Self-Collected Gargle Lavage Allows Reliable Detection of SARS-CoV-2 in an Outpatient Setting

Abstract

Current procurement of specimens for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection requires trained personnel and dedicated equipment. We compared standard nasopharyngeal swabs with self-collected gargle lavage fluid obtained from 80 mostly symptomatic outpatients. After RNA extraction, RT-PCR to detect SARS-CoV-2 was performed. Qualitative results obtained with the paired samples from individual outpatients were 100% congruent. Therefore, self-collected gargle lavage fluid can serve as a suitable specimen for coronavirus disease 2019 (COVID-19) testing in outpatients. IMPORTANCE The SARS-CoV-2 pandemic still strains health care systems worldwide. While COVID-19 testing is considered an essential pillar in combating this infectious disease, shortages in supplies and trained health care personnel often limit the procurement of patient samples, in particular in outpatient settings. Here, we compared the simple self-collection of gargle lavage fluid with the gold standard nasopharyngeal swab as a specimen for COVID-19 testing. By finding complete congruence of results obtained with paired samples of a sizeable patient cohort, our results strongly support the idea that the painless self-collection of gargle lavage fluid provides a suitable and uncomplicated sample for reliable SARS-CoV-2 detection.

Keywords: COVID-19; RT-PCR; SARS-CoV-2; gargle lavage; outpatients.

FIG 1

Cycle threshold (Cq) values of different specimens tested for SARS-CoV-2 by RT-PCR. (A) Volunteers (n = 11) took (nonprofessionally) pharyngeal swabs (Copan eSwab) and then dipped those into the accompanying tubes each containing 1 ml of Amies preservation medium. Gargle lavage was performed by gargling with 5 ml of 0.9% saline for 20 s. RNA was extracted from 200 μl of each sample (QIAamp Viral RNA kit). RNA (5 μl) was added to each RT-PCR mixture (Vulcano3G; myPOLS), and RNase P was detected by TaqMan (CDC-recommended primers/probe). NPS yielded similar but slightly higher Cq values for RNase P than GL (Shapiro-Wilk analysis for normal distribution, P  >  0.1; paired Student’s t test, P  <  0.05). (B) Cq values of the paired NPS and GL specimens from the 26 outpatients which tested positive for SARS-CoV-2. Nasopharyngeal swabs (Copan eSwab with 1 ml preservation medium) were taken by professional medical staff, and gargle lavage samples (5 ml 0.9% saline) were obtained by the patients themselves. After RNA isolation, paired samples (nasopharyngeal swabs and gargle lavage fluid) were evaluated in parallel by RT-PCR. For more details, see the text. Significance was analyzed by Wilcoxon signed rank test. ***, P  <  0.001. (C) ΔCq values were calculated for each NLS/GL pair by subtracting the respective Cq values (GL Cq − NLS Cq). ΔCq values were split in two equal groups based on the Cq value of the NLS sample (high Cq and low Cq; n = 13 each). ΔCq values were significantly higher in the low- than in the high-Cq group (median, 8.8 versus 2.9) (unpaired Student’s t test). ***, P  <  0.001.