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Blood Donor Selection: Guidelines on Assessing Donor Suitability for Blood Donation. Geneva: World Health Organization; 2012.

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Blood Donor Selection: Guidelines on Assessing Donor Suitability for Blood Donation.

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7TTI and donor risk assessment

The microbiological safety of blood donations may be affected by donors' exposure to HIV, hepatitis B, hepatitis C and syphilis and other transfusion-transmissible infections (TTI) via a number of different routes. These primarily include sexual contact and percutaneous exposure through high-risk sexual behaviours, and unsafe blood transfusion and injection practices, cosmetic treatments and rituals. Current or previous country of residence, and travel history also need to be analysed.

The BTS should assess the potential risks of infections present in its donor population and establish donor selection criteria aimed at minimizing the risk of transmission of infections from donors to recipients. These criteria should be based on the prevalence, incidence and epidemiology of TTI, up-to-date information on known and emerging infections, including expert advice regarding the nature of the disease and mode of transmission; taking into consideration the consequences to the blood supply of excluding “at-risk” donors while preserving the sufficiency of the blood supply (157):

  • When there is a proven risk of transfusion-associated transmission but no appropriate screening assays are available, donor selection criteria should be developed to identify and defer potentially infected donors for an appropriate period of time
  • When there is a theoretical risk of transfusion-associated transmission and no appropriate screening assays are available, donor selection criteria may be developed to identify and defer potentially infected donors for an appropriate period of time.

Procedures should be in place for the frequent review and re-evaluation of donor selection criteria in case of emerging infectious diseases, identification of new risks or changes to known risks, cultural practices and evidence from haemovigilance and other surveillance data.

Coordination and cooperation among key national institutions, agencies and major stakeholders, e.g. blood services, public health institutions, hospitals, regulatory agencies and professional bodies is essential for the recognition and control of known and emerging TTI. This includes knowledge of disease prevalence, incidence and epidemiology, active surveillance of emerging infections and potential new endemic areas, the implementation of appropriate donor selection criteria, quality-assured screening of all donations and the systematic monitoring of transfusion recipients (158,159,160,161). Information on the prevalence and epidemiology of certain transfusion-transmissible infections can be found in the WHO Global Health Atlas (162).

7.1. TRANSFUSION-TRANSMISSIBLE INFECTIONS

The microbial agents of importance to a BTS are those that are transmissible by blood transfusion and can cause morbidity and mortality in recipients. In order to be transmissible through transfusion, the infectious agent usually has the following characteristics:

  • Presence of the agent in one or more components of blood for long periods and in an infectious form
  • Stability at temperatures at which whole blood and blood components are stored
  • Generally long incubation period before the appearance of clinical signs and symptoms
  • Asymptomatic phase or only mild symptoms in the blood donor, hence not always identifiable during the blood donor selection process.

Many viruses, bacteria and protozoa can be transmitted by transfusion and new agents that potentially can be transmitted through transfusion continue to emerge (163,164).

WHO recommends that, at a minimum, screening of all blood donations should be mandatory for the following infections and using the following markers (7):

  • HIV-1 and HIV-2: screening for either a combination of HIV antigen-antibody or HIV antibodies
  • Hepatitis B: screening for hepatitis B surface antigen (HBsAg)
  • Hepatitis C: screening for either a combination of HCV antigen-antibody or HCV antibodies
  • Syphilis (Treponema pallidum pallidum): screening for specific treponemal antibodies.

The outcomes of the laboratory screening of donations remain the final decision point in the release of blood components for clinical use; however, even with the high quality assays and systems now available, the screening process cannot be considered to be totally effective because:

  • An infection in donated blood may not be detected due to the collection of the donation during the window period of infection or failure due to assay sensitivity or error
  • There are some emerging infections for which screening is not available or effective
  • A donor may be infected with an infectious agent for which donations are not routinely screened; in such cases, the donor selection process may be able to identify and defer such an individual based on the symptoms or perceived risk.

Routine screening for generally less clinically significant TTI, such as hepatitis A virus or parvovirus B19 is generally neither practical nor cost-effective. The screening tests available, if any, may not be appropriate for blood screening, often being designed primarily to aid the diagnosis of infection in symptomatic individuals. In these situations, the donor selection process is a significant factor in the identification and deferral of donors who might harbour these infections in order to prevent them from entering the blood supply.

7.2. DONOR RISK ASSESSMENT

Blood donor selection is the first crucial step in the process of ensuring blood safety as it helps to significantly reduce risk through the deferral, prior to donation, of any individuals or groups of individuals with identified risks that may be associated with infection (165,166).

Understanding the timing of infection is important in the donor selection process: firstly, the length of the window period i.e. the time between infectivity and the first detection of a defined marker of infection; and secondly, the incubation period, i.e. the time between exposure to infection and the onset of any symptoms of illness. In settings with effective blood screening programmes, donors who donate during the window period generally pose the greatest threat to blood safety and the selection process needs to be able to identify and defer such individuals. In cases where infections are more likely to be symptomatic, the shorter the period between infection and symptoms, the less likely it is that an infectious donation would be collected.

Prospective donors should be asked relevant questions to assess their general health, any history, signs or symptoms indicative of current or past infections, specific high-risk behaviours or activities, travel history, contact with infectious diseases and possible exposure to infection. Environmental factors and lifestyles associated with a high risk of exposure to infection are also discussed in Sections 7.8 and 7.9.

Individuals who have engaged in behaviours that pose a high risk for HIV, HBV and/or HCV infection should not be accepted as blood donors (also refer to Section 7.9 on high-risk behaviours).

