Programme for Nurturing Global Leaders in Tropical and Emerging Communicable Diseases, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
Malar J. 2022 Apr 19;21(1):126. doi: 10.1186/s12936-022-04153-2.
Loss of efficacy of diagnostic tests may lead to untreated or mistreated malaria cases, compromising case management and control. There is an increasing reliance on rapid diagnostic tests (RDTs) for malaria diagnosis, with the most widely used of these targeting the Plasmodium falciparum histidine-rich protein 2 (PfHRP2). There are numerous reports of the deletion of this gene in P. falciparum parasites in some populations, rendering them undetectable by PfHRP2 RDTs. The aim of this study was to identify P. falciparum parasites lacking the P. falciparum histidine rich protein 2 and 3 genes (pfhrp2/3) isolated from asymptomatic and symptomatic school-age children in Kinshasa, Democratic Republic of Congo.
The performance of PfHRP2-based RDTs in comparison to microscopy and PCR was assessed using blood samples collected and spotted on Whatman 903™ filter papers between October and November 2019 from school-age children aged 6-14 years. PCR was then used to identify parasite isolates lacking pfhrp2/3 genes.
Among asymptomatic malaria carriers (N = 266), 49%, 65%, and 70% were microscopy, PfHRP2_RDT, and pfldh-qPCR positive, respectively. The sensitivity and specificity of RDTs compared to PCR were 80% and 70% while the sensitivity and specificity of RDTs compared to microscopy were 92% and 60%, respectively. Among symptomatic malaria carriers (N = 196), 62%, 67%, and 87% were microscopy, PfHRP2-based RDT, pfldh-qPCR and positive, respectively. The sensitivity and specificity of RDTs compared to PCR were 75% and 88%, whereas the sensitivity and specificity of RDTs compared to microscopy were 93% and 77%, respectively. Of 173 samples with sufficient DNA for PCR amplification of pfhrp2/3, deletions of pfhrp2 and pfhrp3 were identified in 2% and 1%, respectively. Three (4%) of samples harboured deletions of the pfhrp2 gene in asymptomatic parasite carriers and one (1%) isolate lacked the pfhrp3 gene among symptomatic parasite carriers in the RDT positive subgroup. No parasites lacking the pfhrp2/3 genes were found in the RDT negative subgroup.
Plasmodium falciparum histidine-rich protein 2/3 gene deletions are uncommon in the surveyed population, and do not result in diagnostic failure. The use of rigorous PCR methods to identify pfhrp2/3 gene deletions is encouraged in order to minimize the overestimation of their prevalence.
诊断检测的效力丧失可能导致未治疗或治疗不当的疟疾病例，从而影响病例管理和控制。人们越来越依赖快速诊断检测（RDT）来诊断疟疾，其中最广泛使用的是针对恶性疟原虫高变区蛋白 2（PfHRP2）的 RDT。有大量报告称，在一些人群中，恶性疟原虫寄生虫中存在 PfHRP2 基因缺失，导致它们无法被 PfHRP2 RDT 检测到。本研究旨在鉴定从金沙萨无症和有症学龄儿童中分离出的缺乏恶性疟原虫高变区蛋白 2 和 3 基因（pfhrp2/3）的恶性疟原虫寄生虫。
使用 2019 年 10 月至 11 月间采集并点在 Whatman 903™滤纸上的血液样本，评估基于 PfHRP2 的 RDT 与显微镜和 PCR 的性能，这些样本来自年龄在 6-14 岁的学龄儿童。然后使用 PCR 鉴定缺乏 pfhrp2/3 基因的寄生虫分离物。
在无症状疟原虫携带者（N=266）中，分别有 49%、65%和 70%的人经显微镜、PfHRP2_RDT 和 pfldh-qPCR 检测为阳性。与 PCR 相比，RDT 的敏感性和特异性分别为 80%和 70%，而与显微镜相比，RDT 的敏感性和特异性分别为 92%和 60%。在有症状疟原虫携带者（N=196）中，分别有 62%、67%和 87%的人经显微镜、基于 PfHRP2 的 RDT 和 pfldh-qPCR 检测为阳性。与 PCR 相比，RDT 的敏感性和特异性分别为 75%和 88%，而与显微镜相比，RDT 的敏感性和特异性分别为 93%和 77%。在 173 个有足够 DNA 进行 pfhrp2/3 PCR 扩增的样本中，分别有 2%和 1%的样本中发现了 pfhrp2 和 pfhrp3 的缺失。在无症状寄生虫携带者中，有 3 个（4%）样本携带 pfhrp2 基因缺失，而在 RDT 阳性亚组中，有 1 个（1%）寄生虫携带 pfhrp3 基因缺失。在 RDT 阴性亚组中未发现缺乏 pfhrp2/3 基因的寄生虫。
在所调查的人群中，恶性疟原虫高变区蛋白 2/3 基因缺失并不常见，也不会导致诊断失败。建议使用严格的 PCR 方法来鉴定 pfhrp2/3 基因缺失，以尽量减少其流行率的高估。
