Blood Donation

by Vikram Singh ECE

A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation.

In the developed world, most blood donors are unpaid volunteers who give blood for a community supply. In poorer countries, established supplies are limited and donors usually give blood when family or friends need a transfusion. Many donors donate as an act of charity, but some are paid and in some cases there are incentives other than money such as paid time off from work. A donor can also have blood drawn for their own future use. Donating is relatively safe, but some donors have bruising where the needle is inserted or may feel faint.

Potential donors are evaluated for anything that might make their blood unsafe to use. The screening includes testing for diseases that can be transmitted by a blood transfusion, including HIV and viral hepatitis. The donor must also answer questions about medical history and take a short physical examination to make sure the donation is not hazardous to his or her health. How often a donor can give varies from days to months based on what he or she donates and the laws of the country where the donation takes place. For example, in the United States donors must wait eight weeks (56 days) between whole blood donations but only three days between plateletphere donations

The amount of blood drawn and the methods vary. The collection can be done manually or with automated equipment that only takes specific portions of the blood. Most of the components of blood used for transfusions have a short shelf life, and maintaining a constant supply is a persistent problem

 

*Types of donation:

A blood collection bus (bloodmobile) from Children’s Hospital Boston at a manufacturing facility in Massachusetts. Blood banks sometimes use a modified bus or similar large vehicle to provide mobile facilities for donation.

Blood donations are divided into groups based on who will receive the collected blood An allogeneic (also called homologous) donation is when a donor gives blood for storage at a blood bank for transfusion to an unknown recipient. A directed donation is when a person, often a family member, donates blood for transfusion to a specific individual Directed donations are relatively rare when an established supply exists. A replacement donor donation is a hybrid of the two and is common in developing countries such as Ghana In this case, a friend or family member of the recipient donates blood to replace the stored blood used in a transfusion, ensuring a consistent supply. When a person has blood stored that will be transfused back to the donor at a later date, usually after surgery, that is called an  donation. Blood that is used to make medications can be made from allogeneic donations or from donations exclusively used for manufacturing.

Blood is sometimes collected using similar methods for therapeutic phlebotomy, similar to the ancient practice of bloodletting which is used to treat conditions such as hereditary hemochromatosis or polycythemia vera. This blood is sometimes treated as a blood donation, but may be immediately discarded if it cannot be used for transfusion or further manufacturing.

The actual process varies according to the laws of the country, and recommendations to donors vary according to the collecting organization. The World Health Organization gives recommendations for blood donation policies, but in developing countries many of these are not followed. For example, the recommended testing requires laboratory facilities, trained staff, and specialized reagents, all of which may not be available or too expensive in developing countries.

An event where donors come to give allogeneic blood is sometimes called a blood driVe or a blood donor session. These can occur at a blood bank but they are often set up at a location in the community such as a shopping center, workplace, school, or house of worship.

* Screening:

Donors are typically required to give consent for the process and this requirement means that minors cannot donate without permission from a parent or guardian In some countries, answers are associated with the donor's blood, but not name, to provide anonymity; in others, such as the United States, names are kept to create lists of ineligible donors. If a potential donor does not meet these criteria, they are deferred. This term is used because many donors who are ineligible may be allowed to donate later. Blood banks in the United States may be required to label the blood if it is from a therapeutic donor, so some do not accept donations from donors with any blood disease. Others, such as the Australian Red Cross Blood Service, accept blood from donors with hemochromatosis. It is a genetic disorder that does not affect the safety of the blood.

All blood donors are asked questions about their medical history.

The donor's race or ethnic background is sometimes important since certain blood types, especially rare ones, are more common in certain ethnic groups. Historically, donors were segregated or excluded on race, religion, or ethnicity, but this is no longer a standard practice.

* Recipient safety:

Donors are screened for health risks that could make the donation unsafe for the recipient. Some of these restrictions are controversial, such as restricting donations from men who have sex with men for HIV risk Autologous donors are not always screened for recipient safety problems since the donor is the only person who will receive the blood. Donors are also asked about medications such as dutasteride since they can be dangerous to a pregnant woman receiving the blood

Donors are examined for signs and symptoms of diseases that can be transmitted in a blood transfusion, such as HIV, malaria, and viral hepatitis. Screening may include questions about risk factors for various diseases, such as travel to countries at risk for malaria or variant Creutzfeldt-Jakob Disease (vCJD). These questions vary from country to country. For example, while blood centers in Québec, Poland, and many other places defer donors who lived in the United Kingdom for risk of vCJD donors in the United Kingdom are only restricted for vCJD risk if they have had a blood transfusion in the United Kingdom.

                                                                                                                           *Donor safety:

The donor is also examined and asked specific questions about their medical history to make sure that donating blood is not hazardous to their health. The donor's hematocrit or hemoglobin level is tested to make sure that the loss of blood will not make them anemic, and this check is the most common reason that a donor is ineligible. Pulse, bLood pressure, and body temperature are also evaluated. Elderly donors are sometimes also deferred on age alone because of health concerns.The safety of donating blood during pregnancy has not been studied thoroughly, and pregnant women are usually deferred

*Blood testing:

The donor's blood typE must be determined if the blood will be used for transfusions. T he collecting agency usually identifies whether the blood is type A, B, AB, or O and the donor's RH (D)type and will screen for antibodies to less common antigens. More testing, including a crossmatch, is usually done before a transfusion. Group O is often cited as the "universal donor" but this only refers to red cell transfusions. For plasma transfusions the system is reversed and AB is the universal donor type.

Most blood is tested for diseases, including some STDs The tests used are high-sensitivity screening tests and no actual diagnosis is made. Some of the test results are later found to be false positives using more specific testing False negatives are rare, but donors are discouraged from using blood donation for the purpose of anonymous STD screening because a false negative could mean a contaminated unit. The blood is usually discarded if these tests are positive, but there are some exceptions, such as autologous donations. The donor is generally notified of the test result

Donated blood is tested by many methods, but the core tests recommended by the World Health Organization are these four:

                                                                                                                                                                                                                                                                                                                                                                                                                       (1) Hepatitis B Surface Antigen

(2) Antibody to Hepatitis C

(3) Antibody to HIV, usually subtypes 1 and 2

(4) Serologic test for Syphilis

The WHO reported in 2006 that 56 out of 124 countries surveyed did not use these basic tests on all blood donations.

A variety of other tests for transfusion transmitted infections are often used based on local requirements. Additional testing is expensive, and in some cases the tests are not implemented because of the cost. These additional tests include other infectious diseases such as West Nile Virus Sometimes multiple tests are used for a single disease to cover the limitations of each test. For example, the HIV antibody test will not detect a recently infected donor, so some blood banks use a p24 antigen or HIV nucleic acid test in addition to the basic antibody test to detect infected donors during that period. Cytomegalovirus is a special case in donor testing in that many donors will test positive for it. The virus is not a hazard to a healthy recipient, but it can harm infants and other recipients with weak immune systems.