Excellent negative predictive value (99.8%) of two rapid molecular COVID-19 tests compared to conventional RT-PCR for SARS-CoV-2 (COVID-19) in 2,011 tests performed in a single centre.

Abstract

Conventional Reverse Transcription Polymerase Chain Reaction (RT-PCR) remains the gold standard for testing SARS-CoV-2. Since their availability, two rapid molecular COVID-19 tests were performed in parallel with RT-PCR in all urgent and emergency admissions, as the negative predictive value was not yet ascertained. In this study, we present the data of 2011 test results using either ID Now COVID-19 (Abbott) (Abbott ID NOW) or Xpert Xpress SARS-CoV-2 (Cepheid) (GeneXpert) tests comparing to conventional RT-PCR results. The negative predictive value is 99.8%(3 false negatives out of 1,964 tests) using a cut-off CT value of 40. Using a cut-off of RT-PCR CT value of 30 (predicting infectivity), the negative predictive value is reduced to 99.9% (1 out of 1,964 tests). With these results, we feel confident to recommend the immediate use of the rapid PCR tests alone and to use conventional RT-PCR for confirmation testing after.