Available online at www.sciencedirect.com
Biologicals 37 (2009) 62e70
www.elsevier.com/locate/biologicals
Transfusion medicine and safety
Roger Dodd a,*, W. Kurt Roth b, Paul Ashford c, Elizabeth M. Dax d, Girish Vyas e
a
American Red Cross Holland Laboratory, 15601 Crabbs Branch Way, Rockville, MD 20855, USA
b
GFE Blut mbH, Frankfurt am Main, Germany
c
ICCBA, Inc, 1615 Orange Tree Lane, Ste 200, Redlands, CA 92374, USA
d
National Serology Reference Laboratory, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia
e
UCSF School of Medicine, San Francisco, CA 94143-0100, USA
Received 9 January 2009; accepted 9 January 2009
Abstract
Advances in safety of blood transfusion in clinical practice principally relate to preventing transfusion-transmitted infections (TTI).
Epidemiological studies of TTI have resulted in the development, standardization, and implementation of an expanding array of immunoassays
employed worldwide in routine screening of blood donated by voluntary blood donors. Exclusion of infected blood and their donors has
remarkably reduced the risk of transmitting HBV, HCV, HIV-1/2, and HTLV-I/II infections. Nucleic acid tests (NAT) using enzymatic amplification of viral gene sequences have augmented the risk reduction in ‘‘window period’’ infections that are undetectable by the serological tests.
Improved viral safety of transfusion therapy has led us to recognize the risk of bacterial contamination, especially in platelet concentrates stored
optimally at room temperature. Besides the current effort devoted to microbial risk reduction, pathogen inactivation technologies promise
reduction of the residual risk of known and emerging infectious agents. The clinical effectiveness of the foregoing measures, international
harmonization/standardization of practices and procedures, and continued hemovigilance portend safest possible safety in the clinical practice of
blood transfusion.
Ó 2009 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.
Keywords: Microbial risk in transfusion; Standards for transfusion safety; Virological screening assays; Hemovigilance
1. Bacterial contamination: are microbial tests the
ultimate solution?
Roger Y. Dodd (dodd@usa.redcross.org)
For a number of years, bacterial contamination of platelets,
with resultant sepsis in the recipient, has been recognized as
the most frequent severe infectious outcome of transfusion. As
a result, there has been widespread adoption of methods to
detect bacteria in platelets, at least in developed countries.
Apheresis platelets and prestorage pooled platelets are most
often tested using automated or semi-automated blood culture
devices, while individual whole-blood derived platelets may
* Corresponding author.
E-mail address: dodd@usa.redcross.org (R. Dodd).
be tested using ineffective surrogate methods, such as pH
determination or measurement of glucose levels.
Current data suggest that, while testing for bacteria has
reduced the incidence of posttransfusion sepsis, it has by no
means eliminated it [1]. Encouraging data from a number of
different hemovigilance programs have indicated that the
addition of methods to divert the first portion of collected
blood to a sampling pouch also significantly decreases the
incidence of residual sepsis attributable to skin bacteria [2].
Further, there are some data suggesting that further improvements may be attained by using iodine-based skin-preparation
methods.
An area of some controversy is the extent to which anaerobic cultures enhance blood safety. While there are only
a small handful of cases in which obligate anaerobes have
been definitively linked to transfusion sepsis, there are data
that show that selected aerobes may grow more readily in
1045-1056/09/$36.00 Ó 2009 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.biologicals.2009.01.006
R. Dodd et al. / Biologicals 37 (2009) 62e70
anaerobic bottles. It remains unclear whether the addition of
an anaerobic bottle increases sensitivity by this mechanism or
by the increased sample volume inherent in this approach, or
indeed, by the additive effect of both. Nevertheless, in the
United States, the regulator briefly permitted extended platelet
storage for up to 7 days only if culturing was performed with
both aerobic and anaerobic bottles. Additional surveillance for
breakthrough contamination was also required.
A number of manufacturers have been developing test
methods that do not depend upon the detection of bacterial
growth in culture. These methods generally detect bacteria in
the platelet concentrate at relatively high levels (i.e. 104 or
more cfu/mL) and are intended for use shortly before the
infusion of the platelet product. One such method has recently
(2007) been approved for use in the US, but only as an adjunct
to existing culture methods [3]. It is hoped that approved
product claims will shortly be extended to cover standalone use of these procedures. Most are based upon rapid
immunologic detection of bacteria.
Because all methods for the detection of bacterial
contamination have some limitations, there is growing interest
in other approaches to assure bacterial safety. Three possible
approaches have been considered; cold-stored platelets,
platelet substitutes and pathogen reduction techniques [4].
Initial enthusiasm for cold-stored platelets was high, based
upon studies suggesting that the cold-lesion could be reversed
by simple galactosylation of the platelet membrane, but this
approach was subsequently shown to be flawed. Although
there has been some success in developing so-called platelet
substitutes, it appears that they are unlikely to be available in
the foreseeable future.
In contrast, significant progress has been made in the
development of pathogen reduction technologies for platelets.
