Upgrading of Kato-Katz technique for diagnosis of S. mansoni infection in rural Egypt.

Processing of the same stool samples was done using standard Kato-Katz (KK) technique with 41.7 mg of stools and one of the three modifications. These included KK technique using a higher concentration of glycerin (one and quarter, usual one) for preparation, or another stain (negrosin-eosin), with a specified formula, instead of the standard malachite green, or processing a smaller volume of stools (20mg). The results showed that, using cumulative infection rate from the two comparable tests as the reference, KK with higher concentration of glycerin was more sensitive than standard KK (sensitivities 77.6% and 61.2%. respectively). Using negrosin-eosin stain showed higher sensitivity (75.0%) in relation to standard KK technique (70.8%). Kato-Katz with higher concentration of glycerin showed the same sensitivity as KK with negrosin-eosin stain (85.7%) in relation to others. All comparisons showed statistically insignificant differences ((P>0.5). Using 20 mg of stools showed very low sensitivity in relation to standard KK technique (57.9% & 100.0% respectively). The statistical difference was highly significant. All specificities were 100%. Other screening indices showed the same trend of sensitivities. Degree of microscope clarity was optimal with higher concentration of glycerin. Negrosin-eosin showed better visualization of ova than the standard KK. All modifications took only an hour after processing to be examined. KK technique used with any of these modifications, is simple, inexpensive. use of either a higher concentration of glycerin or negrosin-eosin stain and recommended for both field studies and primary health care settings.