Performance evaluation of automated chemiluminescence immunoassay based antigen detection – Moving towards more reliable ways to predict SARS-CoV-2 infection

Real-time reverse transcription- polymerase chain reaction (RT-PCR) has been the most reliable armoury for the diagnosis of COVID-19, considered to be the reference standard but fails to reproduce the correct predictability about the infectivity of the disease every time. Antigen detection however puts foothold in this aspect even though lacks in sensitivity, especially conventional Rapid Antigen Tests (RATs). Recently developed Chemiluminescence Immunoassay (CLIA) based antigen detection tests are promising and displayed better sensitivity. In the current study we have evaluated VITROS® SARS-CoV-2 Ag Test CLIA Kit, which was tested on 148 patient’s samples attended to a tertiary care centre for testing of SARS-CoV-2. The performance of the kit was evaluated in comparison to RT-PCR and RAT and found to be a good test for antigen detection, best within the first few days of infection. The test has shown sensitivity of 94.3 % and specificity of 100 % in samples with corresponding Ct values of ≤25 by RT-PCR, which corresponds to high viral load and can predict ability of spreading the disease by the patients. With the results being semiquantitative along with improved sensitivity it can replace RATs for antigen detection for screening, provided good laboratory set up is included under consideration.