Indeed, one such method, based upon a synthetic psoralen, is
available and in use in parts of Europe. The method has been
shown to readily inactivate the levels of relevant bacteria that
are present in platelets around the time of their preparation. A
second approach, based upon the use of riboflavin as a photoinactivating agent is also under development and also appears to
have the potential for assuring bacterial safety.
Thus, in summary, although a number of methods for the
detection of bacteria in platelets exist and are in use, they do
have disadvantages and none seems to assure complete safety.
However technology is currently available that has the ability
to inactivate bacteria and it seems likely that the eventual
adoption of such methods may supplant testing.
2. Future perspectives to achieve a safe blood transfusion
W. Kurt Roth (kurt.roth@gfeblut.de)
During the past decades blood transfusion safety steadily
and rapidly increased, mainly driven by new technological
achievements. However, many other factors and developments
had a significant impact on blood safety. As in early days, it is
still the individual blood donor who determines whether
a recipient gets infected by transfusion or not, although the
risk in total has significantly decreased worldwide. Main
63
determinants for a safe blood donor are: epidemiology, socioeconomic conditions, public awareness and acceptance, donor
education, donor selection (no remuneration, no risk areas,
voluntary donors only, etc.), repeat donors, staff training and
education, and donor testing. The epidemiology of infectious
diseases in a given country or region has the most important
impact on blood safety. New transfusion transmissible agents
for which initially no tests exist are emerging, re-emerging or
conquering new regions in the world, like HIV, SARS, West
Nile virus, or chikungunya virus. In addition, there is still too
high a number of countries where donor testing for the most
relevant infectious agents like HIV, HCV or HBV is not fully
affordable. Many of these countries also suffer from a high
prevalence of additional transfusion transmissible agents with
severe consequences like malaria, dengue and others, without
access to adequate tests. Moreover, the socio-economic
conditions in some countries do not allow a sufficient blood
supply to fit the medical needs. In many countries, the public
awareness and acceptance of donating blood need to be
improved in conjunction with donor education and selection.
Donor remuneration and directed donations need to be
replaced worldwide by populations of voluntary donors, who
should be well educated in order to increase the percentage of
repeat donors. Without staff training and education the latter
cannot be achieved. Above all, adequate testing at the highest
technological standards is the ultimate goal to achieve an
acceptable residual risk, i.e. at the lowest possible level.
2.1. Recent developments
Nucleic acid tests (NAT)
Antibody/antigen combo tests
Bacteria testing
Component filtration
Apheresis
Inactivation
One of the most important technological achievements in
the past decade was the introduction of NAT in routine blood
donor testing. Because of the challenging technology and high
costs it was first introduced in developed countries where the
existing low transfusion risk for infectious diseases was
additionally reduced by a factor of ten. However, developing
countries with a high prevalence of certain infectious diseases
such as HBV may consider adopting this new technology
because they would discard too many precious antibody
positive, virus negative donations if they would rely on antibody testing only. This was enabled by the most recently
introduced fully automated test systems that smoothly integrate into routine testing facilities. In the near future, more
different systems will be available and prices will go down
significantly when patents on HCV and real-time PCR expire
(2011).
Especially for developing countries, the recently introduced
antibody/antigen combo assays will be an alternative to NAT
since they reach similar sensitivities but can be run on the
64
R. Dodd et al. / Biologicals 37 (2009) 62e70
standard immunoassay platform with similar or only marginally increased costs.
Testing for bacteria has moved into the focus in transfusion
medicine after the risk of viral contamination was reduced by
NAT to almost zero. However, testing at sufficiently high
sensitivity is a challenging task even for NAT. And culture
methods, which are already in routine use in some countries,
suffer from very late results (3e10 days after inoculation).
Component filtration and apheresis contribute to a reduction
of intra-cellular infectious agents, which may be especially
relevant for CMV and in the near future for vCJD. Testing for
vCJD may also contribute to a significant risk reduction as soon
as sensitive tests become available. Some test formats have
been examined in the UK. However, current inactivation,
procedures, which are an efficient alternative to testing for
viruses, bacteria, and parasites, will not work with vCJD. Many
studies of pathogen inactivation have been conducted which
prove the efficicacy and absence of toxicity or mutagenicity.
Although it would be a good alternative to testing because of its
broad range of efficiency, especially for developing countries,
costs are still too high to be introduced broadly.
2.2. Future developments
It is foreseeable that in the very near future the spectrum of
NAT will be increased and fully automated systems will be
available for nearly any kind and size of blood transfusion
service. In addition, testing with combo tests will increase
especially in developing countries where they can be used
instead of NAT and stand-alone antibody tests. Total lab
automation is already at the horizon and first systems are
running in routine diagnostic laboratories. Inactivation may
come into routine when costs go down. This may compete
with new technological developments like bio-chips, micro
arrays, cycler on a chip, lab on a chip, which all suffer from
low sensitivity because of the low sample volume (nano liter)
that can be applied. The same holds true for other single
molecule analytic systems like MALDI-TOF and derivatives.
