Self-collected gargle fluids and nasopharyngeal swabs as a strategy for molecular diagnostics of respiratory viruses

Diagnosis of respiratory viruses traditionally relies on deep oropharynx or nasopharynx swabs collected by healthcare workers (HCW). However, outpatients must make an appointment, and the procedure can cause discomfort in patients. Self-collecting has the potential as a strategy to improve participants’ willingness to participate in diagnostics, surveillance, or studies.

We compared self-collected gargle fluids and nasopharyngeal swabs as a strategy for molecular diagnostics of respiratory viruses and compared the average cycle threshold (Ct)-values with those of samples collected by HCW. The study was conducted among technicians of the Laboratory of Clinical Microbiology and Infectious Diseases, Zwolle, the Netherlands, and their family members, between April 2019 and March 2020. It included a questionnaire regarding the severity and date of first symptoms and an assessment of the sampling experience. The primary outcome was the mean Ct of positive PCRs. Similar mean Ct values were obtained using self- or HCW-collected swabs. In addition, gargle fluids and self-swabbed specimens had comparable detection rates of respiratory viruses. Notably, most participants preferred gargling over self-swabbing. Interestingly, but not surprisingly, the time between the onset of symptoms and sampling was shorter in PCR-positive compared to PCR-negative participants.

Though this study was abrogated by the SARS-CoV-2 pandemic, the results indicate that both self-swabs and gargle fluids are acceptable for diagnosing common respiratory viruses in the outpatient population, including influenza virus, rhinovirus, adenovirus, SARS-CoV-2 and endemic human coronaviruses. Gargling could be considered an alternative sampling strategy and may enhance willingness to participate in screenings or diagnostics for respiratory viruses.