CLIA (Chemiluminescence immunoassay) is one type of SARS-CoV-2 neutralizing antibody assay.

The CLIA test detects the presence of neutralizing antibodies in a patient’s serum by measuring the light produced by a chemical reaction. The test is based on the principle of competitive inhibition, where the patient’s serum is mixed with a known amount of SARS-CoV-2 spike protein and a labelled SARS-CoV-2 spike protein. The labelled spike protein competes with the patient’s serum antibodies for binding to the spike protein. The more antibodies present in the patient’s serum, the less labelled spike protein will bind, resulting in a lower signal.

CLIA tests are not used to diagnose COVID-19, as it can take several days or even weeks for the body to produce detectable levels of antibodies after infection. Instead, it is primarily used to determine the body’s immune response to vaccination or after a COVID-19 infection. After receiving a vaccine, the body produces antibodies specific to the vaccine, and an antibody test can determine if a person has mounted an adequate immune response to the vaccine.

Overall, antibody tests play an important role in understanding the prevalence of infections and the effectiveness of vaccines. However, it is important to interpret the results of an antibody test in conjunction with other clinical information, as false-positive and false-negative results can occur.