Performance varies widely in commercial and in-house COVID-19 blood antibody tests

Many different blood tests are available for the COVID-19 virus to detect infection and to evaluate antibody responses developed after infection or vaccination. But not all tests hold to a standard ensuring that their results will be consistent with those of other similar tests. A new study addresses this issue. 

A team of scientists from the Vaccine, Immunity and Cancer Directorate (VICD) at the Frederick National Laboratory, the National Institute of Allergy and Infectious Diseases, and the National Cancer Institute evaluated the performance of 27 blood tests, or assays, tested by 17 institutions. The assays are designed to measure the human antibody response to infection by the COVID-19 virus as well as the response to vaccines against the virus. 

The 27 tests included binding assays made by commercial organizations and academic laboratories to measure the binding of antibodies to their target. The scientists also evaluated neutralization assays that measure viral inhibition. 

Each assay was graded for specificity – how well an assay detects a negative response from samples known to be free of the target – and sensitivity, how well an assay detects a positive response from samples known to have the target. A specificity of 93 percent or better was considered acceptable, as was a sensitivity of 90 percent or greater. Results varied and the sensitivity of some tests lagged when antibody levels were low. 

To see how well the tests compared to existing standards, all 27 assays benchmarked to the World Health Organization International Standard and the U.S. Serology Standard. Commercial tests and many of the neutralization assays correlated well against the standards. In-house assays, however, varied the most when comparing their results against the U.S. standard. Overall, commercial assays were more accurate than in-house and neutralization-based tests, both of which varied in sensitivity and specificity.  

“We’d like to get all the assays to have a similar readout, whether they are being used by hospital A, B, or C, so results are interpreted the same,” said FNL lead author Troy Kemp. “So, if a clinical study is done in Arizona or North Dakota using two assays, if we standardize correctly, we can get similar readouts … so the data may be used for informing regulators on public health matters.” 

“Some assays are right on par and work really great, some have more optimization to do,” Kemp said. 

Results of the study, published in the journal Microbiology Spectrum, include useful data on the performance of a wide range of assays when used on a common collection of participant samples. And it takes a first step toward standardizing tests to measure COVID-19 antibody responses in the population.  

“This is really one-of-a-kind study and one of the largest head-to-head comparison studies for different available COVID-19 antibody tests, showing again the amazing power of collaboration across 17 different institutions,” said Ligia Pinto, director of the Vaccine, Immunity and Cancer Directorate.