Testing and Laboratory
Please note that as things change rapidly, Q&As and guidelines will be updated. Review this website often to ensure you have the most up to date information or consult your leader if you have concerns or identify discrepancies.
FAQ: COVID-19 PCR Testing and Patient Infectivity - Updated May 28, 2020:
- Infectivity or transmissibility of COVID-19 is assessed based on Public Health criteria
- PCR only detects viral RNA and not live virus
- What test is being used to identify COVID-19?
- COVID-19 is diagnosed in the Medical Microbiology laboratory using a molecular test (PCR) that detects SARS-CoV-2 viral RNA. This test only detects viral nucleic acid, not live virus.
- When are COVID-19 patients considered to be non-infectious?
COVID-19 patients are considered to be infectious from 48 hours prior to onset of symptoms to 10 days after onset of symptoms (http://www.bccdc.ca/resource-gallery/Documents/Guidelines%20and%20Forms/Guidelines%20and%20Manuals/Epid/CD%20Manual/Chapter%201%20-%20CDC/2019-nCoV-Interim_Guidelines.pdf).
For patients admitted to a PHC facility, under the direction of VCH Public Health, contact/droplet precautions will be continued for 40 days after symptom onset.
It is no longer recommended to complete follow-up testing for confirmed COVID-19 cases (ie. test-negative strategy) because the diagnostic test (PCR) is highly sensitive and will detect viral genetic material despite the patient being no longer considered infectious.
- If a patient is known to be COVID-19 positive, is repeat testing required?
Repeat testing is not recommended for patients known to be COVID-19 positive.
For patients who have previously been diagnosed with COVID-19 and have been subsequently cleared by Public Health, repeat testing is not indicated. The COVID-19 PCR test may continue to be positive after symptom resolution.
- Does a PCR positive result mean the patient is still infectious?
- Infectiousness is based on criteria set by Public Health. A PCR positive result indicates that viral RNA has been detected, but it does not indicate whether there is still live replicating virus. Viral cultures on 9 patients have been shown to be positive for up to 8 days after symptoms onset (2). A recent study by the National Microbiology Laboratory assessing a larger cross sectional cohort of 90 patients also reported similar results, where viral culture was only found in those patients <8 days from symptom onset (3).
- How long can COVID-19 patients continue to be PCR positive?
- COVID-19 COVID-19 virus PCR from nasopharyngeal swab samples have been reported to remain positive for a prolonged duration up to 48 days (4), but this does not suggest that they are infectious for that duration of time. At PHC, we have seen positive nasopharyngeal swabs samples up to 69 days after an initial positive test (and 80 days from symptom onset).
- VCH COVID-19 Isolation Clearance Criteria. http://www.vch.ca/Documents/Physicians_Update_2020-04-28.pdf
Wolfel R, et al. Virological Assessment of Hospitalized Patients with COVID-2019. Nature. 2020 Apr 1. doi: 10.1038/s41586-020-2196-x.
Bullard J, et al. Predicting infectious SARS-CoV-2 from diagnostic samples. Clinical Infectious Diseases. 2020. https://doi.org/10.1093/cid/ciaa638.
Zhou B, et al. The duration of viral shedding of discharged patients with severe COVID-19. Clinical Infectious Diseases. 2020. https://doi.org/10.1093/cid/ciaa451.
April 30, 2020:
PLEASE WATCH THIS VIDEO: TAKING PROPER NASOPHARYNGEAL SWABS TO REDUCE FALSE NEGATIVES AND IMPROVE PATIENT COMFORT
Dr. Andrew Thamboo, sinus and skull base surgeon, and Dr. Laura Allen, resident in otolaryngology, created an instructional video to help Providence staff and medical staff improve their skills when taking nasopharyngeal swabs (NPS) for respiratory viruses.
In addition to highlighting proper technique and anatomical considerations, the video shows the required personal protective equipment and donning and doffing of PPE.
Watch video here: https://youtu.be/f0xSKPm8IKA
Many PHC Clinical Nurse Educators (CNEs) have already attended hands-on training sessions with Dr. Thamboo. The plan is for CNEs to disseminate this education.
Julie Carleton from Professional Practice will be organizing further sessions for PHC Clinical Nurse Educators. Please review the video before attending future training sessions.
December 17, 2020:
COVID-19: Adult & Pediatric Viral Testing Guidelines for British Columbia. Note that the updated testing guidelines are intended for people not in hospital, and clinical judgement/assessment is necessary for consideration of COVID-19 testing in admitted patients or healthcare workers.
Recommended samples types for COVID-19 testing are:
- Nasopharyngeal (NP) swab
VIDEO: How to perform nasopharyngeal swabs: taking proper nasopharyngeal swabs to reduce false negatives and improve patient comfort (April 30, 2020)
- For hospitalized patients and/or patients with evidence of lower respiratory tract disease, an NP swab is recommended and, if appropriate, a lower respiratory specimen (sputum/tracheal aspirate/BAL).
All specimens (cylindrical tube) must be affixed with a label which states:
- Patient name
- PHN or Date of Birth (DOB)
- Specimen type (e.g., NP swab)
- Date & time of collection
If applicable, please indicate one of the following codes on the specimen label to assist with processing:
- HCW1 – Health Care Worker – Direct Care
- HCW2 – Health Care Worker – Non-Direct Care
- LTC – Long-Term Care Facility
- OBK- Outbreaks, clusters or case contacts
- HOS – Hospital (inpatient)
- CMM – Community (outpatient), including urgent and primary care centre
- CGT – People living in congregate settings such as work-camps, correctional facilities, shelters, group homes, assisted living and seniors’ residences.
- TREEPL – Tree planters
- SCHOOL – People attending school in-person including students, teachers and support staff
Please submit each specimen in an individual, sealed biohazard bag. Include a paper requisition which clearly states the patient information, the ordering physician, and the test name (COVID-19 NAT).
Please refer to the BCCDC Public Health Laboratory eLab Handbook under COVID-19 test for specimen requirements.
Samples collected for Influenza/RSV and/or COVID-19 at St. Paul's Hospital and Mount Saint Joseph's Hospital will be forwarded directly to the SPH Virology Laboratory. All COVID-19 testing for PHC patients will be tested at SPH Virology.
SPH Virology offers testing seven days a week. Multiple runs of testing occur throughout the day, with the expected turnaround time of 24 hours. Please contact the Medical Microbiologist on-call through switchboard if you have questions.
Ordering viral swabs
If you need to reach PHC’s Infection Prevention and Control Team (IPAC), please call local 69357. Do not contact individual IPAC team members.