By
Ahmad Nabil Hamdy
Intended Learning Outcomes (ILOs)
 Compatibility Testing
 Approaches Requiring Less Than a Complete
Crossmatch
 Is the Crossmatch Really Needed?
 What can be given in an emergency transfusion?
Compatibility testing is done to avoid
a hemolytic transfusion reaction
If the Host or Recipient recognizes
the donor RBC surface antigens as foreign,
the host will mount an immune response
to the donor RBC’s
ABO
ABO blood group antigens present on red blood cells
and IgM antibodies present in the serum
Rhesus
47 Antigens make up the Rhesus Blood Group
The most significant is the D antigen
What is compatibility testing?
 Also called pretransfusion testing
 Purpose:
 To select blood components that will not cause harm to
the recipient and will have acceptable survival when
transfused
 If properly performed, compatibility tests will
confirm ABO compatibility between the
component and the recipient and will detect the
most clinically significant unexpected antibodies
Compatibility testing
 Can be divided into 3 categories:
 Preanalytical procedures
 Serological testing
 Postanalytical procedures
Patient Identification
 Must confirm
recipient’s ID from
bracelet ON the
patient
 Full patient name and
hospital number
 Name of physician
http://www.usatoday.com/tech/news/techinnovations/2006-07-17-chips-everywhere_x.htm
Sample Identification
 The sample should also
have the full patient
name, hospital
number, and physician
 Date and time of
collection,
phlebotomist’s initials
 All of this should be on
the request form and
the sample
Specimen Tubes
Pink Top - EDTA
Red Top – no additives
Serological Testing
 3 tests:
 ABO/Rh
 Antibody detection/identification
 Crossmatch
ABO/Rh Typing
 In the ABO typing, the forward and reverse MUST
match
 In the Rh typing, the control must be negative
 Both of these will indicate what type of blood should
be given
Anti A
Anti B
A
Anti B
Anti A
Anti B
B
Anti A
AB
Anti A
Anti B
O
Antibody screen
 Also called the indirect Coombs test or the indirect
antiglobulin test
 The antibody screen will detect the presence of any
unexpected antibodies in patient serum
 If antibodies are detected, identification should be
performed using panel cells (with an autocontrol)
 IS
 37° (LISS)
 AHG
Crossmatching
 Purpose:
 Prevent transfusion reactions
 Increase in vivo survival of red cells
 Double checks for ABO errors
 Another method of detecting antibodies
Crossmatches
 According to the AABB Standards:
The crossmatch “shall use methods that
demonstrate ABO incompatibility and clinically
significant antibodies to red cell antigens and shall
include an antiglobulin phase”
Crossmatch
No agglutination ~ compatible
Agglutination ~ incompatible
Donor RBCs
(washed)
Patient serum
The procedure
 Donor cells are taken
from segments that
are attached to the unit
itself
 Segments are a
sampling of the blood
and eliminate having
to open the actual unit
Crossmatch Procedure
 if antibodies are NOT detected:
 Only immediate spin (IS) is performed using patient
serum and donor blood suspension
 This fulfills the AABB standard for ABO incompatibility
 This is an INCOMPLETE CROSSMATCH
 If antibodies ARE detected:
 Antigen negative units found and X-matched
 All phases are tested: IS, 37°, AHG
 This is a COMPLETE CROSSMATCH
Crossmatches…
Will
Verify donor cell ABO compatibility
Detect most antibodies against donor cells
Will Not
Guarantee normal survival of RBCs
Prevent patient from developing an antibody
Detect all antibodies
Prevent delayed transfusion reactions
Approaches Requiring Less Than a Complete
Crossmatch
Type and Screen
 Determines the ABO-Rh of the
patient and the presence of the
most commonly found unexpected
antibodies(elimination
of
the
crossmatch ).
Type and Screen
 If an emergency transfusion is required after type and
screen alone, an immediate-phase crossmatch is
performed.
 Blood given in this manner is more than 99% effective in
preventing incompatible transfusion reactions due to
unexpected antibodies.
Is the Crossmatch Really Needed?
 If the correct ABO and Rh blood type is given, the
possibility of transfusing incompatible blood is less
than 1 chance in 1000.
 ABO-Rh typing alone results in a 99.8% chance of a
compatible transfusion,
 The addition of an antibody screen increases the safety
to 99.94%, and
 A crossmatch increases this to 99.95%.
Physician responsibility in ordering
uncrossmatched blood
 In an emergency (ER or OR), there may not be enough
time to test the recipient’s sample
 It is your judgment that the risk of the patient dying
from from anemia is greater than the risk of
transfusing the patient without pre-transfusion testing
What can be given in an emergency?
 Type-Specific, Partially Crossmatched Blood
 An ABO-Rh typing and an immediate-phase crossmatch
 An abbreviated format
 Macroscopic agglutination.
 This takes 1 to 5 minutes
What can be given in an emergency?
 Type-Specific, Uncrossmatched Blood
 The ABO-Rh type
 Most ABO type-specific transfusions are successful.
 Caution should be used for patients who have
previously received transfusions or have had
pregnancies.
What can be given in an emergency?
 Type O Rh-Negative (Universal Donor),
Uncrossmatched Blood
 Type O blood lacks the A and B antigens
 Type O Rh-negative, uncrossmatched packed RBCs
should be used in preference to type O Rh-negative whole
blood.
 More than two units of type O Rh-negative,
uncrossmatched whole blood, the patient probably
cannot be switched to his or her blood type .
Specific Recommended Protocol
Infuse crystalloids or colloids.
2. Draw a blood sample for typing and crossmatching.
3. If crossmatched blood is not ready to give, use typespecific or type O Rh-negative cells or type O Rhpositive cells for males or postmenopausal females
without a history of transfusions.
1.
Summary
 The crossmatch “shall use methods that demonstrate ABO
incompatibility and clinically significant antibodies to red
cell antigens
 If an emergency transfusion is required after type and
screen alone, an immediate-phase crossmatch is performed
before transfusion (an abbreviated format )
 If crossmatched blood is not ready to give, use type-specific
or type O Rh-negative cells