Background The pandemic due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has tremendous consequences for our societies. Knowledge of the seroprevalence of SARS-CoV-2 is needed to accurately monitor the spread of the epidemic and to calculate the infection fatality rate (IFR). These measures may help the authorities to make informed decisions and adjust the current societal interventions. The objective was to perform nationwide real-time seroprevalence surveying among blood donors as a tool to estimate previous SARS-CoV-2 infections and the population based IFR. Methods Danish blood donors aged 17–69 years giving blood April 6 to May 3 were tested for SARS-CoV-2 immunoglobulin M and G antibodies using a commercial lateral flow test. Antibody status was compared between geographical areas and an estimate of the IFR was calculated. The seroprevalence was adjusted for assay sensitivity and specificity taking the uncertainties of the test validation into account when reporting the 95% confidence intervals (CI). Results The first 20,640 blood donors were tested and a combined adjusted seroprevalence of 1.9% (CI: 0.8-2.3) was calculated. The seroprevalence differed across areas. Using available data on fatalities and population numbers a combined IFR in patients younger than 70 is estimated at 89 per 100,000 (CI: 72-211) infections. Conclusions The IFR was estimated to be slightly lower than previously reported from other countries not using seroprevalence data. The IFR is likely several fold lower than the current estimate. We have initiated real-time nationwide anti-SARS-CoV-2 seroprevalence surveying of blood donations as a tool in monitoring the epidemic.

Serological SARS-CoV-2 assays are needed to support clinical diagnosis and epidemiological investigations. Recently, assays for large-scale detection of total antibodies (total-Ab) and immunoglobulin (Ig) G and M against SARS-CoV-2 antigens have been developed, but there are limited data on the diagnostic accuracy of these assays. This study was a Danish national collaboration and evaluated fifteen commercial and one in-house anti-SARS-CoV-2 assays in sixteen laboratories. Sensitivity was evaluated using 150 samples from individuals with asymptomatic, mild or moderate COVID-19; nonhospitalized or hospitalized, confirmed by nucleic acid amplification tests (NAAT), collected 13-73 days either from symptom onset or from positive NAAT (patients without symptoms). Specificity and cross reactivity were evaluated in samples collected prior to the SARS-CoV-2 epidemic from >586 blood donors and patients with autoimmune diseases, cytomegalovirus or Epstein-Barr virus infections and acute viral infections. A specificity of ≥99% was achieved by all total-Ab and IgG assays except one, Diasorin/LiaisonXL-IgG (97.2%). Sensitivities in descending order were: Wantai/ELISA total-Ab (96.7%), CUH-NOVO/in-house ELISA total-Ab (96.0%), Ortho/Vitros total-Ab (95.3%), YHLO/iFlash-IgG (94.0%), Ortho/Vitros-IgG (93.3%), Siemens/Atellica total-Ab (93.2%), Roche/Elecsys total-Ab (92.7%), Abbott/Architect-IgG (90.0%), Abbott/Alinity-IgG (median 88.0%), Diasorin/LiaisonXL-IgG (median 84.6%), Siemens/Vista total-Ab (81.0%), Euroimmun/ELISA-IgG (78.0%), and Snibe/Maglumi-IgG (median 78.0%). However, confidence intervals overlapped for several assays. The IgM results were variable, with the Wantai/ELISA-IgM showing the highest sensitivity (82.7%) and specificity (99%). The rate of seropositivity increased with time from symptom onset and symptom severity.

AIMTo detect chronic hepatitis B (CHB), chronic hepatitis C (CHC) and human immunodeficiency virus (HIV) infections in dried blood spot (DBS) and compare these samples to venous blood sampling in real-life.METHODSWe included prospective patients with known viral infections from drug treatment centers, a prison and outpatient clinics and included blood donors as negative controls. Five drops of finger capillary blood were spotted on filter paper, and a venous blood sample was obtained. The samples were analyzed for HBsAg, anti-HBc, anti-HBs, anti-HCV, and anti-HIV levels as well as subjected to a combined nucleic acid test (NAT) for HBV DNA, HCV RNA and HIV RNA.RESULTSSamples from 404 subjects were screened (85 CHB, 116 CHC, 114 HIV and 99 blood donors). DBS had a sensitivity of > 96% and a specificity of > 98% for the detection of all three infections. NAT testing did not improve sensitivity, but correctly classified 95% of the anti-HCV-positive patients with chronic and past infections. Anti-HBc and anti-HBS showed low sensitivity in DBS (68% and 42%).CONCLUSIONDBS sampling, combined with an automated analysis system, is a feasible screening method to diagnose chronic viral hepatitis and HIV infections outside of the health care system.

Anti-HEV prevalence had decreased by half among Danish blood donors over 10 years, but was still highly prevalent. The difference in reactivity of the two assays demonstrates the importance of using the same assay when comparing the anti-HEV prevalence in populations over time.

Background:The pandemic due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has tremendous consequences for our societies. Knowledge of the seroprevalence of SARS-CoV-2 is needed to accurately monitor the spread of the epidemic and also to calculate the infection fatality rate (IFR). These measures may help the authorities to make informed decisions and adjust the current societal interventions. Blood donors comprise approximately 4.7% of the similarly aged population of Denmark and blood is donated in all areas of the country. The objective of this study was to perform real-time seroprevalence surveying among blood donors as a tool to estimate previous SARS-CoV-2 infections and the population based IFR. Methods:All Danish blood donors aged 17-69 years giving blood April 6 to 17 were tested for SARS-CoV-2 immunoglobulin M and G antibodies using a commercial lateral flow test. Antibody status was compared between areas and an estimate of the IFR was calculated. The seroprevalence was adjusted for assay sensitivity and specificity taking the uncertainties of the test validation into account when reporting the 95% confidence intervals (CI).Results: The first 9,496 blood donors were tested and a combined adjusted seroprevalence of 1.7% (CI: 0.9-2.3) was calculated. The seroprevalence differed across areas. Using available data on fatalities and population numbers a combined IFR in patients younger than 70 is estimated at 82 per 100,000 (CI: 59-154) infections. Conclusions:The IFR was estimated to be slightly lower than previously reported from other countries not using seroprevalence data. The IFR, including only individuals with no comorbidity, is likely several fold lower than the current estimate. This may have implications for risk mitigation.We have initiated real-time nationwide anti-SARS-CoV-2 seroprevalence surveying of blood donations as a tool in monitoring the epidemic.