Kato Katz Technique: Principle, Procedure, Results

By Acharya Tankeshwar •  Updated: 05/21/22 •  3 min read

Kato Katz technique is used for qualitative and semi-quantitative diagnosis of intestinal helminthic infestations; caused by  Ascaris lumbricoides, Trichuris trichiura, hookworm, and especially Schistosoma spp. WHO has recommended the Kato Katz technique in areas with moderate to high transmission rates of soil-transmitted helminths (i.e. where the proportion of infected individuals is >20– >50%) or intestinal schistosomiasis (>10–50%). Where the prevalence of soil-transmitted helminths (STH) is <20%, the specificity of this technique makes it less appropriate, and more sensitive tools should be used.

Direct wet mount is the commonly used method for the diagnosis of intestinal parasitic infections but its sensitivity is low. Formal ether concentration (FEC) technique is used to increase the sensitivity of the microscopic detection methods.

Kato Katz Technique 1-3

Principle 

People infected with STH or intestinal schistosomes pass the eggs of the worms through their feces.  In the Kato-Katz technique, feces are pressed through a mesh screen to remove large particles. A portion of the sieved sample is then transferred to the hole of a template on a slide. After filling the hole, the template is removed and the remaining sample is covered with a piece of cellophane soaked in glycerol. The glycerol clears the fecal material from around the eggs. The eggs are then counted and the number is calculated per gram of feces.

Materials

Procedure of Kato-Katz Technique

  1. Label a glass slide with the sample number and then place a plastic template on top of it.Kato Katz Technique 4-6
  2. Place a small amount of the fecal sample on a newspaper and press a piece of nylon screen on top. Using a spatula, scrape the sieved fecal material through the screen so that only the debris remains.
  3. Scrape up some of the sieved feces to fill the hole in the template, avoiding air bubbles and leveling the feces off to remove any excess.
  4. Carefully lift off the template and place it in a bucket of water mixed with concentrated detergent so that it can be reused.
  5. Place one piece of the cellophane, which has been soaked overnight in methylene blue glycerol solution, over the fecal sample.
  6. Place a clean slide over the top and press it evenly downwards to spread the feces in a circle. Carefully remove the slide by gently sliding it sideways to avoid separating the cellophane strip. If done well, it should be possible to read newspaper print through the stool smear. Place the slide with the cellophane upwards.
S mansoni egg in Kato-Katz Preparation
S mansoni egg in Kato-Katz Preparation

Note: If hookworm is present in the area the slide should be read within 30–60 minutes. After that time, the hookworm eggs disappear.

Examination and Results

Further reading and reference 

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.