Independent evaluation of the Nigrosin-Eosin modification of the Kato-Katztechnique

A new modified quantitative Kato-Katz thick-smear technique for the detecti on of helminth eggs in faeces preserves hookworm eggs unaltered for a long time, while with the classic Kato-Katz technique, they disappear after appr oximate to 2 h in tropical climates and thus slides must be read within hou rs after sample collection. For an independent comparison of these two labo ratory techniques, faecal smears from 263 school children were examined in two surveys and prevalence, intensity of infection and costs of surveys cal culated. There was no statistical difference between the methods in detecti ng prevalence and stratification of the sample in different classes of inte nsity While there was no statistical difference for the arithmetic mean of the epg for T. trichiura and only a small difference for A. lumbricoides (P = 0.04), we observed a highly significant difference for hookworm mean int ensities of infections (P < 0.001). From the public health viewpoint both m ethods provided similar results, but due to its simplicity and widespread u se the classical Kato-Katz technique remains first choice for community inv estigation of soil-transmitted nematodes. However, the Nigrosin-Eosin appro ach has several advantages and can be a valuable alternative in certain cir cumstances.