Not all COVID-19 antibody tests are created equal, but which ones are best?

VANCOUVER, British Columbia — The urgent need to scan for the COVID-19 pandemic has led to the swift creation of antibody tests. Although this has cut down the spread of the virus, the tests are not undergoing normal performance evaluations. In a new study, researchers at NSF International and Novateur Ventures say the accuracy of these tests can definitely vary, ranking some good and some bad.

There are currently two main types of diagnostic tests available on the market: antibody tests (also known as serological tests) and molecular tests.

Molecular tests have a high level of accuracy and can detect RNA molecules specific to SARS-CoV-2, the virus responsible for COVID-19, circulating in the body. However, these molecular tests are unable to determine whether the virus is in a highly infectious state or whether it has already been neutralized by the patient. It also can’t determine whether someone is immune to the virus.

Antibody tests, on the other hand, only detects the immune system’s response to coronavirus. These tests can complement molecular tests by potentially detecting people with immunity against the virus.

Differences in antibody tests

In the study, researchers focus on the performance of three types of antibody tests that are currently on the market. They include studies that report sensitivity and specificity, stage of disease (early, intermediate, late), antibody target (IgA, IgG, IgM, or IgG + IgM), and test format (CLIA – chemiluminescence immunoassay, ELISA – enzyme-linked immunosorbent assay, and RDT – rapid diagnostic test). The review includes 5 CLIA, 15 ELISA, and 42 RDT antibody tests.

Study authors evaluated accuracy based on each test’s ability to correctly identify people with COVID-19 and those without. Overall, the researchers found significant variability in the tests. They also found greater variability in test sensitivity (ability to correctly identify those with COVID-19) than specificity (ability to correctly identify those without COVID-19).

Results: The best, worst tests

Of the 62 tests evaluated, five had 100% sensitivity and 100% specificity. These include the following:

Covid-19 IgG/IgM Antibody Test
Manufacturer: Biomerica
Antibody tested: IgG

Acro Biotech COVID-19 Rapid POC Test
Manufacturer: Acro Biotech
Antibody tested: IgG

DiagnoSure COVID-19 IgG/IgM Rapid Test Cassette
Manufacturer: GritOverseas Pte.
Antibody tested: IgG

DiagnoSure COVID-19 IgG/IgM Rapid Test Cassette
Manufacturer: GritOverseas Pte.
Antibody tested: IgM

COVID-19 IgG/IgM Rapid Test Cassette
Manufacturer: Healgen
Antibody tested: IgM

Of the tests that performed poorly, two tests had close to 0% sensitivity. These tests are:

One Step Novel Coronavirus (COVID-19) IgM/IgG Antibody Test
Manufacturer: Artron Laboratories
Antibody tested: IgG

Diagnostic kit IgM/IgG of Novel Coronavirus COVID-19
Manufacturer: Shanghai LiangRun, Biomedicine Tech
Antibody tested: IgM

The sensitivity and specificity of all 62 tests can be found in Figure 7 of the study report.

Given the wide range in accuracy across all antibody tests, the study highlights the importance of continuing to independently evaluate how these products perform.

“Antibody testing is important to understanding the extent of exposure for COVID-19 so it can be effectively monitored and treated,” says Novateur Ventures founder Ali Ardakani in a media release. “It is important for regional and national governments to continue their coordinated efforts to independently validate antibody test performance and also partner with industry to scale up manufacturing and production capacity.”

The study is published in the journal Diagnostics.

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