COVID19 Fact Sheet #3: Diagnostic and testing
These fact sheets will provide data about characteristics, diagnosis, management, and prevention of COVID19. Fact sheet #3 will present known facts about evaluation and diagnosis of the coronavirus disease (COVID19).
COVID19 suspicious symptoms and criteria for testing
The actual approach COVID19 focuses everywhere on early recognition symptoms, immediate isolation, and institution of infection control measures. At present, the possibility of COVID19 should be considered when fever and/or cough and shortness of breath occur in individuals who have had any of the following in the prior 14 days:
- Close contact with a confirmed or suspected case of COVID-19. (Close contact is defined hereby as being within approximately six feet (about two meters) of a patient for a prolonged period of time while not wearing personal protective equipment or having direct contact with infectious secretions while not wearing personal protective equipment.)
- Residence in or travel to areas where widespread COVID19 has been reported:
- South Korea,
- most of Europe [including Italy],
- Attendance at events or spending time in specific settings where COVID-19 cases have been reported.
- Pneumonia when alternative causes cannot be identified, even if there has been no clear exposure.
When COVID-19 is suspected, infection control measures are implemented and public health officials notified. Patients who do not need immediate care are encouraged to call prior to presenting to a health care facility for evaluation. Many patients can be evaluated regarding the need for testing over the phone.
(The specific case definitions and clinical criteria for pursuing diagnostic evaluation differ slightly between expert groups.)
- Case definitions from the World Health Organization are found in its technical guidance online.
- Case definitions from the European Centre for Disease Prevention and Control are found on its website.
COVID19 Laboratory testing
If criteria for suspect cases are met testing for SARS-CoV-2 follows (the virus that causes COVID19).
Usually a swab of mucosal lining of nose / throat is used.
SARS-CoV-2 genetic information is first amplified and then detected by a technique called reverse-transcription polymerase chain reaction (RT-PCR) by a qualified institution. A positive test confirms the diagnosis of COVID19.
If a first test is negative, but the suspicion for COVID19 remains, the WHO recommends re-testing.
The accuracy of COVID19 testing has not been systematically evaluated. Negative tests despite CT of viral pneumonia have been reported in some patients who ultimately tested positive for SARS-CoV-2.
The concomitant testing for other pathogens is likewise important, as patients with suspected COVID-19 can have another virus disease.
Lodish H, Berk A, Zipursky SL, et al.: Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000.(https://www.ncbi.nlm.nih.gov/books/NBK21523/)
Marco Cascella; Michael Rajnik; Arturo Cuomo; Scott C. Dulebohn; Raffaela Di Napoli: Features, Evaluation and Treatment Coronavirus (COVID-19). (https://www.ncbi.nlm.nih.gov/books/NBK554776/ )