3. Lingual swab
The lingual swab (LS) or oral cavity swab (OCS) for detection of SARS-CoV-2 involves swabbing the anterior two-thirds of the tongue or the oral tongue. A Wuhan study compared LS with OPS and found that in 91 patients, the positive rate of OPS was higher than that of LS. However, the authors noted that this difference may have been attributable to a single experienced nurse collecting all of the samples.11
Azzi et al reported the use of OCS and “oral saliva pipette collection” for viral detection. In a cohort of 25 severe to very severe COVID-19 patients (severity not otherwise specified but all patients were mechanically ventilated in intensive care unit), it was reported that SARS-CoV-2 was detected in all 25 patients’ salivary swabs, with different Ct values (range 18.12 – 32.23, mean value 27.16 +/- 3.07). All patients had prior positive nasopharyngeal swabs at point of diagnosis.12 The authors thus concluded that the oral cavity saliva collection was a reliable method of viral detection. It should be noted, however, that these results were from critically-ill patients whose viral shedding patterns may be different from suspect cases. Hence, the utility of oral cavity salivary swabs or LS may not be reproducible in screening scenarios. Although the LS or OCS is simple and presumably causes less discomfort, its use in the current pandemic is unlikely to be prevalent due to the need to maximize sites sampling and secretions collection to accurately diagnose infection.