Department of Medicine I, Division of Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria.
Department of Tropical Medicine, Bernhard Nocht Institute for Tropical Medicine & I. Dep. of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
PLoS Negl Trop Dis. 2024 Mar 14;18(3):e0012054. doi: 10.1371/journal.pntd.0012054. eCollection 2024 Mar.
The parasitic disease loiasis is associated with significant morbidity and mortality. Individuals with hyper-microfilaremia (greater than 20,000 microfilariae per mL of blood) may suffer from serious treatment-related or spontaneous adverse events. Diagnosing loiasis remains complex and primarily relies on direct parasite detection. In this study, we analyzed the performance of various diagnostic tests and the influence of parasitological and clinical factors on test outcomes in samples from individuals living in an endemic region.
Data and samples were collected from rural Gabon. Loiasis was defined as either detectable microfilaremia, or a positive history of eyeworm as assessed by the RAPLOA questionnaire. Diagnostic testing included a quantitative PCR (qPCR) for detection of Loa loa DNA in blood samples, an in-house crude L. loa antigen IgG ELISA, and a rapid test for antibodies against the Ll-SXP-1 antigen (RDT). Sensitivity and specificity were determined for each test and factors potentially influencing outcomes were evaluated in an exploratory analysis.
ELISA, RDT and qPCR results were available for 99.8%, 78.5%, and 100% of the 1,232 participants, respectively. The ELISA and RDT had only modest diagnostic accuracy. qPCR was specific for L. loa microfilaremia and Cycle threshold values correlated with microfilarial density. Anti-L. loa IgG levels were highest in occult loiasis, and antibody levels correlated inversely with L. loa microfilarial density as did RDT line intensities. Only 84.6% and 16.7% of hyper-microfilaremic individuals tested positive by ELISA (11/13) and RDT (2/12), respectively.
None of the tests demonstrated high sensitivity and specificity for loiasis. Indirect diagnostic assays were characterized by low specificity. Additionally, hyper-microfilaremic individuals often tested negative by RDT and ELISA, indicating that these tests are not suitable for individual case management in endemic populations.
寄生虫病罗阿丝虫病与显著的发病率和死亡率相关。血液中微丝蚴超过 20,000 条/毫升的超微丝蚴血症个体可能会遭受严重的治疗相关或自发性不良事件。罗阿丝虫病的诊断仍然很复杂，主要依赖于直接寄生虫检测。在这项研究中，我们分析了各种诊断测试的性能以及寄生虫学和临床因素对来自流行地区个体样本中检测结果的影响。
数据和样本来自加蓬农村地区。罗阿丝虫病的定义为可检测到微丝蚴血症，或通过 RAPLOA 问卷评估的眼丝虫阳性史。诊断检测包括血液样本中 Loa loa DNA 的定量 PCR(qPCR)、内部粗制 L. loa 抗原 IgG ELISA 和针对 Ll-SXP-1 抗原的快速检测（RDT）。评估了每种测试的敏感性和特异性，并在探索性分析中评估了可能影响结果的因素。
ELISA、RDT 和 qPCR 结果分别可用于 1,232 名参与者的 99.8%、78.5%和 100%。ELISA 和 RDT 的诊断准确性仅适中。qPCR 对 L. loa 微丝蚴血症具有特异性，循环阈值与微丝蚴密度相关。隐匿性罗阿丝虫病中的抗 L. loa IgG 水平最高，抗体水平与 L. loa 微丝蚴密度呈负相关，与 RDT 线强度也呈负相关。仅 84.6%和 16.7%的超微丝蚴血症个体通过 ELISA（13 例中的 11 例）和 RDT（12 例中的 2 例）检测呈阳性。
没有一种测试对罗阿丝虫病表现出高敏感性和特异性。间接诊断检测的特异性较低。此外，超微丝蚴血症个体通常通过 RDT 和 ELISA 检测呈阴性，表明这些测试不适合在流行地区的个体病例管理。
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