title: Sensitivity and Specificity of a New Vertical Flow Rapid Diagnostic Test for the Serodiagnosis of Human Leptospirosis.
abstract: Background: Leptospirosis is a growing public health concern in many tropical and subtropical countries. However, its diagnosis is difficult because of non-specific symptoms and concurrent other endemic febrile diseases. In many regions, the laboratory diagnosis is not available due to a lack of preparedness and simple diagnostic assay or difficult access to reference laboratories. Yet, an early antibiotic treatment is decisive to the outcome. The need for Rapid Diagnostic Tests (RDTs) for bedside diagnosis of leptospirosis has been recognized. We developed a vertical flow immunochromatography strip RDT detecting anti-Leptospirahuman IgM and evaluated it in patients from New Caledonia, France, and French West Indies.Methodology/Principal Findings: Whole killedLeptospira faineicells were used as antigen for the test line and purified human IgM as the control line. The mobile phase was made of gold particles conjugated with goat anti-human IgM. Standards for Reporting of Diagnostic Accuracy criteria were used to assess the performance of this RDT. The Microscopic Agglutination Test (MAT) was used as the gold standard with a cut-off titer of ≥400. The sensitivity was 89.8% and the specificity 93.7%. Positive and negative Likelihood Ratios of 14.18 and 0.108 respectively, and a Diagnostic Odds Ratio of 130.737 confirmed its usefulness. This RDT had satisfactory reproducibility, repeatability, thermal tolerance and shelf-life. The comparison with MAT evidenced the earliness of the RDT to detect seroconversion. When compared with other RDT, the Vertical Flow RDT developed displayed good diagnostic performances.
  
  
  CONCLUSIONS
  This RDT might be used as a point of care diagnostic tool in limited resources countries. An evaluation in field conditions and in other epidemiological contexts should be considered to assess its validity over a wider range of serogroups or when facing different endemic pathogens. It might prove useful in endemic contexts or outbreak situations.
authors.affiliation: Institut Pasteur de Nouvelle-Calédonie, Association Pasteur International Network, Nouméa, New Caledonia.
authors.forename: Cyrille
authors.initials: C
authors.lastname: Goarant
authors.forename: Pascale
authors.initials: P
authors.lastname: Bourhy
authors.forename: Eric
authors.initials: E
authors.lastname: D'Ortenzio
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dartevelle
authors.forename: Carine
authors.initials: C
authors.lastname: Mauron
authors.forename: Marie-Estelle
authors.initials: ME
authors.lastname: Soupé-Gilbert
authors.forename: Lilian
authors.initials: L
authors.lastname: Bruyère-Ostells
authors.forename: Ann-Claire
authors.initials: AC
authors.lastname: Gourinat
authors.forename: Mathieu
authors.initials: M
authors.lastname: Picardeau
authors.forename: Faridabano
authors.initials: F
authors.lastname: Nato
authors.forename: Suzanne
authors.initials: S
authors.lastname: Chanteau