Impact of coronavirus disease 2019 (COVID-19) pre-test probability on positive predictive value of high cycle threshold severe acute respiratory coronavirus virus 2 (SARS-CoV-2) real-time reverse transcription polymerase chain reaction (RT-PCR) test results Journal Articles uri icon

  • Overview
  • Research
  • Identity
  • Additional Document Info
  • View All


  • AbstractObjectives:Performance characteristics of SARS-CoV-2 nucleic acid detection assays are understudied within contexts of low pre-test probability, including screening asymptomatic persons without epidemiological links to confirmed cases, or asymptomatic surveillance testing. SARS-CoV-2 detection without symptoms may represent presymptomatic or asymptomatic infection, resolved infection with persistent RNA shedding, or a false-positive test. This study assessed the positive predictive value of SARS-CoV-2 real-time reverse transcription polymerase chain reaction (rRT-PCR) assays by retesting positive specimens from 5 pre-test probability groups ranging from high to low with an alternate assay.Methods:In total, 122 rRT-PCR positive specimens collected from unique patients between March and July 2020 were retested using a laboratory-developed nested RT-PCR assay targeting the RNA-dependent RNA polymerase (RdRp) gene followed by Sanger sequencing.Results:Significantly fewer (15.6%) positive results in the lowest pre-test probability group (facilities with institution-wide screening having ≤3 positive asymptomatic cases) were reproduced with the nested RdRp gene RT-PCR assay than in each of the 4 groups with higher pre-test probability (individual group range, 50.0%–85.0%).Conclusions:Large-scale SARS-CoV-2 screening testing initiatives among low pre-test probability populations should be evaluated thoroughly prior to implementation given the risk of false-positive results and consequent potential for harm at the individual and population level.


  • Gubbay, Jonathan B
  • Rilkoff, Heather
  • Kristjanson, Heather L
  • Forbes, Jessica D
  • Murti, Michelle
  • Eshaghi, AliReza
  • Broukhanski, George
  • Corbeil, Antoine
  • Fittipaldi, Nahuel
  • Hopkins, Jessica
  • Kristjanson, Erik
  • Kus, Julianne V
  • Macdonald, Liane
  • Majury, Anna
  • Mallo, Gustavo V
  • Mazzulli, Tony
  • Melano, Roberto G
  • Olsha, Romy
  • Perusini, Stephen J
  • Tran, Vanessa
  • Allen, Vanessa G
  • Patel, Samir N

publication date

  • September 2022