Skip to main content

Table 2 Proportion of false-positive and false-negative results after a second quality control reading of Kato-Katz thick smears (in case of discordant results, slides were read a third time)

From: Quality control in the diagnosis of Trichuris trichiura and Ascaris lumbricoides using the Kato-Katz technique: experience from three randomised controlled trials

  Trichuris trichiura Ascaris lumbricoides
Total Kato-Katz thick smears read for quality control 1,445 1,445
Positive Kato-Katz thick smears 1,181 290
Negative Kato-Katz thick smears 264 1,155
Percentage of positive Kato-Katz thick smears 81.7% 20.1%
False-positive resultsa 5 4
Percentage of false-positive results 0.35% 0.28%
Percentage of false-positive results among negative Kato-Katz thick smears 1.89%d 0.35%d
Faecal egg counts of the false-positive Kato-Katz thick smearsb 1, 3, 4, 7, 10 2, 2, 2, 12
False-negative resultsc 28 6
Percentage of false-negative results 1.94% 0.42%
Percentage of false-negative results among positive Kato-Katz thick smears 2.37%e 2.07%e
Faecal egg counts from the quality control of the false-negative Kato-Katz thick smearsb 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 5, 6, 9, 10, 11, 12, 15, 16 1, 1, 1, 1, 6, 8
  1. aResults were classified as false-positive if the original result was positive for a specific soil-transmitted helminth, but the results from the quality control (second reading), as well as from the third reading, were negative.
  2. bFaecal egg counts per Kato-Katz thick smear.
  3. cResults were classified as false-negative if the original result was negative, but the quality control as well as the result from the third reading, were positive.
  4. dSignificant difference (p < 0.01).
  5. eNo significant difference (p = 0.76).