Association between clinical symptoms during the COVID‐19 infection and SARS‐CoV‐2 immunoglobulin G titers in COVID‐19 convalescent whole‐blood donors in China

Background Limited studies have explored the association between clinical symptoms and titers of SARS‐CoV‐2 antibodies. Study Design and Methods In this cross‐sectional study, whole‐blood donors who had experienced a confirmed or suspected COVID‐19 infection completed questionnaires at the time of blood donation. Plasma SARS‐CoV‐2 immunoglobulin G (IgG) titers were measured using an enzyme‐linked immunosorbent assay. Logistic regression models were used to calculate odds ratios (ORs) for high‐titer COVID‐19 convalescent plasma (CCP) for each variable. Results Among the total 386 donors, 120 (31%) donors with IgG titers ≥1:160 were classified as high‐titer donors. The multivariable ORs (95% confidence intervals [CIs]) for high titers were 2.33 (1.45–3.75), 2.11 (1.29–3.43), 1.10 (1.01–1.21), 1.19 (1.00–1.43), and 1.97 (1.05–3.71) for sore throat, cough, symptom count, fever duration, and low fever (compared with non‐fever), respectively. No significant association was observed between other symptoms and medical visits and the odds of high‐titer CCP. The association between high‐titer CCP and fever duration was restricted to confirmed COVID‐19‐infected donors, while associations with sore throat and cough remained significant in suspected infected donors. In addition, medical visit was positively associated with high‐titer CCP in suspected donors, but not in confirmed donors. In bootstrapped logistic regression models, the associations remained significant and reproducible for medical visit in suspected donors and for sore throat and cough in both suspected donors and total donors. Discussion Experiencing a sore throat and cough were associated with high‐titer CCP in overall donors. We also identified sore throat, cough, and medical visits as potential predictors of high‐titer CCP for suspected donors during the pandemic.