C. trachomatis epidemics has been reached with the availability of DNA amplification techniques.