The RADAR repository: a resource for studies of infectious agents and their transmissibility by transfusion.

BACKGROUND: An ongoing issue in transfusion medicine is whether newly identified or emerging pathogens can be transmitted by transfusion. One method to study this question is through the use of a contemporary linked donor-recipient repository. STUDY DESIGN AND METHODS: The Retrovirus Epidemiology Donor Study Allogeneic Donor and Recipient (RADAR) repository was established between 2000 and 2003 by seven blood centers and eight collaborating hospitals. Specimens from consented donors were collected, components from their donations were routed to participating hospitals, and recipients of these units gave enrollment and follow-up specimens for long-term storage. The repository was designed to show that zero transmissions to enrolled recipients would indicate with 95 percent confidence that the transfusion transmission rate of an agent with prevalence of 0.05 to 1 percent was lower than 25 percent. RESULTS: The repository contains pre- and posttransfusion specimens from 3,575 cardiac, vascular, and orthopedic surgery patients, linked to 13,201 donation specimens. The mean number of RADAR donation exposures per recipient is 3.85. The distribution of components transfused is 77 percent red cells, 13 percent whole blood-derived platelet concentrates, and 10 percent fresh frozen plasma. A supplementary unlinked donation repository containing 99,906 specimens from 84,339 donors was also established and can be used to evaluate the prevalence of an agent and validate assay(s) performance before accessing the donor-recipient-linked repository. Recipient testing conducted during the establishment of RADAR revealed no transmissions of human immunodeficiency virus, hepatitis C virus, or human T-lymphotropic virus. CONCLUSIONS: RADAR is a contemporary donor-recipient repository that can be accessed to study the transfusion transmissibility of emerging agents.

Analytical and clinical sensitivity of West Nile virus RNA screening and supplemental assays available in 2003.

BACKGROUND: Transfusion-transmitted West Nile virus (WNV) infections were first reported in 2002, which led to rapid development of investigational nucleic acid amplification tests (NAT). A study was conducted to evaluate sensitivities of WNV screening and supplemental NAT assays first employed in 2003. STUDY DESIGN AND METHODS: Twenty-five member-coded panels were distributed to NAT assay manufacturers. Panels included five pedigreed WNV standards (1, 3, 10, 30, and 100 copies/mL), 15 or 16 donor units with very-low-level viremia identified through 2003 screening, and four or five negative control samples. Samples were tested neat in 10 replicates by all assays; for NAT screening assays, 10 replicates were also performed on dilutions consistent with minipool (MP)-NAT. The viral load distribution for 142 MP-NAT yield donations was characterized, relative to the analytical sensitivity of MP-NAT systems. RESULTS: Analytical sensitivities (50% limits of detection [LoD] based on Poisson model of detection of WNV standards) for screening NAT assays ranged from 3.4 to 29 copies per mL; when diluted consistent with MP pool sizes, the 50 percent LoD of screening NAT assays was reduced to 43 to 309 copies per mL. Analytical sensitivity of supplemental assays ranged from 1.5 to 7.7 copies per mL (50% LoD). Detection of RNA in donor units varied consistent with analytical LoD of assays. Detection of low-level viremia after MP dilutions was particularly compromised for seropositive units, probably reflecting lower viral loads in the postseroconversion phase. Based on the viral load distribution of MP-NAT yield donations (median, 3519 copies/mL; range, < 50-690,000), 13 to 24 percent of units had viral loads below the 50 percent LoD of screening NAT assays run in MP-NAT format. CONCLUSION: WNV screening and supplemental assays had generally excellent analytical sensitivity, comparable to human immunodeficiency virus-1 and hepatitis C virus NAT assays. The presence of low-level viremic units during epidemic periods and the impact of MP dilutions on sensitivity, however, suggest the need for further improvements in sensitivity as well as a role for targeted individual-donation NAT in epidemic regions.

Cost-effectiveness of nucleic acid test screening of volunteer blood donations for hepatitis B, hepatitis C and human immunodeficiency virus in the United States.

BACKGROUND AND OBJECTIVES: The aim of this study was to examine the cost-effectiveness of adding nucleic acid testing (NAT) to serological (antibody and antigen) screening protocols for donated blood in the United States (US) with the purpose of reducing the risks of transfusion-transmission of hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV). MATERIALS AND METHODS: The costs, health consequences and cost-effectiveness of adding either minipool or individual-donor NAT to serological screening (SS) testing were estimated using a decision-analysis model. RESULTS: With the given modelling assumptions, adding minipool NAT would avoid an estimated 37, 128 and eight cases of HBV, HCV and HIV, respectively, and save approximately 53 additional years of life and 102 additional quality adjusted life years (QALYs) compared with SS, at a net cost of $154 million. SS + minipool NAT - p24 compared with SS alone resulted in an incremental cost-effectiveness ratio of $1.5 million per QALY gained (range in sensitivity analysis $1.0-2.1 million per QALY gained) in this US analysis. CONCLUSIONS: The cost effectiveness of adding NAT screening is outside the typical range for most healthcare interventions, but not for established blood safety measures.

