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

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

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.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Antigens, Bacterial / blood*
  • Bacteremia / diagnosis*
  • Bacteremia / microbiology
  • Bacterial Typing Techniques
  • Bacteriological Techniques / methods*
  • Blood Culture / methods*
  • Cambodia
  • Child
  • Child, Preschool
  • Chromatography, Affinity / methods*
  • Cryopreservation
  • Culture Media*
  • Democratic Republic of the Congo
  • Developing Countries
  • Early Diagnosis
  • Female
  • Humans
  • Limit of Detection
  • Male
  • Middle Aged
  • Preservation, Biological
  • Proof of Concept Study
  • Reagent Kits, Diagnostic*
  • Salmonella / classification
  • Salmonella / immunology
  • Salmonella / isolation & purification*
  • Salmonella Infections / blood
  • Salmonella Infections / diagnosis*
  • Salmonella Infections / microbiology
  • Sensitivity and Specificity
  • Serogroup
  • Species Specificity
  • Young Adult

Substances

  • Antigens, Bacterial
  • Culture Media
  • Reagent Kits, Diagnostic

Grants and funding

The surveillance of bloodstream infections at the Sihanouk Hospital Center of HOPE is supported by the Belgian Directorate of Development Cooperation (DGD) (https://diplomatie.belgium.be/en/policy/development_cooperation/who_we_are/our_organisation/dgd) through project 2.08 of the Third Framework Agreement between the Belgian DGD (Ministry of Development Cooperation) and the Institute of Tropical Medicine (ITM). This study was further supported by the Strategic Network Laboratory Quality Management (LQM) project SN126 (Belgian Development Cooperation). LMFK is supported by the Flemish Ministry of Sciences (EWI, SOFI project IDIS) (http://www.ewi-vlaanderen.be/en) and received additional travel grants (grant numbers K2.060.16N and K2.065.17N) from the Fund for Scientific Research Flanders (F.W.O.-Vlaanderen, Belgium) (http://www.fwo.be/). One of the authors (MFP) received a scholarship of the Foundation Marguerite-Marie Delacroix, Tienen, Belgium (http://www.fondsmmdelacroix.org/). Standard Diagnostics (SD), Republic of Korea) donated the SD Bioline One Step Salmonella Typhi Ag Rapid Detection kits used for this study. Neither the funders nor the manufacturers of the RDTs had a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript, therefore we report no competing interests.