Individual donor risk may be impossible to ascertain; the application of the precautionary principle may require that a donor is deferred on the basis of knowledge of the risks to which the donor may be exposed. This approach must be reconciled with the duty of the BTS to treat donors and prospective donors with respect, compassion and dignity, avoiding discrimination of any kind.

However, there are other occasions when a donor may have a known infection risk, either due to being infected or exposure through sexual or household contact or other close contact (having cared for, lived with or had direct contact with an individual with a suspected or diagnosed infection). As a general policy, donors should be deferred following any acute infection until they are fully recovered and no longer infectious. If a donor has been in close contact with an infectious disease, he/she should not donate within the incubation period of the infection, even if known to be immune. If the incubation period is unknown, an arbitrary deferral of 28 days from last contact may be implemented. Expert microbiology advice may be needed regarding the mode of transmission and appropriate deferral periods for specific infections, and may be obtained from WHO (http://www.who.int) and national and international health organizations.

Some infections are found only in certain parts of the world. Donor selection criteria will therefore be different in endemic and non-endemic regions. In non-endemic regions, deferral criteria may be applied to donors who have travelled to or lived in endemic regions. Deferral periods may be extended if donors have had any undiagnosed febrile illness during travel or since return (also refer to Section 7.3 on viral infections and Section 7.4 on protozoal infections for deferral periods for individuals who have travelled to and from regions that are endemic for dengue virus, Chikungunya virus, malaria and Chagas disease).

These guidelines are applicable to the selection of donors of whole blood and other labile blood components through whole blood collection and apheresis. In the case of plasma donation for large-scale fractionation purposes, there are circumstances in which plasma donations may be collected from individuals who would not otherwise be eligible to donate whole blood or other labile blood components on the basis of infectious disease risk and/or history.

7.3. VIRAL INFECTIONS

7.3.1. Hepatitis

Prospective blood donors should be given relevant information on the risk of hepatitis transmission in order to provide them with the opportunity to self-defer.

Prospective donors should be asked for a history of jaundice or hepatitis and whether they were further investigated to determine the cause. Individuals with a history of jaundice or hepatitis may, at the discretion of the physician, be accepted as donors based on the tests results.

To exclude donors at risk of transmitting hepatitis, the BTS should ask if the donor, currently or in the past, has had a hepatitis infection (HBV, HCV or other types), assess any specific risks of exposure through sexual and household contacts, and also enquire whether the donor has had an HBV vaccination within the last 14 days.

Individuals with hepatitis infection may be asymptomatic or present with fever, nausea, vomiting, loss of appetite, jaundice, abdominal pain or an enlarged and tender liver.

Hepatitis B

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV). The virus is transmitted from human to human via blood and body fluids; consequently it may be transmitted by transfusion and transplantation, via needles and other items exposed to blood, and from mother to child in utero, at birth or perinatally (167,168,169).

The incubation period of the hepatitis B virus is 90 days on average, but can vary from 30 to 180 days. Most people do not experience any symptoms during the acute infection phase. However, some people have acute illness with symptoms that last several weeks. The virus may be detected 30 to 60 days after infection and persists for variable periods of time. Infection in childhood commonly results in chronic infection (more than 6 months) which may be life-long or resolve spontaneously at any time, whereas infection later in life is usually acute (170).

For individuals with confirmed HBV infection, a deferral period of 12 months from recovery is generally recommended, and suitability to donate blood is assessed based on the results of testing for hepatitis B surface antigen (HBsAg), hepatitis B core antibody (anti-HBc) and antibody to hepatitis B surface antigen (anti-HBs) levels.

All HBsAg positive donors should be considered to be at high risk of transmitting HBV. Additionally, some studies indicate that even when HBsAg is not detectable, some individuals may have low levels of detectable viral DNA which will be transmitted by blood and may cause infection in the recipient (171,172).

Recommendations

Accept
  • The following individuals may be accepted for blood donation provided they have been tested and found to be negative for HBsAg, and negative for anti-HBc; if anti-HBc positive, they must have anti-HBs greater than 100 mIU/ml:

    Individuals with a past history of HBV if more than 12 months ago

    Current sexual contacts of individuals with a history of HBV infection if more than 12 months ago

    Current and former household contacts who have been successfully immunized against HBV and are anti-HBs positive more than 100 mIU/ml but anti-HBc negative

    Donors with initially reactive results for HBsAg but confirmed to be non-reactive: re-entry procedures should be established and followed

Defer
  • Individuals with active HBV infection or a history of infection within the last 12 months
  • Current sexual and household contacts of individuals with active HBV infection
  • Former sexual contacts of individuals with active HBV infection: defer for 12 months since last sexual contact
  • Former household contacts of individuals with active HBV infection: defer for 6 months since last contact
  • Health workers who have suffered an inoculation or mucosal injury: defer for 12 months following the exposure; health workers who have been vaccinated against HBV should be assessed individually

Hepatitis C

Hepatitis C is a liver disease caused by the hepatitis C virus (HCV). The hepatitis C virus is most commonly transmitted through exposure to infectious blood. This can occur through contaminated blood transfusions, blood products and organ transplants; injections given with contaminated syringes and needlestick injuries in health-care settings; injecting drug use; or being born to a hepatitis C-infected mother. Hepatitis C may also be transmitted through sex with an infected person or sharing of personal items contaminated with infectious blood, but these are less common (173,174,175,176,177).

The incubation period for hepatitis C is 2 weeks to 6 months. Following initial infection, approximately 80% of people do not exhibit any symptoms. About 75-85 % of newly infected persons develop chronic disease (178).

