Blood Banking

Blood banking, the process of collecting (donation), testing, processing, and storing blood for later use (transfusion), is a cornerstone of emergency and surgical medicine and is dependent on the clinical laboratory for ensuring the safe use of blood and its components.

blood bank

A blood bank is a cache or bank of blood or blood components, gathered as a result of blood donation, stored and preserved for later use in blood transfusions.

A  number  of  laboratory  tests  must  be  completed  before  blood  or  blood  products  can  be transfused:

-  Determination of the blood type with a cross match.

-  Screening for antibodies that may produce adverse effects if transfused.

-  Screening for possible infectious agents that could be transmitted with transfusion.

The following tests are mandatory on all units of blood collected for transfusion: 

-  ABO group and Rh type

-  Screening for blood-group antibodies

-  Serologic test for syphilis

-  Serologic tests for human retroviruses including:

   o  HIV-1

   o  HIV-2

   o  HTLV I

   o  HTLV II

-  Serologic tests for hepatitis including:

Hepatitis B and Hepatitis C 

If, and only if, all of these markers are negative can blood be conveyed to the Blood Bank for storage until usage. A postive result for some of these tests may prevent further donation by that person. A person with such a test result will be notified by the donor center. Persons with a potential medical condition should see a physician and should not, under any  circumstance, donate only to have blood tested. These measures are done to make the blood supply as safe as possible.

Blood Typing 

Blood typing involves testing a person's blood for the presence or absence of certain antigens that are present on the red blood cells. Two of these antigens, or surface identifiers, are the A and B markers included in ABO  typing.  People  whose  red  blood  cells  have  A  antigens  are considered to  be  blood type  A; those  with B antigens are type B; those  with both  A and B antigens  are  type  AB;  and  those  who  do  not  have  either  of  these  makers  are  considered  to have  blood  type  O.  Our  bodies  produce  antibodies  against  those  ABO  antigens  we  do  not have  on  our  red  blood  cells,  which  is  why  we  can  receive  blood  only  from  donors  with certain blood types.

Another important surface antigen is called Rh factor. If it is present on your red blood cells, your blood is Rh+ (positive); if it is absent, your blood is Rh- (negative(  .

According to American Association of Blood Banks (AABB), the distribution of blood types

is as follows:

-  O Rh-positive 38% 

-  A Rh-positive 34% 

-  B Rh-positive 9% 

-  O Rh-negative 7% 

-  A Rh-negative 6% 

-  AB Rh-positive 3% 

- B Rh-negative 2% 

-  AB Rh-negative 1% 

ABO and Rh blood typing are conducted on all donor units by the collection facility and in the laboratory for hospital patients. There are two steps to ABO typing: forward and reverse typing.  First,  forward  typing  is  performed  by  mixing  a  sample  of  blood  with  anti-A  serum ) serum  that  contains  antibodies  against  type  A  blood)  and  with  anti-B  serum  (serum  that contains  antibodies  against  type  B  blood).  Whether the  blood  cells  stick  together) agglutinate)  in  the  presence  of  either  of  these  sera  determines  the  blood  type.  Second,  in reverse typing, the patient's serum is mixed with blood that is known to be either type A or B to watch for agglutination. A person's blood type is confirmed by the agreement of these two tests.

Similarly, with Rh typing a sample of a person's red blood cells is mixed with an anti -serum containing anti-Rh antibodies.  If agglutination occurs,  then  the  blood  is  Rh-positive;  if  no reaction is observed, then the blood is Rh-negative. Rh testing is especially important during pregnancy because  a  mother  and  her  fetus  could  be  incompatible.  If  the  mother  is  Rh-negative  but  the  father  is  Rh-positive,  the  fetus  may  be  positive  for  the  Rh  antigens.  As a result, the mother's body could develop antibodies against Rh,  which can destroy the baby's red  blood  cells.  To  prevent  development  of  Rh  antibodies,  an  Rh-negative  mother  with  an Rh-positive partner is treated with an injection of Rh immunoglobulin during the pregnancy and again after delivery if the baby is Rh-positive.

Compatibility Testing 

Compatibility testing is performed to determine if a particular unit of blood can be transfused safely into  a  certain  patient.  This  includes  ABO-Rh  blood  typing  ,  antibody  screening  (for unexpected  red  blood  cell  antibodies  that  could  cause  problem  in  the  recipient),  and  cross-matching.