Alternatives to allogenic blood transfusions would revolutionize blood transfusion medicine and significantly contribute
to increase transfusion safety. These comprise, to smaller
extent, blood-saving measures like intra-operative cell salvage,
as well as blood substitutes like artificial oxygen carriers or in
vitro stem cell derived blood components. Transfusion medicine would no longer rely on blood donors at least at high
numbers. Donor recruitment in the face of aging donors and
reduced willingness to donate blood by the younger population
would not pose problems and infectious diseases could no
longer be transmitted from donor to recipient. Safety of blood
substitutes relies on good manufacturing and clinical practice
only.
It is difficult to foresee which methods, developments or
technologies will be introduced and how rapid and significant
blood safety will be affected. NAT has shown that sometimes
new technologies may enter transfusion practice very rapidly
and unexpectedly.
3. ISBT 128 e improving safety by International
Standardization
Paul Ashford (paul.ashford@iccbba.org)
Standardization of information provides significant benefits
in terms of safety and efficiency in the fields of blood transfusion, cellular therapy, and tissue transplantation. All of these
activities are global in scope, both in terms of their widespread
application, and because in specific circumstances donor and
patient may be located in different parts of the world.
Ensuring the accurate, clear and unambiguous transfer of
information is a critical element of the patient safety agenda.
Standardization of both the information and the mechanisms
by which the information is transferred provides a means of
eliminating many of the most error prone steps.
Benefits that can be achieved include:
eliminating the risk of duplicated donation numbers by
providing a globally unique donation identification
number;
providing clarity on product composition by building clear
and unambiguous definitions through an international
consensus process;
overcoming language barriers by the use of an international product database, linked to coded information,
which can be readily translated;
elimination of the need for re-labeling products by using
standardized label design and content;
reduction of costs as instrument manufacturers can build
to a global standard and do not need to provide significant
re-engineering to meet local requirements.
Recognizing the significant benefits of standardization, the
International Society of Blood Transfusion undertook the
development of the ISBT 128 information standard. The
objective of ISBT 128 is to provide a standard information
environment that will support the open movement of blood,
tissue and cellular therapy products around the world in such
a way that critical information is rapidly, accurately and
unambiguously communicated, and to do so in such a manner
that the various regulatory requirements for traceability and
retention of information can be supported.
What is an ‘Information Environment’? Most of us are
familiar with the information printed on product labels, and
have seen and may use barcodes, but may be unaware of the
underlying elements that support this information.
The information environment can be described as a five
layer model as shown in Fig. 1. The model is built up from the
bottom, and each level will be described.
At the base lie the Definitions. It is essential to ensure that
there is clarity over the meanings of the various terms used in
describing products, tests, donor and donation characteristics.
What do we mean by the term ‘Leucodepleted’? This may
seem obvious at first glance, but there are, in fact, many
different interpretations used around the world depending on
the acceptable level of residual leucocytes. In an international
context the term leucodepletion has to be qualified with the
R. Dodd et al. / Biologicals 37 (2009) 62e70
Fig. 1. e The information environment 5 layer model.
level of residual leucocytes to ensure the meaning is
unambiguous.
The production of an international dictionary provides
a way of ensuring a common understanding of the information
itself. A major breakthrough in the cellular therapy field
has been the publication of a new international standard
terminology for CT products [5].
Once definitions have been agreed, then it is possible to
start building the reference tables, which provide the key
lookup for the standard. These tables provide the mapping
from the verbal description that is understood by users of the
system, to the alphanumeric codes used in computer systems
and electronic information carriers such as barcodes.
The reference tables ensure consistent interpretation of the
coded information across multiple platforms. Because of the
rapidly changing transfusion and transplantation environment,
these tables need to be flexible and readily updated within
a strictly managed process.
The next level is described as the ‘Data Structures’. These
are only really of interest to the software developers who write
or read ISBT 128 information, but they are an essential
element as they provide the context for each piece of information, and prevent erroneous interpretation.
To illustrate this point the following example is used. The
piece of information ‘19551015’ describes something about
a patient, but without a context it is of no value. It could be
their social security number, postcode or even bank account
number. If an assumption was made about its meaning, it may
be right, but it would more likely be disastrously wrong. In
particular, if a system were expecting it to be a particular piece
of information (such as the SSN) but did not have a means of
confirming this it could wrongly identify the patient with
serious consequences.
Context is therefore an essential part of information transfer. Once the context is provided, in this case, the information
that this is a date of birth in YYYYMMDD format, then it is
immediately possible to clearly and unambiguously interpret
the data.
The final layer of the model is the Labeling layer. Labeling
provides the means of physically attaching the information to
the product, and for presenting the human readable interpretation of the information.
65
ISBT 128 applies some basic labeling requirements,
including the ‘four quadrant’ label model, and the relative
positions of key barcodes, but allows sufficient flexibility to
accommodate the differing regulatory requirements of
different countries.