Loss of volunteer blood donors because of unconfirmed enzyme immunoassay screening results. Retrovirus Epidemiology Donor Study.

BACKGROUND: Blood donors who test repeatably reactive on enzyme immunoassay (EIA) and are not confirmed as positive are a continuing problem for blood banks. Units are discarded and donors are deferred, in spite of multiple studies indicating that such donors are very rarely infected with the transmissible agents. Few data are available, however, with which to evaluate whether the discarded units are more likely to come from particular demographic subgroups. STUDY DESIGN AND METHODS: The Retrovirus Epidemiology Donor Study database of over 2 million allogeneic whole-blood donations collected in the years 1991 through 1993 was utilized. The prevalence of false-positive and indeterminate test results within demographic subgroups was computed for antibodies to human immunodeficiency virus, hepatitis C virus, and human T-lymphotropic virus (anti-HIV, anti-HCV, anti-HTLV, respectively) and hepatitis B surface antigen (false-positive only) as the proportion of donations that were repeatably reactive on EIA but negative or indeterminate on the confirmatory or supplemental test. RESULTS: Several demographic groups with increased prevalence of false-positive and indeterminate anti-HIV results were the same females, younger age groups, blacks, and first-time donors. Likewise, many of the demographic subgroups with increased prevalence of false-positive and indeterminate anti-HCV results were similar: older age groups, non-whites, lower education levels, first-time donors, donors making directed donations, and donors who had received transfusions. For anti-HTLV, by contrast, the oldest group had the highest prevalence of false-positive results but the lowest prevalence of indeterminate results: blacks had the lowest prevalence of false positive results but the highest prevalence of indeterminate results. CONCLUSION: If units that test repeatably reactive on EIA but that are not confirmed as positive are almost always from individuals not infected with the virus in question, then these results indicate that there may be sex-, race-, and/or age-linked proteins cross-reacting with the test kit materials. Elucidation of these antigenic determinates and their subsequent removal should be a priority.

Frequency of human immunodeficiency virus (HIV) infection among contemporary anti-HIV-1 and anti-HIV-1/2 supplemental test-indeterminate blood donors. The Retrovirus Epidemiology Donor Study.

BACKGROUND: Follow-up studies from the mid-1980s showed that 1 to 5 percent of blood donors testing reactive in anti-human immunodeficiency virus type 1 (HIV-1) enzyme immunoassay (EIA) and testing indeterminate in Western blot were infected with HIV-1 and were in the process of seroconverting. The present study was conducted to establish the rate of HIV infection among contemporary anti-HIV-1/HIV type 2 (HIV-2) EIA-reactive, Western blot-indeterminate donors. STUDY DESIGN AND METHODS: Donations (n = 607) with indeterminate HIV supplemental test results were identified by screening 3,021,342 donations given from November 1990 through August 1993 at five participating blood centers. Consenting donors were enrolled and samples taken 4 to 8 weeks after donation. Follow-up sera were tested by EIA and Western blot for anti-HIV-1 seroconversion and by type-specific peptide assays for antibodies to HIV-2 and HIV-1 subtype O. Peripheral blood mononuclear cells and/or plasma from the follow-up samples were tested for HIV-1 DNA and/or RNA by polymerase chain reaction. The rate of HIV-1 infection among Western blot-indeterminate donors was also estimated by multiplying the incidence rate of HIV-1 seroconversion in this donor population by the estimated duration of the EIA-reactive and Western blot-indeterminate window during seroconversion (8.5 days). RESULTS: Supplemental test-indeterminate donors (n = 355) enrolled a median of 38 days after donation; 265 (75%) of these donors were identified as indeterminate after an anti-HIV-1/2 EIA-reactive donation. Enrolled and non-enrolled donors had similar distributions of demographic characteristics and band patterns. Follow-up samples from all 355 donors tested negative for HIV-1 in polymerase chain reaction. Follow-up sera tested Western blot-negative in 54 cases (15%) and Western blot-indeterminate in 299 (84%). Two follow-up sera (0.6%) were interpreted, according to manufacturer's package insert criteria, as Western blot positive with p24 and gp41 bands and/or gp120/160 bands; however, paired testing of index and follow-up sera from these two cases showed identical Western blot and EIA reactivity, and polymerase chain reaction was negative for HIV RNA and DNA, which ruled out HIV infection. The absence of HIV infection in 355 Western blot-indeterminate donors was consistent with our incidence-based model analysis, which yielded an estimate of one HIV-1 infection for every 215 Western blot-indeterminate donations (95% CI, 1/39-1/8333). CONCLUSION: Contemporary blood donors classified as indeterminate in supplemental HIV testing are infrequently infected with HIV. Donors whose follow-up samples test negative in anti-HIV-1/2 EIAs and negative or persistently indeterminate in Western blots should be considered eligible for reinstatement.

