Antibody Testing (Serology) and What It Means to You

Author: Charles Golub (Market Development Manager – Saint-Gobain Life Sciences, Medical Components)

Overview and why it’s important.

For most viruses, antibody testing isn’t super critical. Traditionally, people know if they got sick or if they had a vaccine for a given illness. However, with COVID-19, things are different. It’s been well documented that a large portion of those who contract it never feel any symptoms. So the ultimate goal of reaching “herd immunity” from this virus needs a multifaceted approach. The first is contact tracing and testing, which many states have implemented. The second is antibody testing, either now or once a vaccine is available, in order to ensure that those receiving vaccines haven’t already been exposed. The two of these together will enable us to pinpoint what percent of the population already has immunity and what further level is required to reach herd immunity. Herd immunity is when enough of a population has immunity that the remaining portion of the population has indirect protection. The level of the population required to be immune for a given pathogen to achieve herd immunity is dependent on how contagious it is, but for most viruses it is estimated to be between 70%-90% of a population. In Massachusetts, on June 1 the department of public health began reporting Antibody testing in their daily COVID19 Dashboard and including positives as retroactive cases.

There are a number of different methods to determine antibodies.  For COVID-19, the main tests are the following:

• Lateral flow tests, where a small blood sample flows across a capillary to two lines on the strip: a control line and a test line
• ELISA (enzyme-linked immunosorbent assay), which is a plate based technique for analyzing antibodies among other things
• CLIA (Chemiluminescence immunoassay), a plate based analysis that uses light to analyze the blood’s response to specific enzyme linked chemistries
• CMIA (Chemiluminescence micro particle assay), a technique where magnetic micro-particles are coated and analyzed with a blood sample

Aside from the lateral flow test, these require a venous blood draw and lab analysis.

Why is there so much doubt about their accuracy?

When the initial antibody tests came out, the FDA only required notification that a company would be providing a test. This resulted in a large number (over 100!) of companies sending notification that they would be producing tests with minimal oversight on the accuracy of these tests.  The most common indicators are sensitivity, the ability to accurately show a positive reading, and specificity, the ability to accurately show a negative reading. Many reports have come out that question the accuracy of the antibody studies in populations; the FDA responded on May 4^th by requiring all antibody tests to be reviewed under Emergency Use Authorizations. This requirement, in turn, removes ambiguity and ensures that test results are highly accurate. In summary, initially many antibody studies were using inaccurate test methods. The FDA reacted by putting in place corrective actions and providing more rigorous oversight around the accuracy  of the tests. This also ensured companies did due diligence in testing for sensitivity and specificity of their tests prior to submitting it to the FDA for review, as well as ending the ability for the prior inaccurate tests to be used.

As of June 2^nd  there are 13 tests that have Emergency Use Authorizations by the FDA, three of which are lateral flow tests with the lowest sensitivity being 87.1% and most of the tests requiring venous blood draw approaching 100% for both sensitivity and specificity. 

What Saint-Gobain can offer to those developing equipment for test methods:

Systems that have automated blood analysis also run automated cleaning cycles. The cleaning fluids can have trace byproducts, so filters are often required in the lines of both the cleaning and the rinse fluids. There is a strong demand for the systems to get smaller which, in turn, creates a need for smaller custom filters to be created. Saint-Gobain’s ability to provide custom sizing and connectivity on your filters can help to ensure your products have the proper parts installed through each maintenance cycle and will continue to operate as originally designed.

Our specialty Tygon® tubing portfolio offers a broad selection of products that are ideal for blood transport and cleaning chemicals used in these instruments; ranging from Non-DEHP PVC’s that offers superior permeation, blood compatibility, adhesion, and cleanability properties; to Tygon LCF® which offers superior low coefficient of friction, to Tygon MPF®.  Tygon® has been the industry benchmark for tubing and continues to serve as a reference due to many of its key attributes. Using our custom formulations help to ensure your product maintains a high level of quality throughout its lifecycle.