OBJECTIVE: To understand the rates of underestimation of Schistosoma japonicum infection by Kato-Katz technique with different stool samples and different smears in field site. METHODS: With 27 Kato-Katz thick smears (3 stool samples with 9 thick smears each) for 3 consecutive years as a "gold standard", the rates of underestimation of schistosome infection by Kato-Katz technique with different stool samples and different smears were evaluated in a schistosomiasis endemic village. RESULTS: The examined rates of schistosome infection increased and the rates of underestimation decreased gradually with the increase of the number of Kato-Katz thick smears examined. The rates of underestimation of 3 smears were 40.98%-50.80% and the rates of underestimation of 6 smears were 25.48%-32.39%. The rates of schistosome infection based on the reading of 27 Kato-Katz thick smears were 10.96% in 2008, 8.54% in 2009 and 3.73% in 2010 respectively, but the rates of underestimation of various Kato-Katz thick smears were similar. There were no significant differences among the readings of 3, 6, and 9 smears of 1 stool sample, 3, 6 and 9 smears of 3 stool samples, 6 smears of 2 stool samples, 6 smears of 1 stool sample, and 6 smears of 3 stool samples. CONCLUSIONS: In a community with low-intensity of schistosome infection, the rate of underestimation is big by Kato-Katz technique with the reading of 3 smears of 1 stool sample. It suggested that it is better to increase smears rather than the number of stool samples examined.
OBJECTIVE: To understand the rates of underestimation of Schistosoma japonicum infection by Kato-Katz technique with different stool samples and different smears in field site. METHODS: With 27 Kato-Katz thick smears (3 stool samples with 9 thick smears each) for 3 consecutive years as a "gold standard", the rates of underestimation of schistosome infection by Kato-Katz technique with different stool samples and different smears were evaluated in a schistosomiasis endemic village. RESULTS: The examined rates of schistosome infection increased and the rates of underestimation decreased gradually with the increase of the number of Kato-Katz thick smears examined. The rates of underestimation of 3 smears were 40.98%-50.80% and the rates of underestimation of 6 smears were 25.48%-32.39%. The rates of schistosome infection based on the reading of 27 Kato-Katz thick smears were 10.96% in 2008, 8.54% in 2009 and 3.73% in 2010 respectively, but the rates of underestimation of various Kato-Katz thick smears were similar. There were no significant differences among the readings of 3, 6, and 9 smears of 1 stool sample, 3, 6 and 9 smears of 3 stool samples, 6 smears of 2 stool samples, 6 smears of 1 stool sample, and 6 smears of 3 stool samples. CONCLUSIONS: In a community with low-intensity of schistosome infection, the rate of underestimation is big by Kato-Katz technique with the reading of 3 smears of 1 stool sample. It suggested that it is better to increase smears rather than the number of stool samples examined.