Chan E L, Brandt K, Horsman G B
Laboratory and Disease Control Services, Saskatchewan Health, Regina, Canada.
J Clin Microbiol. 1994 Sep;32(9):2208-11. doi: 10.1128/jcm.32.9.2208-2211.1994.
TThe Syva MicroTrak Chlamydia enzyme immunoassay (EIA; Syva Company, San Jose, Calif.) with cytospin and direct fluorescent-antibody assay (DFA) confirmation was evaluated on 43,630 urogenital specimens over a 1-year period in the Provincial Laboratory in Regina, Saskatchewan, Canada. This was a two-phase study intended to define a testing algorithm for Chlamydia trachomatis that would be both highly accurate and cost-effective in our high-volume (> 3,000 tests per month) laboratory. The prevalence of C. trachomatis infection in our population is moderate (8 to 9%). In phase 1, we tested 6,022 male and female urogenital specimens by EIA. All specimens with optical densities above the cutoff value and those within 30% below the cutoff value were retested by DFA. This was 648 specimens (10.8% of the total). A total of 100% (211 of 211) of the specimens with optical densities equal to or greater than 1.00 absorbance unit (AU) above the cutoff value, 98.2% (175 of 178) of the specimens with optical densities of between 0.500 and 0.999 AU above the cutoff value, and 83% (167 of 201) of the specimens with optical densities within 0.499 AU above the cutoff value were confirmed to be positive. A total of 12% (7 of 58) of the specimens with optical densities within 30% below the cutoff value were positive by DFA. In phase 2, we tested 37,608 specimens (32,495 from females; 5,113 from males) by EIA. Only those specimens with optical densities of between 0.499 AU above and 30% below the cutoff value required confirmation on the basis of data from phase 1 of the study. This was 4.5% of all specimens tested. This decrease in the proportion of specimens requiring confirmation provides a significant cost savings to the laboratory. The testing algorithm gives us a 1-day turnaround time to the final confirmed test results. The MicroTrak EIA performed very well in both phases of the study, with a sensitivity, specificity, positive predictive value, and negative predictive value of 96.1, 99.1, 90.3, and 99.7%, respectively, in phase 2. We suggest that for laboratories that use EIA for Chlamydia testing, a study such as this one will identify an appropriate optical density range for confirmatory testing for samples from that particular population.
在加拿大萨斯喀彻温省里贾纳市的省级实验室，对43630份泌尿生殖系统标本进行了为期1年的评估，采用赛瓦公司（加利福尼亚州圣何塞）的MicroTrak衣原体酶免疫测定法（EIA），并通过细胞离心涂片法和直接荧光抗体测定法（DFA）进行确认。这是一项两阶段研究，旨在确定一种针对沙眼衣原体的检测算法，该算法在我们这个高检测量（每月超过3000次检测）的实验室中既具有高度准确性又具有成本效益。我们人群中沙眼衣原体感染的患病率为中等水平（8%至9%）。在第一阶段，我们通过EIA对6022份男性和女性泌尿生殖系统标本进行了检测。所有光密度高于临界值以及低于临界值30%以内的标本均通过DFA进行重新检测。这部分标本有648份（占总数的10.8%）。光密度等于或大于高于临界值1.00吸光度单位（AU）的标本中，100%（211份中的211份）被确认为阳性；光密度在高于临界值0.500至0.999 AU之间的标本中，98.2%（178份中的175份）被确认为阳性；光密度在高于临界值0.499 AU以内的标本中，83%（201份中的167份）被确认为阳性。光密度低于临界值30%以内的标本中，共有12%（58份中的7份）通过DFA检测为阳性。在第二阶段，我们通过EIA对37608份标本（32495份来自女性；5113份来自男性）进行了检测。根据研究第一阶段的数据，只有那些光密度在高于临界值0.499 AU至低于临界值30%之间的标本需要进行确认。这部分标本占所有检测标本的4.5%。需要确认的标本比例的降低为实验室节省了大量成本。该检测算法使我们能够在1天内获得最终确认的检测结果。在研究的两个阶段中，MicroTrak EIA的表现都非常出色，在第二阶段，其灵敏度、特异性、阳性预测值和阴性预测值分别为96.1%、99.1%、90.3%和99.7%。我们建议，对于使用EIA进行衣原体检测的实验室，这样的研究将为来自该特定人群的样本确定用于确认检测的合适光密度范围。
