Public perception and performance of different sampling approaches for the diagnosis of COVID‐19

Abstract

To the Editor, For the diagnosis of SARS-CoV-2 to inform timely and appropriate clinical management in an inpatient setting, a number of alternative respiratory specimens, including pooled nasal and throat (N&T) swabs, nasal swabs, throat swabs and saliva or sputum, have been explored.1,2 On the other hand, self-collection of specimens was being increasingly advocated to cater to the expanding testing needs in community settings, for the theoretical benefit of saved manpower requirement and risk minimization for healthcare workers. Comparing to nasopharyngeal swab as the standard sample type accepted for diagnosing COVID-19,3 some studies reported saliva sample as an non-invasive specimen with good diagnostic performance,4,5 while others were either having conflicting results6 or had cautioned the potential of a reduced sensitivity when used in outpatient setting with a low disease prevalence.7 The overall relative diagnostic accuracy of different self-collected specimens, besides remained to be inconclusive, may also be highly dependent on patient s acceptance, confidence and understanding of the required self-collection process. Here, we present our study in a cohort of mild community cases in Hong Kong, comparing reverse transcription polymerase chain reaction (RT-PCR) results from early morning deep throat saliva with pooled N&T swabs, with the finding of a good testing performance. As self-collection samples were being increasingly advocated for the potential benefit of reduced manpower requirement and risk of exposure,8 our results highlighted the importance of taking patients’ differential acceptance and confidence for performing self-collection of different samples into consideration when expanding diagnostic testing in the community. We conducted a cross-sectional study to assess the relative performance and perception of different sampling approaches among adult symptomatic patients presenting to the Accident & Emergency Department of a regional public acute hospital during the heightened period of COVID-19 epidemic (30/3/2020-28/7/2020) in Hong Kong. Patients classified as “Tier 4” under the surveillance system were recruited, specifically including clinically stable outpatients presenting with COVID-19–associated symptoms and having no definitive travel or contact history necessitating quarantine, nor being clinically severe to the extent of indicating for hospitalization. In parallel to the self-collected saliva sample prescribed by attending physicians, an additional pooled N&T swabs collected by our nurses from each consented patient were tested for RT-qPCR assay targeting the N gene of SARS-CoV-2. N&T swabs were collected by rotating a sterile plain swab (CLASSIQSwabsTM; Copan) into the anterior nasal cavity and another swab in the tonsillar fossae. Anterior nasal swab is considered less invasive and is widely accepted in our previous community studies on respiratory virus.9 After sample collection, participants were interviewed for their perception basing on their experience with the two sampling approaches. The study protocol was approved by Research Ethics Committees of the HKU (UW 20-196) and Hospital Authority (KC/KE-20-0067/ER-3).