Nasal swabs are the best way to test for COVID-19
They also collected samples from symptomatic, asymptomatic and post-symptomatic people – people who had recovered from the disease – to better understand testing effectiveness in these populations.
When they compared different types of samples, the researchers found that nasopharyngeal samples provided the best detection rates, ranging from 92 to 100%. This may be because the virus multiplies in the nasal canal, the tissue structures at the top of the nose.
Detection rates from the anterior interstitium and saliva samples were slightly lower, at 92-96% for symptomatic patients. This detection rate is lower when sampling from asymptomatic patients (75% to 92%). The detection of SARS-CoV-2 in sublingual specimens is much worse, with detection rates of only 40 to 60% in symptomatic specimens and 25% to 42% in asymptomatic specimens.
Detection rates in symptomatic, asymptomatic, and post-symptomatic patients are fairly intuitive, with detection being strongest in symptomatic patients, ranging from 92 to 100%, depending on the test. used. For all tests, the virus is more difficult to detect in asymptomatic patients, with a prevalence of 75 to 96%. Once symptoms have resolved in post-symptomatic patients, detection is much more difficult.
Nasal swabs are the right sample choice for COVID-19
The team also investigated infectivity – the extent to which infectious viral particles were excreted in each type of sample and from different types of patients.
As predicted, most infectious specimens come from symptomatic patients, while less than one-third of specimens collected from asymptomatic patients are infectious. Scientists were not able to isolate any infectious virus from patient samples after showing symptoms.
The data are consistent with current CDC guidelines and their decision to reduce the length of patient isolation from the initial 14 days to 10 and ultimately to 5 days. This new data provides medical practitioners with some practical guidance.
This study also serves as a platform for laboratories to test the Cornell COVID-19 surveillance program and validate the use of anterior nape test samples of choice, due to their reasonable sensitivity and ease of collection. their cross.