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Donation testing and Transfusion Transmissible Infections

JOURNAL CLUB PRESENTATION

by:

Dr Che Nurul Ain

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ISBT Science Series, section 10

Original authors: Leesha Roman, Beryl Armstrong & Elizabeth Smart
Reviewer for Second Edition: So‐Yong Kwon

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Introduction

The accurate testing of blood donations plays a vital role in the provision of safe blood for transfusion.

This section covers testing that should be carried out on every unit of blood donated

All donations should be routinely tested for the ABO and Rh blood groups, screened for red cell antibodies and should be tested for transfusion transmissible infections (TTIs) including the human immunodeficiency virus (HIV), hepatitis B and C and syphilis

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Transfusion transmissible infections (TTIs)

2 main categories:

(1) Those that result in chronic infection in the donor:

The donor may have been asymptomatic or experienced an acute illness, but may feel well for years post-infection, and therefore present to donate.

Most TTIs fall into this category.

Hepatitis B (HBV), Hepatitis C (HCV), HIV, and Cytomegalovirus (CMV).

(2) Those that result in a short period of viraemia, which then resolves:

The donor may remain asymptomatic or have symptoms of infection at the end of the period of viraemia.

There is no chronic phase of infection

West Nile Virus (WNV), Zika virus, and Hepatitis A (HAV)

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Blood safety depends on both donor health screening (deferring donors who are aware they are infected by a TTI or are in a high-risk group for a TTI), and donation testing

Anomalous test results should be investigated and resolved before blood is deposited in available stock.

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Window periods

Refers to the period of time during which the donor may transmit infection, but testing performed will be negative.

It is a latent period of immunosilence shortly after infection when laboratory tests for markers of the infection are non-reactive.

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Donation testing and transfusion transmissible infections

ISBT Science Series, Volume: 15, Issue: S1, Pages: 192-206, First published: 11 December 2020, DOI: (10.1111/voxs.12597)

Window period of immunosilence.

Figure 1 shows the window period of immunosilence. A blood donation given during the window period will test negative, be classified safe for use and be placed in available stock yet may be infectious. The term seroconversion refers to the time when the blood of an infected individual shows the presence of antibodies to the infection.

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The window period is of great concern to blood services, as it is not possible to detect an infected blood during this phase.

Although laboratory tests today are very sensitive, and the window period may be narrowed to a few days, no matter how sensitive the test may be, there could still be a window period.

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As illustrated in Table 4, the lag time (cumulative window period) for ability of each serological test to detect an infection present in a donor’s blood is based on the window period data for HIV, HBV and HCV published in 2016 by WHO (see reference related to Table 4).

In general, window periods are shortest for NAT testing, longer for antigen testing, and longest for antibody detection.

Thus, the lag time for anti-HIV to detect HIV infection can be as long as 21 days, for HBsAg test to detect HBV infection as long as 42 days, and for anti-HCV to detect HCV infection as long as 60 days. This lag period gets truncated (shortened) by direct tests for viral gene amplification with NAT. Single unit NAT testing, where each donation is tested separately, is slightly more sensitive than minipool testing, when a small number of donor samples are pooled for testing.

The window period is of great concern to blood services, as it is not possible to detect an infected donation of blood during this phase. Although laboratory tests today are very sensitive, and the window period may be narrowed to a few days, no matter how sensitive the test may be, there could still be a window period.

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Testing Algorithms: Screening and confirmatory�testing

Figure 2 is a guideline algorithm summarising the sequence of actions that may be taken when a laboratory test is initially reactive for HIV, HBV or HCV.
The algorithm does not describe the procedure to follow for a specific TTI

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Specific TTIs: Human Immunodeficiency Virus (HIV), Hepatitis B (HBV), Hepatitis C (HCV), and syphilis�

Of all the transfusion transmissible infections, HIV, HBV, HCV and to a lesser extent syphilis, are the most important with regard to universal screening of blood donations.

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Testing for HIV

Every donation should be tested for antibodies to HIV-1 and HIV-2 and common subtypes, using a test system such as ELISA or EIA/CLIA.

Laboratory markers for HIV include anti-HIV, p24 antigen, and viral RNA.

In order to reduce the window period for HIV, many blood centres use combination tests for HIV antibody and p24 antigen, and/or perform NAT testing in addition to antibody testing.

Western blot is not used routinely for screening blood donations for viral markers. It is a gel electrophoresis technique and requires specialised equipment. It may be useful for confirmatory testing for HIV.

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Testing for HBV

Every donation should be tested for hepatitis B, using a test system such as ELISA, EIA/CLIA or NAT.
Laboratory markers for HBV include HBsAg and viral DNA.
Screening for anti-HBc is used in some countries and reactive donations excluded. However, in hyper-endemic countries, introduction of this marker to the screening algorithm might adversely affect the adequacy of the blood supply.

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Testing for HCV

Every donation should be tested for hepatitis C, using a

test system such as ELISA, EIA/CLIA or NAT.

Laboratory markers for HCV include anti-HCV and viral RNA.

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Rapid plasma reagin test (RPR) for syphilis

The syphilis spirochete (Treponema pallidum) is susceptible to time and temperature and will lose its ability to infect a recipient after several days of storage after donation, particularly if the storage is at 4 ± 2°C

Serum/plasma from the donor is tested for antibodies to

reagin and not for antibodies to T. pallidum. Reagin levels are raised in certain infectious conditions such as syphilis, and this causes an antibody response in the host.

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T. pallidum haemagglutination test (TPHA)

The TPHA test is used to detect antibodies to T. pallidum.
The test uses avian (i.e. related to birds) erythrocytes

coated with antigenic components of the T. pallidum organism. This test can be automated, and results produced are read either by the technologist or by instrument.

