Reliable detection of SARS-CoV-2 with patient-collected swabs and saline gargles: A three-headed comparison on multiple molecular platforms

Abstract

With increasing demands for SARS-CoV-2 testing, as well as the shortages for testing supplies, collection devices, and trained healthcare workers (HCWs) to collect specimens, self-collection is an attractive prospect to reduce the need for HCWs and expenditure of personal protective equipment. Apart from the traditional nasopharyngeal swab used for SARS-CoV-2 detection, alternative specimens have been validated such as a combined swabs of the oropharynx and anterior nares (OP/N), or throat samples using saline gargles. Both the alternative specimen types are amenable to self-collection. Objectives. This study aimed to compare the sensitivity of HCW-collected (OP/N) swabs, self-collected OP/N swabs, and self-collected saline gargles. Among 38 individuals previously testing positive for SARS-CoV-2 (or their close contacts), two self-collected specimen types (OP/N and saline gargles) were compared to HCW-collected OP/N swabs. SARS-CoV-2 testing was performed on three molecular assays: a laboratory-developed test (LDT), and two commercial assays on automated platforms: Cobas 6800 (Roche Diagnostics) and Panther (Hologic). The sensitivity of self-collected OP/N swabs was equivalent to healthcare worker (HCW)-collected OP/N swabs at 100.0% [92.6% to 100.0%] for all three molecular tests. The sensitivity of saline gargles was not significantly different than HCW-collected OP/N swabs, but varied slightly between instruments at 93.8% [85.9% to 93.8%] for the LDT, 96.8% [88.6% to 96.8%] for the Cobas assay, and 96.7% [89.2% to 96.9%] for the Panther assay. Overall, self-collection using OP/N swabs or saline gargles are reasonable alternatives to HCW-based collections for SARS-CoV-2 detection, and could facilitate broader surveillance strategies.

Feasibility of a surveillance programme based on gargle samples and pool testing to prevent SARS-CoV-2 outbreaks in schools

“…Moreover, sample collection can be carried out independently at home, avoiding potential viral spread through testing in schools and minimising costs for personnel and protective clothing 19 , 20 . Gargle sample testing has proven effective in diagnosing viral respiratory tract infections in children 21 and has specifically been demonstrated to enable detection of SARS-CoV-2 infection in self-collected samples 22 – 24 . Nasopharyngeal swab (NPS) sampling has been considered the gold standard in SARS-CoV-2 diagnosis, and gargle sample testing has been shown to provide comparable sensitivity and specificity on polymerase chain reaction (PCR) testing 20 , 25 .…”

Generation of false positive SARS-CoV-2 antigen results with testing conditions outside manufacturer recommendations: A scientific approach to pandemic misinformation

“…Such education could prevent overuse of public health and laboratory resources required to investigate false positive reactions, and may alleviate anxieties for the impacted individuals. [17,19,29,30] Another area for consideration is outdoor testing strategies (e.g. drive-thru testing), where the Panbio kit supplies may be exposed to precipitation and fluctuations in temperature and humidity.…”

“…In low prevalence populations, positive Ag-RDTs are typically confirmed by clinical laboratories with NAATs, thereby limiting the overall public health impact of the possible artifacts described in this study. [1][2][3] However, in programs where home self-testing kits are deployed [20,21,30], it is important to educate users on the importance of strict adherence to manufacturer instructions. Another area for consideration is outdoor testing strategies (e.g.…”

“…Ag-RDT samples included food products (Table S1), water, laboratory buffers, specimen transport media, and 30 each of four different clinical specimens types: 1) nasopharyngeal (NP) swabs in universal transport media (UTM); 2) oropharyngeal and bilateral nares (OP/N) swabs in phosphate buffered saline (PBS) [16,17]; 3) bronchoalveolar lavages (BAL); and 4) saline gargles (Table 1). [18,19]…”

“…Ag-RDT samples included food products (Table 1), water, laboratory buffers, specimen transport media, and four different clinical specimens types previously tested negative by real-time RT-PCR in routine diagnostic testing: 1) 30 nasopharyngeal (NP) swabs in universal transport media (UTM); 2) 30 oropharyngeal and bilateral nares (OP/N) swabs in phosphate buffered saline (PBS) [19,20]; 3) 30 bronchoalveolar lavages (BAL); and 4) 30 saline gargles (Table 1). [21] Antigen and molecular testing SARS-CoV-2 nucleocapsid antigen detection was performed using the Abbott Panbio COVID-19 Rapid Antigen Test (Figure 1) and the BD Veritor System for Rapid Detection of SARS-CoV-2. Each kit's nasal swabs were dipped into the test samples, placed in the appropriate kit buffers, and 3 or 5 drops were used to inoculate the sample wells of the Veritor and Panbio cassettes, respectively, as per the manufacturer recommendations.…”