Experience of German Red Cross blood donor services with nucleic acid testing: results of screening more than 30 million blood donations for human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus

Prevalence of occult hepatitis B virus infection

Occult hepatitis B virus (HBV) infection (OBI) is characterized by the persistence of HBV DNA in the liver tissue in individuals negative for the HBV surface antigen. The prevalence of OBI is quite variable depending on the level of endemic disease in different parts of the world, the different assays utilized in the studies, and the different populations studied. Many studies have been carried out on OBI prevalence in different areas of the world and categories of individuals. The studies show that OBI prevalence seems to be higher among subjects at high risk for HBV infection and with liver disease than among individuals at low risk of infection and without liver disease.

Recipients potentially infected with parvovirus B19 by red blood cell products

BACKGROUND

Since 2000, blood donor screening for parvovirus B19 (B19) by nucleic acid testing (NAT) at the Ulm Institute has been conducted 6 to 8 weeks postdonation, that is, after transfusion of cellular blood products, whereas at the Frankfurt Institute all donations are screened before releasing any blood product. In this study, we evaluated the infectivity of B19-positive blood products in relation to the virus concentration in the transfused blood component.

STUDY DESIGN AND METHODS

Recipients were classified into two groups (A, transfused with blood products with B19 virus load less than 10(5) IU/mL; and B, transfused with blood products with B19 virus load greater than 10(5) IU/mL). Phylogenetic analyses were done for B19 DNA-positive donor and recipient pairs in the variant VP-1u genome region. All samples were investigated for immunoglobulin (Ig)M and IgG B19 antibodies.

RESULTS

B19 DNA was detected in 9 of 18 recipients of red blood cells (RBCs) from Group B, whereas none of the 16 recipients of RBCs from Group A were positive for B19 DNA (p=0.016). Phylogenetic analysis demonstrated identical genomic sequences between the donors and recipients. Because recipient B19 DNA and antibody results were not available before transfusion, we interpret our overall data to indicate equivocal evidence of B19 transmission by RBC transfusion.

CONCLUSION

B19 transmission by cellular blood products correlates with the virus concentration and the concentration of neutralizing antibodies. Thus, blood donor screening for B19 by minipool NAT should be done to supply at-risk patients (e.g., immunosuppressed patients) with B19-negative blood components.

Efficacy of individual nucleic acid amplification testing in reducing the risk of transfusion-transmitted hepatitis B virus infection in Switzerland, a low-endemic region

BACKGROUND

The risk of transfusion-transmitted hepatitis B virus (HBV) in Switzerland by testing blood donors for hepatitis B surface antigen (HBsAg) alone has been historically estimated at 1:160,000 transfusions. The Swiss health authorities decided not to introduce mandatory antibody to hepatitis B core antigen (anti-HBc) testing but to evaluate the investigation of HBV nucleic acid testing (NAT).

STUDY DESIGN AND METHODS

Between June 2007 and February 2009, a total of 306,000 donations were screened routinely for HBsAg and HBV DNA by triplex individual-donation (ID)-NAT (Ultrio assay on Tigris system, Gen-Probe/Novartis Diagnostics). ID-NAT repeatedly reactive donors were further characterized for HBV serologic markers and viral load by quantitative polymerase chain reaction. The relative sensitivity of screening for HBsAg, anti-HBc, and HBV DNA was assessed. The residual HBV transmission risk of NAT with or without anti-HBc and HBsAg was retrospectively estimated in a mathematical model.

RESULTS

From the 306,000 blood donations, 31 were repeatedly Ultrio test reactive and confirmed HBV infected, of which 24 (77%) and 27 (87%) were HBsAg and anti-HBc positive, respectively. Seven HBV-NAT yields were identified (1:44,000), two pre-HBsAg window period (WP) donations (1:153,000) and five occult HBV infections (1:61,000). Introduction of ID-NAT reduced the risk of HBV WP transmission in repeat donors from 1:95,000 to 1:296,000.

