Laboratório de Esquistossomose, Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil.
PLoS One. 2012;7(6):e38947. doi: 10.1371/journal.pone.0038947. Epub 2012 Jun 11.
Schistosomiasis caused by Schistosoma mansoni, one of the most neglected human parasitoses in Latin America and Africa, is routinely confirmed by microscopic visualization of eggs in stool. The main limitation of this diagnostic approach is its lack of sensitivity in detecting individual low worm burdens and consequently data on infection rates in low transmission settings are little reliable. According to the scientific literature, PCR assays are characterized by high sensitivity and specificity in detecting parasite DNA in biological samples. A simple and cost effective extraction method for DNA of Schistosoma mansoni from urine samples in combination with a conventional PCR assay was developed and applied in an endemic area. This urine based PCR system was tested for diagnostic accuracy among a population of a small village in an endemic area, comparing it to a reference test composed of three different parasitological techniques. The diagnostic parameters revealed a sensitivity of 100%, a specificity of 91.20%, positive and negative predictive values of 86.25% and 100%, respectively, and a test accuracy of 94.33%. Further statistical analysis showed a k index of 0.8806, indicating an excellent agreement between the reference test and the PCR system. Data obtained from the mouse model indicate the infection can be detected one week after cercariae penetration, opening a new perspective for early detection and patient management during this stage of the disease. The data indicate that this innovative PCR system provides a simple to handle and robust diagnostic tool for the detection of S. mansoni DNA from urine samples and a promising approach to overcome the diagnostic obstacles in low transmission settings. Furthermore the principals of this molecular technique, based on the examination of human urine samples may be useful for the diagnosis of other neglected tropical diseases that can be detected by trans-renal DNA.
曼氏血吸虫病是由曼氏血吸虫引起的，是拉丁美洲和非洲最被忽视的人类寄生虫病之一，通常通过显微镜观察粪便中的虫卵来确诊。这种诊断方法的主要限制是其检测个体低虫荷的敏感性不足，因此在低传播环境下的感染率数据不太可靠。根据科学文献，PCR 检测法在检测生物样本中的寄生虫 DNA 方面具有高灵敏度和特异性。本研究开发了一种从尿液样本中提取曼氏血吸虫 DNA 的简单、经济有效的方法，并结合常规 PCR 检测法，将其应用于流行地区。在流行地区的一个小村庄人群中，对这种基于尿液的 PCR 系统进行了诊断准确性测试，将其与由三种不同寄生虫学技术组成的参考测试进行了比较。诊断参数显示，该方法的灵敏度为 100%，特异性为 91.20%，阳性预测值和阴性预测值分别为 86.25%和 100%，检测准确性为 94.33%。进一步的统计分析显示，K 指数为 0.8806，表明参考测试和 PCR 系统之间具有极好的一致性。从小鼠模型中获得的数据表明，在尾蚴穿透后一周即可检测到感染，为在疾病的这一阶段进行早期检测和患者管理开辟了新的前景。这些数据表明，这种创新的 PCR 系统为从尿液样本中检测曼氏血吸虫 DNA 提供了一种简单、可靠的诊断工具，为在低传播环境下克服诊断障碍提供了一种很有前途的方法。此外，基于人尿液样本检查的这种分子技术原理可能对其他可通过跨肾 DNA 检测的被忽视热带病的诊断有用。
