Abstract:

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 num? ber 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.

Key words: Schistosomiasis, Kato?Katz technique, Prevalence, Rate of underestimation

摘要：

目的 现场评估Kato?Katz法不同检测粪样次数和涂片数的居民血吸虫感染检出率与低估率。方法 采用 “3检 27片” Kato?Katz法对鄱阳湖区1个血吸虫病流行村人群进行连续3年的粪检， 并以此为金标准， 评估不同检测粪样数和Ka? to?Katz片数的血吸虫感染检出率与低估率。结果 血吸虫感染的检出率随粪检Kato片数的增加而增加， 低估率则逐渐降低。1检3片Kato ?Katz法对人群感染的低估率达40.98%～50.80%， 即使增加到6张Kato片,低估率仍为30%左右（25.48%～32.39%）。观察区人群2008-2010年的粪检阳性率分别为10.96%、 8.54%和3.73%， 各年间差异较大， 但各Kato 片的低估率接近。1检3片、 6片、 9片法分别和3检3片、 6片、 9片法的阳性率之间， 2检6片与1检6片、 3检6片法的阳性率差异均无统计学意义。 结论 在相同Kato片检测数下， 血吸虫感染者的阳性检出率主要取决于Kato片数而不是粪检次数。在血吸虫病低流行状态下，“1检3片”Kato?Katz法对血吸虫病疫情的低估率较大。为提高Kato?Katz法敏感性， 宜首先考虑增加Kato片数而不是粪检次数。

关键词: 血吸虫病；Kato-Katz法；感染率；低估率