Sputum testing provides higher rate of COVID-19 detection

Date:
July 24, 2020
Source:
Brigham and Women's Hospital
Summary:
In a meta-analysis, researchers found that sputum was more accurate
than nasopharyngeal or oropharyngeal swabs. The study also shows
early testing increased rates of COVID-19 diagnosis.



FULL STORY ========================================================================== Early and accurate detection is critical for preventing the spread of
COVID-19 and providing appropriate care for patients. Nasopharyngeal
(NP) swabs, which require inserting a long shaft into the nasal cavity
to collect a sample from the back of the nose and throat, are currently
the gold standard for collecting a specimen for diagnosis. But the
procedure is technically challenging, often uncomfortable for patients and requires personal protective equipment that may be in short supply. Other approaches to collecting specimens -- including from an oropharyngeal
swab and sputum -- have been tested in small studies, but there is
uncertainty about which method is best for detecting the virus.


==========================================================================
In a new study published in EBioMedicine, investigators from Brigham
and Women's Hospital conducted a systematic review and meta-analysis,
analyzing data from more than 3,000 specimens to compare the three
approaches. The team found that sputum testing detected the RNA of
the virus that causes COVID-19 at significantly higher rates while oropharyngeal swab testing had lower rates.

Regardless of the collection method, the earlier samples were collected
after symptoms began, the higher the detection rate.

"The accurate diagnosis of COVID-19 has implications for health care,
return- to-work, infection control and public health," said corresponding author Jonathan Li, MD, a faculty member in the Division of Infectious
Diseases at the Brigham. "Our gold standard in and out of the hospital
is the nasopharyngeal swab, but there's a lot of confusion about which
sampling modality is best and most sensitive. Our study shows that sputum testing resulted in significantly higher rates of SARS-CoV-2 detection
and supports the use of this type of testing as a valuable method for the diagnosis and monitoring of COVID-19 patients." Li and his colleagues
scoured the literature -- both preprints and published papers -- for
studies that assessed at least two respiratory sampling sites using an
NP swab, oropharyngeal swab or sputum. From more than 1,000 studies,
they identified 11 that met their criteria. These studies included
results from a total of 3,442 respiratory tract specimens.

The team examined how often each collection method produced a positive
result.

For NP swabs, the rate was 54 percent; for oropharyngeal swabs,
43 percent; for sputum, 71 percent. The rate of viral detection was significantly higher in sputum than either oropharyngeal swabs or NP
swabs. Detection rates were highest within one week of symptom onset
for all three tests.

"When it comes to testing, the earlier the better, as diagnostic accuracy
is improved earlier after symptom onset, regardless of the sampling site,"
said Li. "Unlike antibody testing, it's very rare to have a false positive
qPCR test when diagnosing COVID-19 early in the course of the disease
using these methods." Nasopharyngeal swabs are collected through the
nasal cavity; oropharyngeal swabs are collected by inserting a shaft
through the mouth; and sputum samples are generally collected by having
a patient cough deeply to produce and expel phlegm. Not all patients
are able to produce a sputum sample; for such patients, a nasopharyngeal
swab may be the best collection method. The meta- analysis included only studies conducted on hospitalized individuals - - additional study will
be needed of patients who are asymptomatic or have mild symptoms. The
current study did not assess alternative testing methods, such as saliva
or anterior nasal swabs (taken from the front of the nose). Li and his colleagues at the Brigham are currently working on a project, funded
by the Massachusetts Consortium on Pathogen Readiness, to collect and
process multiple kinds of samples from patients with COVID-19 to create
a resource for researchers.

"The holy grail will be to find a test that is readily acceptable by
patients, easy to collect, and highly sensitive," said Li.

This study was funded in part by the National Institutes of Health (U01AI106701) and the Harvard University for AIDS Research (NIAID 5P30AI060354). Li reports personal fees from Abbvie and from Jan Biotech, outside the submitted work. A co-author reports personal fees from
Harvard TH Chan School of Public Health, during the conduct of the study,
as well as grants from NIH/NIAID, outside the submitted work.


========================================================================== Story Source: Materials provided by Brigham_and_Women's_Hospital. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Abbas Mohammadi, Elmira Esmaeilzadeh, Yijia Li, Ronald J. Bosch,
Jonathan
Z. Li. SARS-CoV-2 detection in different respiratory sites:
A systematic review and meta-analysis. EBioMedicine, 2020; 102903
DOI: 10.1016/ j.ebiom.2020.102903 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200724141023.htm

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