Selection criteria to protect the blood donor in North America and Europe: past (dogma), present (evidence), and future (hemovigilance).

The safety of the blood supply depends on measures to protect not only the transfusion recipient but also the blood donor. Donor selection criteria have been voluntarily adopted or enforced through regulation in different countries, but review of practices in different blood centers reveals wide disparity in the current approaches. Such variability in practice suggests that the criteria for the protection of donor are often arbitrary or reflect deeply engrained precautionary practices and exposes the inherent uncertainty about the best way to minimize risk to the donor. Certain selection criteria introduced years ago have become dogma in some countries but were never subjected to systematic study and persist despite available evidence that the measures do not measurably improve donor safety. Current efforts to define a rational, evidence-based approach are crucial to eliminate practices that lead to the unnecessary deferral of large numbers of blood donors without improving the safety of the donation process. Future prospects to improve the safety of the donation process rest with hemovigilance initiatives to monitor the effectiveness of interventions to minimize the risks to blood donors.

The impact of discontinuation of 7-day storage of apheresis platelets (PASSPORT) on recipient safety: an illustration of the need for proper risk assessments.

BACKGROUND: Seven-day stored apheresis platelets (APs) were withdrawn from the US market after detection of two culture-positive units from 2571 tested at outdate in the PASSPORT surveillance study. The impact of this discontinuation on recipient safety was explored using mathematical modeling. STUDY DESIGN AND METHODS: Risk models for septic transfusion reactions (STRs) and transfusion-related acute lung injury (TRALI) were developed. Key assumptions were 400,000 annual APs transfused, equivalent STR risk for platelets (PLTs) stored for 5 days or more and zero for PLTs stored for less than 5 days, whole blood-derived PLTs (WBplts) administered in 5-unit pools, a 4.6-fold higher risk of false-negatives with surrogate versus culture-based bacterial testing, an AP TRALI risk between 1 per 1000 and 1 per 10,000, and a delay in TRALI risk reduction implementation in some centers by 6 to 12 months due to limited PLT availability. RESULTS: STR risk could increase, decrease, or remain the same depending on the percentage of inventory replaced by surrogate-tested WBplts versus culture-tested apheresis or whole blood PLTs. A delay in TRALI risk reduction implementation is likely to result in a comparable or greater risk during the delayed implementation period than the safety achieved with regard to STRs, even in the most favorable case scenario. CONCLUSION: A comprehensive risk assessment should have been conducted before the decision to discontinue PASSPORT. Risk assessments using accepted methods (and actual data when available) should precede any major blood safety decisions.

West Nile virus infections projected from blood donor screening data, United States, 2003.

National blood donor screening for West Nile virus (WNV) RNA using minipool nucleic acid amplification testing (MP-NAT) was implemented in the United States in July 2003. We compiled national NAT yield data and performed WNV immunoglobulin M (IgM) testing in 1 WNV-epidemic region (North Dakota). State-specific MP-NAT yield, antibody seroprevalence, and the average time RNA is detectable by MP-NAT were used to estimate incident infections in 2003. WNV donor screening yielded 944 confirmed viremic donors. MP-NAT yield peaked in August with >0.5% of donations positive for WNV RNA in 4 states. Peak IgM seroprevalence for North Dakota was 5.2% in late September. The average time viremia is detectable by MP-NAT was 6.9 days (95% confidence interval [CI] 3.0-10.7). An estimated 735,000 (95% CI 322,000-1,147,000) infections occurred in 2003, with 256 (95% CI 112-401) infections per neuroinvasive case. In addition to preventing transfusion-transmitted WNV infection, donor screening can serve as a tool to monitor seasonal incidence in the general population.

Twelve years of the Brazilian External Quality Assessment Program in Immunohematology: benefits of the program.

The Brazilian External Quality Assessment Program in Immunohematology (BEQAPI) was introduced with the objective of evaluating the quality of diagnosis in immunohematology. From 1992 to 2003, proficiency tests for ABO grouping, Rh (D, C, c, E, e), K phenotyping, direct antiglobulin testing (DAT), antibody screening (AS), and antibody identification (AI) were performed. A total of 41 evaluations were carried out in 223 institutions. Over the period of 12 years, the program included 8,014 ABO typing, 8,000 RhD typing, 5,193 Rh typing (C, c, E, e), 5,101 K phenotyping, 7,939 AS, 4,533 AI, and 7,912 DATs. Erroneous responses were classified as clerical, technical, or undetermined. A substantial proportion of erroneous responses due to clerical errors occurred in ABO typing (76/76 errors), RhD typing (34/58 errors), and Rh phenotyping (50/73 errors). Technical errors occurred predominantly for weak D (91/95 errors), AS (252/301 errors), and AI (321/335 errors). Based on these results, since 1996, participants have received "Questions and Case Studies" in Immunohematology as an incentive for training and education. The results of the present study show an improvement in the performance of participants in the course of the program. We found that a well-organized external proficiency program can contribute to the improvement of quality of testing in Immunohematology.

