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. 2018 Oct 23;11(1):552.
doi: 10.1186/s13071-018-3136-6.

Urogenital schistosomiasis elimination in Zanzibar: accuracy of urine filtration and haematuria reagent strips for diagnosing light intensity Schistosoma haematobium infections

Stefanie Knopp  1   2   3 , Shaali M Ame  4 , Jan Hattendorf  5   6 , Said M Ali  4 , Iddi S Khamis  7 , Faki Bakar  4 , Mwanaidi A Khamis  7 , Bobbie Person  8 , Fatma Kabole  7 , David Rollinson  9
Affiliations

Urogenital schistosomiasis elimination in Zanzibar: accuracy of urine filtration and haematuria reagent strips for diagnosing light intensity Schistosoma haematobium infections

Stefanie Knopp et al. Parasit Vectors. .

Erratum in

Abstract

Background: Urine filtration and microhaematuria reagent strips are basic standard diagnostic methods to detect urogenital schistosomiasis. We assessed their accuracy for the diagnosis of light intensity infections with Schistosoma haematobium as they occur in individuals living in Zanzibar, an area targeted for interruption of transmission.

Methods: Urine samples were collected from children and adults in surveys conducted annually in Zanzibar from 2013 through 2016 and examined with the urine filtration method to count S. haematobium eggs and with the reagent strip test (Hemastix) to detect microhaematuria as a proxy for infection. Ten percent of the urine filtration slides were read twice. Sensitivity was calculated for reagent strips, stratified by egg counts reflecting light intensity sub-groups, and kappa statistics for the agreement of urine filtration readings.

Results: Among the 39,207 and 18,155 urine samples examined from children and adults, respectively, 5.4% and 2.7% were S. haematobium egg-positive. A third (34.7%) and almost half (46.7%) of the egg-positive samples from children and adults, respectively, had ultra-low counts defined as 1-5 eggs per 10 ml urine. Sensitivity of the reagent strips increased significantly for each unit log10 egg count per 10 ml urine in children (odds ratio, OR: 4.7; 95% confidence interval, CI: 4.0-5.7; P < 0.0001) and adults (OR: 2.6; 95% CI: 1.9-3.7, P < 0.0001). Sensitivity for diagnosing ultra-light intensity infections was very low in children (50.1%; 95% CI: 46.5-53.8%) and adults (58.7%; 95% CI: 51.9-65.2%). Among the 4477 and 1566 urine filtration slides read twice from children and adults, most were correctly identified as negative or positive (kappa = 0.84 for children and kappa = 0.81 for adults). However, 294 and 75 slides had discrepant results and were positive in only one of the two readings. The majority of these discrepant slides (76.9% of children and 84.0% of adults) had counts of 1-5 eggs per 10 ml urine.

Conclusions: We found that many individuals infected with S. haematobium in Zanzibar excrete > 5 eggs per 10 ml urine. These ultra-light infections impose a major challenge for accurate diagnosis. Next-generation diagnostic tools to be used in settings where interruption of transmission is the goal should reliably detect infections with ≤ 5 eggs per 10 ml urine.

Trial registration: ISRCTN, ISRCTN48837681 . Registered 05 September 2012 - Retrospectively registered.

Keywords: Control; Diagnosis; Elimination; Macrohaematuria; Microhaematuria; Reagent strip; Schistosoma haematobium; Surveillance; Urine filtration; Urogenital schistosomiasis; Zanzibar.

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Conflict of interest statement

Ethics approval and consent to participate

Our study protocol was approved by the Zanzibar Medical Research Ethics Committee (ZAMREC) in Zanzibar, United Republic of Tanzania (reference no. ZAMREC 0003/Sept/011), the Ethics Committee of Basel, Switzerland (reference no. EKBB 236/11), and the Institutional Review Board of the University of Georgia in the USA (project no. 2012-10138-0) [16]. The study is registered with the International Standard Randomized Controlled Trial Number register (ISRCTN48837681). All children and adults invited to participate in the study received a participant information sheet and a consent sheet. The study was explained in lay terms to the children in school and to the adults in the communities using the local language Kiswahili. Only individuals, who submitted a written informed consent for their participation, were included in the study. In the case of children, parents or their legal guardians were asked to provide their written consent for the child’s participation. All study participants were offered praziquantel (40 mg/kg) against schistosomiasis and albendazole (400 mg) against soil-transmitted helminthiasis free of charge via the biannual island-wide mass drug administration conducted as part of the elimination interventions by the Zanzibar Neglected Diseases Programme in 2013, 2014, 2015 and 2016.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Flowchart detailing study participation and urine sampling procedures. a Children sampled in public primary schools. b Adults sampled in communities in Unguja and Pemba islands, United Republic of Tanzania
Fig. 2
Fig. 2
Boxplots of S. haematobium log egg counts of egg-positive urine samples from Zanzibar, United Republic of Tanzania, stratified by microhaematuria grading, sex and age category. a log S. haematobium egg-counts by microhaematuria grading for female and male children. b log S. haematobium egg-counts by microhaematuria grading for female and male adults. Correlation between positive egg counts and microhaematuria grading (data pooled over both sexes): Spearman’s rho in children= 0.65, P < 0.001 (n = 39,207), Spearman’s rho in adults = 0.32; P < 0.001 (n = 18,155). In contrast to the boxplots, the correlation coefficients were calculated using egg counts from positive and negative urine samples
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