Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland.
Parasit Vectors. 2013 Jan 29;6:29. doi: 10.1186/1756-3305-6-29.
Parasitological methods are widely used for the diagnosis of schistosomiasis. However, they are insensitive, particularly in areas of low endemicity, and labour-intensive. Immunoassays based on detection of anti-schistosome antibodies have the merit of high sensitivity and recently a rapid diagnostic test (RDT), incorporating Schistosoma mansoni cercarial transformation fluid (SmCTF) for detection of anti-schistosome antibodies in blood has been developed. Here, we assessed the diagnostic performance of the SmCTF-RDT for S. mansoni and S. haematobium infections by comparing it with microscopy for egg detection.
A cross-sectional survey was carried out in Azaguié, south Côte d'Ivoire. 118 pre-school-aged children submitted two stool and two urine samples, which were subjected to the Kato-Katz and urine filtration methods for the detection of S. mansoni and S. haematobium eggs, respectively. Urine was also subjected to a commercially available cassette test for S. mansoni, which detects circulating cathodic antigen. A finger-prick blood sample was used for the SmCTF-RDT for detection of anti-S. mansoni and anti-S. haematobium antibodies.
The prevalence of both anti-S. mansoni and anti-S. haematobium antibodies was more than three times higher than the prevalence of infection estimated by egg detection under a microscope. Using quadruplicate Kato-Katz as the reference standard for the diagnosis of S. mansoni infection, the sensitivity, negative predictive value (NPV), and positive predictive value (PPV) of the SmCTF-RDT was 75.0%, 84.2% and 22.5%, respectively. When two urine filtrations were considered as the reference standard for the diagnosis of S. haematobium infection, the sensitivity, NPV and PPV of SmCTF-RDT was 66.7%, 94.9% and 5.1%, respectively. The specificity of SmCTF-RDT, when using egg-detection as the reference standard, was estimated to be 34.4%. This low specificity may be a reflection of the relative insensitivity of the direct diagnostic approaches using microscopy.
The SmCTF-RDT is at least as sensitive as duplicate Kato-Katz and a single urine filtration for detection of S. mansoni and S. haematobium, respectively. Further investigations into the specificity of the test for anti-schistosome antibodies are necessary, but our results suggest that it may be a useful tool for mapping the prevalence of anti-schistosome antibodies in a given population pending intervention.
寄生虫学方法广泛用于血吸虫病的诊断。然而，它们的灵敏度较低，特别是在低流行地区，并且劳动强度大。基于检测抗血吸虫抗体的免疫测定具有高灵敏度的优点，最近开发了一种快速诊断测试（RDT），该测试采用曼氏血吸虫尾蚴转化液（SmCTF）检测血液中的抗血吸虫抗体。在这里，我们通过比较显微镜检测卵来评估 SmCTF-RDT 对曼氏血吸虫和埃及血吸虫感染的诊断性能。
在科特迪瓦南部的阿扎吉进行了一项横断面调查。118 名学龄前儿童提交了两份粪便和两份尿液样本，分别用加藤厚涂片法和尿液过滤法检测曼氏血吸虫和埃及血吸虫卵。尿液也用市售的曼氏血吸虫盒式检测法检测循环阴极抗原。用手指刺破血样进行 SmCTF-RDT 检测抗曼氏血吸虫和抗埃及血吸虫抗体。
抗曼氏血吸虫和抗埃及血吸虫抗体的流行率均高于显微镜下估计的卵检测感染率三倍以上。使用四重加藤厚涂片作为曼氏血吸虫感染的诊断参考标准，SmCTF-RDT 的灵敏度、阴性预测值（NPV）和阳性预测值（PPV）分别为 75.0%、84.2%和 22.5%。当两次尿液过滤被认为是诊断埃及血吸虫感染的参考标准时，SmCTF-RDT 的灵敏度、NPV 和 PPV 分别为 66.7%、94.9%和 5.1%。当使用卵检测作为参考标准时，SmCTF-RDT 的特异性估计为 34.4%。这种低特异性可能反映了使用显微镜的直接诊断方法的相对不敏感性。
SmCTF-RDT 的灵敏度至少与双重加藤厚涂片和单次尿液过滤相当，分别用于检测曼氏血吸虫和埃及血吸虫。需要进一步研究该测试对抗血吸虫抗体的特异性，但我们的结果表明，在等待干预的情况下，它可能是一种有用的工具，用于绘制特定人群中抗血吸虫抗体的流行情况。
