Rapid antigen test as a tool for the identification of SARS-CoV-2 infection and its potential as a self-testing device.

BACKGROUND: SARS-CoV-2 virus originated in Wuhan (China) in December (2019) and quickly spread worldwide. Antigen tests are rapid diagnostic tests (RDT) that produce results in 15-30 min and are an important tool for the scale-up of COVID-19 testing. COVID-19 diagnostic tests are authorized for self-testing at home in some countries, including Brazil. Widespread COVID-19 diagnostic testing is required to guide public health policies and control the speed of transmission and economic recovery. METHODS: Patients with suspected COVID-19 were recruited at the Hospital da Baleia (Belo Horizonte, Brazil). The SARS-CoV-2 antigen-detecting rapid diagnostic tests were evaluated from June 2020 to June 2021 using saliva, nasal, and nasopharyngeal swab samples from 609 patients. Patient samples were simultaneously tested using a molecular assay (RT-qPCR). Sensitivity, specificity, accuracy, and positive and negative predictive values were determined using the statistical program, MedCalc, and GraphPad Prism 8.0. RESULTS: The antigen-detecting rapid diagnostic tests displayed 98% specificity, 60% sensitivity, 96% positive predictive value, and moderate concordance with RT-qPCR. Substantial agreement was found between the two methods for patients tested < 7 days of symptom onset. CONCLUSIONS: Our findings support the use of Ag-RDT as a valuable and safe diagnostic method. Ag-RDT was also demonstrated to be an important triage tool for suspected COVID-19 patients in emergencies. Overall, Ag-RDT is an effective strategy for reducing the spread of SARS-CoV-2 and contributing to COVID-19 control.

COVID-19 in patients with chronic kidney disease: a 2-year study of incidence and mortality in relation to the variants of concern waves in Brazil.

BACKGROUND: Chronic kidney disease (CKD) is a risk factor for severe coronavirus disease (COVID-19). In Brazil, the disease is the 10th highest cause of death. We evaluated the epidemiological impact of COVID-19 in CDK and non-CDK patients. METHODS: Positive patients for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from 2020 to 2022 were classified according to the severity of COVID-19 and the numbers of cases and deaths were correlated to each wave of SARS-CoV-2 variants in Brazil. RESULTS: We compared all variables, and our data show that CDK significantly increased the mortality rate among patients, especially before COVID-19 vaccination, in comparison with non-CKD patients. CONCLUSIONS: CKD patients had a significantly increased mortality rate compared with non-CKD.

Booster dose of BNT162b2 after two doses of CoronaVac improves neutralization of SARS-CoV-2 Omicron variant.

Background: The emergence of the new SARS-CoV-2 Omicron variant, which is known to have a large number of mutations when compared to other variants, brought to light the concern about vaccine escape, especially from the neutralization by antibodies induced by vaccination. Methods: Based on viral microneutralization assays, we evaluated in 90 individuals the impact on antibody neutralization induction, against Omicron variant, by a booster dose of BNT162b2 mRNA vaccine after the CoronaVac primary vaccination scheme. Results: Here we show that the percentage of seroconverted individuals 30 and 60 days after CoronaVac scheme was 16.6% and 10%, respectively. After booster dose administration, the seroconvertion rate increased to 76.6%. The neutralization mean titer against Omicron in the CoronaVac protocol decreased over time, but after the booster dose, the mean titer increased 43.1 times. Conclusions: These results indicate a positive impact of this vaccine combination in the serological immune response against SARS-CoV-2 Omicron variant.