Editing Blood transfusion (section)

=== Compatibility testing ===
[[File:Blausen 0086 Blood Bag.png|thumb|Illustration of labeled blood bag]]
{{Main|Blood compatibility testing}}
Before a recipient receives a transfusion, compatibility testing between donor and recipient blood must be done. The first step before a transfusion is given is to type and screen the recipient's blood. Typing of recipient's blood determines the ABO and Rh status. The sample is then screened for any alloantibodies that may react with donor blood.<ref name=uutah>{{Cite web|url=https://webpath.med.utah.edu/TUTORIAL/BLDBANK/BBPROC.html|archiveurl=https://web.archive.org/web/20090303204956/http://library.med.utah.edu/WebPath/TUTORIAL/BLDBANK/BBPROC.html|url-status=dead|title=Blood Donation and Processing|archivedate=March 3, 2009|website=webpath.med.utah.edu}}</ref> It takes about 45 minutes to complete (depending on the method used). The blood bank scientist also checks for special requirements of the patient (e.g. need for washed, irradiated or CMV negative blood) and the history of the patient to see if they have previously identified antibodies and any other serological anomalies.

[[File:Serology interpretation of antibody panel for blood group antigens.jpg|thumb|300px|Interpretation of antibody panel to detect patient antibodies towards the most relevant [[human blood group systems]] {{further|Blood compatibility testing}}]]
A positive screen warrants an antibody panel/investigation to determine if it is clinically significant. An antibody panel consists of commercially prepared group O red cell suspensions from donors that have been phenotyped for antigens that correspond to commonly encountered and clinically significant alloantibodies. Donor cells may have homozygous (e.g. K+k+), heterozygous (K+k-) expression or no expression of various antigens (K−k−). The phenotypes of all the donor cells being tested are shown in a chart. The patient's serum is tested against the various donor cells using an indirect [[Coombs test]]. Based on the reactions of the patient's serum against the donor cells, a pattern will emerge to confirm the presence of one or more antibodies. Not all antibodies are clinically significant (i.e. cause transfusion reactions, HDN, etc.). Once the patient has developed a clinically significant antibody it is vital that the patient receive antigen-negative red blood cells to prevent future transfusion reactions.<ref>{{Cite book | vauthors = Harmening D |title=Modern Blood Banking and Transfusion Practices |location=Philadelphia |publisher=F. A. Davis |edition=4th |year=1999 |isbn=978-0-8036-0419-3 |url-access=registration |url=https://archive.org/details/isbn_9780803604193 }}</ref>

If there is no antibody present, an immediate spin [[cross-matching|crossmatch]] may be performed where the recipient serum and donor rbc are incubated. In the immediate spin method, two drops of patient serum are tested against a drop of 3–5% suspension of donor cells in a test tube and spun in a serofuge. Agglutination or hemolysis (i.e., positive Coombs test) in the test tube is a positive reaction.  If the crossmatch is positive, then further investigation is needed.  Patients with no history of red cell antibodies may qualify for computer-assisted crossmatch, which does not involve combining patient serum with donor cells.

If an antibody is suspected, potential donor units must first be screened for the corresponding antigen by phenotyping them. Antigen negative units are then tested against the patient plasma using an antiglobulin/indirect crossmatch technique at 37 degrees Celsius to enhance reactivity and make the test easier to read.

In urgent cases where crossmatching cannot be completed, and the risk of dropping hemoglobin outweighs the risk of transfusing uncrossmatched blood, O-negative blood is used, followed by crossmatch as soon as possible. O-negative is also used for children and women of childbearing age. It is preferable for the laboratory to obtain a pre-transfusion sample in these cases so a type and screen can be performed to determine the actual blood group of the patient and to check for alloantibodies.

====Compatibility of ABO and Rh system for Red Cell (Erythrocyte) Transfusion====
This chart shows possible matches in blood transfusion between donor and receiver using ABO and Rh system. The symbol [[File:Blood drop plain.svg|25px]] indicates compatibility.
{| class="wikitable" style="text-align: center"
!colspan=2 rowspan=2|
! colspan="8" |Donor
|-
!O−!!O+!!B−!!B+!!A−!!A+!!AB−!!AB+
|-
! rowspan="8" |Recipient
!AB+
|[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]
|-
!AB−
|[[File:Blood drop plain.svg|25px]]||||[[File:Blood drop plain.svg|25px]]||||[[File:Blood drop plain.svg|25px]]||||[[File:Blood drop plain.svg|25px]]||
|-
!A+
|[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||||||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||||
|-
!A−
|[[File:Blood drop plain.svg|25px]]||||||||[[File:Blood drop plain.svg|25px]]||||||
|-
!B+
|[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||||||||
|-
!B−
|[[File:Blood drop plain.svg|25px]]||||[[File:Blood drop plain.svg|25px]]||||||||||
|-
!O+
|[[File:Blood drop plain.svg|25px]]||[[File:Blood drop plain.svg|25px]]||||||||||||
|-
!O−
|[[File:Blood drop plain.svg|25px]]||||||||||||||
|}
[[File:Agglutinatie rode bloedcellen libtheora.ogg|thumb|Agglutination (clumping) of red blood cells due to an incorrect transfusion]]