Recommendations

Accept
  • Household contacts of individuals with HCV infection
Defer
  • Current sexual contacts of individuals with current or past HCV infection
  • Former sexual contacts of individuals with HCV infection: defer for 12 months since last sexual contact
  • Health workers who have suffered an inoculation or mucosal injury: defer for 12 months following the exposure
Defer permanently
  • Individuals with current or past HCV infection

Hepatitis A

Hepatitis A is a liver disease caused by the hepatitis A virus (HAV). The virus is transmitted primarily by the faecal-oral route, but sexual transmission can occur. The virus can also be transmitted through close physical contact with an infectious person, although casual contact among people does not spread the virus. Cases of transfusion-transmission by blood and blood products have been reported (179,180,181,182).

The incubation period of hepatitis A is usually 14–28 days. Symptoms of hepatitis A range from mild to severe. Unlike hepatitis B and C, hepatitis A infection does not cause chronic liver disease and is rarely fatal, but it can cause debilitating symptoms and fulminant hepatitis (acute liver failure), which is associated with high mortality (183).

Hepatitis E

Hepatitis E virus (HEV) behaves in similar ways to HAV except that chronicity cannot be ruled out. Transfusion-transmission by blood and blood products has been reported (184). Cases of hepatitis E are not clinically distinguishable from other types of acute viral hepatitis (185).

Diagnosis of hepatitis E infection is therefore usually based on the detection of specific antibodies to the virus in the blood. Deferral periods are as for HAV.

Hepatitis of unknown origin

Most cases of hepatitis of unknown origin are due either to undiagnosed hepatitis A or hepatitis E, or to non-viral causes. Deferral periods are the same as for HAV.

Recommendations

Defer
  • Individuals with active HAV, HEV or hepatitis of unknown origin: defer for 12 months after full recovery
  • Sexual contacts, household and other close contacts of individuals with HAV, HEV or hepatitis of unknown origin: defer for 12 months since last contact

7.3.2. Human immunodeficiency virus/Acquired immunodeficiency syndrome (HIV/AIDS)

HIV can be transmitted via unprotected and close contact with a variety of body fluids of infected individuals, such as blood, breast milk, semen and vaginal secretions. Individuals cannot become infected through ordinary day-to-day contact such as kissing, hugging, shaking hands, or sharing personal objects, food or water.

Behaviours and conditions that put individuals at greater risk of contracting HIV include having unprotected anal or vaginal sex (186) (also refer to Section 7.9 on high-risk behaviours); having another sexually transmitted infection such as syphilis, herpes, chlamydia, gonorrhoea or bacterial vaginosis; sharing contaminated needles, syringes and other infected equipment and drug solutions for injecting drug use; receiving unsafe injections, blood transfusions or medical procedures that involve unsterile cutting or piercing; experiencing accidental needlestick injuries, including among health workers.

Infectivity estimates in case of transfusion of infected blood products are much higher (around 95%) than for other modes of HIV transmission owing to the much larger viral load per exposure than for other routes (187)

Recommendations

Accept

  • Household contacts of individuals with HIV infection

Defer

  • Current sexual contacts of individuals with HIV infection
  • Former sexual contacts of individuals with HIV infection: defer for 12 months since last sexual contact

Defer permanently

  • Individuals with present or past clinical or laboratory evidence of HIV infection

7.3.3. HTLV I and HTLV II

Human T-cell lymphotropic viruses (HTLV) are present in the bloodstream in lymphocytes. Non cell-associated virus is rarely found. The infectivity of blood and blood components is reduced but not removed by leucodepletion. HTLV can be transmitted from mother to child, primarily through breast-feeding, and it may also be transmitted through sexual contact (188,189). As infection is considered to persist for life, screening for anti-HTLV identifies donations that may transmit HTLV but does not in itself indicate the timescale of an infection.

Recommendations

Accept

  • Household contacts of individuals with HTLV I and/or II infection
  • Individuals whose mother or maternal grandmother has or had HTLV I and/or II infection, if blood screening for HTLV I and/or II infection is available
  • Former sexual contacts of individuals with HTLV I and/or II infection if more than 12 months after the last sexual contact, and blood screening for HTLV I and/or II infection is available

Defer

  • Current sexual contacts of individuals with HTLV I and/or II infection
  • Former sexual contacts of individuals with HTLV I and/or II infection: defer for 12 months after last sexual contact

Defer permanently

  • Individuals with HTLV I and/or II infection
  • Individuals whose mother or maternal grandmother has or had HTLV I and/or II infection, if blood screening for HTLV I and/or II infection is not available
  • Former sexual contacts of individuals with HTLV I and/or II infection, if blood screening for HTLV I and/or II infection is not available

7.3.4. Herpes viruses

Herpes viruses include herpes simplex types I and II, varicella-zoster, Epstein-Barr virus, cytomegalovirus and Kaposi's sarcoma-associated human herpes virus 8 (HHV8). All these viruses can give rise to latent infection and some are transfusion-transmissible (190,191). Symptomatic donors should be deferred until fully recovered. Because of the high prevalence of exposure to these viruses in donors and recipients, except in the case of HHV8, the exclusion of donors with a history of past infection is neither feasible nor useful.

HHV8 is transmitted by sexual and non-sexual routes and has been reported to be also transmitted by transfusion and transplantation (192,193,194).

Recommendations

Accept

  • Individuals with cold sores and genital herpes, provided there are no active lesions

Defer

  • Individuals who are symptomatic (except HHV8 infection): defer for at least 28 days following full recovery
  • Contacts of individuals who are symptomatic (except HHV8 infection): defer for 28 days

Defer permanently

  • Individuals with HHV8 infection
  • Current and former sexual contacts of individuals with HHV8 infection

7.3.5. Mosquito-borne viruses

West Nile virus

West Nile Virus (WNV) is a flavivirus primarily transmitted by mosquitoes, but also readily transmitted through blood donations from infected individuals (195). It is found in Africa, Europe, Western Asia, the Middle East and North America, although in many regions it is highly seasonal. It causes a rapid onset, acute infection with a relatively brief period of viraemia. Transfusion-transmission has been reported. Symptoms are non-specific and viraemic donors may be asymptomatic at the time of donation (196,197). In endemic areas with reported human cases, blood screening using molecular technology is the only means of preventing transfusion-transmission.

