5. Sputum collection
Sputum collection may be performed during voluntary coughing or
involuntary induction. To et al performed sputum collection by having
patients cough into a sterile container, and demonstrated consistent
detection of viral RNA levels in collected
specimens.15 In another limited study of ten COVID-19
patients, Lo et al reported that SARS-CoV-2 RNA was detected in 90% of
nasopharyngeal swab specimens but falsely absent in 10% (one
patient).16 This patient was ultimately diagnosed
after viral detection in collected sputum after one negative and one
inconclusive result from nasopharyngeal swabs (inconclusive result was
defined as a Ct-value of 36 to 38). The superiority of sputum for
SARS-CoV-2 viral detection was also echoed by Pan et al, who
demonstrated that sputum samples generally showed higher viral loads
than throat swabs.17