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. 2018 Jul 9;13(7):e0192598.
doi: 10.1371/journal.pone.0192598. eCollection 2018.

Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis

Chatanun Eamudomkarn  1   2 , Paiboon Sithithaworn  1   2 , Christine Kamamia  3 , Anna Yakovleva  3 , Jiraporn Sithithaworn  4   5 , Sasithorn Kaewkes  1 , Anchalee Techasen  2   4 , Watcharin Loilome  2   6 , Puangrat Yongvanit  2   6 , Chompunoot Wangboon  7 , Prasert Saichua  8 , Makoto Itoh  9 , Jeffrey M Bethony  3
Affiliations

Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis

Chatanun Eamudomkarn et al. PLoS One. .

Abstract

The diagnosis of strongyloidiasis by coprological methods has a low sensitivity, underestimating the prevalence of Strongyloides stercoralis in endemic areas. Serodiagnostic tests for strongyloidiasis have shown robust diagnostic properties. However, these methods require a blood draw, an invasive and labor-intensive sample collection method, especially in the resource-limited settings where S. stercoralis is endemic. Our study examines a urine-based assay for strongyloidiasis and compares its diagnostic accuracy with coprological and serological methods. Receiver operating characteristic (ROC) curve analyses determined the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the urine ELISA, as well as estimates its positive predictive value and diagnostic risk. The likelihood ratios of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for each diagnostic positivity threshold. The urine ELISA assay correlated significantly with the serological ELISA assay for strongyloidiasis, with a D-Sn of 92.7% and a D-Sp of 40.7%, when compared to coprological methods. Moreover, the urine ELISA IgG test had a detection rate of 69%, which far exceeds the coprological method (28%). The likelihood of a positive diagnosis of strongyloidiasis by the urine ELISA IgG test increased significantly with increasing units of IgG detected in urine. The urine ELISA IgG assay for strongyloidiasis assay has a diagnostic accuracy comparable to serological assay, both of which are more sensitive than coprological methods. Since the collection of urine is easy and non-invasive, the urine ELISA IgG assay for strongyloidiasis could be used to screen populations at risk for strongyloidiasis in S. stercoralis endemic areas.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flow chart of participants in the study.
Data shown for age are mean ± SD, where n is the sample size.
Fig 2
Fig 2. Venn diagrams comparing the distribution of positive and negative results by each diagnostic method.
Fig 3
Fig 3. Tests for cross reactivity with other parasites and disease for strongyloidiasis.
Tests for cross reactivity of the urine ELISA (A) and serum ELISA (B) for strongyloidiasis. (SS, S. stercoralis; OV; O. viverrini; T, Taenia sp.; Tt, T. trichuira; Echi, Echinostomes; MIF, minute intestinal flukes; Ac, A. cantonensis; Pw, P. westernmani; Pm, P. miyazakii; F, Fasciola spp.; Cs, C. sinensis; CCA, cholangiocarcinoma, Cholec, cholecystitis; and Adeno, adenocarcinoma).
Fig 4
Fig 4. The comparison of the ROC curves.
The ROC curve illustrates the comparison between the diagnostic performance of antibody detection using a urine assay and a serum assay. The model used to construct the ROC curve was modeled to include negative controls (strongyloidiasis negative and other infections) and individuals who were infected with strongyloidiasis. A; Primary reference standard for serum and urine ELISA, B; Composite reference standard for serum ELISA, C; Composite reference standard for urine ELISA.
Fig 5
Fig 5. Correlation between urine IgG and serum IgG antibodies.
Log-transformed variables. Correlation coefficient determined by Pearson product-moment correlation test.
See this image and copyright information in PMC

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