Predicting SARS-CoV-2 Variant Spread in a Completely Seropositive Population Using Semi-Quantitative Antibody Measurements in Blood Donors.

SARS-CoV-2 serologic surveys estimate the proportion of the population with antibodies against historical variants, which nears 100% in many settings. New approaches are required to fully exploit serosurvey data. Using a SARS-CoV-2 anti-Spike (S) protein chemiluminescent microparticle assay, we attained a semi-quantitative measurement of population IgG titers in serial cross-sectional monthly samples of blood donations across seven Brazilian state capitals (March 2021−November 2021). Using an ecological analysis, we assessed the contributions of prior attack rate and vaccination to antibody titer. We compared anti-S titer across the seven cities during the growth phase of the Delta variant and used this to predict the resulting age-standardized incidence of severe COVID-19 cases. We tested ~780 samples per month, per location. Seroprevalence rose to >95% across all seven capitals by November 2021. Driven by vaccination, mean antibody titer increased 16-fold over the study, with the greatest increases occurring in cities with the highest prior attack rates. Mean anti-S IgG was strongly correlated (adjusted R2 = 0.89) with the number of severe cases caused by Delta. Semi-quantitative anti-S antibody titers are informative about prior exposure and vaccination coverage and may also indicate the potential impact of future SARS-CoV-2 variants.

Decline in human T-cell lymphotropic virus seroprevalence in blood donors from Minas Gerais, Brazil over a 12-year period (2006-2017).

To investigate a 12-year historical series (2006-2017) of human T-cell lymphotropic virus (HTLV)-positive blood donations from Fundação Hemominas, Minas Gerais, Brazil, an observational retrospective study was performed to evaluate data of blood donor candidates who were screened for HTLV-1/2 by enzyme-linked immunosorbent assay or chemiluminescence assays and confirmed by Western blot. We analyzed 3 309 716 blood donations covering 2006-2017 that were extracted from the institutional database. In a total of 3 308 738 donations that have complete algorithm tests, the global frequency of HTLV-positive donations was 0.012%. The seroprevalence in first-time blood donors was 28.82/100 000 donors; 0.95/100 000 donations were HTLV-positive in repeat blood donors. The frequency of HTLV-seropositive females was significantly higher than males (odds ratio = 1.85, p < 0.001) in first-time donors. The median age of HTLV-positive first-time and repeat donors was similar (36 and 32 years, respectively). First-time donors ≥41 years had higher odds to be infected. There was a clear tendency of decline in the HTLV-positive donations in the period analyzed, going from 19.26/100 000 donations to 8.50/100 000 donations. The increase in the proportion of repeat donors over the period analyzed (from 23% in 2006 to 67% in 2017) must be the principal factor that contributed to this drop. Our results showed a continuous decline in the frequency of HTLV-positive donations from Minas Gerais, Brazil throughout 12 years and emphasize the importance of having a high rate of repeat donors in blood centers to reduce the residual risk of transfusion-transmitted infections.

Distribution of serological screening markers at a large hematology and hemotherapy center in Minas Gerais, Southeastern Brazil.

OBJECTIVE: To assess the distribution of serological markers in blood donors at the blood banks of the Fundação Centro de Hematologia e Hemoterapia de Minas Gerais (Hemominas), Brazil, between January 2006 and December 2012. METHODS: This is a descriptive, retrospective study on blood donors screened using serological tests for markers of transmitted diseases at the state blood-banking network. RESULTS: Approximately 78.9% of the donors were considered eligible for the study after clinical screening. Repeat donors represented 68.2% of the total sample, with males being predominant as blood donors (66.8%). Total serological ineligibility was 3.05%, with total anti-HBc being the most common marker (1.26%), followed by syphilis (0.88%) and human immunodeficiency virus (0.36%). The prevalences of the markers for hepatitis C, Human T-cell lymphotropic virus, Chagas disease and HBs-Ag were 0.15%, 0.09%, 0.13% and 0.18%, respectively. The blood bank of Governador Valadares had the highest percentage of positive anti-HBc donors (2.41%). With regard to human immunodeficiency virus, the blood bank of Além Paraíba had the lowest percentage of positive donors while the blood banks of Juiz de Fora and Betim had the highest percentages. The blood bank in the city of Montes Claros had the highest prevalence of the marker for Chagas disease (0.69%). CONCLUSIONS: Data on the profile of serological ineligibility by the blood banks of the Fundação Hemominas highlights the particularities of each region thereby contributing to measures for health surveillance and helping the blood donation network in its donor selection procedures aimed at improving blood transfusion safety.

