Clinical performance of a semi-quantitative assay for SARS-CoV2 IgG and SARS-CoV2 IgM antibodies.

BACKGROUND: While the diagnosis of SARS-CoV-2 infection is primarily based on detection of viral RNA, the detection of SARS-CoV-2 antibodies is useful for assessing past prevalence of the disease, and in corroborating a current infection in challenging cases. Sensitive and specific immunoassays provide the ability to identify exposure to SARS-CoV-2, to determine seroconversion, to confirm eligibility for donation of convalescent plasma as well as play an essential part in epidemiological studies. We report on the validation of the Ansh Laboratories SARS-CoV-2 IgG and SARS-CoV-2 IgM ELISA immunoassays. These assays were evaluated for detection of anti-SARS-CoV-2 IgG and IgM antibodies for clinical use in our hospital as part of an orthogonal testing algorithm recommended by the CDC. METHODS: Diagnostic specificity and sensitivity of the IgG and IgM ELISA assays were tested using samples confirmed to be negative or positive for COVID-19 by RT-PCR. We also evaluated precision, analytical interference, and cross-reactivity with known cases of infection with other viruses. Additionally, we validated concordance with molecular and other serological testing and evaluated seroconversion in our patient population. RESULTS: The IgG and IgM ELISA assays showed acceptable precision, were robust to analytical interference and did not exhibit cross reactivity with specimens positive for common respiratory viruses. Both assays exhibited 95% agreement with a primary screening serological assay utilized at our institution as well as with a reference laboratory semi-quantitative method. Concordance with RT-PCR was excellent > 6 days after symptom onset (100%). CONCLUSIONS: The Ansh SARS-CoV-2 ELISA assays have good analytical performance suitable for clinical use.

Clinical Validation and Performance Evaluation of the Automated Vitros Total Anti-SARS-CoV-2 Antibodies Assay for Screening of Serostatus in COVID-19.

OBJECTIVES: Evaluation of serostatus against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as an important tool in identification of exposure to coronavirus disease 2019 (COVID-19). We report on the validation of the Vitros Anti-SARS-CoV-2 Total (CoV2T) assay for qualitative serologic testing of SARS-CoV-2 antibodies. METHODS: We performed validation studies according to Commission of Office Laboratories Accreditation guidelines, using samples previously tested for SARS-CoV-2 by reverse transcription-polymerase chain reaction (RT-PCR). We evaluated precision, analytical interferences, and cross-reactivity with other viral infections; evaluated concordance with molecular and other serologic testing; and evaluated seroconversion. RESULTS: The Vitros CoV2T assay exhibited acceptable precision and did not exhibit cross-reactivity with other acute respiratory virus infections. The CoV2T assay exhibited 100% negative predictive agreement (56/56) and 71% positive predictive agreement (56/79) with RT-PCR across all patient samples and was concordant with other serologic assays. Concordance with RT-PCR was 97% more than 7 days after symptom onset. The CoV2T assay was robust to icterus and lipemia but had interference from significant hemolysis. CONCLUSIONS: The Vitros CoV2T assay was successfully validated in our laboratory. We anticipate it will be a useful tool in screening for exposure to SARS-CoV-2; however, the use of the CoV2T and other serologic assays in the clinical management of patients with COVID-19 is unknown and must be evaluated in future studies.