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Interpreting ambiguous 'trace' results in Schistosoma mansoni CCA tests: estimating sensitivity and specificity of ambiguous results with no gold standard

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Title: Interpreting ambiguous 'trace' results in Schistosoma mansoni CCA tests: estimating sensitivity and specificity of ambiguous results with no gold standard
Authors: Clements, MN
Donnelly, CA
Fenwick, A
Kabatereine, NB
Knowles, SCI
Meité, A
N'Goran, EK
Nalule, Y
Nogaro, S
Phillips, AE
Tukahebwa, EM
Fleming, FM
Item Type: Journal Article
Abstract: Background The development of new diagnostics is an important tool in the fight against disease. Latent Class Analysis (LCA) is used to estimate the sensitivity and specificity of tests in the absence of a gold standard. The main field diagnostic for Schistosoma mansoni infection, Kato-Katz (KK), is not very sensitive at low infection intensities. A point-of-care circulating cathodic antigen (CCA) test has been shown to be more sensitive than KK. However, CCA can return an ambiguous ‘trace’ result between ‘positive’ and ‘negative’, and much debate has focused on interpretation of traces results. Methodology/Principle findings We show how LCA can be extended to include ambiguous trace results and analyse S. mansoni studies from both Côte d’Ivoire (CdI) and Uganda. We compare the diagnostic performance of KK and CCA and the observed results by each test to the estimated infection prevalence in the population. Prevalence by KK was higher in CdI (13.4%) than in Uganda (6.1%), but prevalence by CCA was similar between countries, both when trace was assumed to be negative (CCAtn: 11.7% in CdI and 9.7% in Uganda) and positive (CCAtp: 20.1% in CdI and 22.5% in Uganda). The estimated sensitivity of CCA was more consistent between countries than the estimated sensitivity of KK, and estimated infection prevalence did not significantly differ between CdI (20.5%) and Uganda (19.1%). The prevalence by CCA with trace as positive did not differ significantly from estimates of infection prevalence in either country, whereas both KK and CCA with trace as negative significantly underestimated infection prevalence in both countries. Conclusions Incorporation of ambiguous results into an LCA enables the effect of different treatment thresholds to be directly assessed and is applicable in many fields. Our results showed that CCA with trace as positive most accurately estimated infection prevalence.
Issue Date: 8-Dec-2017
Date of Acceptance: 29-Nov-2017
URI: http://hdl.handle.net/10044/1/54413
DOI: https://dx.doi.org/10.1371/journal.pntd.0006102
ISSN: 1935-2727
Publisher: Public Library of Science
Journal / Book Title: PLoS Neglected Tropical Diseases
Volume: 11
Issue: 12
Copyright Statement: © 2017 Clements et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: 06 Biological Sciences
11 Medical And Health Sciences
Tropical Medicine
Publication Status: Published
Article Number: e0006102
Appears in Collections:School of Public Health