Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA.
J Clin Microbiol. 2011 Nov;49(11):3885-91. doi: 10.1128/JCM.01157-11. Epub 2011 Aug 31.
Accurate malaria diagnosis has dual roles in identification of symptomatic persons for effective malaria treatment and also enumeration of asymptomatic persons who contribute to the epidemiologic determinants of transmission. Three currently used diagnostic tests, microscopy, rapid diagnostic tests (RDTs), and real-time PCR, all have different sensitivities and specificities, which are parasite density dependent. Here, we compare their concordance among 451 febrile episodes in a cohort of 2,058 children and adults followed over 6 months in a region in central Tanzania with hypoendemic malaria. Microscopy, a histidine-rich protein-based RDT, and two different real-time PCR gene probes detected Plasmodium falciparum in 20, 54, 41, and 78 episodes of fever, respectively. They had complete concordance in only 9 episodes. Real-time PCR with an 18S probe was more sensitive than with a mitochondrial probe for cytochrome b despite higher copy numbers of mitochondrial DNA. Both PCR yields were increased 4-fold by glycogen/acetate precipitation with low-speed centrifugation. Duplicate PCR increases low-density malaria detection. RDT had the highest number of unique positives, presumably from persistent antigen despite the absence of parasites, although RDT did not detect 3 parasitemias with over 1,000 parasites/μl. In a latent class analysis, real-time PCR had significantly higher sensitivity than did microscopy or RDT. Agreement between real-time PCR, RDT, and microscopy was highest in March and April, when both the P. falciparum parasite rate and parasite densities are highest. Real-time PCR is more sensitive and specific than RDT and microscopy in low-prevalence, low-parasite-density settings.
准确的疟疾诊断在识别有症状的人进行有效治疗方面具有双重作用，同时也可以识别出无症状的人，这些人是传播的流行病学决定因素之一。目前使用的三种诊断测试，即显微镜检查、快速诊断测试（RDT）和实时 PCR，都具有不同的敏感性和特异性，这些特异性取决于寄生虫密度。在这里，我们比较了在坦桑尼亚中部一个地区的 2058 名儿童和成人队列中，451 例发热发作的这些测试之间的一致性，该地区的疟疾呈低流行状态。显微镜检查、一种基于组氨酸丰富蛋白的 RDT 以及两种不同的实时 PCR 基因探针分别在 20、54、41 和 78 例发热发作中检测到恶性疟原虫。它们在仅 9 例中完全一致。实时 PCR 用 18S 探针检测比用线粒体探针检测环氧化酶 b 更敏感，尽管线粒体 DNA 的拷贝数更高。通过糖原/醋酸盐沉淀和低速离心，两种 PCR 产物的产量均增加了 4 倍。重复 PCR 增加了低密度疟疾的检测。RDT 具有最多的独特阳性结果，推测是由于尽管没有寄生虫，但存在持续的抗原，尽管 RDT 没有检测到 3 例寄生虫血症，每微升有超过 1000 个寄生虫。在潜伏类分析中，实时 PCR 的敏感性明显高于显微镜检查或 RDT。在寄生虫率和寄生虫密度均最高的 3 月和 4 月，实时 PCR、RDT 和显微镜检查之间的一致性最高。实时 PCR 在低流行率、低寄生虫密度的情况下比 RDT 和显微镜检查更敏感和更特异。