A critical element of the labeling strategy is to ensure
consistency between information stored in electronic format
and that which is human readable on the label. Demand
printing of bar coded labels can achieve this as both sets of
information are printed at the same time.
So what is ISBT 128 and where does it fit into the information environment model?
ISBT 128 is information standard, which was developed by
the International Society of Blood Transfusion (ISBT) in the
aftermath of the 1991 Gulf War. During this conflict, blood
from many countries was sent to the region and lack of standardized coding and labeling caused significant difficulties in
ensuring its safe use and appropriate traceability.
The standard was first published in 1994 and the earliest
national implementation was in Estonia 1996. In 2000, the
standard was extended to support Tissues and Cellular
Therapy products.
ISBT 128 defines the lower three layers of the model, the
Definitions, Reference Tables and Data Structures. It defines
the way in which Code 128 barcodes are used on product
containers, and it provides basic labeling requirements plus
additional guidance information.
The key elements of ISBT 128 are as follows:
A donation numbering system that ensures global
uniqueness over a 100-year period.
A standard set of data structures that allow independent
systems to communicate via ISBT 128 securely and safely.
An international product database, based upon a dictionary
of well defined terms that clearly and unambiguously
describes and codes products.
Structured formats for other critical information including
blood groups, expiration dates, HLA profiles, etc.
A mechanism, through Technical Advisory Groups with
strong user input, to maintain and develop the standard to
meet future needs.
The Donation Identification Number is built up of four
elements. It commences with the Facility Identification Code,
which is centrally assigned and will be described in more
detail later. A nominal year indicator provides the uniqueness
over a 100-year period. The sequence number is assigned by
the facility to each unit collected in the year. Flag characters
provide a means for improved process control but will not be
discussed further in this presentation. The boxed character at
the end is used to verify correct manual entry.
Facility Identification Codes are assigned by ICCBBA to
collection facilities at the time of registration and licensing.
All numbers used by a facility must commence with one of its
assigned Facility Identification codes and this provides
a means for tracing any product to its originator. ICCBBA
maintains a register of these codes and a means for lookup.
66
R. Dodd et al. / Biologicals 37 (2009) 62e70
The manual entry check character printed at the end of each
donation identification number is used to verify correct manual
entry where this is required.
Manual entry is prone to error, particularly transposition of
characters, and whilst manual entry should be avoided
whenever possible, occasions do arise when its use is essential.
In such circumstances the manual entry check character
provides a means of verifying correct entry.
ISBT 128 Product Codes are linked to an international
database of product descriptions underpinned by clear definitions. This ensures that the characteristics of a product can
be unambiguously presented regardless of the source of the
product. Information is presented in a structured format
using the concepts of component class, modifiers and
attributes.
The product code reference table can be downloaded from
the ICCBBA web site by licensed vendors and used to populate reference tables in their software.
National bodies can determine the subset of ICCBBA
product codes to be used in a particular country, and can provide
approved translations of descriptions into the local language.
ICCBBA maintains the database and has a simple system
for the assignment of new codes on request. The product
database is regularly updated and new versions are published
on the web site.
Many other important pieces of information are supported
within the standard including:
ABO/Rh D type
Expiration Date and Time
Collection Date and Time
Special Testing codes
Red Cell Phenotypes
Platelet Specific Antigens
HLA Phenotypes
HLA Genotypes
Blood Pack Manufacturer Code and Catalogue Number
and Lot Number
Manufacturer Code and Catalogue Number and Lot
Number for other items (filters, irradiation indicators, etc.)
Donor Identification Number
Staff Identification Number
Most importantly, mechanisms are in place to create new
structures, as they are required to meet changes in clinical
practice.
ISBT 128 defines basic rules for labeling blood components. These include the ‘four quadrant’ model, which assigns
specific purposes to each quadrant of the label:
Upper left quadrant holds the donation identification
number
Upper right quadrant holds blood group and donation
status information
Lower left quadrant holds the product description
Lower right quadrant holds expiry information and other
information codes.
The sample label in Fig. 2 shows the positioning of the four
mandatory barcodes.
ISBT 128 usage is growing rapidly with more than 3300
licensed facilities worldwide, processing an estimated 30 million
donations per annum. ISBT 128 is now used extensively for
labeling blood in Europe and the Middle East. In North America,
there has been intense activity in order to achieve the AABB
requirement for implementation of ISBT 128 by May 2008.
China has ISBT 128 operational in two provinces (Shanghai
and Zhejiang) and the standard has been implemented in
Singapore. Implementation is in progress in Macau. The
Australian National Blood Authority has recently confirmed
that ISBT 128 will be used for coding and labeling blood in
Australia. ISBT 128 is also used by some facilities in Brazil.
Many other countries are commencing, or have committed
to, the introduction of ISBT 128 for blood components.
Following the publication of new standards for the terminology and labeling of cellular therapy products, implementation of ISBT 128 is progressing in many countries.
Work is also progressing on the international adoption of
ISBT 128 for Tissue products, with some European countries
already using the standard.
