Linking Statistics With Testing Policy to Manage COVID-19 in the Community

Lee H. Hilborne, MD, MPH; Zachary Wagner, PhD; Irineo Cabreros, PhD; Robert H. Brook, MD, ScD

Disclosures

Am J Clin Pathol. 2020;154(2):142-148. 

In This Article

Abstract and Introduction

Abstract

Objectives: To determine the public health surveillance severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing volume needed, both for acute infection and seroprevalence.

Methods: Required testing volumes were developed using standard statistical methods based on test analytical performance, disease prevalence, desired precision, and population size.

Results: Widespread testing for individual health management cannot address surveillance needs. The number of people who must be sampled for public health surveillance and decision making, although not trivial, is potentially in the thousands for any given population or subpopulation, not millions.

Conclusions: While the contributions of diagnostic testing for SARS-CoV-2 have received considerable attention, concerns abound regarding the availability of sufficient testing capacity to meet demand. Different testing goals require different numbers of tests and different testing strategies; testing strategies for national or local disease surveillance, including monitoring of prevalence, receive less attention. Our clinical laboratory and diagnostic infrastructure are capable of incorporating required volumes for many local, regional, and national public health surveillance studies into their current and projected testing capacity. However, testing for surveillance requires careful design and randomization to provide meaningful insights.

Introduction

As the coronavirus disease 2019 (COVID-19) pandemic enters its sixth month in the United States, much of the public health and prevention discourse focuses on the need for increased diagnostic testing. The purposes of testing, however, receive less attention, leading to confusion about the testing capacity required. Different testing goals require different numbers of tests and different testing strategies.

There are many distinct roles that testing aims to address, including: (1) health care management for individual patients, (2) identifying exposed individuals through contact tracing to inform quarantine, and (3) disease surveillance.

Sufficient tests are generally available to meet the personal health needs of individual patients, and most of the nearly 16 million (as of May 28, 2020) molecular tests administered to this point have been for this purpose. Health policy experts argue that effective contact tracing requires drastic increases in testing capacity.[1] For instance, one highly publicized plan developed by a consortium of experts recommends 20 million tests per day.[2]

In contrast, testing strategies for national or local disease surveillance, including monitoring of prevalence, receive less attention. As a result, there is uncertainty surrounding basic questions: What proportion of the population in a given area is currently infected? What proportion of the population already has been infected? Is acute infection prevalence increasing as shelter at home guidance relaxes? Despite the widespread testing for individual patient care, testing to date cannot answer these questions. Without evidence of the infection dynamics in the population, policy makers are in the difficult position of making decisions without a clear picture of the true prevalence and mortality rate of the virus.

The number of tests required for disease surveillance is manageable but requires carefully designed random testing. This report seeks to provide guidance for public health officials, local governments, and large employers developing testing strategies to track disease prevalence in their respective communities. The central message is that accurate monitoring of disease prevalence can be achieved by testing a relatively small number (typically, thousands) of randomly sampled individuals.

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