Enk Martin Johannes, Lima Anna Carolina Lustosa, Drummond Sandra Costa, Schall Virginia Torres, Coelho Paulo Marcos Zech
Laboratory of Schistosomiasis, René Rachou Research Center/Oswaldo Cruz Foundation, Av. Augusto de Lima 1715, Belo Horizonte, Minas Gerais, Brazil.
Acta Trop. 2008 Nov-Dec;108(2-3):222-8. doi: 10.1016/j.actatropica.2008.09.016. Epub 2008 Oct 5.
Examination of faecal material by Kato Katz (KK) technique is a widely used approach for the diagnosis of intestinal schistosomiasis, particularly in epidemiological surveys. However, this technique lacks diagnostic sensitivity in individuals with low infection intensity or in low endemic areas. In the total population (TP) of 1265 individuals prevalence and infection intensity were established by examining two KK slides. A representative subset of 305 individuals, denominated experimental group (EG), was defined to assess the comparative advantage of an increased sampling effort using the KK technique. In addition stools of the participants of the EG were examined by the formol ether centrifugation technique. The proportion of all positive stool examinations detected by both methods among the experimental group served as reference value for prevalence (diagnostic 'gold' standard). Prevalence of schistosomiasis among TP based on two KK slides was 12.5%. Prevalence among the EG varied from 13.8%, based on one KK slide, over 27.2 based on 10 KK slides of three stool samples to 35.4% as value for the diagnostic 'gold' standard. The comparison of values for prevalence, stratified by age, revealed significant elevated numbers for all age groups, and interestingly, an extension of the highest prevalence levels until an age of 50 years. The overall infection intensity in eggs per gram (epg), calculated as geometric mean, was 83 epg for the TP based on one KK slide, 78 epg for the GE based on one KK slide and 28 epg based on 10 KK slides of three stool samples. In summary our data demonstrate that control programmes based on the examination of a single KK slide, as it is the case in Brazil, tend to underestimate significantly the prevalence and overestimate infection intensity. This applies especially for low endemic areas, where the efficacy and cost-effectiveness of such programmes become questionable. Our data also indicate that the possible solution of this problem lies in targeted mass treatment including age groups with the highest proportions of those infected. This will give high sensitivity together with sustainability and suitability under field conditions.
采用加藤厚涂片法（KK法）检查粪便样本是诊断肠道血吸虫病的一种广泛应用的方法，尤其在流行病学调查中。然而，该技术在感染强度较低的个体或低流行地区缺乏诊断敏感性。在1265人的总人口（TP）中，通过检查两张KK涂片确定了患病率和感染强度。定义了一个由305人组成的代表性子集，称为实验组（EG），以评估增加KK技术采样量的比较优势。此外，还通过甲醛乙醚离心技术检查了实验组参与者的粪便。两种方法在实验组中检测到的所有阳性粪便检查的比例用作患病率的参考值（诊断“金”标准）。基于两张KK涂片，TP中血吸虫病的患病率为12.5%。EG中的患病率从基于一张KK涂片的13.8%，到基于三个粪便样本的10张KK涂片的27.2%，再到作为诊断“金”标准的值35.4%不等。按年龄分层的患病率值比较显示，所有年龄组的患病率均显著升高，有趣的是，最高患病率水平一直延伸到50岁。以几何平均数计算，TP基于一张KK涂片的每克粪便虫卵总数（epg）总体感染强度为83 epg，EG基于一张KK涂片的为78 epg，基于三个粪便样本的10张KK涂片的为28 epg。总之，我们的数据表明，像巴西那样基于检查一张KK涂片的控制方案往往会显著低估患病率并高估感染强度。这尤其适用于低流行地区，在这些地区此类方案的有效性和成本效益令人质疑。我们的数据还表明，解决这个问题的可能办法在于有针对性的群体治疗，包括感染比例最高的年龄组。这将在现场条件下提供高敏感性以及可持续性和适用性。
