How effective of a screening tool are temperature checks for COVID-19?Posted on by
Temperature checks alone are unlikely to be sensitive enough for COVID-19 given the unknown number of subclinical cases. The specificity may not be relevant as anyone with a fever is likely to be asked to self isolate regardless given the current climate. Adding a questionnaire for known epidemiological risk factors in your area may increase sensitivity of the overall screening process.
I. Review on effectiveness of symptoms screening to prevent COVID-19 spread based on clinical data from Jan 29, 2020 (1):
- Mean incubation period 5.5 days, with a plausible range of 4.5-6.5 days
- Subclinical cases with no fever or cough varied significantly from 5% to 50%, true number currently unknown
- These two points suggest that symptomatic screening on its own could miss up to half of all cases
- Furthermore, sensitivity of infrared thermal scanners for fever is 60%-90% depending on device used, body area targeted and ambient temperature
- Screening by questionnaire could be added to symptomatic screening, however; the effectiveness of this depends on eliciting risk factors that are reasonably specific and sensitive to SARS-CoV-2 infection
- At the time of publication, author’s had limited evidence of specific risk factors for SARS-CoV-2 infection
- Concluded that screening for COVID-19 would detect no more than half of infected people in progressing epidemic where prevalence is increasing
II. WHO news release on international travel Feb 29, 2020 (2):
- Temperature screening alone is not an effective way to stop international spread since infected individuals could be early in their disease course or may have taken antipyretics
- More efficient prevention measures would be proper symptom declarations, traveller’s contact information, and subsequent contact tracing
- Anyone with symptoms should self isolate for 14 days
III. Screening principles:
- Picking up true positive cases with screening tools depends on the true prevalence of the disease, as the number of true cases in the population increases, the effectiveness of screening increases. Following these basic principles, the US CDC recommends that if there is widespread community transmission of COVID-19, active temperature measurements of patients/staff can be considered as a screening tool (3)
Note: Research regarding screening for COVID-19 revolves around international travel and as such we draw on this research for our review.
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- Gostic K, Gomez AC, Mummah RO, Kucharski AJ, Lloyd-Smith JO. Estimated effectiveness of symptom and risk screening to prevent the spread of COVID-19. eLife. 2020 Feb 24;9.
- World Health Organization: WHO. Updated WHO recommendations for international traffic in relation to COVID-19 outbreak [Internet]. Who.int. World Health Organization: WHO; 2020 [cited 2020 May 2]. Available from: https://www.who.int/news-room/articles-detail/updated-who-recommendations-for-international-traffic-in-relation-to-covid-19-outbreak#:~:text=Temperature%20screening%20alone%2C%20at,tracing%20of%20incoming%20travellers.
- CDC. Screening and Triage at Intake [Internet]. Centers for Disease Control and Prevention. 2020 [cited 2020 May 2]. Available from: https://www.cdc.gov/coronavirus/2019-ncov/hcp/dialysis/screening.html
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