Prognostic Value of SARS-CoV-2 Anti-RBD IgG Antibody Quantitation on Clinical Outcomes in Hospitalized COVID-19 Patients

Luai Madanat,1 Melinda Sager,1 Daniel O’Connor,1 Bijaya Thapa,1 Nishant Aggarwal,1 Bipin Ghimire,1 Carl Lauter,1– 4 Gabriel N Maine,5,6 Matthew Sims,1,2,4 Alexandra Halalau1,4 1Internal Medicine, William Beaumont Hospital, Royal Oak, MI, USA; 2Infectious Diseases, William Beaumont Hospital, Royal Oak, MI, USA; 3Allergy and Immunology, William Beaumont Hospital, Royal Oak, MI, USA; 4Oakland University William Beaumont School of Medicine, Rochester, MI, USA; 5Pathology and Laboratory Medicine, William Beaumont Hospital, Royal Oak, MI, USA; 6Pathology, Oakland University William Beaumont School of Medicine, Rochester, MI, USACorrespondence: Luai Madanat, Internal Medicine, William Beaumont Hospital, Royal Oak, MI, USA, Tel +1 248-551-3000, Email Luai.madanat@beaumont.orgBackground: Antibody levels against SARS-CoV-2 can be used as an indicator of recent or past vaccination or infection. However, the prognostic value of antibodies targeting the receptor binding protein (anti-RBD) in hospitalized patients is not widely reported.Purpose: Determine prognostic impact of SARS-CoV-2 antibody quantification at the time of admission on clinical outcomes in hospitalized COVID-19 patients.Methods: We conducted a pilot observational study on patients hospitalized with SARS-CoV-2 infection to determine the prognostic impact of antibody quantitation within the first two days of admission. Anti-nucleocapsid IgG (anti-N) and Anti-RBD levels were measured. Anti-RBD level of 500 AU/mL was used as a cutoff to stratify patients. Spearman’s rank Coefficient (rs) was used to demonstrate association.Results: Of the 26 patients included, those who were vaccinated more frequently tested positive for Anti-RBD (100% vs 46.2%, P = 0.005) with higher median titer level (623 vs 0, P = 0.011) compared to unvaccinated patients. Anti-N positivity was more frequently seen in unvaccinated patients (53.9% vs 7.7%, P = 0.03). Anti-RBD levels > 500 were associated with lower overall hospital length of stay (LOS)(5 vs 10 days, P = 0.046). The analysis employing a Spearman Rank coefficient demonstrated a strong negative correlation between anti-S titer and LOS (rs=− .515, p = 0.007) and a moderate negative correlation with oxygen needs (rs =− .401, p = 0.042).Conclusion: Anti-RBD IgG levels were associated with lower LOS and oxygen needs during hospitalization. Further studies are needed to determine if levels on admission can be used as a prognostic indicator.Keywords: SARS-CoV-2, anti-RBD IgG, anti-nucleocapsid IgG, hospitalized patients, prognosis, outcomes