SARS-CoV-2 seroprevalence trends in healthy blood donors during the COVID-19 outbreak in Milan: Blood transfusion = Trasfusione del sangue

L. Valenti, A. Bergna, S. Pelusi, F. Facciotti, A. Lai, M. Tarkowski, A. Lombardi, A. Berzuini, F. Caprioli, L. Santoro, G. Baselli, C.D. Ventura, E. Erba, S. Bosari, M. Galli, G. Zehender, D. Prati, Covid-19 Donors Study (CoDS) network (Appendix

Research output: Contribution to journalArticlepeer-review


BACKGROUND: The Milan metropolitan area in Northern Italy was among the most severely hit by the SARS-CoV-2 outbreak. The aim of this study was to examine the seroprevalence trends of SARS-CoV-2 in healthy asymptomatic adults, and the risk factors and laboratory correlates of positive tests. MATERIALS AND METHODS: We conducted a cross-sectional study in a random sample of blood donors, who were asymptomatic at the time of evaluation, at the beginning of the first phase (February 24th to April 8th 2020; n=789). Presence of IgM/IgG antibodies against the SARS-CoV-2-Nucleocapsid protein was assessed by a lateral flow immunoassay. RESULTS: The test had a 100/98.3 sensitivity/specificity (n=32/120 positive/negative controls, respectively), and the IgG test was validated in a subset by an independent ELISA against the Spike protein (n=34, p45 years (p=0.002). DISCUSSION: SARS-CoV-2 infection was already circulating in Milan at the start of the outbreak. The pattern of IgM/IgG reactivity was influenced by age: IgM was more frequently detected in participants aged >45 years. By the end of April, 2.4-9.0% of healthy adults had evidence of seroconversion.
Original languageEnglish
Pages (from-to)181-189
Number of pages9
JournalBlood Transfus
Issue number3
Publication statusPublished - 2021


  • coronavirus spike glycoprotein
  • immunoglobulin G
  • immunoglobulin M
  • spike glycoprotein, SARS-CoV
  • virus antibody
  • adult
  • age
  • asymptomatic infection
  • Bayes theorem
  • blood
  • blood donor
  • confidence interval
  • cross-sectional study
  • female
  • human
  • immunology
  • Italy
  • male
  • middle aged
  • pandemic
  • procedures
  • regression analysis
  • risk factor
  • seroconversion
  • seroepidemiology
  • Adult
  • Age Factors
  • Antibodies, Viral
  • Asymptomatic Infections
  • Bayes Theorem
  • Blood Donors
  • Confidence Intervals
  • COVID-19
  • COVID-19 Serological Testing
  • Cross-Sectional Studies
  • Female
  • Humans
  • Immunoglobulin G
  • Immunoglobulin M
  • Male
  • Middle Aged
  • Pandemics
  • Regression Analysis
  • Risk Factors
  • SARS-CoV-2
  • Seroconversion
  • Seroepidemiologic Studies
  • Spike Glycoprotein, Coronavirus


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