New developments in coding technologies and patient care
are kept under constant review by ICCBBA. Areas of particular interest at the current time are the use of 2-Dimensional
(2-D) or Reduced Space Symbology (RSS) codes which can
hold more information in a much smaller space than linear
barcodes and radio frequency identification (RFID) tags that
have the benefit of not requiring ‘line of sight’ access to read.
New data structures to support improved bedside identification
have also been developed.
ICCBBA is the organization charged with the management
and protection of the ISBT 128 Standard. The mission of
ICCBBA is to enhance safety for patients by managing the
ISBT 128 international information standard for use in transfusion and transplantation.
ICCBBA is a non-profit organization that is funded entirely
by the license fees paid by collection facilities and vendors. It
is responsible for the development and maintenance of the
standard including the assignment of new codes, for providing
technical and educational support, and for promoting the
international adoption of the standard.
Further information on the standard and ICCBBA is
available from the web site at www.iccbba.org.
4. Screening assays for viral infection: are we satisfied
with their performances, globally?
Elizabeth M. Dax (liz@nrl.gov.au)
4.1. Threats to safety from transmission of infection
Screening assays for the major transfusion transmissible
infections (TTIs) have been implemented in most transfusion
services. Threats to blood safety from transmissible infections are
obvious only in low human development index (HDI) countries
where assays are not available or only inappropriate assays are
R. Dodd et al. / Biologicals 37 (2009) 62e70
67
Fig. 2. e A standard ISBT 128 label layout.
available as a result of poor regulation. Transmission in systems
that screen for all TTIs with assays of very high sensitivity and
specificity, occurs only when donors who are infected and have
not sero-converted or when donors have viral loads that are below
detectable limits or when there are a series of human errors [6].
Human errors have been severely curtailed with the introduction
and implementation of quality management systems. However,
such systems may not be present in blood services of medium to
low HDI countries. There, the threat of transmission to blood
safety may be aggravated by the threat of poor management over
and above the threat imposed by poor or inadequate assays and
their inherent performance characteristics [7].
4.2. Are TTI assays performing satisfactorily, globally?
The major subject of this paper was to offer the evidence
on whether assays used to screen blood donations are performing at the expected levels and whether they continue
to do so. Further, it was asked, ‘‘Is this true across all
transfusion facilities across the globe?’’ The answer to the
question posed for the present paper is undoubtedly, ‘‘That
well-appointed screening assays for viral diseases do yield
highly satisfactory performances when used in facilities
where effective quality management is implemented.’’
However, caveats still exist.
4.3. Screening assays
The first-used assays were immunoassays which detected
either antibody or antigen for human immunodeficiency virus,
hepatitis C and B viruses and syphilis as well as other infections
that may be endemic. Nucleic acid testing for some infections
and in some countries has been implemented to assure that early
infections are detected; i.e. before detection antibody develops
[6]. Where screening tests or assays used for detecting transfusion transmissible infections have been implemented, the
transmission of these infections has been brought to extremely
low levels. Transmission may only occur from 1 in 100s of
thousands to 1 in millions of transfusions [8e10]. Nevertheless,
in some parts of the world, the efficacy of screening programs
is jeopardized not only by poorer quality tests and testing
but by lack of quality management of donation testing. This
lack of quality management may extend from the governmentregulatory level to performances in individual blood service
laboratories. Therefore, until all screening is performed in
quality-managed programs and facilities, we cannot say that we
are satisfied fully with screening performances globally.
R. Dodd et al. / Biologicals 37 (2009) 62e70
68
4.4. Evidence for satisfactory screening assay
performances
Evidence for the satisfactory performances of screening
tests may be drawn from several sources. The risk of transmission of TTIs can be extremely low [8,9]. Evaluation of test
kits on national levels and conducted by reputable institutions
is a good indicator that a test is likely to perform satisfactorily.
However, evaluations are conducted at a point in time. They
cannot account for any ongoing or sporadic manufacturing
glitches or for damage inflicted on kits during transport, for
example. Therefore, some countries have instituted batch
checks either at the central level (e.g. FDA in the United
States) or regulate that each batch should be validated before
use (Code of GMP [cGMP], Australia). Quality assurance
practices such as External Quality Assessment Schemes
(EQAS) and quality control (QC) monitoring can assist in
following the performances of kits during use. Manufacturer
recalls are not helpful on an ongoing basis because they are
retrospective. Most companies which manufacture under
cGMP are vigilant about their batch controls, but it is the duty
of the customer to ask for some proof of batch integrity.