To identify “at-risk” donors for WNV in non-endemic areas, BTS should elicit information on travel history during the donor selection process and maintain up-to-date knowledge of disease epidemiology. Some countries have implemented a 28-day deferral after visiting an endemic area, extended to 6 months from full recovery if the donor has had any symptoms suggestive of WNV (198 199,200).

As a result of increasing numbers of cases of WNV in some countries where there were previously only sporadic cases, a number of non-endemic countries have introduced the identification and deferral of at-risk donors; and the screening of donations from these donors using molecular technology.

Recommendations

NON-ENDEMIC AREAS (IF BLOOD SCREENING IS NOT PERFORMED)

  • At-risk donors with symptoms appearing within 14 days following donation should be advised to report to the BTS
Defer
  • Individuals who:

    Have known West Nile virus infection or symptoms suggestive of WNV: defer for 6 months from full recovery

    Have visited an area endemic for WNV with human cases, in the WNV season within the last month: defer for 28 days following return

Dengue and chikungunya viruses

Dengue and chikungunya viruses are transfusion-transmissible mosquito-borne arboviruses. Both give rise to acute infections with no chronic infection, but re-infection with dengue virus can have very serious sequelae. Although both are potentially transmissible, there have been no proven cases of transfusion-transmission of chikungunya and relatively few reports of transmission of dengue (201,202).

Before 1970, only nine countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and Western Pacific. South-east Asia and the Western Pacific are the most affected (203).

Chikungunya occurs in Africa, Asia and the Indian subcontinent and outbreaks have been reported in all the three regions. There was a large number of imported cases in Europe and South East Asia during some of the outbreaks (204).

BTS in non-endemic areas wishing to exclude at-risk donors should include questions about travel history during the donor selection process and maintain up-to-date knowledge of disease epidemiology.

Recommendations

ENDEMIC AREAS

Defer
  • Individuals with a history of dengue or chikungunya virus: defer for 6 months following full recovery from infection

NON-ENDEMIC AREAS

Defer
  • Individuals who:

    Have visited an area endemic for dengue or chikungunya: defer for 28 days following return

    Have suffered a febrile illness during or following return from an endemic region: defer for 6 months following full recovery from infection

7.3.6. “Childhood illnesses”: measles, rubella, mumps and chickenpox

Infections with childhood illnesses such as measles, rubella, mumps and chickenpox are known to occur in adults. Individuals suffering from any of these childhood illnesses and their close contacts should be identified as ‘at-risk’ donors and should be deferred for a defined period of time (205,206).

Recommendations

Defer

  • Individuals with measles, rubella, mumps or chickenpox: defer for 14 days after full recovery
  • Individuals in close contact with patients having active measles, rubella, mumps or chickenpox and who are asymptomatic: defer for 21 days following last day of close contact

7.3.7. Influenza

For sporadic cases, individuals with active infection should be deferred until 14 days after full recovery; susceptible contacts should be deferred for 7 days after the implicated individual has recovered.

In a pandemic situation the risk of blood shortage far outweighs any theoretical risk of transfusion transmission. The usual donor selection criteria for influenza and any specific measures relating to donor deferral should be carefully reviewed. Following the precautionary principle, selective donor deferral may be considered (25,207).

Recommendations

Accept

  • Asymptomatic individuals with no close contact with those having active infection

Defer

  • Asymptomatic household contacts and other close contacts of symptomatic individuals with active infection: defer for 7 days after last day of close contact
  • Symptomatic individuals with active infection: defer for 14 days after full recovery and cessation of any therapy
  • Individuals who have received vaccination against influenza: defer for 48 hours after vaccination; the deferral period should be extended as above if the donor is in a specific risk category

7.4. PROTOZOAL INFECTIONS

Protozoa are predominantly intracellular organisms. Prospective donors from non-endemic countries who are at risk of any of the following parasitic protozoal infections may be considered suitable to donate plasma for large-scale fractionation purposes only, until such time as they meet the specific criteria that would allow the collection of whole blood and other labile blood components for direct clinical use.

7.4.1. Malaria

Malaria is caused by Plasmodium species. There are four parasite species that cause malaria in humans: P. falciparum, P. vivax, P. malariae and P. ovale, of which P. falciparum and P. vivax are the most common. P. falciparum is the most deadly. In recent years, some human cases of malaria have also occurred with P. knowlesi – a species that causes malaria among monkeys and occurs in certain forested areas of South-East Asia.

Malaria is primarily transmitted to humans through the bite of the female Anopheles mosquito. In many places, transmission is seasonal, with the peak during and just after the rainy season. Increased malaria prevention and control measures are dramatically reducing the malaria burden in many places. Nonimmune travellers from malaria-free areas are very vulnerable to the disease when they become infected (208).

Malaria is also readily transmitted by blood transfusion through donations collected from asymptomatic, parasitaemic donors. The parasite is released into the bloodstream during its lifecycle and will therefore be present in blood donated by infected individuals. The parasites are stable in plasma and whole blood for at least 18 days when stored at +4°C and for extended periods in a frozen state (209). Donor selection criteria to exclude collecting blood from individuals with current or past history of malarial infection and at risk of transmitting malaria through transfusion, should be based on local epidemiological evidence and endemicity of the infection.

