日本血吸虫病常用诊断方法应用价值的评估IIHA筛查法对血吸虫病疫区人群感染率的评价

目的分析IHA筛查法评估血吸虫病疫区人群感染率的可靠性。方法在江西省鄱阳湖血吸虫病疫区选取一个村的居民为研究对象，对每位对象收集2次新鲜粪便标本各制作6张Kato片（2粪12片）进行病原学检测，同时采用IHA法进行血清学定量检测，分析常规1粪3张Kato片的阳性检出率与漏检率、IHA的诊断效率及IHA与Kato-Katz法结果的相关性。结果3张Kato片漏检率达19．7％～66．1％，1粪较2粪漏检率为23．0％。IHA的敏感度和特异度分别为69．6％、89．4％，与Kato-Katz法的总符合率为86．7％。IHA的阴性预测值为96．8％，但阳性预测值较低（36．8％），阳性漏检率高达30．4％；IHA筛查法对试点区人群感染率估算的漏检率达35．8％。结论IHA筛查法对疫区人群实际感染率估算有较大的偏差，IHA作为筛查工具仍需提高其敏感性和特异性，IHA阳性阈值有待进一步探讨。

Evaluation on application of common diagnosis methods for schistosomiasis japonica in endemic areas of China I Evaluation on estimation of prevalence of Schistosoma japonicum infection by IHA screening method

Objectives To evaluate the utility of IHA screening method for estimation of the prevalence of Schistosoma japonicum infection in endemic areas. Methods The Kato-Katz method （Kato＇s method） and indirect hemagglutination assay （IHA） were used to detect Schistosoma japonicum infection in one endemic village named Xinhua, which was located in Poyang Lake region, Jiangxi Province. Twice fresh stool samples with intervals of 3 to 5 days and blood samples were collected from each participant. Twelve Kato slides prepared from the twice stool specimens （ 6 slides each sample） were examined by using Kato~s method and the sera were tested by using IHA with quantity. The result of 12 Kato slides was defined as the gold standard, and then the diagnostic yield of current routine Kato＇s method （3 Kato slides） and IHA, as well as the correlation of the intensity of infection and IHA were analyzed systematically. Results The missing rate of triplet Kato slides was 19.7%-66.1%. The missing rate of the positive derived from one stool sample was 23.0% compared with the results of twice samples. The sensitivity, specificity and coincidence of IHA was 69.6%, 89.4% and of 86. 7%, respectively. The predicted value of the negative was high of 96. 8% but 36.8% in the positive. The missing rate of IHA was up to 30. 4% compared the results of posi-tives derived from the Kato＇s method. Consequently, the missing rate of IHA screening method was estimated to 35.8%. Conclusions There are bigger underestimation on actual schistosomiasis prevalence in endemic areas by IHA screening method. It is indispensable to improve the sensitivity and specificity of IHA and study further the cut-off value of IHA.