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Diagnosis of soil-transmitted helminths in the era of preventive chemotherapy: effect of multiple stool sampling and use of different diagnostic techniques.

Knopp S, Mgeni AF, Khamis IS, Steinmann P, Stothard JR, Rollinson D, Marti H, Utzinger J - PLoS Negl Trop Dis (2008)

Bottom Line: The examination of multiple stool samples instead of a single one resulted in an increase of the observed prevalence; e.g., an increase of 161% for hookworm using the K-K method.The observed prevalences for T. trichiura, hookworm, A. lumbricoides, and S. stercoralis were 47.9%, 22.5%, 16.5%, and 10.8% after examining 3 stool samples.These values are close to the 'true' prevalences predicted by a mathematical model.

View Article: PubMed Central - PubMed

Affiliation: Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland.

ABSTRACT

Background: Soil-transmitted helminth infections are common throughout the tropics and subtropics and they disproportionately affect the poorest of the poor. In view of a growing global commitment to control soil-transmitted helminthiasis, there is a need to elucidate the effect of repeated stool sampling and the use of different diagnostic methods in areas targeted for preventive chemotherapy that are characterized by low-infection intensities. In this study, we focused on schoolchildren on Unguja Island, Zanzibar, an area where anthelminthic drugs have been repeatedly administered over the past decade.

Methodology/principal findings: Three serial stool samples from each of 342 schoolchildren were examined using the Kato-Katz (K-K), Koga agar plate (KAP), and Baermann (BM) techniques. These methods were used individually or in combination for the diagnosis of Ascaris lumbricoides (K-K), Trichuris trichiura (K-K), hookworm (K-K and KAP), and Strongyloides stercoralis (KAP and BM). The examination of multiple stool samples instead of a single one resulted in an increase of the observed prevalence; e.g., an increase of 161% for hookworm using the K-K method. The diagnostic sensitivity of single stool sampling ranged between 20.7% for BM to detect S. stercoralis and 84.2% for K-K to diagnose A. lumbricoides. Highest sensitivities were observed when different diagnostic approaches were combined. The observed prevalences for T. trichiura, hookworm, A. lumbricoides, and S. stercoralis were 47.9%, 22.5%, 16.5%, and 10.8% after examining 3 stool samples. These values are close to the 'true' prevalences predicted by a mathematical model.

Conclusion/significance: Rigorous epidemiologic surveillance of soil-transmitted helminthiasis in the era of preventive chemotherapy is facilitated by multiple stool sampling bolstered by different diagnostic techniques.

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Related in: MedlinePlus

Flow chart detailing the study participation and compliance of randomly selected children from Chaani and Kinyasini schools, Zanzibar.Those children who provided 3 stool samples were included in the final analysis. The final cohort comprised those children who had complete data records, i.e., 3 stool samples examined with 3 different diagnostic methods.
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pntd-0000331-g001: Flow chart detailing the study participation and compliance of randomly selected children from Chaani and Kinyasini schools, Zanzibar.Those children who provided 3 stool samples were included in the final analysis. The final cohort comprised those children who had complete data records, i.e., 3 stool samples examined with 3 different diagnostic methods.

Mentions: Figure 1 shows that among the 401 children selected for the study in Kinyasini and Chaani schools, 221 (55.1%) were girls and 180 (44.9%) were boys. The children were aged between 7 and 20 years. The median age was 12 years and 80% of the children were between 9 and 14 years. Overall, 342 children submitted 3 stool samples over consecutive days, resulting in a compliance rate of 85.3%. Among them, 340 individuals (99.4%) had 3 samples examined with the K-K method, 318 (93.0%) with the KAP method, and 292 (85.4%) with the BM method. Since the combination of the KAP and K-K techniques (for hookworm detection) and the combination of the KAP and the BM methods (for S. stercoralis detection) were of particular interest, the analysis focused on 316 (97.5%) and 277 (81.0%) schoolchildren, respectively. Complete data records, i.e., 3 stool samples examined with all 3 diagnostic tests, were available for 277 out of 401 individuals, resulting in an overall compliance rate of 69.1%.