The 2003 West Nile virus United States epidemic: the America's Blood Centers experience.

BACKGROUND: A detailed assessment of West Nile virus (WNV) yield is needed to evaluate the effectiveness of the WNV nucleic acid amplification technology (NAT) screening implemented in 2003. STUDY DESIGN AND METHODS: WNV NAT screening and donation data were compiled from members of America's Blood Centers, which collect nearly 50 percent of the US blood supply. WNV RNA screening was performed with either the Gen-Probe/Chiron Procleix transcription-mediated amplification assay or the Roche TaqScreen polymerase chain reaction. Results of alternate NAT and WNV immunoglobulin M (IgM) antibody assays conducted on index and follow-up samples were obtained from test manufacturers. Presumed WNV positivity was based on NAT repeat reactivity of the individual index donation whereas confirmatory status was based on additional IgM testing of the index donation and NAT and serology testing of follow-up samples. RESULTS: From July through October 2003, 2.5 million donations were screened for WNV RNA. Of 877 NAT-reactive donations (screening positivity rate of 3.5 per 10,000 units), 430 (49%) were confirmed positive, whereas 68 (8%) lacking follow-up data remained presumed positive. The sensitivity and positive predictive value of a presumed viremic result relative to final confirmatory status were 92 and 99 percent, respectively. WNV activity was highest in the central plains with prevalence per 10,000 peaking August 1 to 15 in Colorado (67.7) and South Dakota (77.5) and August 16 to 31 in Wyoming (74.1) and North Dakota (102.0). CONCLUSIONS: WNV screening interdicted many viremic units, thereby reducing transfusion-transmitted infections. This study demonstrates that a national collaborative effort facilitates timely surveillance of blood donor infectious disease prevalence rates.

Protecting the blood supply from emerging pathogens: the role of pathogen inactivation.

Although the risk of infection by blood transfusion is relatively low, breakthrough infections still occur, Transfusion-related fatalities caused by infections continue to be reported, and blood is not tested for many potentially dangerous pathogens. The current paradigm for increasing the safety of the blood supply is the development and implementation of laboratory screening methods and restrictive donor criteria. When considering the large number of known pathogens and the fact that pathogens continue to emerge, it is clear that the utility of new tests and donor restrictions will continue to be a challenge when considering the cost of developing and implementing new screening assays, the loss of potential donors, and the risk of testing errors. Despite improving the safety of blood components, testing remains a reactive approach to blood safety. The contaminating organisms must be identified before sensitive tests can be developed. In contrast, pathogen inactivation is a proactive strategy designed to inactivate a pathogen before it enters the blood supply. Almost all pathogen inactivation technologies target nucleic acids, allowing for the inactivation of a variety of nucleic acid-containing pathogens within plasma, platelets, or red blood cells thus providing the potential to reduce transfusion-transmitted diseases. However, widespread use of a pathogen inactivation technology can only be realized when proven safe and efficacious and not cost-prohibitive.

Technical considerations for the performance of Nucleic acid Amplification Technology (NAT). The NAT Task Force Group.

The complexity of Nucleic acid Amplification Technology (NAT(1)), comprising sample preparation, amplification and detection methods, requires specific design considerations for both the laboratory and the procedures utilized in such testing. The purpose of this paper is to establish technical considerations for the performance of NAT. These include the collection, handling and assay of specimens and the design of laboratories to routinely and reliably detect low levels of nucleic acid sequences. The sensitivity of NAT due to the exponential amplification of nucleic acids makes contamination a major concern from specimen collection to sample detection. Therefore, laboratories need to be designed to prevent and control contamination through adequate equipment and appropriate workflow. These technical considerations should provide a basis for establishing a robust and reproducible NAT system.

Detection of human T-lymphotropic virus (HTLV) tax sequences in New York City blood donors seronegative for HTLV types 1 and 2.

A potential public health concern is the reported detection of the human T-lymphotropic virus (HTLV) tax gene in the lymphocytes of up to 11% of a low-risk group of New York City blood donors (NYBD). This study aimed to independently confirm the prevalence of HTLV tax sequences in 293 NYBD. All NYBD tested negative for antibodies to HTLV types 1 and 2 and HTLV Tax. HTLV tax sequences were not detected in the NYBD lymphocytes. These data demonstrate the lack of HTLV-1 tax in this group of NYBD at low risk for HTLV infection.