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Transmissible bacteria

Blood components provide a hospitable, conducive environment for bacterial growth.

This is especially true for platelets, since they are stored at room temperature. Bacteria present in the blood component may multiply during storage and cause severe transfusion reactions and septic shock when transfused

Blood collection kits are sterile, and steps are taken in donor screening, venepuncture, and processing and storage to ensure sterility
Despite precautions, occasionally bacterial contamination and proliferation does occur.

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Main mechanism of contamination

Inadequate skin disinfection, with primarily Gram positive organisms that are part of normal skin bacterial flora, such as Staphylococcus epidermidis and Staphylococcus aureus introduced into the blood collection bag at the time of phlebotomy

Intermittent donor bacteraemia with Gram-negative organisms, sometimes related to gastroenteritis (Yersinia enterocolitica) or chronic intestinal pathology, such as colon cancer (Streptococcus bovis). Yersinia enterocolitica in particular is cold tolerant and may survive and proliferate in refrigerated whole blood and red cells

Environmental contaminants (Serratia liquifaciens, Pseudomonas) during storage or processing of components, particularly if there is a defect in the storage bags, such as a micropuncture or leaky seal.

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Some blood services test all platelet components for bacteria.
The sample is injected into one or several blood culture bottles that are incubated in an automated culture system. If the blood culture becomes positive. Components from the same donation are also recalled. Further confirmatory testing may be done to confirm that bacteria are present and identify the precise microorganism.

In PDN- test for bacteria done routinely by our Quality department on expired platelet.

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Transmissible parasites

Malaria (caused by protozoa -Plasmodium)
Transfusion transmitted Plasmodium falciparum may cause severe malaria and lead to the death of the recipient.
Malaria should always be considered in a blood recipient who develops a febrile condition some weeks after transfusion.

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Red cells, whole blood, and platelets prepared from infected donations can infect recipients, but cell-free plasma from such donors should be safe for use.

Red cells and whole blood are most likely to transmit infection.

Individuals who have recovered from malaria may remain carriers for many years. They may experience occasional relapses or be asymptomatic. Those who are asymptomatic for some time may feel quite well and donate their blood, only to infect a recipient.

Individuals who have recently become infected may also appear well and donate their blood. This is why it is so important to question prospective donors thoroughly about recent travel, or residence in a malaria area, and defer donation according to local guidelines

In endemic areas, most individuals, including donors, and patients who might be transfusion recipients, carry some immunity to the disease.

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Screening tests option for Malaria

• Screening for parasites found within the red cells.

• Screening for antibodies to the malaria parasite.

• Screening for the presence of malaria antigens.

• Screening for the presence of plasmodial DNA.

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According to our 4th Transfusion Practice Guideline- MALARIA

-defer for 6 months after completion of treatment & full recovery whenever is longer

-defer for 4 weeks after completion of malarial prophylaxis

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Option suggested

In endemic areas where it is likely that all available blood donors could have had exposure to malaria, it may be unavoidable to use them as blood donors. In this case, donations should be confined for use within the malaria area, for local patients, and the use of concomitant anti-malaria therapy advised for susceptible transfusion recipients

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Pandemics

A blood service should develop an action plan in case of pandemics that may occur, such as the outbreak of coronavirus disease in 2019/2020 (COVID-19) .
Although it was not immediately apparent whether or not the causative virus (designated Severe Acute Respiratory Syndrome Coronavirus 2 or SARS CoV-2) was transmissible via blood transfusion, blood services acted quickly to implement strategies to identify at risk donors and defer them from donating.

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Lookback procedures

Look-back investigations may be done when a donation from a donor who had given blood before, and which was then non-reactive for TTIs and therefore considered safe for transfusion into a patient, now tests positive for a TTI.
Recipients of previous transfusions from the donor may be contacted and tested for the specific TTI

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Traceback procedures

When a recipient becomes positive for a TTI following a transfusion, donors who contributed components to the transfusion may be contacted and tested, if they have not already returned to donate.

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Key Points

Testing for TTIs is subject to ongoing change, as additional or more sensitive tests become available or new infections are identified.

The length of the window period varies by infectious agent and the test method used in screening, with Nucleic acid testing (NAT testing) having shorter window periods than antigen or antibody testing.

An algorithm is used for a sequence of steps to be taken when a donation is initially found to be reactive. Depending on the TTI concerned, the algorithm is unique.

Every unit of blood should be screened for HIV, hepatitis B, hepatitis C and syphilis, as well as any other TTIs that relate to the geographical area of the blood service

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5. A blood service should be constantly on the alert for the emergence of new agents that may impact on the safety of the blood supply and take action to begin screening donations if possible.

6. National authorities should establish guidelines to outline the scope and algorithm for managing the lookback and traceback processes

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REFERENCES

Leesha Roman,Beryl Armstrong,Elizabeth Smart,Reviewer for Second Edition: So-Yong Kwon, Donation testing and transfusion transmissible infections ,11 December 2020 https://doi.org/10.1111/voxs.12597

Alex K. Owusu-Ofori, Christopher Parry, Imelda Bates, Transfusion-Transmitted Malaria in Countries Where Malaria Is Endemic: A Review of the Literature from Sub-Saharan Africa, Clinical Infectious Diseases, Volume 51, Issue 10, 15 November 2010, Pages 1192–1198, https://doi.org/10.1086/656806

Verra, F., Angheben, A., Martello, E. et al. A systematic review of transfusion-transmitted malaria in non-endemic areas. Malar J 17, 36 (2018). https://doi.org/10.1186/s12936-018-2181-0