在巴西亚马逊地区，一种针对 vivax 疟疾诊断进行了验证的敏感血铁红素疟疾诊断检测的性能。
Performance of a sensitive haemozoin-based malaria diagnostic test validated for vivax malaria diagnosis in Brazilian Amazon.
机构信息
Fundação de Medicina Tropical Dr Heitor Vieira Dourado, Manaus, Amazonas, 69040-000, Brazil.
Universidade do Estado do Amazonas (UEA), Manaus, Amazonas, 69040-000, Brazil.
出版信息
Malar J. 2021 Mar 12;20(1):146. doi: 10.1186/s12936-021-03688-0.
BACKGROUND
Vivax malaria diagnosis remains a challenge in malaria elimination, with current point of care rapid diagnostic tests (RDT) missing many clinically significant infections because of usually lower peripheral parasitaemia. Haemozoin-detecting assays have been suggested as an alternative to immunoassay platforms but to date have not reached successful field deployment. Haemozoin is a paramagnetic crystal by-product of haemoglobin digestion by malaria parasites and is present in the food vacuole of malaria parasite-infected erythrocytes. This study aimed to compare the diagnostic capability of a new haemozoin-detecting platform, the Gazelle™ device with optical microscopy, RDT and PCR in a vivax malaria-endemic region.
METHODS
A comparative, double-blind study evaluating symptomatic malaria patients seeking medical care was conducted at an infectious diseases reference hospital in the western Brazilian Amazon. Optical microscopy, PCR, RDT, and Gazelle™ were used to analyse blood samples. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Kappa values were calculated.
RESULTS
Out of 300 patients, 24 test results were excluded from the final analysis due to protocol violation (6) and inconclusive and/or irretrievable results (18). Gazelle™ sensitivity was 96.1 % (91.3-98.3) and 72.1 % (65.0-78.3) when compared to optical microscopy and PCR, respectively whereas it was 83.9 % and 62.8 % for RDTs. The platform presented specificity of 100 % (97.4-100), and 99.0 % (94.8-99.9) when compared to optical microscopy, and PCR, respectively, which was the same for RDTs. Its correct classification rate was 98.2 % when compared to optical microscopy and 82.3 % for PCR; the test's accuracy when compared to optical microscopy was 98.1 % (96.4-99.7), when compared to RDT was 95.2 % (93.0-97.5), and when compared to PCR was 85.6 % (82.1-89.1). Kappa (95 % CI) values for Gazelle™ were 96.4 (93.2-99.5), 88.2 (82.6-93.8) and 65.3 (57.0-73.6) for optical microscopy, RDT and PCR, respectively.
CONCLUSIONS
The Gazelle™ device was shown to have faster, easier, good sensitivity, specificity, and accuracy when compared to microscopy and was superior to RDT, demonstrating to be an alternative for vivax malaria screening particularly in areas where malaria is concomitant with other febrile infections (including dengue fever, zika, chikungunya, Chagas, yellow fever, babesiosis).
背景
在消除疟疾的过程中， vivax 疟疾的诊断仍然是一个挑战，目前的即时检测（RDT）由于外周寄生虫血症通常较低而错过了许多具有临床意义的感染。血红素检测法已被提议作为免疫测定平台的替代品，但迄今为止尚未成功进行现场部署。血红素是疟原虫消化血红蛋白的副产物，呈顺磁性晶体，存在于疟原虫感染的红细胞的食物泡中。本研究旨在比较一种新的血红素检测平台——Gazelle™设备与光学显微镜、RDT 和 PCR 在 vivax 疟疾流行地区的诊断能力。
方法
在巴西西部亚马逊的一家传染病参考医院，对寻求医疗的有症状疟疾患者进行了一项比较性、双盲研究。使用光学显微镜、PCR、RDT 和 Gazelle™来分析血液样本。计算了灵敏度、特异性、阳性预测值（PPV）、阴性预测值（NPV）和 Kappa 值。
结果
在 300 名患者中，由于违反方案（6 例）和结果不确定和/或不可检索（18 例），有 24 例检测结果被排除在最终分析之外。与光学显微镜和 PCR 相比，Gazelle™的灵敏度分别为 96.1%（91.3-98.3）和 72.1%（65.0-78.3），而 RDT 的灵敏度分别为 83.9%和 62.8%。该平台的特异性分别为 100%（97.4-100）和 99.0%（94.8-99.9），与光学显微镜和 PCR 相比，与 RDT 相比则为 100%。其正确分类率与光学显微镜相比为 98.2%，与 PCR 相比为 82.3%；与光学显微镜相比，该检测的准确率为 98.1%（96.4-99.7），与 RDT 相比为 95.2%（93.0-97.5），与 PCR 相比为 85.6%（82.1-89.1）。Gazelle™与光学显微镜、RDT 和 PCR 的 Kappa（95%CI）值分别为 96.4（93.2-99.5）、88.2（82.6-93.8）和 65.3（57.0-73.6）。
结论
与显微镜相比，Gazelle™设备具有更快、更容易、灵敏度高、特异性和准确性，优于 RDT，证明是 vivax 疟疾筛查的一种替代方法，特别是在疟疾与其他发热性感染（包括登革热、寨卡病毒、基孔肯雅热、恰加斯病、黄热病、巴贝斯虫病）并存的地区。
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