Clinical Utility of SARS-CoV-2 Antibody Titers in the Management of Patients With Long COVID Infected With the Omicron Variant.
Long COVID (LC) presents persistent symptoms that pose a major clinical challenge. Identification of reliable biomarkers to evaluate LC pathophysiology is needed.
To investigate whether serum S- and N-antibody titers against SARS-CoV-2 spike and nucleocapsid proteins reflect the clinical features of LC.
This retrospective observational study included patients diagnosed with Omicron variant-related LC who attended a post-COVID-19 outpatient clinic between July 2023 and November 2024 and provided informed consent for antibody testing.
Among 275 patients (129 men and 146 women), 57 (21%) were unvaccinated. Median S- and N-antibody titers in vaccinated versus unvaccinated patients were 20,963 U/mL and 24.8 cut-off index (COI) versus 24 U/mL and 44.5 COI, respectively. S-antibody titers were associated with the number of vaccine doses received, whereas N-antibody titers correlated with disease severity during the acute phase of COVID-19 infection, with females having higher titers by multivariable analysis. N-antibody titers in unvaccinated patients with LC were negatively correlated with time interval from infection to clinic visit, with an estimated daily decline of 0.34% in measured N-antibody levels. Patients with LC having memory impairment had low S-antibody titers by multivariable logistic regression analysis, and low S-antibody levels were associated with reduced quality of life (QOL). Additionally, N-antibody titers positively correlated with lymphocyte counts and immunoglobulin levels.
Serum N-antibody titers reflect immune responses to COVID-19, although they are affected by gender differences and interval between infection and evaluation. Lower S-antibody titers were associated with brain fog symptoms and reduced QOL in patients with LC.
To investigate whether serum S- and N-antibody titers against SARS-CoV-2 spike and nucleocapsid proteins reflect the clinical features of LC.
This retrospective observational study included patients diagnosed with Omicron variant-related LC who attended a post-COVID-19 outpatient clinic between July 2023 and November 2024 and provided informed consent for antibody testing.
Among 275 patients (129 men and 146 women), 57 (21%) were unvaccinated. Median S- and N-antibody titers in vaccinated versus unvaccinated patients were 20,963 U/mL and 24.8 cut-off index (COI) versus 24 U/mL and 44.5 COI, respectively. S-antibody titers were associated with the number of vaccine doses received, whereas N-antibody titers correlated with disease severity during the acute phase of COVID-19 infection, with females having higher titers by multivariable analysis. N-antibody titers in unvaccinated patients with LC were negatively correlated with time interval from infection to clinic visit, with an estimated daily decline of 0.34% in measured N-antibody levels. Patients with LC having memory impairment had low S-antibody titers by multivariable logistic regression analysis, and low S-antibody levels were associated with reduced quality of life (QOL). Additionally, N-antibody titers positively correlated with lymphocyte counts and immunoglobulin levels.
Serum N-antibody titers reflect immune responses to COVID-19, although they are affected by gender differences and interval between infection and evaluation. Lower S-antibody titers were associated with brain fog symptoms and reduced QOL in patients with LC.
Authors
Kawaguchi Kawaguchi, Sakurada Sakurada, Tokumasu Tokumasu, Otsuka Otsuka, Nakano Nakano, Matsuda Matsuda, Honda Honda, Omura Omura, Matsuki Matsuki, Furukawa Furukawa, Higashikage Higashikage, Otsuka Otsuka
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