Evaluation of water gargle samples for SARS-CoV-2 detection using Abbott ID NOW COVID-19 assay.

The Abbott ID NOW™ COVID-19 assay has been shown as a reliable and sensitive alternative to reverse transcription-polymerase chain reaction (RT-PCR) testing from nasopharyngeal or nasal samples in symptomatic patients. Water gargle is an acceptable noninvasive alternative specimen for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) detection by RT-PCR. The objective of this study was to evaluate the performance of water gargle samples for the detection of SARS-CoV-2 using the ID NOW. Residual gargle samples were randomly selected among positive standard of care (SOC)-nucleic acid amplification test (NAAT) samples. For testing on ID NOW, the manufacturer's instructions were followed, except for the specimen addition step: 500 µl of the gargle specimen was added to the blue sample receiver with a pipette and gently mixed. Among the 202 positive samples by SOC-NAAT, 185 were positive by ID NOW (positive percent agreement [PPA]) = 91.6% (95% confidence interval [CI]: 86.9-95.0). For the 17 discordant samples, cycle threshold (Ct ) values were all ≥31.0. The PPA was significantly lower among asymptomatic patients (84.4%; 95% CI: 73.2-92.3) versus symptomatic patients (95.2%; 95% CI: 89.8-98.2). The performance of the ID NOW for the detection of SARS-CoV-2 infection on gargle samples is excellent when Ct values are <31.0 and for patients that have COVID-19 compatible symptoms.

Natural spring water gargle samples as an alternative to nasopharyngeal swabs for SARS-CoV-2 detection using a laboratory-developed test.

The objective of this study was to validate the use of spring water gargle (SWG) as an alternative to oral and nasopharyngeal swab (ONPS) for SARS-CoV-2 detection with a laboratory-developed test. Healthcare workers and adults from the general population, presenting to one of two COVID-19 screening clinics in Montréal and Québec City, were prospectively recruited to provide a gargle sample in addition to the standard ONPS. The paired specimens were analyzed using thermal lysis followed by a laboratory-developed nucleic acid amplification test (LD-NAAT) to detect SARS-CoV-2, and comparative performance analysis was performed. An individual was considered infected if a positive result was obtained on either sample. A total of 1297 adult participants were recruited. Invalid results (n = 18) were excluded from the analysis. SARS-CoV-2 was detected in 144/1279 (11.3%) participants: 126 from both samples, 15 only from ONPS, and 3 only from SWG. Overall, the sensitivity was 97.9% (95% CI: 93.7-99.3) for ONPS and 89.6% (95% CI: 83.4-93.6; p = 0.005) for SWG. The mean ONPS cycle threshold (Ct ) value was significantly lower for the concordant paired samples as compared to discordant ones (22.9 vs. 32.1; p < 0.001). In conclusion, using an LD-NAAT with thermal lysis, SWG is a less sensitive sampling method than the ONPS. However, the higher acceptability of SWG might enable a higher rate of detection from a population-based perspective. Nonetheless, in patients with a high clinical suspicion of COVID-19, a repeated analysis with ONPS should be considered. The sensitivity of SWG using NAAT preceded by chemical extraction should be evaluated.

The PRONTO study: Clinical performance of ID NOW in individuals with compatible SARS-CoV-2 symptoms in walk-in centres-accelerated turnaround time for contact tracing.

BACKGROUND: This PRONTO study investigated the clinical performance of the Abbott ID NOWTM (IDN) COVID-19 diagnostic assay used at point of care and its impact on turnaround time for divulgation of test results. METHODS: Prospective study conducted from December 2020 to February 2021 in acute symptomatic participants presenting in three walk-in centres in the province of Québec. RESULTS: Valid paired samples were obtained from 2,372 participants. A positive result on either the IDN or the standard-of-care nucleic acid amplification test (SOC-NAAT) was obtained in 423 participants (prevalence of 17.8%). Overall sensitivity of IDN and SOC-NAAT were 96.4% (95% CI: 94.2-98.0%) and 99.1% (95% CI: 97.6-99.8), respectively; negative predictive values were 99.2% (95% CI: 98.7-99.6%) and 99.8% (95% CI: 99.5-100%), respectively. Turnaround time for positive results was significantly faster on IDN. CONCLUSION: In our experience, IDN use in symptomatic individuals in walk-in centres is a reliable sensitive alternative to SOC-NAAT without the need for subsequent confirmation of negative results. Such deployment can accelerate contact tracing, reduce the burden on laboratories and increase access to testing.