Diagnosis of soil-transmitted helminths in the era of preventive chemotherapy: effect of multiple stool sampling and use of different diagnostic techniques.

Knopp S, Mgeni AF, Khamis IS, Steinmann P, Stothard JR, Rollinson D, Marti H, Utzinger J - PLoS Negl Trop Dis (2008)

Flow chart detailing the study participation and compliance of randomly selected children from Chaani and Kinyasini schools, Zanzibar.Those children who provided 3 stool samples were included in the final analysis. The final cohort comprised those children who had complete data records, i.e., 3 stool samples examined with 3 different diagnostic methods.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2570799&req=5

pntd-0000331-g001: Flow chart detailing the study participation and compliance of randomly selected children from Chaani and Kinyasini schools, Zanzibar.Those children who provided 3 stool samples were included in the final analysis. The final cohort comprised those children who had complete data records, i.e., 3 stool samples examined with 3 different diagnostic methods.
Mentions: Figure 1 shows that among the 401 children selected for the study in Kinyasini and Chaani schools, 221 (55.1%) were girls and 180 (44.9%) were boys. The children were aged between 7 and 20 years. The median age was 12 years and 80% of the children were between 9 and 14 years. Overall, 342 children submitted 3 stool samples over consecutive days, resulting in a compliance rate of 85.3%. Among them, 340 individuals (99.4%) had 3 samples examined with the K-K method, 318 (93.0%) with the KAP method, and 292 (85.4%) with the BM method. Since the combination of the KAP and K-K techniques (for hookworm detection) and the combination of the KAP and the BM methods (for S. stercoralis detection) were of particular interest, the analysis focused on 316 (97.5%) and 277 (81.0%) schoolchildren, respectively. Complete data records, i.e., 3 stool samples examined with all 3 diagnostic tests, were available for 277 out of 401 individuals, resulting in an overall compliance rate of 69.1%.

Bottom Line: The examination of multiple stool samples instead of a single one resulted in an increase of the observed prevalence; e.g., an increase of 161% for hookworm using the K-K method.The observed prevalences for T. trichiura, hookworm, A. lumbricoides, and S. stercoralis were 47.9%, 22.5%, 16.5%, and 10.8% after examining 3 stool samples.These values are close to the 'true' prevalences predicted by a mathematical model.

View Article: PubMed Central - PubMed

Affiliation: Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland.

ABSTRACT

Background: Soil-transmitted helminth infections are common throughout the tropics and subtropics and they disproportionately affect the poorest of the poor. In view of a growing global commitment to control soil-transmitted helminthiasis, there is a need to elucidate the effect of repeated stool sampling and the use of different diagnostic methods in areas targeted for preventive chemotherapy that are characterized by low-infection intensities. In this study, we focused on schoolchildren on Unguja Island, Zanzibar, an area where anthelminthic drugs have been repeatedly administered over the past decade.

Methodology/principal findings: Three serial stool samples from each of 342 schoolchildren were examined using the Kato-Katz (K-K), Koga agar plate (KAP), and Baermann (BM) techniques. These methods were used individually or in combination for the diagnosis of Ascaris lumbricoides (K-K), Trichuris trichiura (K-K), hookworm (K-K and KAP), and Strongyloides stercoralis (KAP and BM). The examination of multiple stool samples instead of a single one resulted in an increase of the observed prevalence; e.g., an increase of 161% for hookworm using the K-K method. The diagnostic sensitivity of single stool sampling ranged between 20.7% for BM to detect S. stercoralis and 84.2% for K-K to diagnose A. lumbricoides. Highest sensitivities were observed when different diagnostic approaches were combined. The observed prevalences for T. trichiura, hookworm, A. lumbricoides, and S. stercoralis were 47.9%, 22.5%, 16.5%, and 10.8% after examining 3 stool samples. These values are close to the 'true' prevalences predicted by a mathematical model.

Conclusion/significance: Rigorous epidemiologic surveillance of soil-transmitted helminthiasis in the era of preventive chemotherapy is facilitated by multiple stool sampling bolstered by different diagnostic techniques.

Show MeSH
Related in: MedlinePlus