Endemic areas

Donor selection and deferral strategies should be developed to identify individuals with evidence of current malarial infection and defer them for a period of 6 months after symptoms (fever with rigors) or on completion of treatment and full recovery, whichever is longer. Alternatively, the BTS should screen all donations for parasitaemia using thick blood films or for evidence of malarial antigen using a highly sensitive enzyme immunoassay.

Non-endemic areas

Malaria is increasingly a matter of concern to BTS in non-endemic countries (210,211,212). Significant numbers of blood donors from non-endemic countries travel to malarious areas and there is wide migration from endemic areas to non-endemic areas where migrants may then become blood donors. Malaria is gradually spreading into non-endemic areas or regions where it had previously been eradicated.

Recommendations

ENDEMIC AREAS

  • The BTS should develop:

    Donor selection criteria to identify and collect blood from donors at the lowest risk of infection, both during the malaria season and during the rest of the year

    Strategies to maximize the collection of blood from donors from geographical areas with low endemicity

    Screen all donations for parasitaemia using thick blood films (smear microscopy) or for evidence of malarial antigen using a highly sensitive enzyme immunoassay

Defer
  • Individuals with a recent infection with malaria: defer for 6 months after completion of treatment and full recovery, whichever is longer

NON-ENDEMIC AREAS

The BTS should:

  • Define the donor population with a risk of exposure to malaria and thus the potential for transmission through blood donations
  • Implement donor selection and deferral strategies to identify individuals with a recent history of malaria or a specific identifiable exposure risk, such as travel to malarious areas; these donors should be deferred for a period defined by the country
  • Question prospective donors regarding:

    Place of birth

    Previous residence in endemic areas

    Travel during the previous 12 months

    History of malaria or any undiagnosed febrile illness during or after visiting an endemic area

If sensitive and multi-specific antibody screening tests are available

Defer
  • Individuals who:

    Have travelled to malaria endemic areas and who have had no symptoms: defer for 12 months from last return from a malarious area

    Have travelled to malaria endemic areas and who have had febrile symptoms, but not diagnosed as malaria: defer for 12 months following full recovery or last return from a malarious area, whichever is the longer

    Lived in a malaria endemic area in the first 5 years of life or for a continuous period of 6 months or more: defer for 5 years after last return from a malarious area

Defer permanently
  • Individuals who have ever had a diagnosis of malaria

If sensitive and multi-specific antibody screening tests are available

Accept
  • Asymptomatic individuals with identified malaria exposure risk (travel and/or residence): accept if more than 6 months after their last return from an endemic area
Defer
  • Individuals with:

    Identified malaria exposure risk (travel and/or residence), but no symptoms: defer for 6 months after last return from malarious area

    Identified malaria exposure risk (travel and/or residence) who have had febrile symptoms, but not diagnosed as malaria: defer for 6 months from cessation of symptoms or last return from a malarious area, whichever is the longer

    A current infection or history of malaria: defer for 3 years following completion of treatment and full recovery, whichever is the longer

7.4.2. Chagas disease

Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite, Trypanosoma cruzi (T. cruzi). It is found mainly in Latin America, where it is mostly transmitted to humans by the faeces of triatomine bugs, known as “kissing bugs”, among other names, depending on the geographical area. T. cruzi can also be transmitted by food contaminated with T. cruzi through for example the contact with triatomine bug faeces, transfusion of blood from infected donors, passage from an infected mother to her newborn during pregnancy or childbirth, organ transplants using organs from infected donors and laboratory accidents.

Chagas disease is endemic throughout South and Central America, although effective vector control procedures have been implemented in recent years (213,214,215,216). In the past decades, it has also been increasingly detected in the United States of America, Canada, many European and some Western Pacific countries. This is due mainly to population mobility between Latin America and the rest of the world. Less frequently, it is due to infection through blood transfusion, vertical transmission (from infected mother to child) or organ donation (217).

Infection is life long and infected individuals may be asymptomatic; individuals with a history of T. cruzi infection should be permanently deferred.

Endemic areas

In endemic areas, donor selection is not feasible; the prevention of transfusion-transmission depends on the serological testing of all blood donations and treatment of the blood with trypanocidal agents (213,218,219).

Non-endemic areas

In non-endemic countries, individuals are identified as having been exposed to risk of infection if they, their mother or maternal grandmother were born in South or Central America (including Southern Mexico), have had a blood transfusion in these areas or have lived and/or worked in rural communities in these countries for a continuous period (arbitrarily 28 days or more). These individuals should be permanently deferred from blood donation unless a validated T. cruzi antibody test is available, in which case they may be accepted 6 months after the last exposure if sero-negative (220,221).

Recommendations

NON-ENDEMIC AREAS

If sensitive antibody assays for T. cruzi are not available

Defer permanently
  • Individuals who have ever had a diagnosis of Chagas disease
  • Individuals with an identified risk of Chagas disease:

    Born in, resided in for 6 months or more, or have mother or maternal grandmother born in an endemic area

    Received blood transfusion or organ transplant in an endemic area

    Travel for 28 days or more in a rural community in an endemic area

If sensitive antibody assays for T. cruzi are available (184)

Accept
  • Individuals with an identified risk of exposure to Chagas disease: accept if more than 6 months after last return from an endemic area
Defer
  • Individuals with an identified risk of exposure to Chagas disease: defer for 6 months after last return from an endemic area
Defer permanently
  • Individuals who have ever had a diagnosis of Chagas disease

7.4.3. Babesiosis

Babesiosis (Babesia sp.) is transmitted by tick-borne intraerythrocytic parasites. Most cases of Babesia infection are asymptomatic, but can include mild fever and diarrhoea. The symptoms are often unnoticed or unexplained. In more severe cases, the symptoms are similar to those of malaria. The infection may also have a chronic asymptomatic phase and the parasite can survive blood storage conditions. B. microti is endemic in parts of North America; the reservoir of infection is small rodents. Transfusion-transmission has been reported (222,223). Prevention relies on checking for a history of previous infection among residents or visitors to endemic areas (224,225,226).

