CONTINUING EDUCATION :: ANTIBODIES
The current state of SARS-CoV-2 antibody tests and their future potential uses
By Jared Gresh, MT(ASCP), and Brian DuChateau, PhD, D(ABMLI)
S
erological tests have long been a bellwether for the clinical laboratory evaluation of infectious diseases but to date have played only a very limited role in the evaluation of
SARS-CoV-2 infections. Here, we discuss the current state of SARS-CoV-2 antibody (Ab) tests and their future potential uses.
Human antibody response to infection with SARS-CoV-2 Almost all immunocompetent individuals mount an antibody response to SARS-CoV-2 infection,1
and 90% of individuals that do mount an antibody response develop detectable, neutral- Earning CEUs
See test on page xx or online at
www.mlo-online.com under theSee test on page16 or online at
www.mlo-online.com under the CE Tests tab. Passing scores of 70 percent or higher are eligible
for 1 contact hour of P.A.C.E. credit. LEARNING OBJECTIVES
Upon completion of this article, the reader will be able to: 1. 2. 3. 4.
1. Name the most effective testing methods for diagnosing current SARS-CoV-2 infection.
2. Compare and contrast how many days after infection IgG, AgA, and IgM antibodies can be detected for SARS-CoV-2.
3. Discuss possible causes of false positive and false negative test results.
4. Discuss when monoclonal antibody therapy is best used for SARS-CoV-2 patients.
8 DECEMBER 2021
MLO-ONLINE.COM izing antibodies to SARS-CoV-2.2 Asymptomatic individuals
may seroconvert later in the course of infection, or not at all, and have lower IgG levels compared to symptomatic patients, suggesting that asymptomatic patients may mount a weaker response, and titers may diminish earlier.3,4 These findings, however, may not directly correlate with immune status as individuals with asymptomatic SARS-CoV-2 infection were found to mount vigorous T cell responses.5 Other studies have shown that disease severity modulates the magni- tude but not the kinetics of the antibody response.6 Antibodies resulting from SARS-CoV-2 infection are generally detectable within 10-14 days post symptom onset (Figure 1).6-9
A study
profiling early humoral response demonstrated that IgA and IgM antibodies can be detected as early as five days after infec- tion, with levels increasing in the second and third weeks.10,11 IgG antibodies were shown to be detectable later, around 7-14 days after symptom onset.10,11
The results of a study by Seow
J, Graham C, Merrick B, et al, suggest that most individuals ultimately seroconvert with an IgG, IgM, and IgA response, but a subset of individuals were demonstrated to seroconvert with only an IgG, IgM, or IgA response.6
tend to decrease fairly rapidly with IgG responses being much more durable over time (Figure 1).2,6
IgM and IgA responses Antibodies to SARS-CoV-2
are known to persist for months following infection, but levels do wane over time.2,6,12,13
However, the clinical significance of
this finding is not fully understood, as a minimum threshold of antibody necessary to confer immunity has not been es- tablished. Vaccination is known to be efficacious at mitigating SARS-CoV-2 infection and in preventing severe disease.14-16 Furthermore, convalescent serum is known to be an effective therapy for individuals with severe COVID-19 disease.17,18
Col-
Photo 12184512|@ Getty Images
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