Increased detection of schistosomiasis with Kato-Katz and SWAP-IgG-ELISA in a Northeastern Brazil low-intensity transmission area

Teiliane Rodrigues Carneiro,Sara Menezes De Oliveira,Ana Lúcia De Paula Hanemann,Marta Cristhiany Cunha Pinheiro,José Ajax Nogueira Queiroz,Fernando Schemelzer Moraes Bezerra

doi:10.1590/s0037-86822012000400019

Teiliane Rodrigues Carneiro, Sara Menezes De Oliveira + Show 4 more

Open Access

https://doi.org/10.1590/s0037-86822012000400019

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Abstract

The laboratory diagnosis of schistosomiasis is based mainly on the detection of parasite eggs in stool samples through the Kato-Katz (KK) technique, reading one slide by test. However, a widely known limitation of parasitological methods is reduced sensitivity, particularly in low endemic areas. To increase sensitivity, we conducted further slide readings from the same stool sample using the parasitological method associated with a serological test. We used the KK method (three slides) and the IgG anti-Schistosoma mansoni-enzyme-linked immunosorbent assay (ELISA) technique to diagnose schistosomiasis in low endemic areas in the Brazilian State of Ceará. Fecal samples and sera from 250 individuals were analyzed. Sixteen percent and 47.2% of samples were positive in parasitological tests and serological tests, respectively. Parasitological methods showed that 32 (80%) individuals tested positive on the first slide, 6 (15%) on the second slide, and 2 (5%) on the third. The performance of the ELISA test in the diagnosis, using the KK method as diagnostic reference, showed a negative predictive value of 100%, with specificity and positive predictive values of 62.8% and 33.9%, respectively. In this study, the increase from one to three slides analyzed per sample using the KK technique was shown to be a useful procedure for increasing the diagnostic sensitivity of this technique.

Highlights

The laboratory diagnosis of schistosomiasis is based mainly on the detection of parasite eggs in stool samples through the Kato-Katz (KK) technique, reading one slide by test
It is worth noting that the control of schistosomiasis-related morbidity has become feasible due to the development of single-dose oral drugs such as oxamniquine and praziquantel, which are given to heavily infected patients who are detected by field-applicable parasitological methods
The worldwide methodological strategy currently applied for the diagnosis of mansoni schistosomiasis, using the KK method with one sample and one slide to determine the infection rate, does not have the sensitivity required for such diagnosis and in areas of low endemicity underestimates the prevalence of this parasitosis[15]

Summary

Introduction

The laboratory diagnosis of schistosomiasis is based mainly on the detection of parasite eggs in stool samples through the Kato-Katz (KK) technique, reading one slide by test. KK smears and other parasitological methods frequently fail to detect low-intensity infections[4], which leads to an underestimation of the actual prevalence of disease[5,6]. To overcome this limitation, examination of a larger quantity of fecal material is necessary[7]. With the transition to lower morbidity, more sensitive diagnostic methods are needed[9] In this context, the enzyme-linked immunosorbent assay (ELISA) immunological technique has been proposed for use in the PCE10.

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