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To assess the diagnostic performance of lateral flow immunochromatographic assays (LFA) of four different manufacturers to identify SARS-CoV-2 antibodies (IgM, IgG or total), comparing them with the nucleic acid amplification test (NAAT) or clinical defined (definite or probable SARS-CoV-2 infection respectively). Methods. 119 serum samples were randomly selected by convenience and distributed in the groups: (1) Group with SARS-CoV-2 infection [n=82; RT-qPCR positive (definite, n=70), and probable (n=12)]; (2) other diseases [n= 27; other viruses identified (n=8), SARS of other etiologies (n=19)]; (3) healthy control group (n=10). LFA essays of four manufacturers were compared: MedTest Coronavírus (COVID-19) IgG/IgM (MedLevensohn, Brazil); COVID-19 IgG/IgM ECO Test (Ecodiagnóstica, Brazil); Camtech COVID-19 IgM/IgG Rapid Test Kit (Camtech Diagnostics Pte Ltd, Singapore); and one Step COVID-19 Test for total antibodies (Guangzhou Wondfo Biotech Co, China). Results. The four tests studied showed high diagnostic performance characteristics for the diagnoses of definite or probable SARS-CoV-2 infection. The best measures were for the Wondfo test: sensitivity (86.59%; 95%CI, 77.26-93.11%); specificity (100%; 90.51-100%); DOR (257; 60-1008); LR+ (33.43; 4.82-231.85); LR− (0.13; 0.08 - 0.23); accuracy (90.76%; 84.06- 95.29%); Matthews Correlation coefficient (MCC) 0.82. Although considering only the probable SARS-CoV-2 infection (PCR-) cases, all the kits studied showed limited values. Conclusion. Our data demonstrate the excellent performance of LFA for the diagnoses of definite or probable SARS-CoV-2 infection. There was substantial heterogeneity in sensitivities of IgM and IgG antibodies among the manufacturers. LFA tests cannot replace molecular diagnostics, but should be used as additional screening tool.

Background: This study aimed to calculate the seroconversion rate of the CoronaVac vaccine in healthcare workers (HCWs) 40 days after administration. Methods: Serum samples from 133 HCWs from Southern Brazil were collected one day before (Day 0) and 10, 20, and 40 days after administering the vaccines first dose. Immunoglobulin G (IgG) was quantified using immunoassays for anti-N-protein antibodies (Abbott, Sligo, Ireland) and for anti-S1 (spike) protein antibodies (Euroimmun, Lubeck, Germany). Results: Seroconversion by D 40 (20 days after the second dose) occurred in 129 (97%) HCWs for the S1 protein, and in 69 (51.87%) HCWs for the N protein. An absence of IgG antibodies (by both methodologies), occurred in two (1.5%) HCWs undergoing semiannual rituximab administration, and also in another two (1.5%) HCWs with no apparent reason. Conclusion: This study showed that CoronaVac has a high seroconversion rate when evaluated in an HCW population.

Conducted the experiments, Acquisition, analysis and interpretation of data; Participated in writing the paper and its critical review; GG: Collection of samples and conduction of the experiments; SMR: Conception and design of the study, Participated in writing the paper and its critical review; SMdA: Conception and design of the study, Participated in writing the paper and its critical review; LAP: Collection of samples and conduction of the experiments; IR: Collection of samples and conduction of the experiments; BMC: Collection of samples and conduction of the experiments; FBM: Collection of samples and conduction of the experiments; CLTD: Collection of samples and conduction of the experiments; GRdAT: Collection of samples and conduction of the experiments; RCRC: Collection of samples and conduction of the experiments, Participated in writing the paper and its critical review; BSS: Collection of samples and conduction of the experiments; LB: Collection of samples and conduction of the experiments; Participated in writing the paper and its critical review; JCdO: Conduction of the experiments, Analysis and interpretation of data, Participated in writing the paper and its critical review; DA: Conduction of the experiments, Analysis and interpretation of data, Participated in writing the paper and its critical review; DFG: Conduction of the experiments, Analysis and interpretation of data, Participated in Participated in writing the paper and its critical review; ACB: Conduction of the experiments, Analysis and interpretation of data, Participated in writing the paper and its critical review; RW: Conduction of the experiments, Analysis and interpretation of data, Participated in writing the paper and its critical review; JMA: Acquisition and organization of clinical data from medical records; RdSP: Acquisition and organization of clinical data from medical records; VJWB: Acquisition and organization of clinical data from medical records; BMMdA: Participated in writing the paper and its critical review; MBN: Conception and design of the study, Conducted the experiments, Acquisition, analysis and interpretation of data, Writing the paper and its critical, Study supervisor.