In our previous blog, we republished an online article titled “Interpreting Diagnostic Tests for SARS-CoV-2” from JAMA which was originally published online on May 6, 2020 (doi:10.1001/jama.2020.8259)
Link: See Original Blog Post
The JAMA article provides an excellent comparison between RT-PCR (reverse transcriptase-polymerase chain reaction) and serology testing. It also provides a vivid graphic presentation of the timeline of detection for these two types of testing.
Generally, molecular testing detects the presence of the Sars-CoV2 virus in samples collected from nasopharyngeal swabs, throat swabs or saliva. The testing method utilized is RT-PCR. In contrast, antibody testing indirectly detects the COV ID-19 virus through the body’s immune response and production of antibodies.
A review of different serology testing platforms follows.
Antibody Testing platforms for Sars-CoV2:
Although most current tests are designed to detect IgG and IgM, the selection of format and platform should depend on laboratory setting and desired applications. There are three main formats currently available.
Point of Care Lateral Flow Rapid tests:
IgG and IgM antibody rapid tests were the first serology tests deployed in the US market. The advantage of rapid antibody tests is that they can be do not require the use of an analyzer and can potentially be used in used in a range of settings. For on-site point of care testing, such as a physician’s office, ER or a drive-through setting, a finger stick capillary whole blood sample can be obtained using a safety lancet. For reference and hospital labs, who normally receive venipuncture blood tubes, venous whole blood, plasma or serum may be used. There have been some concerns regarding inconsistent results and varying quality from the many tests currently in distribution. This should resolve once tests have been subjected to greater FDA oversight and received Emergency Use Authorization.
When selecting a test, it is best to use a test with good clinical data and one that has received Emergency Use Authorization. Notified tests, without Emergency Use Authorization (EUA), are restricted to Highly Complex Labs. Emergency Use Authorized tests have, to date, been given CLIA Highly Complex and Moderately Complex designations. In the future, based on clinical studies and performance data, they may be given a Waived designation. However, at this time, no point-of-care rapid antibody tests have received Waived status.
Antibody Testing on Immunoassay Analyzers:
There are several platforms currently available, such as the Abbott Architect and Roche Cobas systems, that have received EUA clearance. If these analyzers are present in your lab, they are a good option. Throughput is analyzer-specific and, in some cases, may be too limited. For labs who wish to implement serological IgG and IgM testing, the equipment cost and delivery backlog may be prohibitive. In situations where a lab prefers an analyzer-based solution, there are several ELISA analyzers that can run as a dedicated platform for COVID-19.
ELISA (enzyme-linked immunosorbent assay):
This technology is extremely flexible and can provide qualitative or quantitative results. It is also accurate and scalable. The technology lends itself to labs performing 500 to 5000 panels per day. The flexibility of this format allows the user to process and read results on a variety of automation platforms based on lab volume and menu. While our emphasis here is on COVID-19 testing, an extensive menu of ELISA applications exist, including tests for infectious diseases, parasitology, autoimmune diseases, fertility, thyroid function, diabetes, cardiac markers and others. If a lab desires a dedicated solution for COVID-19 testing that is efficient, scalable and cost effective, ELISA is an excellent option.