喀麦隆现场评估点检测试剂盒（POC-CCA）横向流动条用于定量检测尿液中曼氏血吸虫循环阴极抗原。
Field assessment in Cameroon of a reader of POC-CCA lateral flow strips for the quantification of Schistosoma mansoni circulating cathodic antigen in urine.
机构信息
Molecular Parasitology and Entomology Unit, Department of Biochemistry, Faculty of Science, University of Dschang, Dschang, Cameroon.
Department of Biological sciences, Faculty of Science, University of Maroua, Maroua, Cameroon.
出版信息
PLoS Negl Trop Dis. 2021 Jul 14;15(7):e0009569. doi: 10.1371/journal.pntd.0009569. eCollection 2021 Jul.
BACKGROUND
Determining Schistosoma mansoni infection rate and intensity is challenging due to the low sensitivity of the Kato-Katz (KK) test that underestimates the true disease prevalence. Circulating cathodic antigen (CCA) excreted in urine is constantly produced by adult worms and has been used as the basis of a simple, non-invasive point of care test (POC-CCA) for Schistosoma mansoni infections. Although the abundance of CCA in urine is proportional to worm burden, the POC-CCA test is marketed as a qualitative test, making it difficult to investigate the wide range of infection intensities. This study was designed to compare the prevalence and intensity of S. mansoni by KK and POC-CCA and quantify, on fresh and frozen (<-20°C) urine samples, CCA using the visual scores and the ESEquant LR3 reader.
METHODOLOGY
Stool and urine samples were collected from 759 school-aged children. The prevalence and intensity of S. mansoni were determined using KK and POC-CCA. The degree of the positivity of POC-CCA was estimated by quantifying CCA on fresh and frozen urine samples using visual scores and strip reader. The prevalence, the infection intensity as well the relative amounts of CCA were compared.
RESULTS
The S. mansoni infection rates inferred from POC-CCA and KK were 40.7% and 9.4% respectively. Good correlations were observed between infection intensities recorded by; i) the reader and visual scoring system on fresh (Rho = 0.89) and frozen samples (Rho = 0.97), ii) the reader on fresh urine samples and KK (epg) (Rho = 0.44). Nevertheless, 238 POC-CCA positive children were negative for KK, and sixteen of them had high levels of CCA. The correlation between results from the reader on fresh and frozen samples was good (Rho = 0.85). On frozen samples, CCA was not detected in 55 samples that were positive in fresh urine samples.
CONCLUSION
This study confirmed the low sensitivity of KK and the high capacity of POC-CCA to provide reliable data on the prevalence and intensity of S. mansoni infections. The lateral flow reader enabled accurate quantification of CCA under field conditions on fresh and frozen urine samples with less time and effort than KK.
背景
加藤厚涂片（Kato-Katz，KK）检测法的灵敏度较低，低估了疾病的真实流行率，因此难以确定曼氏血吸虫感染率和强度。循环阴极抗原（Circulating cathodic antigen，CCA）是由成虫不断分泌到尿液中的，已被用作曼氏血吸虫感染的一种简单、非侵入性即时检测（Point of care test，POC-CCA）的基础。尽管尿液中 CCA 的丰度与虫负荷成正比，但 POC-CCA 检测法被宣传为定性检测法，因此难以调查广泛的感染强度。本研究旨在比较 KK 和 POC-CCA 检测法检测的曼氏血吸虫的流行率和强度，并使用视觉评分和 ESEquant LR3 读数器，定量检测新鲜和冷冻（<-20°C）尿液样本中的 CCA。
方法
从 759 名学龄儿童中采集粪便和尿液样本。使用 KK 和 POC-CCA 检测曼氏血吸虫的流行率和感染强度。通过对新鲜和冷冻尿液样本进行视觉评分和条带阅读器定量检测 CCA，来估计 POC-CCA 的阳性程度。比较 POC-CCA 和 KK 检测的流行率、感染强度和 CCA 的相对含量。
结果
POC-CCA 和 KK 推断的曼氏血吸虫感染率分别为 40.7%和 9.4%。在新鲜（Rho=0.89）和冷冻样本（Rho=0.97）上，阅读器和视觉评分系统记录的感染强度之间观察到良好的相关性；在新鲜尿液样本上阅读器与 KK（epg）（Rho=0.44）之间也观察到良好的相关性。然而，238 名 POC-CCA 阳性儿童 KK 检测为阴性，其中 16 名儿童 CCA 水平较高。阅读器在新鲜和冷冻样本上的结果之间相关性良好（Rho=0.85）。在冷冻样本中，在新鲜尿液样本中为阳性的 55 个样本中未检测到 CCA。
结论
本研究证实了 KK 的低灵敏度和 POC-CCA 高能力，能够可靠地提供曼氏血吸虫感染的流行率和强度数据。在现场条件下，使用 lateral flow 阅读器可以在新鲜和冷冻尿液样本上准确地定量 CCA，所需时间和精力比 KK 少。
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