4.5. Evaluations and/or validations of assays
Assessment of tests’ performances before institution into
a screening program is a mandatory requirement of quality
management standards and guidelines. If a full and valid
evaluation is to be carried out, a repository of known positive
and negative samples is required for the assessment. This is
a resource-intensive requirement and one that may not be
available in many countries or blood safety systems. To
establish an assay’s performance it is necessary to have
sufficient samples available to yield statistically valid estimates of parameters for the assay’s performance including
sensitivity, specificity, precision, seroconversion sensitivity,
reproducibility. Manufacturers should produce results of their
evaluations (often called validations by manufacturers) on
request. Similarly, they should be able to direct their
customers to any independent evaluation results. While it is
a manufacturer’s obligation to inform its customers; it is the
customer’s obligation to ask for this information. It is notable
that assay kits’ manufacturers conducting production under the
code of GMP are more likely to produce kits of acceptable
quality from companies that do not conform. If resources are
not available within a national transfusion system to perform
evaluations, screening should not proceed without validation
of the assays to be used. WHO has produced a series of papers
on prequalification of test kit performances which can be used
as a guide against which performances may be verified [10].
Having emphasized requirements for evaluations, it is
notable that there are relatively few evaluations available of
sufficient quality and scale. This may be because the production
of such information is so resource intensive. In Australia, to
evaluate fully an assay for blood screening, 200e300 positive
samples, 8e10 thousand negative samples, seroconversion
panels, etc. may be tested with 3 batches or lots, which are also
used to assess reproducibility and precision. It may cost from
AUD1-150 per mL to procure and characterize a sample and up
to 10,000 samples may be required for assessing kits for
a country or region. The labor resources and training requirements are also extensive, not to mention the logistics for
organizing the tests, trainers and training, operators, other
reagents, appropriate documentation and equipment; all to be
located suitably. Furthermore, appropriate quality management
procedures including quality control materials need to be
established for the evaluation. Therefore, the estimated cost for
a full scale quality evaluation may exceed AUD150,000 or even
AUD200,000. Evaluations not only have advantages of offering
understanding tests performances but also they familiarize
personnel with the methods. Thus, the costs must be weighed
against the costs of transmission should flaws in performances
of the tests in use not have been recognized. An example of
evaluation results by the NRL, Australia is shown in Table 1.
4.6. Quality assurance programs
There are several methods used to check quality managed
systems and to assure quality in screening tests or assays used in
blood service laboratories. They are encompassed principally in
EQAS, QC programs, assessing quality management outcomes
and others including the monitoring of assay specificity [7].
In NRL’s EQAS results in 2004e2005, the overall error
rates, i.e. the number of incorrect test interpretations expressed
as a ratio of the total reported interpretations, for HIV and
HCV assays were similar in the anti-HIV EQAS and the antiHCV EQAS at 1.6% and 1.4%, respectively [7]. Breakdown of
the errors as falsely reactive or falsely negative was different.
False reactive results for anti-HIV and anti-HCV were 85.9%
vs 60.7%, whereas the false negative rates were 14.1% and
39.3%, respectively [7]. This suggested that the more serious
error rates were higher in central laboratories outside Australia
Table 1
Characteristics of HIV e Combo Assays evaluated at the National Serology Reference Laboratory, Australia. The delta value describes the removal of the positive
(þdelta) or negative (delta) sample results from the cutoff in standard deviations when the results are each expressed as log10[S:CO].
Assay
Estimated sensitivity % (þdelta value)
Estimated specificity % (delta value)
Ortho Vitros anti-HIV-1 þ 2
Abbott AxSYM HIV Ag/Ab Combo
Murex HIV Ag/Ab Combo EIA
BioRad Access HIV-1/2 NEW
BioRad Genscreen HIV Ag/Ab
100
100
100
100
100
99.85
99.96
99.78
99.84
99.81
a
Tested in blood donations (BD).
95%CI
95%CI
95%CI
95%CI
95%CI
98.60e100.0 (þ13.11)
96.90e100.0 (þ10.85)
97.00e99.90 (þ8.09)
97.0e99.9 (þ6.46)
97.0e100.0 (þ18.35)
(95%CI 99.67e99.93) (10.65)
(BD)a (95%CI 99.80e100.0) (11.74)
(BD) (95%CI 99.88e99.59) (4.60)
(BD) (95%CI 99.55e99.95) (4.78)
(BD) (95%CI 99.62e99.91) (5.93)
R. Dodd et al. / Biologicals 37 (2009) 62e70
69
outcomes for testing. There continues to be the need for significant effort to elevate the quality of laboratory performances.
9
8
7
Error
rates (%)
6
5. Hepatitis viruses and blood transfusion: lessons from
the past
5
4
Girish Vyas (girish.vyas@ucsf.edu)
3
2
5.1. Viral hepatitis and evolution of transfusion safety
1
0
HBV
HCV
HIV
HTLV
Virus
Fig. 3. - In External Quality Assessment Scheme results the error rates are
typically around 1e2%. In 2006e07 the error rates for HBV testing in the
Asia-Pacific region were nearly 8%. This rate could be attributed to the use of
HBsAg screening tests with inadequate sensitivity because samples with low
antigen concentrations were not identified.
compared with all testing laboratories within Australia. (HIV
and HCV testing in Australia is highly regulated.) For HBV
testing, the error rates were nearly 8% (Fig. 3).
