Background: COVID serological tests are essential to determine the overall seroprevalence of a population, and to facilitate exposure estimates within that population. Methods: We performed a head-to-head assessment of enzyme immunoassays (EIA) and point of care lateral flow assays (POCT) to detect SARS-CoV-2 antibodies. Demographics, symptoms, co-morbidities, treatment, and mortality of patients whose sera was used were also reviewed. Results: Six EIAs (Abbott, Affinity, BioRad, DiaSorin, Euroimmun, and Roche), and six POCTs (BTNX, Biolidics, Deep Blue, Genrui, Getein BioTech, and Innovita) were evaluated for the detection of SARS-CoV-2 antibodies in known COVID-19 infected individuals. Sensitivity of EIAs ranged from 50-100%, with only four assays having overall sensitivities >95% after 21 days post symptom onset. Notably, cross-reactivity with other respiratory viruses (PIV-4 (n=5), hMPV (n=3), rhinovirus/enterovirus (n=1), CoV-229E (n=2), CoV-NL63 (n=2), and CoV-OC43 (n=2) was observed; however, overall specificity for EIAs was good (92-100%; where all but one assay had specificity above 95%). POCTs were 0-100% sensitive >21 days post onset, with specificity ranging from 96-100%. However, many POCTs had faint banding and were often difficult to interpret. Conclusions: Serology assays can detect SARS-CoV-2 antibodies as early as 10 days post onset. Serology assays vary in their sensitivity based on the marker (IgA/M vs. IgG vs. total) and by manufacturer; however, overall only 4 EIA and 4 POCT assays had sensitivities >95% >21 days post symptom onset. Cross-reactivity with other seasonal coronaviruses is of concern. The use of serology assays should not be used for the diagnosis of acute infection, but rather for use in carefully designed serosurveys to facilitate understanding of seroprevalence in a population and to identify previous exposure to SARS-CoV-2.

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SARS-CoV-2 antigen tests used at the point-of-care, such as the Abbott Panbio, have great potential to help combat the COVID-19 pandemic. The Panbio is Health Canada approved for the detection of SARS-CoV-2 in symptomatic individuals within the first 7 days of COVID-19 symptom onset(s). Symptomatic adults recently diagnosed with COVID-19 in the community were recruited into the study. Paired nasopharyngeal (NP), throat, and saliva swabs were collected, with one paired swab tested immediately with the Panbio, and the other transported in universal transport media and tested using real-time reverse-transcriptase polymerase chain reaction (RT-PCR). We also prospectively evaluated results from assessment centers within the community. For those individuals, an NP swab was collected for Panbio testing and paired with RT-PCR results from parallel NP or throat swabs. One hundred and forty-five individuals were included in the study. Collection of throat and saliva was stopped early due to poorer performance (throat sensitivity 57.7%, n=61, and saliva sensitivity 2.6%, n=41). NP swab sensitivity was 87.7% [n=145, 95% confidence interval (CI) 81.0-92.7%]. There were 1641 symptomatic individuals tested by Panbio in assessment centers with 268/1641 (16.3%) positive for SARS-CoV-2. There were 37 false negatives and 2 false positives, corresponding to a sensitivity and specificity of 86.1% [95% CI 81.3-90.0%] and 99.9% [95% CI 99.5-100.0%], respectively. The Panbio test reliably detects most cases of SARS-CoV-2 from adults in the community setting presenting within 7 days of symptom onset using nasopharyngeal swabs. Throat and saliva swabs are not reliable specimens for the Panbio.

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Background Staphylococcus aureus bacteriuria (SABU) may represent multiple processes ranging from asymptomatic colonization to a marker of S. aureus bacteremia (SAB). Our objective was to describe SABU at a population-based level and determine patient characteristics associated with SAB. Methods A retrospective study was performed using electronic databases. All urine cultures positive for S. aureus between 2010 and 2013 within the Calgary Health Zone were included. Patient characteristics were compared among patients with and without SAB and risk factors identified using multiple logistic regression modeling. Results A total of 2540 urine cultures positive for S. aureus from 2054 patients were analyzed. The incidence of SABU was greatest among geriatric males with multiple comorbidities. SAB occurred in 175 (6.9%) of SABU patients. Those with SAB were more likely to be hospitalized, male, have a recent urinary procedure, have pure S. aureus culture in urine, and have laboratory findings suggesting systemic infection. Patients with isolated SABU were more likely to be ≥65 years, have dementia, and have abnormal urinalyses with pyuria and urine nitrites. In-hospital mortality in patients with SABU and SABU+SAB was 9.2% and 17.5%, respectively. Patients with SABU detected ≥48 hours before SAB had the highest risk of death. Conclusions Less than 7% of patients with SABU have or will develop SAB. Characteristics associated with SABU were identified that established higher risk for systemic infection. Investigating SABU patients with these characteristics for systemic infection is warranted because a delay in diagnosis is associated with increased mortality.

Frequent screening of SARS-CoV-2 among asymptomatic populations using antigen-based point of care tests (APOCT) is occurring globally with limited clinical performance data. The positive predictive value (PPV) of two APOCT used in the asymptomatic screening of SARS-CoV-2 among healthcare workers (HCW) at continuing care (CC) sites across Alberta, Canada was evaluated. Between February 22 and May 2, 2021, CC sites implemented SARS-CoV-2 voluntary screening of their asymptomatic HCW. Onsite testing with Abbott Panbio or BD Veritor occurred on a weekly or twice weekly basis. Positive APOCT were confirmed with a real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) reference method. A total of 71,847 APOCT (17,689 Veritor and 54,158 Panbio) were performed among 369 CC sites. Eighty-seven (0.12%) APOCT were positive, of which 39 (0.05%) confirmed as true positives using rRT-PCR. Use of the Veritor and Panbio resulted in a 76.6% and 30.0% false positive detection, respectively (p<0.001). This corresponded to a 23.4% and 70.0% PPV for the Veritor and Panbio, respectively. Frequent screening of SARS-CoV-2 among asymptomatic HCW in CC, using APOCT, resulted in a very low detection rate and a high detection of false positives. Careful assessment between the risks vs benefits of APOCT programs and prevalence of infection in this population needs to be thoroughly considered before implementation.

INTRODUCTIONPoint of care diagnostic tests for SARS-CoV-2, such as the ID NOW, have great potential to help combat the COVID-19 pandemic. The ID NOW is approved by the United States Food and Drug Administration (FDA) for the detection of SARS-CoV-2 in symptomatic individuals within the first 7 days of symptom onset for COVID-19 if tested within 1 hour of specimen collection. However, clinical data on the performance of the ID NOW is limited, with many studies deviating from the manufacturer’s instructions and/or having small sample size.METHODSAdults with COVID-19 in the community or hospital were recruited into the study. Paired throat swabs were collected, with one throat swab transported immediately in an empty sterile tube to the laboratory for ID NOW testing, and the other transported in universal transport media and tested by an in-house SARS-CoV-2 RT-PCR assay targeting the E-gene. Positive percent agreement (PPA) was calculated.RESULTS133 individuals were included in the study. 129 samples were positive on either the ID NOW and/or RT-PCR. Assuming any positive result on either assay represents a true positive, PPA of the ID NOW compared to RT-PCR with 95% confidence intervals was 89.1% [82.0% - 94.1%] and 91.6% [85.1% - 95.9%], respectively. When analyzing individuals with symptoms ≤ 7 days and who had the ID NOW performed within an hour, ID NOW PPA increased to 98.2%.DISCUSSIONIn this study, SARS-CoV-2 results from the ID NOW were reliable, especially when testing was adhered to manufacturer’s recommendations.