Recommendations

Defer permanently

  • Individuals who have ever had a diagnosis of babesiosis

7.4.4. Leishmaniasis

Leishmaniasis is a parasitic disease endemic in the tropics and subtropics, transmitted by the bite of infected sand-flies. The parasite (Leishmania sp.) has the potential for transfusion-transmission, but this has been only rarely reported, possibly because parasitaemia is transient and low level (227). The prevention of transfusion-transmission relies on the permanent deferral of infected individuals (228).

Recommendations

Defer

  • Individuals who have spent extended periods in endemic areas: defer for at least 12 months since their last return

Defer permanently

  • Individuals who have ever had a diagnosis of leishmaniasis

7.5. BACTERIAL INFECTIONS

Bacterial contamination of blood components with organisms carried by the donor may be exogenous, due to skin contaminants entering the donated blood at the time of collection, or endogenous, due to bacteria present in the donor's blood (229,230).

The role of donor selection in minimizing exogenous bacterial infection includes inspection of the skin at the venepuncture site and deferral of donors with obvious skin lesions (also refer to Sections 4.2 on donor appearance and inspection and 5.11 on skin diseases). Other techniques for bacterial reduction (231), including skin cleansing, venepuncture technique, use of diversion pouches and leucoreduction play an important role in preventing the contamination of blood components by exogenous bacteria. Guidance on safe phlebotomy techniques can be found in WHO Guidelines on drawing blood: best practices in phlebotomy (31).

Most prospective donors with endogenous bacterial infections present with symptoms, such as fever, rash, diarrhoea and malaise, and should be deferred from blood donation as part of the general health assessment (also refer to Section 4.2 on donor appearance and inspection).

Endogenous bacteria that are transfusion-transmissible include Treponema pallidum, Borrelia burgdorferi, Brucella melitensis and Yersinia enterocolitica, but blood donations are routinely screened only for T. pallidum.

7.5.1. Syphilis, yaws and gonorrhoea

Syphilis, yaws and gonorrhoea are common sexually-transmitted diseases; it should be noted that a history of sexually transmitted disease is an important indicator for sexual behaviours associated with HIV transmission. Controlling sexually transmitted infections is important for preventing HIV infection, particularly in people with high risk sexual behaviours (232).

The risk of transmission of syphilis (T. pallidum) through the transfusion of processed and stored blood is low as the spirochaetae are released into the bloodstream only intermittently during the course of infection, and are destroyed within 72 hours of storage at +40°C (63); however T. pallidum can be transmitted through fresh blood and platelets. It is not transmitted by plasma products fractionated from pooled plasma such as Factor VIII.

Yaws (Treponema pallidum pertenue) is not transmitted through transfusion, but is serologically indistinguishable from syphilis. Serological tests for syphilis may remain positive for many years after successful treatment.

The causative agent of gonorrhoea (Neisseria gonorrhoeae) is not transmissible by blood transfusion. Nevertheless most BTS defer individuals with gonorrhoea for 12 months following completion of treatment.

Recommendations

Accept

  • Household contacts of individuals with syphilis

Defer

  • Current sexual contacts of individuals with syphilis
  • Former sexual contacts of individuals with syphilis: defer for 12 months since last sexual contact
  • Individuals with gonorrhoea: defer for 12 months following completion of treatment and assess for high-risk behaviour
  • Current sexual contacts of individuals with gonorrhoea
  • Former sexual contacts of individuals with gonorrhoea: defer for 12 months since last sexual contact

Defer permanently

  • Individuals who have ever had a diagnosis of syphilis

7.5.2. Lyme disease

The spirochete Borrelia burgdorferi is carried by insect vectors including ticks, horseflies and mosquitoes. It can survive blood storage temperatures. Transfusion-transmission is possible but has not been reported. Infected individuals usually exhibit symptoms of rash, fever, lymphadenopathy, often progressing to chronic arthropathy and/or neurological involvement, and are likely to be Identified and excluded by careful donor selection (222).

Recommendation

Defer

  • Individuals with a current diagnosis of Lyme disease: defer for 28 days following completion of treatment and full recovery, whichever is longer

7.5.3. Brucellosis

Brucellosis (undulant fever) is caused by the bacterium Brucella melitensis. It is usually acquired from an infected animal source but is not usually transmitted from person to person. Transfusion-transmission has been reported in endemic regions. Infection is usually chronic; this may last for many years with bouts of sometimes quite serious illness.

Recommendation

Defer permanently

  • Individuals who have ever had a diagnosis of brucellosis

7.5.4. Yersinia infection

This gram-negative bacterium (Yersinia enterocolitica) causes enteritis and is of particular concern as it can multiply at +4°C; thus a low-grade bacteraemia in a donor is capable of causing severe, sometimes fatal post-transfusion sepsis and toxic shock in the recipient. The incidence of this complication has been estimated at 1:6 million red cell transfusions (233).

Donors should be asked about any recent abdominal symptoms, particularly diarrhoea, and deferred if they have a history suggestive of Y. enterocolitica. They should be asked to inform the BTS if they develop such symptoms within 14 days of donation. As symptoms may be absent or non-specific, potentially infected donors cannot reliably be Identified.