The high error rate reflected the inadequate sensitivity of
some HBsAg tests used in the Asian region. So in this case, the
global performance of all HBV tests did not meet sensitivity
requirements.
In April 2007, the NRL distributed EQAS panels to 204
laboratories in 34 countries. (Not all laboratories were blood
service laboratories, but the participants are all in more central
laboratories.) Results were received from 193 participants and
each had received 10 samples so that there were 1930 results.
Seven participants were using expired kits, 22 samples received
the wrong interpretation of the results and 11 delivered the
wrong final result. Thirty five results were outlying (Tukey’s
filter test). Thus, it would appear that, even recently, mistakes do
occur and quality management principles are violated.
4.7. QC program results
The use of quality controls, i.e. the same sample assayed
independently of the kit controls, will enable an ongoing
assessment of precision. Comparison between laboratories of the
same sample’s results used in the same testing system allows the
assessment of an assay’s ongoing accuracy. NRL has conducted
a QC program delivering standardized samples for inclusion in
serological and nucleic acid based assays for several years.
Overall the performances of the assays are precise and accurate.
However a series of problems have been identified such as
pending instrument failures, pipetting carryover, batch differences, operator errors or lack of competency. Conversely the data
have been used to confer integrity on testing performances where
there has been a possibility of failure kit integrity across laboratories, as opposed to difficulties in a single laboratory.
4.8. Conclusions
The data support the high integrity and satisfactory performances of test kits globally. They do not support best practice
Since the inception of blood transfusion in clinical practice,
multiple risks have been recognized and measures to eliminate
them continue to evolve. The most major risk of posttransfusion
hepatitis (PTH) was clinically recognized among 20e25% of
transfusion recipients prior to 1970. Thus, viral hepatitis, PTH,
and transfusion safety became the principal research endeavor
when I was appointed as the Director of Blood Bank at UCSF
Medical Center, San Francisco in 1969 [11]. Routine screening
of donated blood for hepatitis B virus (HBV) surface antigen
(HBsAg, originally termed Australia antigen), simultaneously
with blood donations accepted only from healthy voluntary
blood donors, led to PTH declining to 3e5% among transfusion
recipients in mid-70s. The remainder of the PTH was enigmatic
and categorized as non-A, non-B (NANB) hepatitis after
eliminating known etiologies of Hepatitis A or B viruses.
The discovery of hepatitis C virus (HCV) by molecular
methods and introduction of serological screening tests for antiHCV in the early 1990s rapidly led to virtual elimination of PTH
[12]. In the meantime, blood products, especially factor VIII
transmitting AIDS to hemophiliacs in early 1980s, led to an
unprecedented public concern about safety of blood and blood
products. Thanks to the 1984 discovery of HIV-1 as the etiology
of AIDS, serological screening of donated blood with anti-HIV
enzyme immunoassay (EIA) was introduced in 1986. The
milestones in eliminating PTH and HIV are shown in Fig. 4.
Routine screening of donated blood for anti-HBc was
initiated in Europe and U.S.A. to further enhance transfusion
safety. Screening of donated blood for anti-HBc has been
1966:
1968:
Discovery of the Australia Antigen.
Recognition of the HBV viremic(HBsAg)
state.
1970:
Introduction of HBsAg testing.
1978:
Recognition of NANB hepatitis as a clinical
entity.
1980-90: NANB surrogate (ALT, and/or anti-HBc)
testing.
1988:
HCV recognized.
1990:
Anti-HCV (1.0) testing introduced.
1999:
Minipool NAT testing for HIV and HCV
introduced.
2000:
Residual risk of HBV again enunciated
(~1:50,000).
Fig. 4. Chronology of transfusion safety improvement beginning with
screening for HBV.
R. Dodd et al. / Biologicals 37 (2009) 62e70
70
Risk per Unit
Transfusion
Transmission Rate
Window Period
HIV 1&2
1:2,135,000
90%
11 days
HCV
1:1,935,000
90%
10 days
HBV
1:205,000
70%
59 days
HTLV
1:3,000,000
30%
51 days
WNV
1:10,000 to 1,000
(prior to NAT)
Unknown
-
Parvo B19
1:40,000 to 3,000
Low
-
1:1,000,000
Low
-
Virus
Hepatitis A/E
Fig. 5. Contemporary risk of transmitting any of the blood-borne viruses for which screening is performed. [Transfusion: 2002; 42: 975e979].
justified because (A) anti-HBc is a specific marker of HBV
infection and occult persistence of HBV is recognized [11e
13], (B) HBV DNA is detectable in 1e3% of HBsAg-negative/anti-HBc-positive blood transmitting HBV infection
[14,15], (C) among gay men with AIDS the occurrence of high
incidence anti-HBc (84%) correlated with circulating immune
complexes (76%) [16].
Besides the host immune response to the blood-borne viral
infections serologically screened by EIA for viral antigens/
antibodies, the discovery of gene amplification technologies in
1990s led to direct testing for presence of viral nucleic acids.
