AUTHOR=Sullivan Adam , Alfego David , Poirier Brian , Williams Jonathan , Adcock Dorothy , Letovsky Stan 

TITLE=Follow-Up SARS-CoV-2 PCR Testing Outcomes From a Large Reference Lab in the US

JOURNAL=Frontiers in Public Health

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2021.679012

DOI=10.3389/fpubh.2021.679012

ISSN=2296-2565

ABSTRACT=Analysis of large-scale patient cohorts is needed to understand how follow-up RT-PCR testing for SARS-CoV-2 dynamics change throughout the lifecycle of infection, as well as provide qualitative evidence to the lack of a significant basal false positive rate. Retrospective cohort study of a registry of RT-PCR testing results for all patients tested at any of the reference labs operated by Labcorp® including both positive, negative, and inconclusive results, from March 1, 2020 to January 28, 2021, including patients from all 50 states and outlying US territories.  The study included 22 million patients with RT-PCR qualitative test results for SARS-CoV-2, of which 3.9 million had more than one test at Labcorp.  For patients who have a second test after a first RT-PCR, 30% across the cohort tested negative on the second test.  For patients who test positive first and subsequently negative within 96 hours (40% of positive test results), 18% of tests will subsequently test positive within another 96-hour span.  For those who first test negative and then positive within 96 hours (2.3% of negative tests), 56% will test negative after a third and subsequent 96-hour period.  While these dynamics were observed during active infection, we observed a minuscule <0.1% basal positive rate for follow up tests >115 days, which could account for false positives, long-haulers, and/or reinfection.  The sudden changes in RT-PCR test results for SARS-CoV-2 from this large cohort study suggest that negative test results during active infection or exposure can have sudden dynamic state changes.  We also demonstrate that there does not appear to be a basal false positive rate among patients who test positive >115 days after their first RT-PCR positive test while failing to observe any evidence of widespread reinfection.