Loading...
SARS-CoV-2–specific polymerase chain reaction testing from nasopharyngeal swabs (NPS) has become the standard for diagnosing COVID-19. Whether other specimens from the upper respiratory tract would work as well is unclear. Could patient self-collected saliva or swabs of the anterior nasal region (ANS) provide similar results to those of the uncomfortable NPS? A prospective study involving 354 patients with suspected COVID-19 (average age, 35 years; 47% female) provides some answers.
Patients were enrolled in a drive-through testing facility if they reported having at least one typical COVID-19 symptom (fever, cough, shortness of breath, sore throat, malaise, chills, decreased sense of smell or taste). Patients were asked to self-swab both nostrils and then spit at least 1 mL saliva into a sterile empty tube. Finally, a healthcare worker obtained an NPS using the IDSA/CDC-recommended technique for diagnosing COVID-19. All specimens were analyzed with the Hologic Aptima SARS-CoV-2 test. Invalid or discrepant results within an individual patient were clarified with repeated testing, confirmatory test using the Hologic Panther Fusion RT-PCR, or both.
Of the 354 patients, 66 (18.6%) were SARS-CoV-2 positive in all three specimen types, 13 (3.7%) in two types, 7 (2%) in one type; 268 patients (75.7%) tested negative in all specimens. NPS (n=80; 22.6%) and saliva (n=81; 22.9%) showed numerically but not statistically significantly higher positivity rates than ANS (n=70; 19.8%). The highest detection rate occurred with a combination of NPS and saliva (n=86; 24.3%).
Hanson KE et al. Self-collected anterior nasal and saliva specimens versus healthcare worker–collected nasopharyngeal swabs for the molecular detection of SARS-CoV-2. J Clin Microbiol 2020 Aug 12; [e-pub]. (https://doi.org/10.1128/JCM.01824-20)
Comment
The lack of a “gold-standard” COVID-19 test precludes calculation of sensitivities and specificities for the various sample types. No sample type identified all cases, but the self-performed ANS detected the fewest cases and should not be recommended. This study adds to the growing evidence that saliva and NPS have similar detection rates, making saliva an interesting alternative sample as it is easily obtained (even from children) and can be patient self-collected, thereby minimizing potential exposure of healthcare workers (NEJM JW Gen Med Oct 15 2020 and N Engl J Med 2020; 383:1283). The limited stability of viral RNA in saliva has to be kept in mind, though. The need for additional stabilization media was avoided in this study by immediately refrigerating saliva samples at 4° C.