Introduction of NAT in routine screening of blood supply has
resulted in virtual elimination of any blood-borne viral infection from transfusion. The time between a viral infection
occurring in a donor and an EIA test detecting the infection is
termed ‘‘window period’’. NAT has narrowed the window
period infections present in donated blood. The evolution of
unprecedented safety of blood transfusion accomplished in the
economically advanced nations in Americas, Europe, Japan,
and Australia is summarized in Fig. 5. However, similar
degree of transfusion safety is desirable but economically not
feasible in many nations of Africa, Asia, and South America.
The International Symposium on Viral Hepatitis and Liver
Disease (ISVHLD), originally convened in 1972 at the
University of California, San Francisco (UCSF), was focused
on blood transfusion. These triennial ISVHLD symposia are
now broadened in their scope and convened in different
continents for the contemporary assessment of advances in
virology, immunology, epidemiology, prevention, and treatment of hepatitides AeE. Similarly, in 1999, UCSF initiated
the symposium on Advances in Transfusion Safety (ATS)
under the aegis of the International Association for Biological
Standardization (IABS). The success of the biennial ATS
symposia is to be assessed for its educational effort in
advancing transfusion safety worldwide.
Acknowledgements
The financial support of the NRLs EQAS in Asia by World
Health Organisation, Essential Health Technologies Branch,
Geneva and also by the Australian Agency for International
Development (AusAID) are acknowledged. The NRL also
acknowledges with gratitude, the ongoing and efficient
participation of laboratories that test for TTIs across Australia,
Asia and in other parts of the world.
References
[1] Eder AF, Kennedy JM, Dy BA, Notari EP, Weis JW, Fang CT, et al.
Bacterial screening of apheresis platelets and the residual risk of septic
transfusion reactions: the American Red Cross experience (2004e2006).
Transfusion 2007;47:1134e42.
[2] de Korte D, Curvers J, de Kort WL, Hoekstra T, van der Poel CL,
Beckers EA, et al. Effects of skin disinfection method, deviation bag, and
bacterial screening on clinical safety of platelet transfusions in the
Netherlands. Transfusion 2006;46:476e85.
[3] http://www.fda.gov/bbs/topics/NEWS/2007/NEW01702.html.
[4] Webert KE, Cserti CM, Hannon J, Lin Y, Pavenski K, Pendergrast JM, et al.
Proceedings of a Consensus Conference: pathogen inactivation-making
decisions about new technologies. Transfus Med Rev 2008;22:1e34.
[5] Ashford P, Distler P, Gee A, Lankester A, Larsson S, Feller I, et al.
Standards for the terminology and labeling of cellular therapy products.
Transfusion 2007;47:1319e27.
[6] Wendel S. Rational testing for transmissible diseases. ISBT Sci Ser 2007;
2:19e24.
[7] Dax EM, Walker S. Advances in quality assurance of laboratory testing
for transfusion safety. In: Dax EM, Farrugia A, Vyas G, editors.
Advances in transfusion safety e vol. IV. Dev Biol (Basel). Basel,
Karger 2007;127:183e95.
[8] Busch MP. Evolving approaches to estimate risks of transfusion transmitted viral infections: incidence-window period model after 10 years.
In: Dax EM, Farrugia A, Vyas G, editors. Advances in transfusion safety
e vol. IV. Dev Biol (Basel). Basel, Karger 2007;127:87e112.
[9] O’Brien SF, Yi QL, Fan W, Scalia V, Kleinman SH, Vamvakas EC.
Current incidence and estimated residual risk of transfusion-transmitted
infections in donations made to Canadian blood services. Transfusion
2007 Feb;47(2):316e25.
[10] World Health Organization. HIV test kit evaluations. Available from:
http://www.who.int/diagnostics_laboratory/evaluations/hiv/en/.
[11] Vyas GN. Participating in the evolution of transfusion medicine from
a dispensary into a discipline. Transfus Med Rev 2008;22:162e7.
[12] Alter HJ, Klein HG. The hazards of blood transfusion in historical
perspective. Blood 2008;112:2617e26.
[13] Vyas GN, Perkins HA. Non-B posttransfusion hepatitis associated with
hepatitis B core antibodies in donor blood. N Engl J Med 1982;306:749e50.
[14] Reesink HW, Engelfriet CP, Henn G, Mayr WR, Delage G, Bernier F, et al.
Occult hepatitis B infection in blood donors. Vox Sang 2008;94:153e66.
[15] Silva CM, Costi C, Costa C, Michelon C, Oravec R, Ramos AB, et al. Low
rate of occult hepatitis B virus infection among anti-HBc positive blood
donors living in a low prevalence region in Brazil. J Infect 2005;51:24e9.
[16] Anderson RE, Winkelstein W, Blum HE, Vyas GN. Hepatitis B virus
infection in the acquired immune deficiency syndrome (AIDS). In:
Vyas GN, Dienstag JL, Hoofnagle JH, editors. Viral hepatitis and liver
disease. Orlando: Grune & Stratton; 1984. p. 339e43.