CONCLUSIONS

Triplex NAT screening reduced the HBV WP transmission risk approximately threefold. NAT alone was more efficacious than the combined use of HBsAg and anti-HBc. The data from this study led to the decision to introduce sensitive HBV-NAT screening in Switzerland. Our findings may be useful in designing more efficient and cost-effective HBV screening strategies in low-prevalence countries.

Occult hepatitis B virus infection in Thai blood donors

BACKGROUND

An evaluation by the National Blood Center, the Thai Red Cross Society, of two commercial multiplex nucleic acid tests (NATs; the Chiron PROCLEIX ULTRIO test and the Roche Cobas TaqScreen MPX test) for screening Thai blood donors for hepatitis B virus (HBV), hepatitis C virus, and human immunodeficiency virus Type 1 identified 175 HBV NAT-reactive/hepatitis B surface antigen (HBsAg)-negative donors. The classification of the HBV infection of these donors was confirmed by follow-up testing.

STUDY DESIGN AND METHODS

Index samples were tested for HBV serologic markers and HBV viral loads were determined. Donors were followed for up to 13 months and samples were tested with both NAT assays and for all HBV serological markers.

RESULTS

Of 175 HBV NAT-yield donors, 72 (41%) were followed. Based on the follow-up results, the majority of donors who were followed had an occult HBV infection (66.7%), followed by donors with a primary, acute infection (26.4%). The majority of donors in this latter group (20.8%) were in the window period. Three donors (4.2%), who were anti-HBs positive, had a reinfection or breakthrough infection.

CONCLUSION

The majority of donors detected during routine screening, who were HBsAg negative and NAT reactive, had an occult HBV infection, thus validating the decision to introduce NAT for blood donations in Thailand.

Anemia and transfusion therapy: an update

Anemia is one of the most prevalent diseases in the general population and is a very frequently found condition in medical and surgical patients in all medical specialties. A good evaluation of its clinical impact and its therapeutic possibilities is essential. Allogenic blood transfusion is a useful procedure in anemia management, although it has important adverse effects. It is the responsibility of the clinician to know and to take into account all the available alternatives for the treatment of anemia. Blood transfusions, erythropoiesis-stimulating agents, iron therapy (oral and endovenous) and other therapeutic alternatives must be rationally used, in accordance with the currently available clinical evidence. This review article summarizes some epidemiological characteristics of anemia, its clinical evaluation and the main therapeutic possibilities based on the present knowledge, placing special emphasis on the critically ill patient.

A cost-benefit analysis of blood donor vaccination as an alternative to additional DNA testing for reducing transfusion transmission of hepatitis B virus

A survey-based, cost-benefit analysis was performed comparing blood screening strategies with vaccination strategies for the reduction of transfusion transmission of HBV. 231 whole blood donors and 126 apheresis donors were eligible and completed a questionnaire detailing their donation habits. The cost-benefit analysis included current mandatory HBV testing (HbsAg+anti-Hbc, A1), A1 with additional nucleic acid testing (NAT) for minipool (A2) or individual donation testing (A3), as well as HBV vaccination strategies using time-dependant (B1) or titre dependent booster vaccination solely (B2), or B2 in addition to current mandatory testing procedures (B3). Different cost models were applied using a 5% rate of discount. Absolute costs for current mandatory testing procedures (A1) over 20 years in Germany were €1009 million. Additional NAT would lead to incremental costs of 43% (A2) or 339% (A3), respectively. Vaccination strategies B1 and B2 showed cost-reductions relative to A1 of 30% and 14%, respectively. The number of remaining HBV infections could be reduced from 360 (for A1) to 13, using vaccination, compared with 144 or 105 remaining infections for A2 or A3, respectively. Absolute cost per prevented infection is similar (€2.0 million) for A2 and B3. HBV vaccination offers the near-elimination of transfusion infections while representing a potential cost-reduction.

