Resources

Methodology

The methodology for this application comes from our paper which is currently under peer review and is available on medRxiv.

In short, we use a compartmental model with compartments for susceptible, infections - asymptomatic, infectious - symptomatic, and removed. We assume mixing happens over 8 hours of a 24 hour day and that infections are seeded within the community being tested as well as by the external community.

Test Details

Estimates for cost, accuracy, and speed by type of COVID-19 test used in the simple dashboard are as follows.

 
Test Type
Speed of Results
Sensitivity
Specificity
Cost
Pooling Possible
PCR
4 days
98%
99.5%
$100
YES
PCR rapid turnaround
<3 hours
98%
99.5%
$130
YES
LAMP
<1 hour
90%
98%
$20
NO
Antigen
<1 hour
80%
98%
$10
NO

Note that numbers and ranges are approximate and not linked to any specific test or test manufacturer. To investigate how different ranges affect outcomes, see the detailed calculator.

Most EUA's are for symptomatic patients and a small sample size. These numbers may change as more information about performance in practice becomes available.

Testing Strategy and Disease Parameters

  • $\boldsymbol{R_0}$: Number of cases generated by one case when no other individuals in the population are infected or immune. The scientific community has not yet reached consensus on the $ R_0 $ value for COVID-19, but a median value of $R_0$ that can be used for this COVID-19 testing projection is 2.5.
  • Average number of infectious days: Debate surrounds this number, as well. A median value that can be used for this COVID-19 testing projection is 9 days. See references here, here, here, and here. An additional resource explaining disease progression is available in the article Charting a Coronavirus Infection

Community Prevalence

To account for the introduction of infections from the surrounding community, we added a time-dependent term that represents the rate (in people/time) of infections from outside interactions. With frequent testing, this external forcing drives the behavior of the model.

We examine three scenarios for this external forcing. We took all case counts from the New York Times on September 23, 2020 and considered all counties with at least 30 deaths reported by September 23, 2020. We then considered a seven day rolling average of the most recent 100 days and found counties whose average number of new cases, per person, per day were representative of the 25th, 50th, and 75th percentile. The represenative counties chosen were (low) Winnebago County, Illinois, (medium) Pottawattamie County, Iowa, and (high) Harris County, Texas.

Contact

We encourage suggestions of new features and improvements to make the visualizations more helpful.

Send questions for the authors, questions about the calculator or its code, and media requests to admin@unitedinresearch.com.

References

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  4. Abdalhamid B, Bilder CR, McCutchen EL, Hinrichs SH, Koepsell SA, Iwen PC. Assessment of Specimen Pooling to Conserve SARS CoV-2 Testing Resources. Am J Clin Pathol. Published online April 18, 2020. doi:10.1093/ajcp/aqaa064

  5. The New York Times. NYT COVID-19 Data. COVID-19 Data. Published September 23, 2020. Accessed September 23, 2020. https://github.com/nytimes/covid-19-data

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