Prospective, clinical comparison of self-collected throat-bilateral nares swabs and saline gargle compared to health care provider collected nasopharyngeal swabs among symptomatic outpatients with potential SARS-CoV-2 infection

Background

In British Columbia (BC), self-collected saline gargle (SG) is the only alternative to health care provider (HCP)-collected nasopharyngeal (NP) swabs to detect SARS-CoV-2 in an outpatient setting by polymerase chain reaction (PCR). However, some individuals cannot perform a SG. Our study aimed to assess combined throat-bilateral nares (TN) swabbing as a swab-based alternative.

Methods

Symptomatic individuals greater than 12 years of age seeking a COVID-19 PCR test at one of two COVID-19 collection centres in Metro Vancouver were asked to participate in this study. Participants provided a HCP-collected NP sample and a self-collected SG and TN sample for PCR testing, which were either HCP observed or unobserved.

Results

Three-hundred and eleven individuals underwent all three collections. Compared against HCP-NP, SG was 99% sensitive and 98% specific (kappa 0.97) and TN was 99% sensitive and 99% specific (kappa 0.98). Using the final clinical test interpretation as the reference standard, NP was 98% sensitive and 100% specific (kappa 0.98), and both SG and TN were 99% sensitive and 100% specific (both kappa 0.99). Mean cycle threshold values for each viral target were higher in SG specimens compared to the other sample types; however, this did not significantly impact the clinical performance, because the positivity rates were similar. The clinical performance of all specimen types was comparable within the first 7 days of symptom onset, regardless of the observation method. SG self-collections were rated the most acceptable, followed by TN.

Conclusions

TN provides another less invasive self-collection modality for symptomatic outpatient SARS-CoV-2 PCR testing.

Pre-enriched saline gargle samples for detection of SARS-CoV-2

A self‑collected gargle sample, which avoids discomfort and largely reduces the dependency on medical resources, is emerging for detection of SARS‑CoV‑2. However, the incomplete usage of starting materials for both routine oropharyngeal swabs (OPS)/nasopharyngeal swabs (NPS) and saline gargle (SG) samples implies sensitivity can be further improved. Presented here is a bead‑based strategy for pre‑enrichment of SG samples, and results revealed that it acquired about 20 times the starting materials obtained from OPS samples for downstream detection of SARS‑CoV‑2. The sensitivity and specificity of this pre‑enrichment strategy were validated in 100 paired pre‑enriched saline gargle (PenSG) and OPS samples and 89 PenSG samples from healthy volunteers. In addition to detection of SARS‑CoV‑2, this pre‑enrichment strategy may also be implemented in more clinical settings to optimize detection of other diseases.

Verification of the efficiency of saline gargle sampling for detection of the Omicron variant of SARS-CoV-2, a pilot study

A saline gargle (SG) has proven to be an efficient method of sampling to detect SARS-CoV-2. The aim of this pilot study was to verify the efficiency of SG sampling in detecting the Omicron variant of SARS-CoV-2. Subjects were a total of 68 patients with COVID-19 (Omicron variant), and 167 pairs of samples were collected. A conventional oropharyngeal swab (OPS) was obtained and SG sampling was performed immediately afterward; both were subjected to RT-qPCR. A subgroup analysis of symptomatic and asymptomatic patients was performed. Results revealed no significant differences in the distribution of patients and cycle threshold (CT) values between the SG and OPS in overall data and data on days 1-3, 4-7, and 8-14. The subgroup analysis revealed no significant differences between the SG and OPS results in symptomatic patients. In asymptomatic patients, the CT values for the SG were significantly lower than those for the OPS, implying that SG sampling had better sensitivity in the context of the Omicron variant. These data indicate that the SG had satisfactory efficiency (vs. the OPS). An SG is a simple and less invasive method of sampling that is suited to mass, frequent, and repeated sampling to detect SARS-CoV-2.