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. 2021 Dec;61(12):3381-3389.
doi: 10.1111/trf.16693. Epub 2021 Oct 14.

Trends and risk factors of SARS-CoV-2 infection in asymptomatic blood donors

Luca Valenti  1   2 , Serena Pelusi  2 , Alessandro Cherubini  2 , Cristiana Bianco  2 , Luisa Ronzoni  2 , Sara Uceda Renteria  3 , Elena Coluccio  2 , Alessandra Berzuini  2 , Angela Lombardi  2 , Leonardo Terranova  4 , Francesco Malvestiti  1 , Giuseppe Lamorte  2 , Elisa Erba  2 , Massimo Oggioni  3 , Ferruccio Ceriotti  3 , Daniele Prati  2
Affiliations

Trends and risk factors of SARS-CoV-2 infection in asymptomatic blood donors

Luca Valenti et al. Transfusion. 2021 Dec.

Abstract

Background: A large proportion of SARS-CoV-2-infected individuals does not develop severe symptoms. Serological tests help in evaluating the spread of infection and disease immunization. The aim of this study was to prospectively examine the trends and risk factors of SARS-CoV-2 infection in blood donors.

Study design and methods: We screened 8798 asymptomatic donors presenting in Milan from July 2020 to February 2021 (10,680 presentations) before the vaccination campaign for anti-nucleoprotein (NP) antibodies, and for anti-spike receptor-binding domain (RBD) antibodies and nasopharyngeal swab PCR in those who tested positive.

Results: The prevalence of anti-NP+/RBD+ tests increased progressively with time up to ~15% (p < .0001), preceded by a peak of PCR+ tests. Anti-RBD titers were higher in anti-NP IgG+/IgM+ than in IgG+/IgM- individuals and in those with a history of infection (p < .0001); of these 197/630 (31.2%) displayed high titers (>80 AU/ml). Anti-RBD titers declined during follow-up, depending on baseline titers (p < .0001) and time (p = .025). Risk factors for seroconversion were a later presentation date and non-O ABO blood group (p < .001). A positive PCR was detected in 0.7% of participants in the absence of SARS-CoV-2 viremia.

Conclusions: During the second wave of SARS-CoV-2 infection in Northern Italy, we detected an increase in seroprevalence in healthy blood donors from ~4% to ~15%, with a trend paralleling that observed in the general population. Seroconversion was more frequent in carriers of non-O blood groups. The persistence of anti-RBD antibodies was short-lived.

Keywords: ABO blood group; COVID-19; anemia; epidemiology; ferritin.

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Conflict of interest statement

The authors have disclosed no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Study flowchart. CoDS, Fondazione IRCCS Ca′ Granda COVID‐19 Donors Study; NPS, nasopharyngeal swab; RBD, receptor‐binding domain
FIGURE 2
FIGURE 2
Prevalence of SARS‐CoV‐2 infection. (A) Serological pattern of SARS‐CoV‐2 anti‐NP in participants stratified by the study presentation time. p < .0001 for the increasing prevalence of IgG+ with presentation times; (B) histograms and kernel density smoothing lines show the frequency of anti‐nucleocapsid (anti‐NP)‐positive (+), and of anti‐spike receptor‐binding domain (anti‐RBD+ and nasopharyngeal swab (NPS) PCR+ tests in anti‐NP+ by evaluation date, as a fraction of all participants tested; (C) predicted percentages of true anti‐NP+/RBD+ calculated with a logistic regression model (red curve); the rate curve is shown in pink. Dots indicate participants with positive (bottom) and negative (above) tests; (D) cumulative incidence estimates of seroconversion to anti‐NP+/RBD+ in 1747 susceptible participants after the first evaluation with available follow‐up. The 95% CI is shown by dashed lines [Color figure can be viewed at wileyonlinelibrary.com]
FIGURE 3
FIGURE 3
Impact of anti‐NP serological pattern on anti‐RBD and risk of infection. IQR, Interquartile range; NPS, nasopharyngeal swab; RBD, receptor‐binding domain. p‐values at logistic regression models are reported [Color figure can be viewed at wileyonlinelibrary.com]
See this image and copyright information in PMC

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