key: cord-0933571-7q2owkad
authors: Liotti, Flora Marzia; Menchinelli, Giulia; Marchetti, Simona; Morandotti, Grazia Angela; Sanguinetti, Maurizio; Posteraro, Brunella; Cattani, Paola
title: Evaluating the newly developed BioFire® COVID-19 test for SARS–Cov-2 molecular detection
date: 2020-07-28
journal: Clin Microbiol Infect
DOI: 10.1016/j.cmi.2020.07.026
sha: ba8a1a682214c9d06d35e8f7d1ba86b37ea666f8
doc_id: 933571
cord_uid: 7q2owkad

nan

To the Editor, 20 It was not until March 24, 2020 that the newly developed BioFire® COVID-19 test (BioFire syndrome coronavirus 2 (SARS-Cov-2) in clinical samples received a Food and Drug 23 Administration (FDA) emergency use authorization (EUA) (https://www.fda.gov/medical-24 devices/emergency-situations-medical-devices/emergency-use-authorizations). It is then not 25 surprising that no published studies to date have evaluated BioFire® COVID-19 test in clinical 26 microbiology practice. 27 We compared the performance of BioFire® COVID-19 test with that of Quanty COVID-19 assay 28 (Clonit S.r.l, Milan, Italy), which also provides quantitative results, for detection of SARS-Cov-2 29 RNA in nasal/oropharyngeal (N/OP) patient samples. Both molecular tests detect SARS-Cov-2 30 specifically, with the first targeting two viral open reading frame sequences (ORF1ab and ORF8)-31 in three independent PCR assays-and the second targeting three viral nucleocapsid (N) sequences 32 (N1, N2, and N3). Such comparison is essential for defining the cause of potential false-negative 33 results [1] , which may undermine the clinical utility of various molecular diagnostic tests available 34 currently [2, 3]. 35 We analysed the results of 120 N/OP samples tested with both BioFire® COVID-19 test and 36 Quanty COVID-19 assay. Samples that were kept frozen -70°C until testing to ensure RNA COVID-19 test-had no detections in all three assays (hence interpreted as "not detected"), whereas four samples initially yielded detection in only one assay (hence interpreted as "equivocal") but 48 resulted as "not detected" at retesting. Interestingly, viral loads (expressed as RNA copies per mL) 49 of the six samples were 2.20 × 10 1 to 1.60 × 10 2 . However, these loads were below the limit of If two or more assays are "detected", the test result will be "detected"; if all assays are "not detected", the test result will be "not detected"; if only one of the assays is "detected", the test result will be "equivocal". An "equivocal" test result requires sample retesting; if the test result is "equivocal" or "detected", the overall interpretation will be "detected"; otherwise, a "not detected" test result needs confirmatory testing. b To quantitate SARS-CoV-2 RNA, the instrument software automatically calculates the viral load in each sample by interpolation of the corresponding cycle threshold value with the standard curve. This curve was built with the cycle threshold values obtained following the amplification of standards containing, respectively, 10 1 , 10 2 , 10 3 , 10 4 , and 10 5 copies/µL of synthetic viral N1-encoding RNA. c The sample with an "equivocal" test result at first testing yielded a "not detected" test result at retesting.

Negative nasopharyngeal and oropharyngeal swabs do not rule out COVID-19

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France) for providing reagents for this study.