A Comparison of Five SARS-CoV-2 Molecular Assays With Clinical Correlations

Gary W. Procop, MD, MS; Jay E. Brock, PhD; Edmunds Z. Reineks, MD; Nabin K. Shrestha, MD, MPH; Ryan Demkowicz, MD; Eleanor Cook, MD; Emad Ababneh, MD; Susan M. Harrington, PhD


Am J Clin Pathol. 2021;155(1):69-78. 

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The findings from the clinical correlation are consistent with the presence of high viral loads (lower Ct values) at the onset of symptoms. This pattern of high viral shedding at symptom onset has been demonstrated by others and is a significant factor in transmission of SARS-CoV-2.[19,20] Our data suggest that the CDC 2019 nCoV Real-Time RT-PCR Diagnostic Panel, TIB MOLBIOL/Roche z 480 Assay, and Xpert Xpress SARS-CoV-2 (Cepheid) assays perform well at any stage of illness. However, the Simplexa COVID-19 Direct Kit (DiaSorin) and ID Now COVID-19 (Abbott) assays had false-negative rates exceeding 10%, with false-negative results associated with low viral loads, suggesting that they are likely to perform less well when viral loads are lower, which is generally later in the course of illness. This finding concerning the ID Now COVID-19 (Abbott) has been confirmed by others.[17,18]