Associations between self-reported SARS-CoV-2 infection status, serology and common longer-term COVID-19 symptoms among adults in Canada, a cross-sectional study

TL;DR

This study in Canada finds that self-reported SARS-CoV-2 infection status and antibody testing can lead to different conclusions about infection rates and long-term symptoms.

Contribution

The study highlights discrepancies between self-reported infection status and antibody testing in estimating SARS-CoV-2 prevalence and symptom associations.

Findings

37.9% of adults self-reported a confirmed or suspected SARS-CoV-2 infection, while 52.9% had antibodies.

Antibody presence was linked to self-reported certainty of infection but not to symptom severity or long-term symptoms.

Over 20% of adults were unaware they had been infected, suggesting self-reporting may misclassify infection status.

Abstract

A variety of methods, including self-report and antibody testing, has been used to estimate the prevalence of SARS-CoV-2 infections and related longer-term symptoms, but the impact of employed methods on conclusions has not been thoroughly explored.

We examined associations between self-report and antibody findings in the Canadian adult (aged 18 years and older) population.

We used data from a large population-based cross-sectional probability survey conducted between April and August 2022. Self-reported infection status and experiences with common longer-term COVID-19 symptoms since the start of the pandemic was collected, as well as a dried blood spot to measure SARS-CoV-2 antibodies.

As of August 2022, the number of adults reported having had a confirmed or suspected infection was 37.9% (95% CI: 36.8%–39.1%), while the overall mean probability of having infection-related antibodies was 52.9% (95% CI: 51.8%–54.0%) and increased with respondent certainty they had been infected. However, the mean probability of having infection-related antibodies was not associated with infection severity or the reporting of common longer-term COVID-19 symptoms. More than one in five adults were unaware they had been infected.

Self-report surveys may misclassify the SARS-CoV-2 infection status of a substantial proportion of untested people and may bias estimates of the percentage infected, the severity of infections and the risk of developing infection-related longer-term symptoms. Common longer-term COVID-19 symptoms reported by some could have been caused by other infections or diseases.

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