Kato technique

The Kato technique (also called the Kato–Katz technique) is a laboratory method for preparing human stool samples prior to searching for parasite eggs.

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Indications

The Kato technique is now most commonly used for detecting schistosome eggs.^[1] It has in the past been used for other helminth eggs as well. It cannot be used to identify hookworm eggs because they collapse within 30 to 60 minutes of preparation using this method. One study of 299 subjects infected with Schistosoma mansoni found that the method had poor reproducibility and is therefore no longer recommended for primary health care settings:^[2] the problem may be that eggs of S. mansoni tend to clump together which means that even slides prepared from the same specimen may contain widely different egg counts.^[3] The other main argument against the Kato technique is that it is messy and therefore exposes technicians to an unnecessarily high risk of infection.

Method

The published methods vary in detail, but generally involves a standardized amount of sieved feces being examined under light microscopy, and subsequently get a standardized count of the amount of eggs therein, in terms of number of eggs per gram.^[1]^[4] It can possibly involve staining the fecal sample.^[1]

History

It was developed in 1954 by Japanese medical laboratory scientist Dr. Katsuya Kato (1912–1991).^[5]^[6] The technique was modified for use in field studies in 1972 by a Brazilian team of researchers led by Brazilian parasitologist Naftale Katz (b.1940),^[7]^[8] and this modification was adopted by the WHO as a gold standard for multiple helminth infections.^[8]

References

^ ^a ^b ^c Cheesbrough M (1998). "Parasitological Tests". District Laboratory Practice in Tropical Countries, Part 1. Cambridge: Cambridge University Press. pp. 220–221. ISBN 978-0-521-66547-6.
^ Kongs A, Marks G, Verlé P, Van der Stuyft P (2001). "The unreliability of the Kato=Katz method for evaluating S. mansoni infection". Trop Med Int Health. 6 (3): 163–69. doi:10.1046/j.1365-3156.2001.00687.x. PMID 11299032. S2CID 20816779.
^ Engels D, Sinzinkayo E, De Vlas SJ, Gryseels B (1997). "Intraspecimen fecal egg count variation in Schistosoma mansoni infection". Am J Trop Med Hyg. 57 (5): 571–7. doi:10.4269/ajtmh.1997.57.571. PMID 9392598.
^ Turner HC, Bettis AA, Dunn JC, Whitton JM, Hollingsworth TD, Fleming FM, Anderson RM (2017). "Economic Considerations for Moving beyond the Kato-Katz Technique for Diagnosing Intestinal Parasites As We Move Towards Elimination". Trends in Parasitology. 33 (6): 435–443. doi:10.1016/j.pt.2017.01.007. ISSN 1471-4922. PMC 5446322. PMID 28187989.
^ Neves Santos FL, Lima Cerqueira EJ, Matos Soares N (2005). "Comparison of the thick smear and Kato-Katz techniques for diagnosis of intestinal helminth infections". Revista da Sociedade Brasileira de Medicina Tropical. 38 (2): 196–198. doi:10.1590/S0037-86822005000200016. ISSN 1678-9849. PMID 15821801.
^ J Richardson D, Gross J, Smith MC (July 2008). "Comparison of Kato–Katz Direct Smear and Sodium Nitrate Flotation for Detection of Geohelminth Infections". Comparative Parasitology. 75 (2): 339–341. doi:10.1654/4340.1. S2CID 72451405.
^ Katz N, Chaves A, Pellegrino J (November 1972). "A simple device for quantitative stool thick-smear technique in Schistosomiasis mansoni". Revista do Instituto de Medicina Tropical de Sao Paulo. 14 (6): 397–400. ISSN 0036-4665. PMID 4675644.
^ ^a ^b Santos FL, Cerqueira EJ, Soares NM (March 2005). "Comparison of the thick smear and Kato-Katz techniques for diagnosis of intestinal helminth infections". Revista da Sociedade Brasileira de Medicina Tropical. 38 (2): 196–198. doi:10.1590/S0037-86822005000200016. ISSN 0037-8682. PMID 15821801.

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