Comparison of the Kato-Katz technique, hatching test and indirect hemagglutination assay (IHA) for the diagnosis of Schistosoma japonicum infection in China

The Kato-Katz technique (duplicate 41.7 mg fecal smears), hatching test and indirect hemagglutination assay (IHA) were compared for their ability to detect human Schistosoma japonicum infection in two endemic villages (Zhonjiang and Zhuxi) in rural China. The hatching test (using a nylon bag, and based on about 30 g of feces) and IHA are conventional Chinese diagnostic methods. In both villages, the trends of prevalences with age and sex were comparable for the different methods. In Zhuxi, Kato-Katz examinations of stools from 7 different days and hatching were available, which could be used as a reliable gold standard. This resulted for IHA in a sensitivity of 80% and a specificity of 48%. The sensitivity of the Kato-Katz technique using one stool specimen was 68%, twice that of hatching (33%). In Zhonjiang, however, hatching resulted in more positive cases than Kato-Katz (prevalence 31% vs. 24%). Apparently, the result of the hatching test depends on environmental factors such as temperature and water quality. Although imperfect, Kato-Katz is recommended out of the three evaluated techniques as the method of choice for large-scale screening of S. japonicum. Hatching is much more tedious, provides inconsistent and only qualitative results, and is not much more sensitive than Kato-Katz. Its poor specificity makes IHA unsuitable for individual screening, but it may be more effective for community diagnosis.