Recommendation

Defer

  • Individuals with recent abdominal symptoms, particularly diarrhoea, suggestive of Y. enterocolitica infection: defer for 28 days following full recovery

7.5.5. Salmonella, campylobacter, streptococcus and staphylococcus

Post-transfusion sepsis may result from donor bacteraemia associated with gastrointestinal, urinary or wound infections (also refer to Section 4.3 on minor illnesses).

Recommendations

Defer

  • Individuals with:

    Symptoms suggestive of recent infection with salmonella, campylobacter or streptococcus: defer for 28 days following full recovery

    Other evidence of potential infection with staphylococcus: e.g. recent superficial but significant wounds: defer for 14 days following full wound healing

7.5.6. Tuberculosis

There is no published report of transfusion-transmission of tuberculosis (Mycobacterium tuberculosis) even though the organism is blood-borne.

Recommendations

Defer

  • Individuals with tuberculosis: defer for 2 years following confirmation of cure
  • Contacts of individuals with tuberculosis: defer household contacts and other close contacts until screened and confirmed clear of infection

7.6. RICKETTSIAL INFECTIONS

Rickettsiae are organisms that are smaller than bacteria and, except for Q fever (Coxiella burnetii), require an insect vector. Transfusion-transmissions of Q fever and Rocky Mountain spotted fever have rarely been reported. Deferral periods implemented for Q fever range from 2 years to permanent deferral (234).

Recommendations

Defer

  • Individuals with:

    Rickettsial infection: defer for 6 months following completion of treatment or cessation of symptoms

    Acute Q fever: defer for 2 years following completion of treatment and full recovery, whichever is the longer

Defer permanently

  • Individuals with chronic Q fever

7.7. PRION DISEASES

7.7.1. Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is the human form of transmissible spongiform encephalopathy. It exists in four distinct forms: sporadic, genetic (familial), iatrogenic and variant (vCJD).

There is no evidence of transfusion-transmission of sporadic and familial CJD; nevertheless, donors with symptoms suggestive of CJD or a family history of CJD should be permanently deferred (235). Iatrogenic CJD has been described following treatment with pituitary-derived human growth hormone, human gonadotrophin, dura mater grafts, corneal transplants and through contaminated neurosurgical instruments. There is no evidence of transfusion-transmission of iatrogenic CJD; however donors with a history of such interventions should be permanently deferred (236).

7.7.2. Variant Creutzfeldt-Jakob disease

Variant Creutzfeldt-Jakob disease (vCJD) emerged in the United Kingdom of Great Britain and Northern Ireland (UK) in 1996 as a result of oral transmission of spongiform encephalopathy from infected cattle. Data on the number of cases worldwide are collected and published by the UK National Creutzfeldt-Jakob Disease Research & Surveillance Unit (237). The outbreak of cases in the UK has declined but a “second wave” cannot be excluded and cases have occurred in other European Union countries (70)

Epidemiological evidence from the UK indicates that vCJD can be transmitted by blood transfusion, with important implications for public health worldwide (238,239,240,241). WHO guidelines on tissue infectivity distribution in transmissible spongiform encephalopathies (242) recommend that national authorities should prepare plans for measures to minimize the risk of transfusion-transmission of vCJD by blood and blood products, whilst not compromising the adequacy of the blood supply, and provide guidance on risk assessment.

To date, many countries have addressed this risk by excluding blood donors with a history of travel or residence in the UK and parts of Europe, for defined cumulative exposure periods. The United States Food and Drug Administration currently requires deferral of individuals who have spent 3 months or more cumulatively in the UK between 1980 and the end of 1996, when effective measures were implemented to prevent oral transmission, or who have spent 5 years or more cumulatively in Europe between 1980 and the present (236). In the UK, France and Ireland, recipients of blood transfusion (including fractionated blood products) since 1980 are now permanently deferred. Other countries defer donors who have received blood transfusions in the UK or France since 1980.

Recommendations

  • Countries should conduct a risk assessment and risk-benefit analysis taking into account national and international data on the epidemiology of vCJD in order to implement appropriate risk-mitigating measures to prevent the transmission of vCJD through blood transfusion
  • The decision to defer blood donors with a history of travel or residence for defined cumulative exposure periods in specified countries or areas, as a measure to reduce the risk of transmitting vCJD by blood transfusion, should be based on the findings of the risk assessment and risk-benefit analysis and the impact on the blood supply

Defer permanently

  • Individuals with sporadic or familial CJD
  • First-degree relatives of individuals with sporadic or familial CJD
  • Individuals with vCJD
  • Individuals who have received a transfusion or any other human-derived therapeutic products since 1980 in a country in which the risk of vCJD has been identified
  • Individuals with a history of treatment with pituitary-derived human growth hormone, human gonadotrophin, dura mater graft, corneal transplant or neurosurgery

7.8. COUNTRY OF RESIDENCE AND TRAVEL HISTORY

Donor exposure to TTI is affected by their current and previous country (or region) of residence and their travel history. In areas that are non-endemic for specific infections, travel history is of particular importance as prospective donors may be unaware of the geographical distribution of TTI such as malaria, Chagas disease, West Nile virus and vCJD. Donor selection and donation testing strategies should be based on up-to-date and readily available information on the epidemiology and prevalence of known and emerging TTI in specific geographical areas (243,244,245) (also refer to Sections 7.3 to 7.7). The deferral of prospective donors who have visited or been resident in disease-endemic areas should be balanced against the sufficiency of the blood supply.

7.9. HIGH-RISK BEHAVIOURS

7.9.1. High-risk sexual behaviours

Certain sexual behaviours have been shown by surveillance data to be associated with a high risk of transmission of HIV, HBV and HCV (246,247). It is essential that BTS identify and defer from blood donation individuals whose sexual behaviour puts them at high risk of acquiring infectious diseases that can be transmitted through blood. Deferral policies for high-risk behaviours should be supported by public education. Deferral criteria should be simple and easily understood by staff and prospective donors and should ideally enable self-deferral, without the need for detailed intrusive questioning about an individual's sexual behaviour (248,249); they should be applied with sensitivity, a non-judgemental approach and assurance of confidentiality.

