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Clinical Trial
. 2018 Mar 8;13(3):e0194024.
doi: 10.1371/journal.pone.0194024. eCollection 2018.

Diagnostic accuracy of antigen-based immunochromatographic rapid diagnostic tests for the detection of Salmonella in blood culture broth

Laura M F Kuijpers  1   2 , Panha Chung  3 , Marjan Peeters  1 , Marie-France Phoba  4 , Chun Kham  3 , Barbara Barbé  1 , Octavie Lunguya  4 , Jan Jacobs  1   2
Affiliations
Clinical Trial

Diagnostic accuracy of antigen-based immunochromatographic rapid diagnostic tests for the detection of Salmonella in blood culture broth

Laura M F Kuijpers et al. PLoS One. .

Abstract

Background: In low resource settings, Salmonella serovars frequently cause bloodstream infections. This study investigated the diagnostic performance of immunochromatographic rapid diagnostic tests (RDTs), which detect Salmonella antigens, when applied to stored grown blood culture broth.

Material/methods: The SD Bioline One Step Salmonella Typhi Ag Rapid Detection Kit (Standard Diagnostics, Republic of Korea), marketed for the detection of Salmonella enterica serovar Typhi (Salmonella Typhi) in stool and the Salmonella Ag Rapid Test (Creative Diagnostics, USA), marketed for the detection of all Salmonella serotypes in stool, were selected for evaluation based on a pre-test evaluation of six RDT products. The limits of detection (LOD) for culture suspensions were established and the selected RDT products were assessed on 19 freshly grown spiked blood culture broth samples and 413 stored clinical blood culture broth samples, collected in Cambodia and the Democratic Republic of the Congo.

Results: The LOD of both products was established as 107-108 CFU/ml. When applied to clinical blood culture broth samples, the diagnostic sensitivity and specificity of the SD Bioline RDT were respectively 100% and 79.7% for the detection of Salmonella Typhi; 94.4% (65/69) of false-positive results were caused by Salmonella Enteritidis. When considering the combined detection of Salmonella Typhi and Enteritidis (both group D Salmonella), sensitivity and specificity were 97.9% and 98.5% respectively. For Creative Diagnostics, diagnostic sensitivity was 78.3% and specificity 91.0% for all Salmonella serotypes combined; 88.3% (53/60) of false negative results were caused by Salmonella Paratyphi A.

Conclusions: When applied to grown blood culture broths, the SD Bioline RDT had a good sensitivity and specificity for the detection of Salmonella Typhi and Salmonella Enteritidis. The Creative Diagnostics product had a moderate sensitivity and acceptable specificity for the detection of all Salmonella serovars combined and needs further optimization. A RDT that reliably detects Salmonella Paratyphi A is needed.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Variable background clearance.
Both tests shown (Standard Diagnostics Bioline One Step Salmonella Typhi Ag Rapid Detection Kit) with the presence of a control line and absence of a test line, show a negative test result. Background clearance is scored poor for the test above (more reddish) and good for the test below.
Fig 2
Fig 2. Presence of black and red colored test lines.
Samples applied to both tests (Salmonella Ag Rapid Test, Creative diagnostics) contained Salmonella Enteritidis and both were scored as a positive test result. The test above shows a red colored control line and a black colored test line. The picture below shows a red colored control and test line.
See this image and copyright information in PMC

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