Is it possible to identify pre-symptomatic and asymptomatic COVID-19 clinically?

The COVID-19 pandemic has severely impacted morbidity and mortality in nursing home residents across the world. Earlier detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may help better mitigate the risk of viral transmission. As both pre-symptomatic and asymptomatic transmission is common in these outbreaks, screening for threshold temperatures of 38°C or higher could miss timely detection in most infected people.

The US Veterans Health Administration (VA) made daily clinical and temperature screening of all residents of its Community Living Centers mandatory starting March 1, 2020, like non-VA nursing homes. In addition to systematic testing based on clinical screening, the VA also mass tested its nursing home residents starting April 10, 2020. The clinical and laboratory data from these testing have been captured in the VA’s electronic health records, which allows the evaluation of temperature trends in individuals with and without SARS-CoV-2 infection.

Study: Can we clinically identify pre-symptomatic and asymptomatic COVID-19? Image Credit: NIAID

Using temperature trends in SARS-CoV-2 infection in nursing home residents to identify asymptomatic and pre-symptomatic infection earlier

A retrospective cohort study by researchers from the US in the VA’s 133 nursing homes in the United States used electronic health records of SARS-CoV-2 daily screening and testing results. The VA made all clinical and laboratory data in the centralized computerized patient record system (CPRS) available for analysis.

The subjects of the study included 6,176 residents of the VA nursing homes who underwent SARS-CoV-2 trigger testing. They hypothesized that temperature trends in SARS-CoV-2 infection in long-term care residents could identify infection in asymptomatic and pre-symptomatic individuals earlier. This study is available on the preprint server medRxiv.*

The researchers collected information about age, other demographics, baseline temperature, and comorbidities and created standardized definitions and an alternative hypothetical model to determine measures of temperature variation and compare outcomes to the VA reality.

Individual or combined measures of temperature variability can help earlier detection of SARS-CoV-2 infection in nursing homes

The results showed that a change from baseline temperature of >0.4C identifies 47% of the SARS-CoV-2 positive nursing home residents early and this helps in earlier detection by 42.2 hours. Range improved early detection to 55% at a 37.2C cutoff and this achieves earlier detection by 44.4 hours.

Temperature elevation of >0.4C from baseline, combined with a 0.7C range, would detect 52% of positive cases early, which could lead to earlier detection by over 3 days in 22% of the residents. This earlier detection was achieved after triggering 57,793 tests, compared to the 40,691 trigger tests ordered in the VA system.

“Our data show that earlier detection of SARS-CoV-2 infection in the nursing home can be achieved using only individual or combined measures of temperature variability.”

According to the authors, some of the challenges to clinical implementation include several readings required to calculate the temperature range. Also, change from baseline requires an on-file record of the baseline temperature of the residents.

“Changing the temperature threshold to 37.2°C could give nursing facilities a major advantage in early detection of SARS-CoV-2.”

Findings show that tracking early temperature variations in SARS-CoV-2 infection can lead to earlier detection and cost reduction

The model described in the study suggests that current SARS-CoV-2 clinical screening in nursing homes can be significantly improved by trigger testing using a patient-derived baseline temperature with a 0.4C degree relative elevation or a temperature variability of 0.7C trigger threshold for testing.

The triggers could be automated in facilities that track temperatures in their electronic health records. These data can be utilized to create early detection algorithms that will be substantially enhanced with continuous temperature monitoring among high-risk nursing home residents.

“Understanding early temperature trends with SARS-CoV-2 infection can allow for earlier detection, better infection control, and cost reduction by transitioning away from mass testing strategies.”

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Can we clinically identify pre-symptomatic and asymptomatic COVID-19? Salaheldin Elhamamsy, Frank DeVone, Tom Bayer, Chris Halladay, Marilyne Cadieux, Kevin McConeghy, Ashna Rajan, Moniyka Sachar, Nadia Mujahid, Aman Nanda, Lynn McNicoll, James L Rudolph, Stefan Gravenstein medRxiv 2021.07.23.21260676; doi:,

Posted in: Men's Health News | Medical Research News | Women's Health News | Disease/Infection News | Healthcare News

Tags: Coronavirus, Coronavirus Disease COVID-19, Infection Control, Laboratory, Mortality, Nursing, Pandemic, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Syndrome

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Written by

Susha Cheriyedath

Susha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments.

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