A Persistent Positive Antibody Test in a Patient With No History of COVID-19 Infection

Jordan McMurry; Ezekiel Fink, MD

Disclosures

Lab Med. 2022;53(1):e1-e3. 

In This Article

Abstract and Introduction

Abstract

Antibody testing for SARS-CoV-2 has been established as a tool with broad utility in the surveillance and control of the COVID-19 pandemic. However, because of limited knowledge about the duration of humoral immunity to COVID-19 and the existence of unique individual immune responses, the potential role of antibody testing in the diagnosis of current and past infections of COVID-19 remains ambiguous. Herein, we describe a unique case of an asymptomatic patient showing a persistent positive total antibody test for SARS-CoV-2 while testing negative for SARS-CoV-2 RNA and IgG-specific antibodies. This case study shows how a combination of tests can be employed to identify a false positive and draw conclusions about a patient's COVID-19 status. It also highlights the complexity of using antibody testing for the diagnosis of COVID-19.

Introduction

The infectious disease COVID-19, caused by SARS-CoV-2, has spread rapidly around the world, causing a pandemic. Many recent studies have focused on the utility of SARS-CoV-2 antibody testing for identifying current and past infections.[1,2] In addition, antibody testing has been explored as a tool for obtaining information on the stage of disease progression,[2–4] for identifying undiagnosed infections past the point of viral shedding,[5,6] and as a promising option for monitoring the portion of a population previously infected.[7,8] However, despite the development of tests offering high levels of sensitivity and specificity for SARS-CoV-2 antibodies,[9] many limitations exist for these potential uses. These include a lack of knowledge of the duration of SARS-CoV-2 antibodies after infection[10] and the impact of low population seroprevalence on the ability to make accurate predictions using antibody testing.[9] In addition to these limitations, multiple unique cases have been reported that illustrate the complexity and lack of clarity of the role that antibody tests should play in diagnosing COVID-19 infection.[6,11] Additional research is needed to explore the factors that influence antibody test accuracy and to clarify how to manage patients in whom the test results do not give a straightforward answer. Here, we report a unique case of a patient with no evidence of current or past infection with COVID-19 who persistently tested positive for SARS-CoV-2 antibodies on 1 test while testing negative on another.

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