Identification of acute SARS-CoV-2 (COVID-19) infection is made by Nucleic Acid Testing (NAT) on respiratory tract sampling.
The sensitivity of testing depends on the stage of disease, the quality of sample collection, the nature of the swab used, and assay performance.
Self-collection of nose and throat swabs can be used for respiratory virus NAT. The validity of self-swabbing for influenza has been reviewed, and suggests reasonable sensitivity (pooled estimate 87%) compared to swabs taken by healthcare workers (HCWs).
This approach was suggested for use in influenza research and surveillance and studies. Throat washes and gargles have also been used for the diagnosis of SARS with reasonable efficacy (including monitoring hospitalised patients already known to be NAT positive), and also for influenza and respiratory tract bacteria.
Self-collection has been used in the current SARS-CoV-2 outbreak, particularly in busy screening clinics, or in the context of reduced availability of personal protective equipment (PPE). Laboratory validation of self- collected samples for the identification of SARS-CoV-2 is limited but shows reasonable concordance with HCW swabbing. Without care and training, self-collection in the home environment may pose issues of contamination of collection material and transport packaging.
- In the context of identifying COVID-19 patients with maximal sensitivity, self-collected swabs are likely to be somewhat less sensitive than recommended HCW-collected upper respiratory tract swabs.
In the current shortage of flocked swabs, sample collection using other swab types and transport media may further compromise sensitivity.
- If self-collection is used, it should be done under the instruction of a HCW. Mid-turbinate and anterior nares swabs can be self-collected. Other self-collection samples such as saliva are being assessed.
The request form should identify that the specimen has been self-collected, and the laboratory should evaluate the sensitivity of self-collected swabs compared to HCW collected samples.
- In the emergency department, wards and hospital environment, swabs should be collected by HCW using appropriate PPE.
- Home self-collection is not the preferred option for sample collection in NSWHP.
- Professor Dominic Dwyer, NSW Health Pathology (NSWHP), Director of Public Health Pathology
- Tracey McCosker, Chief Executive, NSWHP
- NSWHP Emergency Operations Centre Incident Controller