Comparison of SARS-CoV-2 detection with the Cobas® 6800/8800 system on gargle samples using two sample processing methods with combined oropharyngeal/nasopharyngeal swab.

BACKGROUND: Gargle samples have been proposed as a noninvasive method for detection of SARS-CoV-2 RNA. The clinical performance of gargle specimens diluted in Cobas® PCR Media and in Cobas® Omni Lysis Reagent was compared to oropharyngeal/nasopharyngeal swab (ONPS) for the detection of SARS-CoV-2 RNA. STUDY DESIGN: Participants were recruited prospectively in two COVID-19 screening clinics. In addition to the ONPS, participants gargled with 5 ml of natural spring water split in the laboratory as follows: 1 ml was added to 4.3 ml of polymerase chain reaction (PCR) media and 400 µl was added to 200 µl of lysis buffer. Testing was performed with the Cobas® SARS-CoV-2 test on the Cobas® 6800 or 8800 platforms. RESULTS: Overall, 134/647 (20.7%) participants were considered infected because the ONPS or at least one gargle test was positive. ONPS had, respectively, a sensitivity of 96.3% (95% confidence interval [CI]: 91.3-98.5); both gargle processing methods were slightly less but equally sensitive (90.3% [95% CI: 83.9-94.3]). When ONPS and gargle specimens were both positive, the mean cycle threshold (Ct ) was significantly higher for gargles, suggesting lower viral loads. CONCLUSION: Gargle specimens directly added in PCR Media provide a similar clinical sensitivity to chemical lysis, both having a slightly, not significantly, lower sensitivity to ONPS.

Does BCG provide long-term protection against SARS-CoV-2 infection? A case-control study in Quebec, Canada.

BACKGROUND: Early in the coronavirus disease 2019 (COVID-19) pandemic, before severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines became available, it was hypothesized that BCG (Bacillus Calmette-Guérin), which stimulates innate immunity, could provide protection against SARS-CoV-2. Numerous ecological studies, plagued by methodological deficiencies, revealed a country-level association between BCG use and lower COVID-19 incidence and mortality. We aimed to determine whether BCG administered in early life decreased the risk of SARS-CoV-2 infection in adulthood and the severity of COVID-19. METHODS: This case-control study was conducted in Quebec, Canada. Cases were patients with a positive SARS-CoV-2 nucleic acid amplification test performed at two hospitals between March-October 2020. Controls were identified among patients with non-COVID-19 samples processed by the same microbiology laboratories during the same period. Enrolment was limited to individuals born in Quebec between 1956 and 1976, whose vaccine status was accessible in a computerized registry of 4.2 million BCG vaccinations. RESULTS: We recruited 920 cases and 2123 controls. Fifty-four percent of cases (n = 424) and 53% of controls (n = 1127) had received BCG during childhood (OR: 1.03; 95% CI: 0.89-1.21), while 12% of cases (n = 114) and 11% of controls (n = 235) had received two or more BCG doses (OR: 1.14; 95% CI: 0.88-1.46). After adjusting for age, sex, material deprivation, recruiting hospital and occupation there was no evidence of protection conferred by BCG against SARS-CoV-2 (AOR: 1.01; 95% CI: 0.84-1.21). Among cases, 77 (8.4%) needed hospitalization and 18 (2.0%) died. The vaccinated were as likely as the unvaccinated to require hospitalization (AOR: 1.01, 95% CI: 0.62-1.67) or to die (AOR: 0.85, 95% CI: 0.32-2.39). CONCLUSIONS: BCG does not provide long-term protection against symptomatic COVID-19 or severe forms of the disease.