[Anemia and transfusion therapy: an update]

Anemia is one of the most prevalent diseases in the general population and is a very frequently found condition in medical and surgical patients in all medical specialties. A good evaluation of its clinical impact and its therapeutic possibilities is essential. Allogenic blood transfusion is a useful procedure in anemia management, although it has important adverse effects. It is the responsibility of the clinician to know and to take into account all the available alternatives for the treatment of anemia. Blood transfusions, erythropoiesis-stimulating agents, iron therapy (oral and endovenous) and other therapeutic alternatives must be rationally used, in accordance with the currently available clinical evidence. This review article summarizes some epidemiological characteristics of anemia, its clinical evaluation and the main therapeutic possibilities based on the present knowledge, placing special emphasis on the critically ill patient.

Real-time RT-PCR for automated detection of HIV-1 RNA during blood donor screening

Real-time RT-PCR has become the method of choice for automated detection of viral RNA target sequences in the clinical laboratory. Besides commercially available certified test systems, a variety of so-called in-house methods have been described in the literature. Generally, appropriate validation and continuous quality control are mandatory if these in-house-developed assays are used in clinical diagnostics. In this chapter, an in-house HIV-1 real-time RT-PCR assay for blood donor screening is described. The procedure includes the pooling of plasma samples, viral RNA isolation, and subsequent detection of amplification in real-time one-step RT-PCR. The validation considers the specificity, the sensitivity on HIV-1 genomic variants, and the robustness of the assay.

Improvement of an ultrasensitive human immunodeficiency virus type 1 real-time reverse transcriptase-polymerase chain reaction targeting the long terminal repeat region

BACKGROUND

Human immunodeficiency virus Type 1 (HIV-1) assays applying nucleic acid testing (NAT) rely on HIV-1 sequence-specific primers and probes. Their hybridization can be limited or abolished by genetic polymorphisms occurring in the target sequence.

STUDY DESIGN AND METHODS

Blood donations are routinely tested for HIV-1/2 antibodies and for HIV-1 RNA in our blood transfusion unit. Recently, HIV-1 RNA was undetectable with an established in-house real-time long terminal repeat (LTR) reverse transcriptase-polymerase chain reaction (RT-PCR) in two cases, whereas serologic assays were positive. The reason for this discrepancy was elucidated by sequencing of the NAT target region in the respective single donations. An improved primer was designed and tested on HIV-1 reference panels and blood donations to ensure reliable detection of HIV-1 RNA.

RESULTS

Direct sequencing of the target region, isolated from samples of two unrelated HIV-positive blood donors, revealed one and four mismatches in the hybridization domain of the forward primer, respectively. Both viruses belong to HIV-1 Subtype B. LTR RT-PCR with an additional forward primer was suitable for all strains of HIV-1 tested with high sensitivity.

CONCLUSIONS

Surveillance of HIV-1 genetic diversity is essentially required to continually evaluate its impact on performance of diagnostic and patient monitoring assays.

Transfusion-transmitted hepatitis B virus infection

Hepatitis B virus (HBV) remains a major risk of transfusion-transmitted infection due to the pre-seroconversion window period (WP), infection with immunovariant viruses, and with occult carriage of HBV infection (OBI). Reduction of HBV residual risk depends upon developing more sensitive HBV surface antigen (HBsAg) tests, adopting anti-HBc screening when appropriate, and implementing HBV nucleic acid testing (NAT), either in minipools or more efficiently in individual samples. HBV NAT combines the ability to significantly reduce the window period and to detect occult HBV carriage substantiating decades of clinical observation that HBsAg-negative/anti-HBc-positive blood could transmit HBV. Clinical observations suggest limited transmission rate of occult HBV compared to WP. Low transmission rate might be related to low viral load observed in OBIs or to the presence of mutants associated with occult carriage. OBIs carrying detectable anti-HBs ( approximately 50%) are essentially not infectious by transfusion. However, recent data suggest that the neutralizing capacity of low anti-HBs may be inefficient when overcome by exposure to high viral load. Anti-HBc blood units without detectable anti-HBs appear moderately infectious except in immunocompromised recipients. Immunodeficient elderly and patients receiving immunosuppressive treatments may be susceptible to infection with lower infectious dose even in the presence of anti-HBs. The immune status of blood recipients should be taken into consideration when investigating "post-transfusion" HBV infection. Pre-transfusion testing and post-transfusion long-term follow-up of recipients, and molecular analysis of the virus infecting both donor and recipient are critical to definitively incriminate transfusion in the transmission of HBV.

