Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA.
Malar J. 2022 Nov 6;21(1):319. doi: 10.1186/s12936-022-04323-2.
Detection of malaria parasitaemia in samples that are negative by rapid diagnostic tests (RDTs) requires resource-intensive molecular tools. While pooled testing using a two-step strategy provides a cost-saving alternative to the gold standard of individual sample testing, statistical adjustments are needed to improve accuracy of prevalence estimates for a single step pooled testing strategy.
A random sample of 4670 malaria RDT negative dried blood spot samples were selected from a mass testing and treatment trial in Asembo, Gem, and Karemo, western Kenya. Samples were tested for malaria individually and in pools of five, 934 pools, by one-step quantitative polymerase chain reaction (qPCR). Maximum likelihood approaches were used to estimate subpatent parasitaemia (RDT-negative, qPCR-positive) prevalence by pooling, assuming poolwise sensitivity and specificity was either 100% (strategy A) or imperfect (strategy B). To improve and illustrate the practicality of this estimation approach, a validation study was constructed from pools allocated at random into main (734 pools) and validation (200 pools) subsets. Prevalence was estimated using strategies A and B and an inverse-variance weighted estimator and estimates were weighted to account for differential sampling rates by area.
The prevalence of subpatent parasitaemia was 14.5% (95% CI 13.6-15.3%) by individual qPCR, 9.5% (95% CI (8.5-10.5%) by strategy A, and 13.9% (95% CI 12.6-15.2%) by strategy B. In the validation study, the prevalence by individual qPCR was 13.5% (95% CI 12.4-14.7%) in the main subset, 8.9% (95% CI 7.9-9.9%) by strategy A, 11.4% (95% CI 9.9-12.9%) by strategy B, and 12.8% (95% CI 11.2-14.3%) using inverse-variance weighted estimator from poolwise validation. Pooling, including a 20% validation subset, reduced costs by 52% compared to individual testing.
Compared to individual testing, a one-step pooled testing strategy with an internal validation subset can provide accurate prevalence estimates of PCR-positivity among RDT-negatives at a lower cost.
在快速诊断检测（RDT）呈阴性的样本中检测疟疾寄生虫血症需要资源密集型分子工具。虽然两步策略的汇集检测提供了一种比个体样本检测的金标准更具成本效益的替代方案，但需要进行统计调整，以提高单步汇集检测策略的流行率估计的准确性。
从肯尼亚西部阿森博、杰姆和卡雷莫的大规模检测和治疗试验中随机抽取了 4670 份疟疾 RDT 阴性干血斑样本。通过一步定量聚合酶链反应（qPCR）对这些样本进行个体和五份样本的汇集检测，共 934 个汇集样本。采用最大似然方法，假设汇集敏感性和特异性均为 100%（策略 A）或不完美（策略 B），估计亚隐性寄生虫血症（RDT 阴性，qPCR 阳性）的患病率。为了改进和说明这种估计方法的实用性，从随机分配的汇集样本中构建了一个验证研究，分为主样本（734 个汇集）和验证样本（200 个汇集）子集。使用策略 A 和 B 以及逆方差加权估计器来估计患病率，并根据区域的不同抽样率对估计值进行加权。
个体 qPCR 的亚隐性寄生虫血症患病率为 14.5%（95%CI 13.6-15.3%），策略 A 为 9.5%（95%CI 8.5-10.5%），策略 B 为 13.9%（95%CI 12.6-15.2%）。在验证研究中，个体 qPCR 的患病率在主样本中为 13.5%（95%CI 12.4-14.7%），策略 A 为 8.9%（95%CI 7.9-9.9%），策略 B 为 11.4%（95%CI 9.9-12.9%），使用来自汇集验证的逆方差加权估计器为 12.8%（95%CI 11.2-14.3%）。与个体检测相比，包括 20%验证子集的一步汇集检测策略可以以更低的成本提供 RDT 阴性样本中 PCR 阳性的准确流行率估计。
与个体检测相比，具有内部验证子集的一步汇集检测策略可以以更低的成本提供 RDT 阴性样本中 PCR 阳性的准确流行率估计。
