Optimizing SARS-CoV-2 Surveillance in the United States: Insights From the National Football League Occupational Health Program

Abstract

Background: Evidence to understand effective strategies for surveillance and early detection of SARS-CoV-2 is limited.

Objective: To describe the results of a rigorous, large-scale COVID-19 testing and monitoring program.

Design: The U.S. National Football League (NFL) and the NFL Players Association (NFLPA) instituted a large-scale COVID-19 monitoring program involving daily testing using 2 reverse transcription polymerase chain reaction (RT-PCR) platforms (Roche cobas and Thermo Fisher QuantStudio), a transcription-mediated amplification platform (Hologic Panther), and an antigen point-of-care (aPOC) test (Quidel Sofia).

Setting: 32 NFL clubs in 24 states during the 2020 NFL season.

Participants: NFL players and staff.

Measurements: SARS-CoV-2 test results were described in the context of medically adjudicated status. Cycle threshold (Ct) values are reported when available.

Results: A total of 632 370 tests administered across 11 668 persons identified 270 (2.4%) COVID-19 cases from 1 August to 14 November 2020. Positive predictive values ranged from 73.0% to 82.0% across the RT-PCR platforms. High Ct values (33 to 37) often indicated early infection. For the first positive result, the median Ct value was 32.77 (interquartile range, 30.02 to 34.72) and 22% of Ct values were above 35. Among adjudicated COVID-19 cases tested with aPOC, 42.3% had a negative result. Positive concordance between aPOC test result and adjudicated case status increased as viral load increased.

Limitations: Platforms varied by laboratory, and test variability may reflect procedural differences.

Conclusion: Routine RT-PCR testing allowed early detection of infection. Cycle threshold values provided a useful guidepost for understanding results, with high values often indicating early infection. Antigen POC testing was unable to reliably rule out COVID-19 early in infection.

Primary funding source: The NFL and the NFLPA.

Visual Abstract.. SARS-CoV-2 Surveillance in the National Football League.

This study describes the experience of the National Football League (NFL)/NFL Players Association COVID-19 Testing and Surveillance Program during the 2020 NFL season and sheds insight into the utility of daily testing across multiple platforms in mitigating the spread of infection.

Figure 1.. COVID-19 case adjudication algorithm.

RT-PCR = reverse transcription polymerase chain reaction. * Any “positive” result includes positive, presumptive positive, or inconclusive results. † If the adjudication team learned of symptoms that presented later, case status was updated to a COVID-19 case, regardless of subsequent test results. ‡ Same-sample confirmatory testing began on 24 August 2020 and was performed for all samples. From 1 August to 23 August, samples with a positive next-day RT-PCR result were considered COVID-19 cases. Positive results required 2 consecutive days of negative follow-up testing to be considered an adjudicated negative case. Any other test result sequence required case determination by medical team consensus. If insufficient follow-up testing was done, the case status was deemed “unable to determine.” § Persons with a positive point-of-care test result were largely considered COVID-19 cases, regardless of the same-day confirmatory test result, although these results were discussed by the medical team. || If no symptoms were present, clubs were encouraged to do follow-up PCR testing of all asymptomatic/presymptomatic persons, regardless of the confirmatory test result. Sixty-five of 709 initial positive results were among asymptomatic/presymptomatic persons who did not have follow-up testing, 52 of which were adjudicated as COVID-19 cases due to positive same-sample confirmatory test results. ¶ Of 709 initial positive test results, 270 were adjudicated as COVID-19 cases (87 of which were symptomatic at the time of the positive result), 429 were adjudicated as negative, and 10 were deemed “unable to determine.” ** Medical team consensus considered testing history, further testing (if available), serologic status, and exposure to other positive persons. All persons reviewed by the medical team were assigned a case status of “COVID-19 case” or “adjudicated negative.”.

Figure 2.. COVID-19 incidence per 1000 persons, by week, 1 August to 14 November 2020.

CDC = Centers for Disease Control and Prevention; NFL = National Football League. * Includes cases from all 50 states and the District of Columbia. Data were obtained on 7 May 2021 from https://data.cdc.gov/Case-Surveillance/United-States-COVID-19-Cases-and-Deaths-by-State-o/9mfq-cb36. † All intervals represent 7-day weeks except the first interval, which represents 1 August to 8 August.