Egg count variability and sensitivity of a thin smear technique for the diagnosis of Schistosoma mansoni

Abstract

Variation in daily egg counts, and in counts for samples of the same stool, was investigated in children with Schistosoma mansoni and Ascaris lumbricoides infections, using a thin smear technique. The results indicated that counts vary according to the stool consistency; drier stools from the same person producing up to seven times greater counts than wet ones. The sensitivity of the technique was tested in schoolchildren living in an endemic S. mansoni area, and found to detect all infections with intensities of greater than 50 eggs per gram of stool, after examination of only one slide containing 40mg stool. The sensitivity varied with the intensity of infection. The relevance of these findings to diagnosis in field situations is discussed.

Cost Analysis of Tests for the Detection of Schistosoma mansoni Infection in Children in Western Kenya

“…5 However, this assay offers poor sensitivity, especially in lowintensity infections, is laborious, and may expose workers to infectious stool. [5][6][7][8][9][10][11] To address some of the concerns with the Kato-Katz technique, considerable research has been devoted to alternative tests for S. mansoni infections. This research has led to the development of a urine-based point-of-contact test for schistosome circulating cathodic antigen (POC-CCA) as a method for detecting infection with S. mansoni.…”

Detection of Schistosoma mansoni Antibodies in a Low-Endemicity Area Using Indirect Immunofluorescence and Circumoval Precipitin Test

“…In addition, using the Kato-Katz method, samples from different days showed only a 6% positivity increase compared with the first sample. 10 We are thus faced with a challenge both in the individual and collective context, because this is a chronic infection that, even without progressing to severe forms, triggers debilitating sequelae secondary to parasitism, especially in childhood.…”

Low transmission areas of schistosomiasis in Venezuela: consequences on the diagnosis, treatment, and control

“…Although the examination of more samples of feces increase the probability of schistosomiasis diagnosis, the quantitative reproducibility of the Kato-Katz method has shown variations, especially when the amount of S. mansoni eggs is low (Kong et al 2001). Teesdale et al (1985) and Engels et al (1996) judge that due to the daily variation of the number of eggs, the analysis with two smears would be enough in order to increase the sensibility of the method. Teesdale et al (1985) found that only 6% of positive samples were identified after a second exam accomplished in different days, suggesting that for epidemiological purposes, the effort and logistics to obtain two samples of a same person are not worthwhile.…”

“…Teesdale et al (1985) and Engels et al (1996) judge that due to the daily variation of the number of eggs, the analysis with two smears would be enough in order to increase the sensibility of the method. Teesdale et al (1985) found that only 6% of positive samples were identified after a second exam accomplished in different days, suggesting that for epidemiological purposes, the effort and logistics to obtain two samples of a same person are not worthwhile.…”