There are many antigens besides A, B, and Rh. However, neither the donor nor the recipient is  tested  routinely  for  these  other  antigens.  However,  if  a  patient  has  had  a  previous transfusion  or  been  pregnant,  they  may  have  developed  antibodies  to  one  of  these  other antigens. Therefore, it  will  be important in all  future transfusions that the  donor's red  blood cells  do  not  have  that  particular  antigen;  otherwise,  the  recipient  may  have  a  transfusion reaction. The presence of such an antibody is determined by doing an antibody screening test by mixing the patient's serum with red cells of a known antigenic makeup.

Cross-matching  is  performed  to  determine  if  the  patient  has  antibodies  that  react  with  the donor's cells. If there is a reaction, the laboratory staff will investigate further to identify the specific  antibody  and  locate  donor  units  that  lack  the  antigen  that  matches  the  patient's antibody. This unit will then be tested to confirm that this is a safe match.

It  is  ideal  to  receive  a  blood  transfusion  with  blood  that  matches  your  blood  type  exactly. However, anyone can receive type O red blood cells in an emergency. Therefore, people with type  O  blood  (particularly  O  Rh-negative)  are  called  "universal  donors."  People  with  type AB Rh-positive blood  can  be transfused  with red  blood  cells  from individuals  of any  ABO type and are commonly referred to as "universal recipients."

There are two types of crossmatches: 

-  Major  crossmatch:  This  is  the  most  important  crossmatch,  comparing  donor erythrocytes  to  recipient  serum  (i.e.  you  are  checking  for  preformed  (acquired  or naturally occurring) antibodies in recipient serum against donor erythrocytes. For the major crossmatch, you need red blood cells from the donor (this ca n be whole blood from a  donor animal  or  packed  red  blood  cells) in EDTA  or  citrate and  serum  from the recipient (non-anticoagulant tube).

-  Minor crossmatch: This compares donor serum to recipient erythrocytes and checks for preformed antibodies in donor serum that could hemolyse recipient red cells. This crossmatch  is  less  important  as  usually  the  donor  serum  is  markedly  diluted  after transfusion and is unlikely to produce a significant transfusion reaction. This type of crossmatch could be important if transfusing small patients, in which hemodilution is less likely to occur. 

For  the  major  crossmatch:  Donor  erythrocytes  are  washed  and  incubated  with  recipient serum.

For  the  minor  crossmatch:  Donor  serum  is  incubated  with  washed  recipient  erythrocytes.

 Apheresis

Apheresis is a medical technology in which the blood of a donor or patient is passed through an  apparatus  that  separates  out  one  particular  constituent  and  returns  the  remainder  to  the circulation. It is thus an  extracorporeal therapy.   An extracorporeal  medical procedure is a medical procedure which is performed outside the body.

Plasmapheresis

Plasmapheresis is the removal, treatment, and return of (components of)  blood plasma from blood circulation. It is thus an extracorporeal therapy. The method can also be used to collect plasma for further manufacturing into a variety of medications. The procedure is used to treat a  variety  of  disorders,  including  those  of  the  immune  system,  such  as  Guillain-Barré syndrome, lupus, and thrombotic thrombocytopenic purpura.

Transfusion Reactions

Hemolytic Reactions

Hemolytic reactions occur when the recipient's serum contains antibodies directed against the corresponding antigen  found  on  donor red  blood  cells. This can be an  ABO incompatibility or an incompatibility related to a different blood group antigen.

Allergic Reactions

Allergic  reactions  to  plasma  proteins  can  range  from  complaints  of  hives  and  itching  to anaphylaxis. Such reactions may  occur in up to 1 in 200 transfusions  of RBCs and 1  in 30 transfusions of platelets.

Febrile Reactions

White  blood  cell  reactions  (febrile  reactions)  are  caused  by  patient  antibodies  directed against  antigens  present  on  transfused  lymphocytes  or  granulocytes.  The  risk  for  febrile reaction is 1 in 1,000 to 10,000.Symptoms usually consist of chills and a temperature rise > 1 degree C.

Bacterial Contamination

Bacterial contamination  of  blood  can  occur  during  collection.  Bacteria  can  grow  during storage  at  room  temperature  and  during  refrigeration  (psychrophilic  organisms).  Platelet products  carry the greatest risk, because they are  stored at  room temperature. Transfusing a contaminated unit can result in septic shock and death.

Circulatory Overload

Circulatory  overload  can  occur  with  administration  of  blood  or  any  intravenous  fluid, particularly in patients with diminished cardiac function.