title: Cholera Rapid Test with Enrichment Step Has Diagnostic Performance Equivalent to Culture.
abstract: Cholera rapid diagnostic tests (RDT) could play a central role in outbreak detection and surveillance in low-resource settings, but their modest performance has hindered their broad adoption. The addition of an enrichment step may improve test specificity. We describe the results of a prospective diagnostic evaluation of the Crystal VC RDT (Span Diagnostics, India) with enrichment step and of culture, each compared to polymerase chain reaction (PCR), during a cholera outbreak in South Sudan. RDTs were performed on alkaline peptone water inoculated with stool and incubated for 4-6 hours at ambient temperature. Cholera culture was performed from wet filter paper inoculated with stool. Molecular detection of Vibrio cholerae O1 by PCR was done from dry Whatman 903 filter papers inoculated with stool, and from wet filter paper supernatant. In August and September 2015, 101 consecutive suspected cholera cases were enrolled, of which 36 were confirmed by PCR. The enriched RDT had 86.1% (95% CI: 70.5-95.3) sensitivity and 100% (95% CI: 94.4-100) specificity compared to PCR as the reference standard. The sensitivity of culture versus PCR was 83.3% (95% CI: 67.2-93.6) for culture performed on site and 72.2% (95% CI: 54.8-85.8) at the international reference laboratory, where samples were tested after an average delay of two months after sample collection, and specificity was 98.5% (95% CI: 91.7-100) and 100% (95% CI: 94.5-100), respectively. The RDT with enrichment showed performance comparable to that of culture and could be a sustainable alternative to culture confirmation where laboratory capacity is limited.
authors.affiliation: Médecins Sans Frontières Operational Center Geneva, Geneva, Switzerland.|Amref Health Africa Headquarters, Nairobi, Kenya.
authors.forename: Lameck N
authors.initials: LN
authors.lastname: Ontweka
authors.affiliation: National Public Health Laboratory, Ministry of Health, Juba, South Sudan.
authors.forename: Lul O
authors.initials: LO
authors.lastname: Deng
authors.affiliation: Enteric Bacterial Pathogens Unit, National Reference Centre for Vibrios and Cholera, Institut Pasteur, Paris, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Rauzier
authors.affiliation: Department of International Health, Johns Hopkins University, Baltimore, United States of America.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Debes
authors.affiliation: Field epidemiology, Epicentre, Paris, France.
authors.forename: Fisseha
authors.initials: F
authors.lastname: Tadesse
authors.affiliation: Médecins Sans Frontières Operational Center Geneva, Geneva, Switzerland.
authors.forename: Lucy A
authors.initials: LA
authors.lastname: Parker
authors.affiliation: World Health Organization, Juba, South Sudan.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Wamala
authors.affiliation: National Public Health Laboratory, Ministry of Health, Juba, South Sudan.
authors.forename: Bior K
authors.initials: BK
authors.lastname: Bior
authors.affiliation: National Public Health Laboratory, Ministry of Health, Juba, South Sudan.
authors.forename: Michael
authors.initials: M
authors.lastname: Lasuba
authors.affiliation: National Public Health Laboratory, Ministry of Health, Juba, South Sudan.
authors.forename: Abiem Bona
authors.initials: AB
authors.lastname: But
authors.affiliation: Field epidemiology, Epicentre, Paris, France.
authors.forename: Francesco
authors.initials: F
authors.lastname: Grandesso
authors.affiliation: Médecins Sans Frontières Operational Center Geneva, Geneva, Switzerland.
authors.forename: Christine
authors.initials: C
authors.lastname: Jamet
authors.affiliation: Field epidemiology, Epicentre, Paris, France.
authors.forename: Sandra
authors.initials: S
authors.lastname: Cohuet
authors.affiliation: Médecins Sans Frontières Operational Center Geneva, Geneva, Switzerland.
authors.forename: Iza
authors.initials: I
authors.lastname: Ciglenecki
authors.affiliation: Médecins Sans Frontières Operational Center Geneva, Geneva, Switzerland.
authors.forename: Micaela
authors.initials: M
authors.lastname: Serafini
authors.affiliation: Department of International Health, Johns Hopkins University, Baltimore, United States of America.
authors.forename: David A
authors.initials: DA
authors.lastname: Sack
authors.affiliation: Enteric Bacterial Pathogens Unit, National Reference Centre for Vibrios and Cholera, Institut Pasteur, Paris, France.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Quilici
authors.affiliation: Department of Epidemiology, Johns Hopkins University, Baltimore, United States of America.|Médecins Sans Frontières Operational Center Geneva, Geneva, Switzerland.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Azman
authors.affiliation: Department of International Health, Johns Hopkins University, Baltimore, United States of America.|Field epidemiology, Epicentre, Paris, France.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Luquero
authors.affiliation: Field epidemiology, Epicentre, Paris, France.
authors.forename: Anne-Laure
authors.identifier: http://orcid.org/0000-0001-7952-3178
authors.initials: AL
authors.lastname: Page
mesh_terms: D000328:Adult; D015373:Bacterial Typing Techniques; D001431:Bacteriological Techniques / Q000379:methods*; D002771:Cholera / Q000175:diagnosis* / Q000453:epidemiology; D003955:Diagnostic Tests, Routine / Q000379:methods*; D004196:Disease Outbreaks; D005243:Feces / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D058889:Molecular Typing; D011159:Population Surveillance; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D000068037:South Sudan / Q000453:epidemiology; D014734:Vibrio cholerae / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D011933:Reagent Kits, Diagnostic