Transfusion transmission of retroviruses: human T-lymphotropic virus types I and II compared with human immunodeficiency virus type 1.

BACKGROUND: The incidence of transfusion transmission of human T-lymphotropic virus type I (HTLV-I) and HTLV type II (HTLV-II) has not been compared directly or to that of human immunodeficiency virus type 1 (HIV-1). The effects of refrigerator storage of the blood component on infectivity of the viruses needs definition. STUDY DESIGN AND METHODS: The circumstances influencing the transmission of HTLV-I, HTLV-II, and HIV-1 via blood of donors whose sera were stored in a repository and who were retrospectively documented as having been infected at blood donation were examined. Confirmation and typing of anti-HTLV positivity in donors and recipients used polymerase chain reaction, supplemented by specific peptide testing. RESULTS: Overall, 27 percent (26/95) of the recipients of blood components from anti-HTLV-I- and -II-positive donors became infected (9 with HTLV-I and 17 with HTLV-II). No recipients of acellular blood components became infected with HTLV-I or -II. There was no probable transmission by components stored > 10 days. The rates of transmission for both viruses were similar: 0 to 5 days' storage, 17 (74%) of 23; 6 to 10 days, 8 (44%) of 18; and 11 to 14, 0 (0%) of 10 (trend, p = 0.0002). In comparison, 89 percent (112/126) of the recipients of anti-HIV-1-positive blood were infected regardless of component type, and no effect on transmission occurred with storage for < 26 days. CONCLUSION: Transfusion-transmitted HTLV-I and -II are similar. The data suggest that a donor's lymphocytes become noninfectious when they lose the ability to be activated or to proliferate.

Evaluation of a p21e-spiked western blot (immunoblot) in confirming human T-cell lymphotropic virus type I or II infection in volunteer blood donors. The Retrovirus Epidemiology Donor Study Group.

Current algorithms for the serologic confirmation of human T-cell lymphotropic virus type I and II (HTLV-I/II) antibody reactivity are complicated. We evaluated the performance of an HTLV-I Western blot (immunoblot) spiked with recombinant p21e protein (p21e WB) as an alternative to current confirmatory methods. These methods include the HTLV-I viral lysate Western blot and either a radioimmunoprecipitation assay or a p21e enzyme-linked immunosorbent assay. Five hundred fifty nine blood donations obtained from five U.S. blood centers and classified as HTLV-I/II seropositive (n = 149) or seroindeterminate (n = 410) by routine testing methods were further evaluated by PCR for proviral DNA and by the p21e WB. On the basis of serologic and PCR testing, 155 donations were classified as HTLV-I/II infected. The sensitivity of the p21e WB was 97.4%, slightly exceeding that of routine confirmatory testing. The specificity of the p21e WB was 97.5%, as determined by testing of 404 seroindeterminate samples that were negative in the PCR. The positive predictive value of the p21e WB was 94%. In contrast, the specificity and positive predictive value of routine confirmatory testing were both 100%. Follow-up sampling of presumptive p21e WB false-positive donors substantiated the absence of HTLV-I/II infection. Although the p21e WB used in this study has high sensitivity and may be useful as a confirmatory assay in epidemiologic research studies, it may not be ideal as a confirmatory test for the notification of blood donors.

Accuracy of supplementary serologic testing for human T-lymphotropic virus types I and II in US blood donors. Retrovirus Epidemiology Donor Study.

Blood donations in the United States have been screened for antibody to human T-lymphotropic virus type I (HTLV-I) by HTLV-I enzyme immunoassay (EIA) since November 1988. Specimens repeatedly found to be reactive by EIA undergo confirmation by supplementary serologic tests. We assessed the accuracy of blood center testing of 994 HTLV-I EIA repeat-reactive specimens in five US blood centers between November 1988 and December 1991. Of 410 confirmed HTLV-I/II donations, 407 (99.3%) were infected with HTLV-I/II, as determined by polymerase chain reaction (PCR) (403 cases) and by repeat serologic testing (4 cases). The three false-positive results occurred in the first year of testing. Of 425 HTLV-indeterminate specimens, 6 (1.4%) were found to be infected by PCR (5 with HTLV-II and 1 with HTLV-I). None of 159 confirmatory test-negative donations was PCR positive. Of HTLV-I/II-seropositive specimens, 80.2% to 95.4% could be typed as HTLV-I or HTLV-II by type-specific serologic assays. These results support recommendations that HTLV-I/II-seropositive donors should be advised that they are infected with HTLV-I, HTLV-II, or HTLV-I/II (depending on results of type-specific assays). HTLV-indeterminate donors should be advised that their results only rarely indicate HTLV infection. HTLV confirmatory test-negative donors should be reassured that they are not infected with HTLV-I or HTLV-II.