Distribution of serological screening markers at a large hematology and hemotherapy center in Minas Gerais, Southeastern Brazil

Objective: To assess the distribution of serological markers in blood donors atthe blood banks ofthe Fundac¸ão Centro de Hematologia e Hemoterapia de Minas Gerais (Hemominas), Brazil, between January 2006 and December 2012. Methods: This is a descriptive, retrospective study on blood donors screened using serological tests for markers of transmitted diseases at the state blood-banking network. Results: Approximately 78.9% of the donors were considered eligible for the study after clinical screening. Repeat donors represented 68.2% of the total sample, with males being predominant as blood donors (66.8%). Total serological ineligibility was 3.05%, with total anti-HBc being the most common marker (1.26%), followed by syphilis (0.88%) and human immunodeficiency virus (0.36%). The prevalences of the markers for hepatitis C, Human T-cell lymphotropic virus, Chagas disease and HBs-Ag were 0.15%, 0.09%, 0.13% and 0.18%, respectively. The blood bank of Governador Valadares had the highest percentage of positive anti-HBc donors (2.41%). With regard to human immunodeficiency virus, the blood bank of Além Paraíba had the lowest percentage of positive donors while the blood banks of Juiz de Fora and Betim had the highest percentages. The blood bank in the city of Montes Claros had the highest prevalence of the marker for Chagas disease (0.69%). Conclusions: Data on the profile of serological ineligibility by the blood banks of the Fundac¸ão Hemominas highlights the particularities of each region thereby contributing to measures for health surveillance and helping the blood donation network in its donor selection procedures aimed at improving blood transfusion safety

Evaluation of the use of real-time PCR for human T cell lymphotropic virus 1 and 2 as a confirmatory test in screening for blood donors.

INTRODUCTION: HTLV-1/2 screening among blood donors commonly utilizes an enzyme-linked immunosorbent assay (EIA), followed by a confirmatory method such as Western blot (WB) if the EIA is positive. However, this algorithm yields a high rate of inconclusive results, and is expensive. METHODS: Two qualitative real-time PCR assays were developed to detect HTLV-1 and 2, and a total of 318 samples were tested (152 blood donors, 108 asymptomatic carriers, 26 HAM/TSP patients and 30 seronegative individuals). RESULTS: The sensitivity and specificity of PCR in comparison with WB results were 99.4% and 98.5%, respectively. PCR tests were more efficient for identifying the virus type, detecting HTLV-2 infection and defining inconclusive cases. CONCLUSIONS: Because real-time PCR is sensitive and practical and costs much less than WB, this technique can be used as a confirmatory test for HTLV in blood banks, as a replacement for WB.

Evaluation of the use of real-time PCR for human T cell lymphotropic virus 1 and 2 as a confirmatory test in screening for blood donors / Análise do uso da PCR em tempo real para HTLV-1 e 2 como teste confirmatório na triagem de doadores de sangue

INTRODUCTION: HTLV-1/2 screening among blood donors commonly utilizes an enzyme-linked immunosorbent assay (EIA), followed by a confirmatory method such as Western blot (WB) if the EIA is positive. However, this algorithm yields a high rate of inconclusive results, and is expensive. METHODS: Two qualitative real-time PCR assays were developed to detect HTLV-1 and 2, and a total of 318 samples were tested (152 blood donors, 108 asymptomatic carriers, 26 HAM/TSP patients and 30 seronegative individuals). RESULTS: The sensitivity and specificity of PCR in comparison with WB results were 99.4 percent and 98.5 percent, respectively. PCR tests were more efficient for identifying the virus type, detecting HTLV-2 infection and defining inconclusive cases. CONCLUSIONS: Because real-time PCR is sensitive and practical and costs much less than WB, this technique can be used as a confirmatory test for HTLV in blood banks, as a replacement for WB.

INTRODUÇÃO: A triagem para HTLV-1/2 em doadores de sangue geralmente utiliza imunoensaio enzimático, seguido de um método confirmatório como Western blot quando o EIA é positivo, mas este algoritmo mostra alta taxa de resultados inconclusivos, e elevado custo. MÉTODOS: Dois ensaios qualitativos de PCR em tempo real foram desenvolvidos para detectar HTLV-1 e 2 e um total de 318 amostras foram testadas por PCR (152 de doadores de sangue, 108 de portadores assintomáticos, 26 de pacientes HAM/TSP e 30 de indivíduos soronegativos). RESULTADOS: A sensibilidade e especificidade das PCR em relação aos resultados de WB foram de 99,4 por cento e 98,5 por cento, respectivamente. As PCR foram mais eficientes em identificar o tipo viral, a infecção pelo HTLV-2 e úteis para definir casos inconclusivos. CONCLUSÕES: Por serem sensíveis, práticas e de custo muito inferior ao do WB, as técnicas de PCR em tempo real podem ser usadas como teste confirmatório do HTLV em bancos de sangue, em substituição ao WB.