Why COVID-19 Screening Protocols Won’t Work

Many facilities are using COVID-19 screening protocols to determine how to cohort patients in the ED. Although this sounded like a good idea initially, this strategy is destined to fail.  Early on in the pandemic, we thought we could identify potential COVID-19 patients based on the presence of fever and cough. However, multiple studies are coming out showing a high prevalence of asymptomatic patients with positive tests for SARS-CoV-2.  Identifying asymptomatic patients is important to improve outpatient quarantine (i.e. maximize physical distancing) and to improve staff safety (i.e. incorrectly admitting patients to the wrong area of the hospital). In most regions, there are simply not enough tests to test everyone, but a universal testing strategy needs to be implemented, especially for admitted patients as this can have major ramifications to staff and patient safety.

Study #1 [1]

Between March 22nd and April 4th, 2020, 215 pregnant patients delivered infants at two New York hospitals.  All women were screened on admission for symptoms of COVID-19.

  • Symptoms of COVID-19 + Positive for SARS-CoV-2: 4/210 (1.9%)
  • No Symptoms of COVID-19 + Positive for SARS-CoV-2: 29/210 (13.7%)
  • These findings may not be generalizable to geographic regions with lower rates of infection and the true prevalence of infection may be underreported due to false negative results of tests

Study #2 [2]

Universal testing for SARS-CoV-2of 408 individuals from a single large homeless shelter in Boston, MA

  • Positive for SARS-CoV-2: 147/408 (36.0%)
  • Cough, SOB, Diarrhea, or Fever = 26/147 (17.7%)
  • No Cough, SOB, Diarrhea, or Fever = 121/147 (82.3%)
  • A large percentage of undomiciled people in this shelter were SARS-CoV-2 carriers without symptoms and could have potentially infected other people in the shelter despite any type of screening

Study #3 [3]

  • Tested people living in Iceland based on two strategies (targeted population vs open population) to measure the success of measures implemented to curb the spread of the virus:
    • Targeted Population: Mainly those who were high risk (symptomatic, had recently traveled to high-risk countries, or had contact with infected persons) – Tested Jan 31st – March 31st
    • Open Invitation Population – Tested March 13th – April 1st
    • Random Invitation Population – Tested April 1st – 4th
    • All positive patients were contacted by telephone to track infection, people they had been in contact with during the previous 24 hours before symptoms, and requested to go into 2 weeks of quarantine
  • Positive SARS-CoV-2 Testing in Targeted Population: 1221/9199 (13.3%)
  • Positive SARS-CoV-2 Testing in Open Invitation Population: 87/10,797 (0.8%)
  • Positive SARS-CoV-2 Testing in Random Population: 13/2283 (0.6%)
  • 93% of patients in targeted-testing group had symptoms consistent with COVID-19 whereas only 57% had symptoms consistent with COVID-19 in the overall population screening groups (43% of patients in the open population screening group did not have symptoms of COVID-19)
  • This is an excellent example of what population level screening with universal testing could look like

Study #4 [4]

Assessed a spectrum of symptoms at onset of COVID-19 among healthcare workers  from 22 health care settings including long-term care facilities, outpatient clinics, and acute care hospitals

  • Onset with Fever, Cough, SOB, or Sore Throat = 40/48 (83.3%)
  • Onset without Fever, Cough, SOB, or Sore Throat = 8/48 (16.7%)
  • Another study showing that “typical” symptoms for COVID-19 cannot be relied upon for detecting infection

Clinical Bottom Line:

  • Based on these 4 studies the rate of asymptomatic patients with positive SARS-CoV-2 was 13.7 – 43.0% (CAVEAT: In a single homeless shelter, 82.3% of residents had asymptomatic disease)
  • Patients in confined areas such as homeless shelters, prisons, and/or jails can have a high rate of asymptomatic disease and should be tested more readily
  • A universal testing strategy, rather than a symptom triggered approach, is a superior strategy for identifying COVID-19, mitigating COVID-19, and protecting healthcare staff as a significant portion of the population may be asymptomatic during the course of their illness.


  1. Sutton, D et al. Universal Screening for SARS-CoV-2 in Women Admitted for Delivery. NEJM 2020. [Epub Ahead of Print]
  2. Baggett TP et al. COVID-19 Outbreak at a Large Homeless Shelter in Boston: Implications for Universal Testing. medRxiv Preprint 2020 [Epub Ahead of Print]
  3. Gudbjartsson DF et al. Spread of SARS-CoV-2 in the Icelandic Population. NEJM 2020. [Epub Ahead of Print]
  4. Chow EJ et al. Symptom Screening at Illness Onset of Health Care Personnel with SARS-CoV-2 Infection in King county, Washington. JAMA 2020. [Epub Ahead of Print]

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter: @EMSwami)

Cite this article as: Salim Rezaie, "Why COVID-19 Screening Protocols Won’t Work", REBEL EM blog, April 19, 2020. Available at: https://rebelem.com/why-covid-19-screening-protocols-wont-work/.

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