COVID-19 Antibody Tests and Their Limitations

Abstract

COVID-19, caused by the SARS-CoV-2 virus, has developed into a global health crisis, causing over 2 million deaths and changing people’s daily life the world over. Current main-stream diagnostic methods in the laboratory include nucleic acid PCR tests and direct viral antigen tests for detecting active infections, and indirect human antibody tests specific to SARS-CoV-2 to detect prior exposure. In this Perspective, we briefly describe the PCR and antigen tests and then focus mainly on existing antibody tests and their limitations including inaccuracies and possible causes of unreliability. False negatives in antibody immunoassays can arise from assay formats, selection of viral antigens and antibody types, diagnostic testing windows, individual variance, and fluctuation in antibody levels. Reasons for false positives in antibody immunoassays mainly involve antibody cross-reactivity from other viruses, as well as autoimmune disease. The spectrum bias has an effect on both the false negatives and false positives. For assay developers, not only improvement of assay formats but also selection of viral antigens and isotopes of human antibodies need to be carefully considered to improve sensitivity and specificity. For clinicians, the factors influencing the accuracy of assays must be kept in mind to test patients using currently imperfect but available tests with smart tactics and realistic interpretation of the test results.

Cross-validation of ELISA and a portable surface plasmon resonance instrument for IgG antibody serology with SARS-CoV-2 positive individuals

“…[11][12][13][14][15] These IAs typically detect the immunoglobulin M (IgM) and immunoglobulin G (IgG) produced in response to SARS-CoV-2 infection or vaccination. 16 While a highly valuable tool in the context of a viral epidemic, antibody tests, similarly to other tests, also have limitations such as false positives or false negatives related to technological or biological origin (for example, too early following an infection) that one should be aware of 17 and the factors defining their performance. 18,19 Central to the development of these tests is access to viral antigenic proteins.…”

Clinical Significance of an IgM and IgG Test for Diagnosis of Highly Suspected COVID-19

“…For 1 year, the SARS-CoV-2 antibody method including an enzymelinked immunosorbent assay, a rapid immunochromatographic assay, and a chemiluminescent immunoassay has been applied and its clinical value is being evaluated (21). A study revealed that IgM/IgG-based detections can also result in false positive/false negative outcomes (22). Some limitations are present in our study.…”

Systematic evaluation of SARS‐CoV‐2 antigens enables a highly specific and sensitive multiplex serological COVID‐19 assay

“…The assay is here focused on the detection of IgG antibodies, thereby excluding the aspects of COVID‐19 serology associated with IgA and IgM, 31,32 even though it is certainly also applicable to the detection of those immunoglobulin classes. All these biases can have an influence on both the false‐positive and false‐negative results and should be kept in consideration 33 …”