Infectious Diseases Unit (NDI), Center for Health Sciences, Universidade Federal do Espírito Santo, Vitória, ES, Brazil; Research Group on Biomedical Parasitology, School of Sciences, Pontíficia Universidade Católica do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Research Group on Biomedical Parasitology, School of Sciences, Pontíficia Universidade Católica do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Acta Trop. 2021 May;217:105863. doi: 10.1016/j.actatropica.2021.105863. Epub 2021 Feb 13.
A point-of-care test for detecting schistosome circulating cathodic antigen in urine (POCCCA) has been proposed for mapping infection and defining prevalence thresholds for mass drug administration (MDA). However, there is increasing evidence that POCCCA may yield false-positive results, which requires rigorous specificity evaluation in non-endemic areas. POCCCA was applied in an area known to be free from infection and devoid of any condition for schistosomiasis transmission as part of a multicentre study to evaluate the performance of POCCCA in Brazil's low or potentially endemic settings. Besides POCCCA detection in urine, a search for eggs in stool was performed by Kato-Katz (KK) and Helmintex (HTX) methods. One-hundred-and-seventy-four participants returned urine samples, 140 of which delivered stool samples. All these were HTX-negative for Schistosoma mansoni, and all 118 tested with KK were negative for both S. mansoni and soil-transmitted helminths. POCCCA results from freshly collected urine yielded a specificity of 62.1% (95% CI: 53.6% - 70.2%), taking trace outcomes as positive according to the manufacturer's instructions. Retesting urine from the 140 HTX-negatives after one-year storage at -20 °C with two new POCCCA batches simultaneously yielded significantly different specificities (34.3%; 95%CI: 26.5% - 42.8% and 75.0%; 95% CI: 67.0% - 81.9%). These two batches had a weak agreement (Cohen's kappa: 0.56; 95%CI: 0.44-0.68) among the 174 urine samples retested. At present, POCCCA cannot be recommended either as a cut-off point for MDA or a reliable diagnostic tool for treatment of the infection carriers (selective chemotherapy) in low endemic areas and at final stages of transmission interruption. Manufacturers should be required to optimize production standardization and to assure quality and reproducibility of the test. Extended rigorous performance evaluations by different users from different regions are needed before POCCCA is widely recommended.
一种用于检测尿液中血吸虫循环阴极抗原（POCCCA）的即时检测方法已被提议用于绘制感染图谱并定义大规模药物治疗（MDA）的流行阈值。然而，越来越多的证据表明，POCCCA 可能产生假阳性结果，这需要在非流行地区进行严格的特异性评估。POCCCA 被应用于一个已知没有感染且没有任何血吸虫病传播条件的地区，作为在巴西低流行或潜在流行地区评估 POCCCA 性能的多中心研究的一部分。除了尿液中的 POCCCA 检测外，还通过加藤厚涂片（KK）和 Helmintex（HTX）方法检测粪便中的虫卵。174 名参与者返回了尿液样本，其中 140 名提供了粪便样本。所有这些样本均 HTX 检测结果为阴性，没有曼氏血吸虫感染，所有 118 名用 KK 检测的结果均为阴性，未感染曼氏血吸虫和土壤传播的蠕虫。使用新鲜采集的尿液进行 POCCCA 检测，其特异性为 62.1%（95%CI：53.6%-70.2%），根据制造商的说明，将微量结果视为阳性。对 140 名 HTX 阴性者的尿液进行重新检测，将尿液在-20°C 下储存一年，同时使用两个新的 POCCCA 批次进行检测，得到的特异性有显著差异（34.3%；95%CI：26.5%-42.8%和 75.0%；95%CI：67.0%-81.9%）。这两个批次对 174 个重新检测的尿液样本的一致性较弱（科恩氏kappa：0.56；95%CI：0.44-0.68）。目前，POCCCA 既不能作为 MDA 的截止值，也不能作为低流行地区和传播中断最后阶段治疗感染携带者（选择性化学疗法）的可靠诊断工具。制造商应要求优化生产标准化，并保证测试的质量和可重复性。在广泛推荐 POCCCA 之前，需要不同地区的不同用户进行更严格的性能评估。
