Abstract:

Objective To explore the cut?off value of the indirect haemagglutination test （IHA） method for schistosomiasis japonica diagnosis in different endemic areas. Methods Totally 55 nature villages of the lake?type endemic counties， Yugan and Xinzi， in Poyang Lake Region of Jiangxi Province were chosen as the study fields， and all the villagers over 5 years old were parallelly examined by Kato?Katz method + miracidial hatching test and IHA method. The detection data were analyzed by the correlation analysis， and the threshold values of the IHA method in different endemic areas were decided by the receiver operating characteristic （ROC） curve. Results The positive rate of stool examinations of the villagers was correlated with the distribution trend of the antibody level of whole population （r = 0.588， P ＜ 0.05）， but no correlation with the antibody level of the positive population （r = 0.221， P ＞ 0.05）. The antibody level of stool?negative population during the period of 2008 to 2011 detected by IHA method dropped year by year， and the annual difference was statistically significant （F = 3.650， P ＜ 0.05）. While the antibody level of stool?positive population found during the period of 2008 to 2011 maintained a certain high level in the 4 years， and there was no statistically significant difference among them （F = 2.461， P ＞ 0.05）. When the positive rates were <1%， 1%-5% or >5%， the specificity of diagnosis could be improved when 1∶80， 1∶20 and 1∶10 were used as the cut?off values of IHA correspondingly. Conclusion The different threshold values for diagnosis of schistosomiasis japonica should be considered while using IHA method to screen out patients in different endemic areas.

Key words: Schistosomiasis japonica； Endemic level； Endemic area； Indirect haemagglutination test （IHA） method； Cut?off value

摘要：

目的 探讨日本血吸虫病不同流行程度流行区IHA法的阳性诊断阈值。方法 选择江西省鄱阳湖区湖沼型血吸虫病流行区2个县（余干和星子）共55个自然村作为研究现场，对5岁以上常住居民采用病原学方法（Kato?Katz法+尼龙绢集卵孵化法）和血清学方法（IHA法）进行平行检测；检测结果采用相关分析和ROC曲线等方法分析，计算不同流行程度流行区IHA抗体水平阳性临界值。结果 血吸虫病流行区人群粪检阳性率与人群IHA血吸虫病特异性抗体水平分布趋势一致（r = 0.588， P ＜ 0.05），与IHA阳性人群抗体水平无相关性（r = 0.221，P ＞ 0.05）；流行区2008-2011年连续4年血吸虫粪检阴性人群的IHA阳性抗体水平呈逐年下降趋势，年间差异有统计学意义（F = 3.650，P ＜ 0.05），2008-2011年中任意1年血吸虫粪检阳性人群的IHA阳性抗体水平在4年内均维持较高水平且年间差异无统计学意义（F = 2.461，P ＞ 0.05）。流行村人群粪检阳性率< 1%、1%～5%和> 5%时，对应IHA的阳性诊断阈值分别为1∶80、1∶20和1∶10时，可提高IHA检测结果的特异性。结论 不同程度流行区采用IHA筛查血吸虫病或选择化疗对象时，可考虑选择不同的IHA阳性诊断阈值。

关键词: 日本血吸虫病； 流行程度； 流行区； IHA法； 阈值