Blood donor screening with cobas s 201/cobas TaqScreen MPX under routine conditions at German Red Cross institutes

BACKGROUND

In 1997 the German Red Cross (GRC) blood donor services introduced mini-pool nucleic acid testing (NAT) for human immunodeficiency virus (HIV)-1, hepatitis C virus (HCV) and hepatitis B virus (HBV) to increase blood safety. With the new cobas s 201/cobas TaqScreen MPX, a fully automated extraction method and a multiplex amplification system specifically adapted to the needs of blood donation services is available.

METHODS

The cobas s 201 system was evaluated at the GRC BTS locations Hagen, Springe and Frankfurt. In phase A, the analytical sensitivity for the detection of HBV, HCV and HIV-1 was investigated and in phase B, at least 60,000 samples at each test site were screened in parallel with the MPX test on s 201 system and the existing routine mini-pool NAT system to compare the diagnostic specificity and the diagnostic sensitivity.

RESULTS

Comparable analytical sensitivities in a range of 1.6-3.6 IU/ml, 4.9-10.9 IU/ml and 14.7-26.6 IU/ml for HBV, HCV HIV, respectively, for the MPX test on s 201 system (95% probability based on probit analysis) were determined at all test sites. The diagnostic sensitivity was 99.8% and the diagnostic specificity was 99.85%.

CONCLUSIONS

The MPX test on s 201 system is a fully automated NAT system suitable for routine blood donor screening. The analytical sensitivity as well as the diagnostic sensitivity fulfilled all requirements of the Paul Ehrlich Institute for blood donor screening in mini-pools up to 96 donations per pool. A major benefit of the automated NAT system is the reduced personnel time and the extensive complete barcode-controlled process documentation.

Experience of mandatory nucleic acid test (NAT) screening across all blood organizations in Germany: NAT yield versus breakthrough transmissions

BACKGROUND

Mandatory nucleic acid test (NAT) blood screening was introduced in Germany in 1999 for hepatitis C virus (HCV) RNA and in 2004 for human immunodeficiency virus Type 1 (HIV-1) RNA. Minimal sensitivity limits of 5000 IU HCV RNA/mL and 10,000 IU HIV-1 RNA/mL were defined for the individual donation facilitating testing of minipools (MPs). The NAT yield obtained from all blood organizations is summarized. Transfusion-associated virus transmissions despite NAT screening ("breakthrough transmissions") are analyzed.

STUDY DESIGN AND METHODS

In Germany, a variety of NAT assays is applied for NAT screening pool sizes of up to 96 donations. Subsets of NAT yield cases were characterized with regard to viral loads by quantitative NAT and with regard to viral genotypes. Confirmed breakthrough transmissions were analyzed using different molecular and serologic assays.

RESULTS

Ninety-two HCV NAT yield cases among 40.8 million and 11 HIV-1 NAT yield cases among 17.1 million donations were identified. During this period, one transmission case was confirmed for HCV and one for HIV-1. The two incidents escaped NAT detection because of low-level viremia and/or suboptimal amplification efficiency. Evidence was obtained for a case of HIV-1 nontransmission by a low-level HIV-1 contaminated red blood cell unit.

CONCLUSION

NAT screening of MPs identified the vast majority of window-phase donations. A significant number of transmission cases was interdicted; breakthrough transmissions may still occur as rare events, even with individual-donation NAT in place. Sensitivity limits might be adapted to the current "state of the art" taking account of viral dynamics during early infection, incidence rates, and costs.

