title: Analytical Performance Characteristics of the Cepheid GeneXpert Ebola Assay for the Detection of Ebola Virus.
abstract: BACKGROUND
  The recently developed Xpert® Ebola Assay is a novel nucleic acid amplification test for simplified detection of Ebola virus (EBOV) in whole blood and buccal swab samples. The assay targets sequences in two EBOV genes, lowering the risk for new variants to escape detection in the test. The objective of this report is to present analytical characteristics of the Xpert® Ebola Assay on whole blood samples.
  
  
  RESULTS
  This study evaluated the assay's analytical sensitivity, analytical specificity, inclusivity and exclusivity performance in whole blood specimens. EBOV RNA, inactivated EBOV, and infectious EBOV were used as targets. The dynamic range of the assay, the inactivation of virus, and specimen stability were also evaluated. The lower limit of detection (LoD) for the assay using inactivated virus was estimated to be 73 copies/mL (95% CI: 51-97 copies/mL). The LoD for infectious virus was estimated to be 1 plaque-forming unit/mL, and for RNA to be 232 copies/mL (95% CI 163-302 copies/mL). The assay correctly identified five different Ebola viruses, Yambuku-Mayinga, Makona-C07, Yambuku-Ecran, Gabon-Ilembe, and Kikwit-956210, and correctly excluded all non-EBOV isolates tested. The conditions used by Xpert® Ebola for inactivation of infectious virus reduced EBOV titer by ≥6 logs.
  
  
  CONCLUSIONS
  In summary, we found the Xpert® Ebola Assay to have high analytical sensitivity and specificity for the detection of EBOV in whole blood. It offers ease of use, fast turnaround time, and remote monitoring. The test has an efficient viral inactivation protocol, fulfills inclusivity and exclusivity criteria, and has specimen stability characteristics consistent with the need for decentralized testing. The simplicity of the assay should enable testing in a wide variety of laboratory settings, including remote laboratories that are not capable of performing highly complex nucleic acid amplification tests, and during outbreaks where time to detection is critical.
authors.affiliation: Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America.|Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Pinsky
authors.affiliation: Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Malaya K
authors.initials: MK
authors.lastname: Sahoo
authors.affiliation: Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America.|Clinical Microbiology Laboratory, Stanford Health Care and Stanford Children's Health, Palo Alto, California, United States of America.
authors.forename: Johanna
authors.initials: J
authors.lastname: Sandlund
authors.affiliation: Cepheid, Solna, Sweden.
authors.forename: Marika
authors.initials: M
authors.lastname: Kleman
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Medha
authors.initials: M
authors.lastname: Kulkarni
authors.affiliation: Cepheid, Solna, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Grufman
authors.affiliation: Cepheid, Solna, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Nygren
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Kwiatkowski
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Ellen Jo
authors.initials: EJ
authors.lastname: Baron
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Fred
authors.initials: F
authors.lastname: Tenover
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Blake
authors.initials: B
authors.lastname: Denison
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Russell
authors.initials: R
authors.lastname: Higuchi
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: Reuel
authors.initials: R
authors.lastname: Van Atta
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California, United States of America.
authors.forename: Neil Reginald
authors.initials: NR
authors.lastname: Beer
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California, United States of America.
authors.forename: Alda Celena
authors.initials: AC
authors.lastname: Carrillo
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California, United States of America.
authors.forename: Pejman
authors.initials: P
authors.lastname: Naraghi-Arani
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Chad E
authors.initials: CE
authors.lastname: Mire
authors.affiliation: Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Charlene
authors.initials: C
authors.lastname: Ranadheera
authors.affiliation: Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Allen
authors.initials: A
authors.lastname: Grolla
authors.affiliation: The Public Health Agency of Sweden, Solna, Sweden.
authors.forename: Nina
authors.initials: N
authors.lastname: Lagerqvist
authors.affiliation: Cepheid, Sunnyvale, California, United States of America.
authors.forename: David H
authors.initials: DH
authors.lastname: Persing
mesh_terms: D000818:Animals; D002522:Chlorocebus aethiops; D029043:Ebolavirus / Q000235:genetics* / Q000502:physiology; D005814:Genes, Viral / Q000235:genetics; D019142:Hemorrhagic Fever, Ebola / Q000097:blood / Q000175:diagnosis* / Q000821:virology; D054884:Host-Pathogen Interactions; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D012367:RNA, Viral / Q000097:blood / Q000235:genetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D014709:Vero Cells; D038301:Virus Inactivation
chemical_list: D012367:RNA, Viral