Clinical evaluation of the UMELISA SARS-CoV-2 antigen assay

Abstract

Introduction: The detection of the viral antigen constitutes one of the alternatives to the diagnosis of SARS-CoV-2, and implies replication of the virus, so a positive result would indicate current infection by SARS-CoV-2. The Immunoassay Center of Havana, Cuba developed the UMELISA SARS-CoV-2 Antigen assay, and this article describes its validation following the CECMED criteria.

Objective: To evaluate the clinical performance of the UMELISA SARS-CoV-2 Antigen assay.

Methods: A panel of positive and negative clinical samples tested by Real Time PCR was used. The samples were collected in a transport medium that did not contain substances that inactivate the agent (BTV viral transport medium, BIOCEN, Cuba and CITOSWAB VTM, China). It was carried out in a BSL-2 Laboratories equipped with a Class II Biological Safety Cabinet and the personnel used complete Personal Protection Equipment.

Results: The UMELISA SARS-CoV-2 Antígeno assay obtains the results in approximately 4 hours. It had a sensitivity of 80,9 %, which increases to 85,5 % for samples with Ct values ≤ 33 by RT-PCR. The clinical specificity was 97,2 % or 100 % in samples analyzed 48 and 24 hours after collection, respectively. The assay did not show cross-reactivity with samples positive for ARI-causing agents. The positive and negative predictive values were 98,0 % and 84,8 % respectively. Concordance with RT-PCR in collected samples was 90,08 %. The Kappa index was 0,800 with a good concordance strength. The assay could be useful in the follow-up of patients at the 5th. day of evolution of the disease.

Conclusions: The UMELISA SARS-CoV-2 Antígeno assay has very good analytical characteristics in accordance with the requirements established by the WHO for this type of test. Being a national technology, it allows its extension and application in the network of laboratories that carry out diagnosis and epidemiological surveillance of COVID-19.