Human immunodeficiency virus infection and indeterminate western blot patterns. Prospective studies in a low prevalence population.

Interpretation of human immunodeficiency virus (HIV) antibody results that are "indeterminate" rather than clearly positive or negative is problematic for the person delivering the result as well as for the individual being tested. To improve counseling messages for these individuals, we evaluated data collected from a well-characterized cohort of 387 blood donors who had been monitored for up to 2 years. We sought to determine if persons with indeterminate Western blot patterns were infected with HIV, and whether information derived from follow-up monitoring would assist in the development of counseling messages for persons on whom no follow-up information was available. Donors were studied by laboratory assays, clinical evaluation, and assessment of risk for HIV. The absence of HIV infection in 97 of 98 donors with indeterminate Western blot patterns was confirmed by clinical follow-up, Western blot assays of sequential samples, and negative gene amplification results. We propose supplemental guidelines to be used as an adjunct to existing interpretive criteria for counseling individuals when they first present with an indeterminate Western blot finding.

Screening of selected male blood donors for p24 antigen of human immunodeficiency virus type 1. The Transfusion Safety Study Group.

BACKGROUND: The p24 antigen of human immunodeficiency virus type 1 (HIV-1) is sometimes detected before antibody (anti-HIV-1) is detectable in the serum of recently infected persons. This has led to the consideration of p24-antigen testing for routine screening of blood donors. METHODS: To estimate how many HIV-infected seronegative donors would be identified if p24-antigen screening was introduced, we tested selected donations from a repository of 200,000 serum samples from voluntary donors that was established in late 1984 and early 1985. The 8597 serum samples selected for p24-antigen screening were chosen because their donors had demographic characteristics known to be associated with a high prevalence of seropositivity. RESULTS: The prevalence of anti-HIV-1 antibodies in the 1984-1985 serum samples selected for p24-antigen screening was 1.54 percent--more than 100 times the 0.012 percent prevalence in present-day donations in the United States. The antigen was detected in 15 of 132 serum samples (11.4 percent) from donors who had already been confirmed as seropositive. No instance of confirmed positivity for p24 antigen was found among the 8465 seronegative serum samples. CONCLUSIONS: These data indicate that the yield of screening for p24 antigen in volunteer donors to identify HIV-1 carriers would be negligible. We therefore recommend against routine screening with currently available p24-antigen assays.

Epidemiologic background of blood donors with antibody to human T-cell lymphotropic virus. Transfusion Safety Study Group.

We interviewed 51 blood donors in four major US metropolitan areas subsequently found to have had antibodies to human T-cell lymphotropic virus (anti-HTLV) in late 1984-early 1985. Sixteen donors (31%) reported that they or a sexual contact had a history of blood transfusion. Twelve donors (24%) reported that they or a sexual contact used intravenous drugs. Ten donors (20%) were blacks born in the southeastern US. Four of the male donors (15%) reported homosexual contact. The most common characteristic was an association with Japan or the Caribbean basin (61%). These results show a broader variation of epidemiologic backgrounds than anticipated.

Prevalence of antibodies to human immunodeficiency virus type 1 among blood donors prior to screening. The Transfusion Safety Study/NHLBI Donor Repository.

The Transfusion Safety Study (TSS) and the National Heart, Lung, and Blood Institute (NHLBI) established a repository of approximately 200,000 sera from blood donors in late 1984 and early 1985. Collections were made in the four metropolitan areas with the highest prevalence of AIDS. Retrospective testing showed an overall anti-HIV-1 prevalence of 16 cases per 10,000 donations. In this study, the predictive value of a negative initial enzyme-linked immunoassay was estimated from both quality control specimens and the rescreening of 13,461 sera to be greater than 99.99 percent with respect to technical error. Among anti-HIV-1-positive persons, there was a 1.3- to 1.5-fold excess of first-time donors. The anti-HIV-1 prevalence among donors showed that infection was more common among young men than suggested by national reporting of AIDS cases. Anti-HIV-1 prevalence varied among the four metropolitan areas less than did reported AIDS cases, but, by 1987, the differences in the latter had decreased. Anti-HIV-1 prevalence in collection areas outside of the four major cities differed much more widely than that among the cities themselves. The TSS/NHLBI Donor Repository will remain available for the indefinite future for further evaluation of screening procedures for HIV-1 and other viruses for which transfusion is found to be an important route of transmission.