First transmission of human immunodeficiency virus Type 1 by a cellular blood product after mandatory nucleic acid screening in Germany

BACKGROUND

In February 2007, a 63-year-old man underwent surgery. Retrospective testing with nucleic acid testing (NAT) showed that the patient was human immunodeficiency virus Type 1 (HIV-1) positive 10 days after transfusion. The transfusion-transmitted infection had been identified by a donor-related lookback started in April 2007 after anti-HIV seroconversion.

METHODS

Sequence analysis was performed in the gag-pol region as well as in the V3 loop env region. Archived plasma from the transmitting donation was investigated for the individual-donation NAT with the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 test (Roche CAP/CTM HIV-1 test) and for HIV antigen/antibody combination testing (Abbott Architect). Additional testing was done on the donor's follow-up sample and on the recipient's sample.

RESULTS

The Roche CAP/CTM HIV-1 test failed to detect viral RNA by minipool NAT in the index donation (April 2007) as well as in the donation that caused the infection (January 2007). Phylogenetic analysis showed a very high genetic similarity among viral sequences from both donor and recipient, proving the HIV-1 transmission by sequence data.

CONCLUSION

This case represents the first documented HIV-1 transmission by transfusion of red blood cells after mandatory introduction of HIV-1 NAT for blood screening in Germany. Low viral load and mismatches in the primer/probe region might explain the detection failure of the NAT screening assay. A certain risk remains that new virus variants contain mutations at positions critical for amplification or detection of viral genomes. An option to reduce the risk of a detection failure by NAT is the simultaneous use of several conserved regions as amplification targets.

A novel diagnostic target in the hepatitis C virus genome

BACKGROUND

Detection and quantification of hepatitis C virus (HCV) RNA is integral to diagnostic and therapeutic regimens. All molecular assays target the viral 5'-noncoding region (5'-NCR), and all show genotype-dependent variation of sensitivities and viral load results. Non-western HCV genotypes have been under-represented in evaluation studies. An alternative diagnostic target region within the HCV genome could facilitate a new generation of assays.

METHODS AND FINDINGS

In this study we determined by de novo sequencing that the 3'-X-tail element, characterized significantly later than the rest of the genome, is highly conserved across genotypes. To prove its clinical utility as a molecular diagnostic target, a prototype qualitative and quantitative test was developed and evaluated multicentrically on a large and complete panel of 725 clinical plasma samples, covering HCV genotypes 1-6, from four continents (Germany, UK, Brazil, South Africa, Singapore). To our knowledge, this is the most diversified and comprehensive panel of clinical and genotype specimens used in HCV nucleic acid testing (NAT) validation to date. The lower limit of detection (LOD) was 18.4 IU/ml (95% confidence interval, 15.3-24.1 IU/ml), suggesting applicability in donor blood screening. The upper LOD exceeded 10(-9) IU/ml, facilitating viral load monitoring within a wide dynamic range. In 598 genotyped samples, quantified by Bayer VERSANT 3.0 branched DNA (bDNA), X-tail-based viral loads were highly concordant with bDNA for all genotypes. Correlation coefficients between bDNA and X-tail NAT, for genotypes 1-6, were: 0.92, 0.85, 0.95, 0.91, 0.95, and 0.96, respectively; X-tail-based viral loads deviated by more than 0.5 log10 from 5'-NCR-based viral loads in only 12% of samples (maximum deviation, 0.85 log10). The successful introduction of X-tail NAT in a Brazilian laboratory confirmed the practical stability and robustness of the X-tail-based protocol. The assay was implemented at low reaction costs (US$8.70 per sample), short turnover times (2.5 h for up to 96 samples), and without technical difficulties.

CONCLUSION

This study indicates a way to fundamentally improve HCV viral load monitoring and infection screening. Our prototype assay can serve as a template for a new generation of viral load assays. Additionally, to our knowledge this study provides the first open protocol to permit industry-grade HCV detection and quantification in resource-limited settings.