7. Kato Thick Smear Technique

MICROSCOPIC EXAMINATION OF FECAL SPECIMEN: “Kato Thick Smear Technique” INTRODUCTION A technique introduced by Kato and Miura (1954) involving a simple, thick smear method and using a cellophane cover for the examination of helminth eggs in stools. The Kato technique in the past has been used for the detection of helminth eggs but nowadays it is most commonly used for detecting schistosomal eggs. However, it cannot be used to identify hookworm eggs because they collapse within 30 to 60 minutes of preparation using this method. This technique differs from the ordinary direct smear in that a larger quantity of stool will be used and coverslips are substituted for cellulose acetate film soaked in glycerine. Schistosoma mansoni, a significant parasite of humans, is a trematode that is one of the major agents of the disease schistosomiasis of intestinal origin.

PROCEDURE AND METHODS Place 40-60 mg of stool on a clean glass slide

Cover with cellophane soaked with glycerin-

malachite green solution

Observe under LPO *suspicious objects: HPO

Press with rubber stopper

At room temp., allow to stand 2030 minutes

RESULTS AND INTERPRETATIONS Result: FECALYSIS Name of patient: Luigi Gomez Age: 7 y/o Sex: Male PHYSICAL: Character: Mushy Color: Dark Brown Mucus: None Blood: None

Date: November 6, 2014

MICROSCOPIC: RBC: None WBC: None Parasite: No ova or parasite seen

Interpretation: The patient’s Physical and Microscopic results based from the experiment obtained shows an abnormal stool specimen for the physical examination but no ova or parasites were seen.

ANSWERS TO GUIDE QUESTIONS AND THE QUESTIONS FOR RESEARCH Guide Questions: 1. What is the purpose of the malachite green and glycerin? Malachite green is for staining the background to make a contrasting environment so that we can easily visualize the number of eggs that is present in the stool sample. Glycerin on the other hand is used as a clearing solution and it dissolves fecal debris. Questions for Research: Draw and Label A. Important phases of the Kato thick smear technique.

B. A schematic diagram of any abnormal microscopic structures found in your preparation.

1. Give the advantages and disadvantages of the Kato thick smear technique. ADVANTAGES     

Simple Time saving Economical High chances to find eggs Useful in mass examination of common soil transmitted helminth infections

  

DISADVANTAGES It cannot be used in liquid, soft, or diarrheic stool. It cannot be used for detection of protozoan infection. Limited within 1hour because after 1hour it would be disintegrated.

2. What are some precautions that should be observed in the performance of the Kato Thick smear technique? a) Remember that liquid, soft and diarrheic stools are not suitable for Kato Thick. b) Specimen should be spread evenly, not too thick nor too thin. c) Do not let preparation to dry up while letting it stand d) The clearing process will not begin until the cellophane covered smear is turned up so that it can absorb the solution.

e) Perform the Kato Thick immediately because it disintegrates after an hour.

UPDATES Comparison of the Bell technique, a modified Kato thick smear technique, and a digestion method for the field diagnosis of schistosomiasis mansoni A modification of the Kato thick smear technique, the Bell filtration technique, and a digestion method were investigated to determine the relative merits of each for the detection of schistosome eggs in human faecal samples. The modified Kato technique was the method of choice because it was sensitive, simple to perform, and suitable for field use. The Bell filtration technique was equally sensitive in detecting light infections, but was more tedious and more complicated to perform than the thick smear technique. http://journals.cambridge.org/action/displayAbstract?aid=5196260

REFERENCE/S:  Elizabeth A. Zeibig, Clinical Parasitology: A Practical Approach, Second Edition, 2013  John and Petri, Markell and Voge’s Medical Parasitology 9th edition, 2010  http://www.popline.org/node/468732  http://www.atitesting.com/ati_next_gen/skillsmodules/content/specimen-collectionnew/images/ap_stool_spec_cnt_sld_lbl.jpg  http://www.parasitol.or.kr/kjp/Synapse/Data/PDFData/0066KJP/kjp-7-48.pdf  http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=5196260