Performance of a recombinase - aided amplification assay for detection of Schistosoma japonicum infections in Oncomelania hupensis

Abstract

Objective To evaluate the efficiency of a recombinase-aided amplification (RAA) assay for the detection of Schistosoma japonicum infections in Oncomelania hupensis snails.

Methods A group test was employed. Fifty Oncomelania snails were collected as a detection sample. The detection samples without infected snails were designated as negative specimens, while the detection samples that contained different numbers of infected snails were designated as positive specimens. A total of 10 negative specimens, 10 positive specimens containing 1 infected snail, 20 positive specimens containing 2 infected snails and 10 positive specimens containing 3 infected snails were assigned. Following random grouping, 40 specimens were subject to the florescent RAA assay using a blind method. The miradium shedding method served as a gold standard, and the sensitivity, specificity, Youden’s index and coincidence rate of the florescent RAA assay were estimated. In addition, 20 samples consisted of 5 negative specimens and 15 positive specimens with 1, 2 and 3 infected snails respectively were grouped randomly. The same specimens were detected using the crushing method and fluorescent RAA assay with the blind method in a paired-design manner. Then, the test results were compared and analyzed.

Results Florescent RAA assay detected 29 positives in the 30 specimens containing different numbers of infected snails, with a sensitivity of 96.67%, and 8 negatives in the 10 detection specimens without infected snails, with a specificity of 80.00%, showing a Youden’s index of 0.77. The coincidence rate was 100% among 10 repeated assays for a detection specimen. In addition, there was no significant difference in the detection of infected snails between the florescent RAA assay and the crushing method ( χ ² = 0, P > 0.05), and the actual coincidence rates of the florescent RAA assay and crushing method were 95.00% (19/20) and 90.00% (18/20) with the real results, respectively.

Conclusion Fluorescent RAA assay has a favorable efficiency for the detection of S. japonicum infections in Oncomelania snails, which shows a potential in screening of S. japonicum-infected Oncomelania snails.

Abstract

［摘要］ 目的 评价重组酶介导的核酸等温扩增 (recombinase -aided amplification, RAA) 荧光法检测日本血吸虫感染性钉螺的效能。 方法 采用群体法检测。每50只钉螺作为1个检测样本, 阴性样本不含感染性钉螺, 阳性样本含不同数量感染性钉螺。设置阴性样本10个和分别含有1、2、3只感染性钉螺的阳性样本各10个, 40个样本随机分组后, 以盲法经荧光RAA法检测, 并以逸蚴法检测结果为金标准, 计算荧光RAA法检测灵敏度、特异度、正确指数及符合率。设置阴性钉螺样本5个和分别含有1、2、3只感染性钉螺的阳性样本各5个, 20个样本随机分组后, 采用配对设计法对同一个样本以盲法分别经压碎镜检法和荧光RAA法进行检测并比较检测结果。 结果 荧光RAA法检测30个阳性样本, 29个检测结果为阳性, 灵敏度为96.67%; 检测10个阴性样本, 其中8个检测结果为阴性, 特异度为80.00%; 约登指数为0.77, 同一样本重复检测10次符合率为100%。荧光RAA法与压碎镜检法检测感染性钉螺结果差异无统计学意义 ( χ ² = 0, P > 0.05), 检测结果与实际符合率分别为95.00% (19/20) 和90.00% (18/20) 。 结论 荧光RAA法对日本血吸虫感染性钉螺具有良好检测效能, 在日本血吸虫感染性钉螺筛查中具有一定应用前景。