High-risk sexual behaviours include having multiple sex partners, receiving or paying money or drugs for sex, including sex workers and their clients, men having sex with men (MSM) (250,251) and females having sex with MSM (246,247,252). MSM account for the largest subpopulation of HIV-infected people in most developed countries (253,254,255,256) and many countries therefore permanently defer men who have ever had oral or anal sex with another man (254,257,258).

The permanent deferral of MSM has been criticized as being selectively discriminatory and lacking scientific rigour (253,259,260,261) and has undergone review in some countries in the light of increasingly sensitive and reliable technologies for donation screening (249,262). Studies using mathematical modelling to predict the effect of reducing deferral intervals for MSM to one or five years have suggested that the increased risk of an HIV-infected donation entering the blood supply is small, but not zero, with little gain in terms of additional donations (263,264,265,266). These studies rely on some assumptions, are applicable only to the populations studied, and relate to testing methodologies that are not available in some countries and have been superseded in others. However, no comparable evidence is currently available. The permanent deferral of MSM therefore continues to be endorsed as the default position based on the principle of risk reduction to “as low as reasonably achievable” (ALARA).

Deferral criteria for high-risk sexual behaviours in a particular country or region should be determined and reviewed frequently, based on the residual risk of transfusion-transmitted viral infections, taking into account changes in disease epidemiology, improvements in available technologies for donation testing and on-going research.

Recommendations

Defer

  • Current sexual contacts of individuals whose sexual behaviours put them at high risk of transfusion-transmissible infections
  • Former sexual contacts of individuals whose sexual behaviour put them at high risk of transfusion-transmissible infections: defer until 12 months since last sexual contact

Defer permanently

  • Individuals whose sexual behaviour put them at high risk of transfusion-transmissible infections

7.9.2. Injecting drug use

The use of injected “recreational” drugs and non-prescribed steroids is commonly associated with unsafe practices such as the sharing and re-use of needles. It carries a high risk of blood-borne infections, most commonly HCV, but also HBV and HIV (246,267,268,269,270,271,272,273,274).

Many injected drugs are highly addictive and their use may be life-long. The safest policy is therefore permanent deferral of anyone who has ever injected non-prescribed drugs. Deferral policies should be regularly reviewed as new evidence emerges.

Recommendations

Defer

  • Current sexual contacts of injecting drug users
  • Former sexual contacts of injecting drug users: defer for 12 months since last sexual contact

Defer permanently

  • Individuals with a history of injecting drug use

7.9.3. Non-injected drugs and alcohol use

The use of alcohol and non-injected “recreational” drugs is widespread in most cultures, and many local practices exist.

Prospective donors who demonstrate signs and symptoms of intoxication should be deferred as their capacity to give informed consent is likely to be impaired. A further consideration is whether regular heavy drinking or use of illicit drugs and other dependence-producing psychoactive substances is a marker for other high-risk behaviours.

The use of intranasal cocaine has been found to be a risk factor for HCV (275).

There is no documented evidence that recent ingestion of a “recreational” drug (e.g. kava) or alcohol by a donor has caused harm to the recipient of their blood. As is the case for prescribed medication, the dilution factor is such that the blood recipient receives a very small residual quantity, which is unlikely to have any adverse effect.

Considerations regarding possible allergic reactions to non-prescribed drugs in recipients are the same as for prescribed medications (also refer to Section 6.2 on medications).

Recommendations

Accept

  • If no signs of intoxication

Defer

  • If displaying signs and symptoms of intoxication

7.9.4. Detention in prisons and penal institutions

Inmates of prisons and penal institutions should not be accepted as blood donors as there is evidence of a higher incidence of HIV, HBV and HCV in these populations (276,277). In addition, there is a risk that there may be undue coercion to donate blood in these settings and that the donation may not be voluntary. The acceptance of individuals with a history of previous imprisonment requires assessment of their exposure to risk from drug use, injuries or unsafe sexual practices with the consequent appropriate deferral period.

Recommendation

Defer

  • Inmates of prisons and penal institutions

7.9.5. Cosmetic treatments and rituals

Any procedures involving penetration of the skin carry a risk of bloodborne infections, especially HIV, HBV and HCV, unless performed under sterile conditions. These include body piercing, tattooing, scarification, injections with collagen or botulinum toxoid (botox), electrolysis and semi-permanent make-up (267,268,270,271,278,279,280,281,282).

Individuals who present with a history of any procedures involving penetration of the skin should be assessed for the risk of TTI, based on when, where, by whom and how the procedure was performed. The BTS should define the deferral period, based on the sterility and safety of the procedure. If it is not possible to ascertain the sterility and safety of the procedure, the individual should be deferred for a period of 12 months.

Recommendation

Defer

  • Individuals who have had acupuncture, piercing, tattoos, ritual scarification or any other invasive cosmetic procedures: defer for 12 months following the last procedure
Copyright © 2012, World Health Organization.

All rights reserved. Publications of the World Health Organization are available on the WHO web site (www.who.int) or can be purchased from WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel.: +41 22 791 3264; fax: +41 22 791 4857; e-mail: tni.ohw@sredrokoob). Requests for permission to reproduce or translate WHO publications – whether for sale or for noncommercial distribution – should be addressed to WHO Press through the WHO web site (http://www.who.int/about/licensing/copyright_form/en/index.html).

Bookshelf ID: NBK138223

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