Evaluation of the Performance of a Multiplexed Serological Assay in the Detection of SARS-CoV-2 Infections in a Predominantly Vaccinated Population.

SARS-CoV-2 seroprevalence studies may be complicated by vaccination efforts. It is important to characterize the ability of serology methods to correctly distinguish prior infection from postvaccination seroreactivity. We report the performance of the Meso Scale Discovery (MSD) V-PLEX COVID-19 Coronavirus Panel 2 IgG assay. Using serum samples from a prospective cohort of paramedics, we calculated the performance of the V-PLEX nucleocapsid ("N") assay to classify prior SARS-CoV-2 infections, defined as a (i) history of a positive SARS-CoV-2 PCR test or (ii) positive serology results using the Roche Elecsys total nucleocapsid anti-SARS-Cov-2 assay. We calculated sensitivity and specificity at the optimal threshold (defined by the highest Youden index). We compared subgroups based on vaccination status, and between models that excluded prior infections 3 to 12 months before sample collection. Of 1119 participants, 914 (81.7%) were vaccinated and 60 (5.4%) had evidence of a preceding SARS-CoV-2 infection. Overall and within vaccinated and unvaccinated subgroups, the optimal thresholds were 828 AU/mL, 827 AU/mL, and 1324 AU/mL; with sensitivities of 0.95 (95% CI: 0.94 to 0.96), 0.95 (0.94 to 0.96), 0.94 (0.92 to 0.96) and specificities of 0.88 (0.86 to 0.90), 0.87 (0.85 to 0.89), and 0.94 (0.89 to 0.98), respectively. N-assay specificity was significantly better in unvaccinated (versus vaccinated) individuals (P = 0.005). Overall optimal thresholds based on the AUC values were higher for samples from unvaccinated participants, especially when examining infections within the preceding 9 months (5855 versus 1704 AU/mL). Overall, V-PLEX nucleocapsid assay cutoff values were higher among unvaccinated individuals. Specificity was also significantly higher among unvaccinated individuals. Different thresholds were required to achieve optimal test performance, especially for detecting SARS-CoV-2 infections within the preceding 9 months. IMPORTANCE Among a cohort of adult paramedics in Canada, we investigated the performance of nucleocapsid (N) antibody detection (measured with a V-PLEX assay) to identify previous COVID-19 infections and compared differences among vaccinated and unvaccinated. Our data indicate that vaccinated and unvaccinated groups require different thresholds to achieve optimal test performance, especially for detecting COVID-19 within the preceding 9 months. Overall, specificity was significantly higher among unvaccinated, compared to vaccinated individuals.

A pragmatic parallel group implementation study of a prehospital-activated ECPR protocol for refractory out-of-hospital cardiac arrest.

OBJECTIVES: Extracorporeal membrane oxygenation within CPR (ECPR) may improve survival among patients with refractory out-of-hospital cardiac arrest (OHCA). We evaluated outcomes after incorporating ECPR into a conventional resuscitation system. METHODS: We introduced a prehospital-activated ECPR protocol for select refractory OHCAs into one of four metropolitan regions in British Columbia. We prospectively identified ECPR-eligible patients in both the ECPR region and the three other regions to serve as the control group. We compared the proportion with favorable neurological outcomes at hospital discharge (cerebral performance category ≤2) and used logistic regression to estimate the association with treatment region. RESULTS: The study was terminated prematurely due to changes in hospital protocols and COVID-19. In the ECPR region, 15/58 (25.9%) patients had favourable neurological outcomes owing to conventional resuscitation and 2/58 (3.4%) owing to ECPR, for a total of 17/58 (29.3%). In the control regions, 67/250 (26.8%) patients had a favourable outcome owing to conventional resuscitation, for a between-group difference of 2.5% (95% CI -10 to 15%). We did not detect a statistically significant association between treatment region and outcomes. CONCLUSION: In this prematurely-terminated study of ECPR for refractory OHCA, we did not detect an association between a regional ECPR protocol and neurologically favorable outcomes. However, our data suggests that outcomes owing to conventional resuscitation were similar, with the potential for additional survivors due to ECPR therapies.

Decrease in emergency medical services utilization during early stages of the COVID-19 pandemic in British Columbia.

OBJECTIVE: To date in the COVID-19 pandemic, there has been a decrease in patients accessing emergency health services, (EHS) but research has been conducted in areas with a very high incidence of COVID-19. In an area with a low COVID-19 incidence, we estimate changes in EHS use. METHODS: We compared EHS encounters in British Columbia from March 15 (the date of school and business closures) to May 15, 2020, when compared to the same period in 2019. We categorized EHS encounters into 18 presenting complaints and prespecified critical care complaints including major trauma, cardiac arrest, stroke, and ST-elevation myocardial infarction. We analyzed by descriptive methods. RESULTS: Comparing 2019 to 2020, total EHS encounters decreased from 83,925 (incidence rate 834 per 100,000 person-months) to 71,611 (incidence rate 701 per 100,000 person-months) for a decrease of 133 per 100,000 person-months (95% CI 126-141). The top 18 codes had a significant decrease in every category except respiratory and anxiety. Encounters for critically ill patients decreased significantly overall from 3019 to 2753 (incidence rate difference 3.1 per 100,000 person-months, 95% CI 1.6-4.5), including stroke, trauma, and STEMI, but the incidence of OHCA appeared stable. CONCLUSION: In a single province with a low incidence of COVID-19, there was a 15% reduction in overall EHS use and a 9% reduction in critical illness. EHS planners will need to match patient need with available resources.

RéSUMé: OBJECTIFS: Jusqu'à présent dans la pandémie de Covid-19, il y a eu une diminution du nombre de patients ayant accès aux services de santé d'urgence, mais des recherches ont été menées dans des zones à très forte incidence de Covid-19. Dans une zone à faible incidence de Covid-19, nous estimons les changements dans l'utilisation des services de santé d'urgence. MéTHODES: Nous avons comparé les cas des services de santé d'urgence en Colombie-Britannique du 15 mars (date de fermeture des écoles et des entreprises) au 15 mai 2020, par rapport à la même période en 2019. Nous avons classé les cas des services de santé d'urgence en 18 plaintes de présentation et des plaintes de soins intensifs pré-spécifiées, y compris un traumatisme majeur, un arrêt cardiaque, un accident vasculaire cérébral et un infarctus du myocarde avec élévation du segment ST. Nous avons analysé par des méthodes descriptives. RéSULTATS : En comparant 2019 à 2020, le nombre total des cas des services de santé d'urgence est passé de 83 925 (taux d'incidence de 834 pour 100 000 personnes-mois) à 71 611 (taux d'incidence de 701 pour 100 000 personnes-mois) pour une diminution de 133 pour 100 000 personnes-mois (IC à 95 % 126 à 141). Les 18 codes principaux ont connu une diminution significative dans toutes les catégories, sauf respiratoire et anxiété. Les cas chez les patients gravement malades ont globalement diminué de manière significative de 3 019 à 2 753 (différence de taux d'incidence de 3,1 pour 100 000 personnes-mois, IC à 95 % de 1,6 à 4,5), y compris les accidents vasculaires cérébraux, les traumatismes et les STEMI, mais l'incidence des arrêts cardiaque hors hôpital semble stable. CONCLUSIONS: Dans une seule province avec une faible incidence de Covid-19, il y a eu une réduction de 15 % de l'utilisation globale des services de santé d'urgence et une réduction de 9 % des maladies graves. Les organisateurs des services de santé d'urgence devront faire correspondre les besoins des patients avec les ressources disponibles.