Reviewed by Dr. Michael Payne, MD, London Health Sciences Centre
Nasopharyngeal swabs/nasal swabs are the most common sample type for COVID-19 PCR testing. However, saliva testing offers several advantages: avoidance of swab supply shortages, reduced reliance on health care provider collection, and less invasive collection procedures, particularly for children and individuals requiring repeat testing/screening. This study enrolled 300 adults and children and compared nasopharyngeal swabs (NPS) and saliva samples (no coughing) tested by RT-PCR. Test performance was calculated by comparing saliva and NPS positives versus total positives, regardless of specimen type. The overall agreement for saliva and NPS was 91.0% (273/300) and 94.7% (284/300), respectively. Positive percent agreement (PPA) for saliva and NPS was 81.4% (79/97) and 89.7% (87/97), respectively. Saliva yielded detection of 10 positive cases that were negative by NPS and NPS detected 18 cases that were negative by saliva testing. For symptomatic and asymptomatic pediatric patients not previously diagnosed with COVID-19, the performances of saliva and NPS were comparable (PPA, 82.4% versus 85.3%), however performance in asymptomatic versus symptomatic adults was less ideal (PPA, 68.2% versus 86.4). This study supports that saliva is an acceptable sample type for asymptomatic/symptomatic children and symptomatic adults. Updated guidelines from IDSA support that saliva specimens, with or without coughing, are comparable specimens to a NPS and can be used for diagnostic testing.
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