Ostergaard L
Faculty of Health Sciences, University of Aarhus, Denmark.
APMIS Suppl. 1999;89:5-36.
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.
自1990年首次描述用于检测临床样本中沙眼衣原体的聚合酶链反应（PCR）以来，已经开展了许多关于DNA扩增和沙眼衣原体感染诊断的研究，但仍缺乏最佳的样本制备程序。评估DNA扩增方法诊断性能的主要问题在于，目前尚无针对沙眼衣原体感染的临床或微生物学参考标准。因此，所评估的诊断性能始终会反映所选比较方法的情况。尽管如此，DNA扩增方法似乎比细胞培养技术和基于免疫学的技术更为灵敏。与基于免疫学的检测方法相比，其特异性也有所提高，这使得DNA扩增方法适用于那些在基于免疫学的方法中会与交叉反应生物发生污染的样本类型，即咽拭子和直肠拭子样本。然而，其特异性以及阳性检测的预测价值并非最佳。由于阳性检测的预测价值受受检人群患病率的影响很大，因此持续需要对应用的检测方法进行评估，特别是考虑到随着检测活动的加强以及艾滋病出现后安全性行为的变化，患病率可能会下降。DNA扩增方法提高的灵敏度使得可以使用衣原体生物含量低于传统拭子样本的样本材料，即尿液、精液和阴道分泌物可作为样本材料。这些样本可由个体自行获取，而且由于运输条件对检测性能的影响似乎较小，样本也可在私密的家中采集，随后由个体直接邮寄至诊断实验室。与在医生办公室进行的传统拭子检查相比，这种检测策略改善了性伴侣追踪和普遍筛查。尚未实现具有最佳诊断性能的检测方法，而且对几种样本类型的研究也不够充分。虽然尚未全面研究使用自行采集的样本和普遍筛查的社会影响，但随着DNA扩增技术的出现，在检测和预防泌尿生殖系统沙眼衣原体流行的新策略方面已取得了一个里程碑式的进展。
