Rapid Serological Tests for SARS-CoV-2: Diagnostic Performance of 4 Commercial Assays.

OBJECTIVE: To assess the diagnostic performance of lateral flow immunochromatographic assays (LFAs) of 4 different manufacturers to identify SARS-CoV-2 antibodies (IgM, IgG, or total), comparing them with the nucleic acid amplification test (NAAT) or the clinical defined test (definite or probable SARS-CoV-2 infection, respectively). METHODS: One hundred nineteen serum samples were randomly selected by convenience and distributed in the following 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] and SARS of other etiologies [n = 19]); and (3) healthy control group (n = 10). LFAs of 4 manufacturers were compared: MedTest Coronavirus (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 1-Step COVID-19 Test for total antibodies (Guangzhou Wondfo Biotech Co., China). RESULTS: The 4 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; 60-1,008), LR+ (33.43; 4.82-231.85), LR- (0.13; 0.08-0.23), accuracy (90.76%; 84.06-95.29%), and 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 different kits. LFA tests cannot replace molecular diagnostics but should be used as an additional screening tool.

Comparison of immunoperoxidase and immunofluorescence assays for pp65 cytomegalovirus antigen in immunocompromised patients

We compared the pp65 antigen detection by an in house method (immunoperoxidase assay) and by a commercial kit (immunofluorescence assay) available for cytomegalovirus infection diagnosis in immunocompromised patients. Sixty-four blood samples were analyzed in duplicate for both techniques. Eight-six percent of the samples had concordant qualitative results. The discordant results occurred more frequently in samples with low quantity of positive cells. There were no significant differences with qualitative and quantitative results of the methods.

Comparison of immunoperoxidase and immunofluorescence assays for pp65 cytomegalovirus antigen in immunocompromised patients.

We compared the pp65 antigen detection by an in house method (immunoperoxidase assay) and by a commercial kit (immunofluorescence assay) available for cytomegalovirus infection diagnosis in immunocompromised patients. Sixty-four blood samples were analyzed in duplicate for both techniques. Eight-six percent of the samples had concordant qualitative results. The discordant results occurred more frequently in samples with low quantity of positive cells. There were no significant differences with qualitative and quantitative results of the methods.

Viral respiratory infection in Curitiba, Southern Brazil.

OBJECTIVE: Viral infection is the major cause of respiratory tract pathology affecting individuals of all ages, especially children and immunocompromised patients. There is a paucity of data on etiological and epidemiological infection caused by virus, in Southern Brazil. The aim of this study was to evaluate the seasonality, and the incidence of the viruses involved in respiratory infections in Curitiba, South Brazil. METHODS: Two hundred seventy-three nasopharyngeal aspirates (NPA) from primary care health units and 1348 NPA or bronchoalveolar lavages from a tertiary-care teaching hospital were studied. Viruses were identified by indirect immunofluorescence and cellular culture. RESULTS: Thirty percent of tested samples scored positive for the presence of virions. The percentages of infection for each virus from outpatients and hospitalized, respectively, were 3.3, 19.3 for respiratory syncytial virus; 13.9, 3.5 for influenza A, 3.0, 1.7 for influenza B; 3.3, 5.6 for parainfluenza virus and 2.2, 0.8 for adenovirus. A higher incidence of positive results was found during the winter season, thus showing a pattern of seasonality. CONCLUSION: Viral agents are one of the main etiologies of respiratory tract pathology in the population studied.