8 - COMPATIBILITY TESTING

COMPATIBILITY TESTING

Includes all pre-transfusion testing performed on a potential transfusion recipient and the appropriate donor blood

1. ABO and RhD group testing on donor and recipient

2. Screening for donor’s and recipient’s sera for unexpected abs

3. Crossmatch

Compatibility testing for Homologous transfusion (3)

1. ABO and RhD group testing on autologous units and recipient

2. Ab screening

3. Major xmatch (not required; immediate spin is often required)

Compatibility testing for Autologous transfusion (3)

• infant

• infant ; mother

• crossmatch

• group O ; ABO compatible RBC ; crossmatch

Compatibility testing for Neonatal transfusion:

• ABO and Rh on the _____

• Antibody screen on the ______ or the ______

• lf the antibody screen is negative, a _________ is not necessary

• If the donor cells are not _________, the infant must be tested for anti-A and anti-B antibodies. If either is present, _______________________ should be used. A _____________ is not necessary

compatibility testing

Its primary purpose is to ensure best possible results of a blood transfusion

• survival rate

• recipient's

Compatibility testing:

• The transfused red cells should have an acceptable _____________

• There should be no significant destruction of the ___________ own red cells

clerical errors

The blood bank must use a system that ensures proper patient identification and labelling of specimens. Most fatal transfusion reactions are due to?

Clotted non-anticoagulated blood

Blood spx that should be used for compatibility testing

EDTA

complement activating antibodies

Most anticoagulants (______) chelate calcium making it unavailable to participate in complement activation. Thus, some ________________________________ may not be detected during compatibility testing if anticoagulated blood is used

serum

plasma

Most blood bank technologists prefer ______, ______ may cause small fibrin clots to form and may be mistaken as that of true agqlutination

72 hours

The freshest sample possible should be used for compatibility testing (not older than _________)

2.5% saline suspension of red cells

Blood sample used for most serologic tests

1 to 6°C

7 days

Both donor and recipient samples must be stored at _______, a minimum of ______ following transfusion

ARASC

1. ABO Grouping

2. Rh Typing

3. Antibody Screening

4. Selection of Appropriate units

5. Crossmatching

COMPATIBILITY TESTING PROTOCOL (5)

ABO group of red cells

• Determined by two procedure: red cell grouping and serum grouping

• The results of both procedures should agree

• Any discrepancies should be thoroughly investigated and resolved prior to transfusion

AB

universal

ABO antibodies

A recipient can be transfused with donor blood that is not identical. These recipients are those whose phenotype ___ are called _________ recipients. Their plasma do not contain _______________; therefore, they can be transfused with any blood group

Group O individuals

They are universal donors because their blood can be transfused to any individual regardless of ABO group

Serum grouping

It is not performed with Rh typing because most Rh-negative individuals do not have anti-D in their serum

Anti-D

are present in the sera of Rh-negative individuals only if they are exposed to Rh-positive red cells through transfusion or pregnancy

Du typing

Du positive red cells bind anti-D antiserum but not enough to cause agglutination. The cell bound anti-D can be detected by performing indirect antiglobulin test

Antibody Screening

The patient serum or plasma must be tested for unexpected antibodies.

antibody screening

Its obiective is to detect as many clinically significant antibodies as possible.

Clinically sianificant antibodies

refer to antibodies that are reactive at 37°C and/or in the antihuman globulin test and are known to cause a transfusion reaction or unacceptably short survival of the transfused red cells.

group O cells

antibody screen

To ensure detection of all clinically significant antibodies, the patient's serum is incubated with 2 or 3 selected _____________ that express most of the common antigens in the major blood group system. This is termed?

D, C, c, E, e, Fya, Fyb, Jka, Jkb, K, k, Lea, Leb, M, N, PI, S, s

Blood group systems for Antibody screening

Agglutination with the Group O screening cells

indicates that a specific antibody is present in patient's serum

antibody identification

Testing the patient's serum against a panel of phenotype red cells can identify this antibody

ABO group of the recipient

It must be the most important consideration for selecting donor units for transfusion

• ABO compatible ; same

• packed RBC

• Whenever possible, the donor units should be the _____ ABO group as the recipient

• lf not possible, the donor units must be _______________ with the recipient's serum and must be given as _________

None

Alternative Blood (Packed RBC) or Non-ABO Identical Donors for O type

O

Alternative Blood (Packed RBC) or Non-ABO Identical Donors for A type

O

Alternative Blood (Packed RBC) or Non-ABO Identical Donors for B type

A, B, O

Alternative Blood (Packed RBC) or Non-ABO Identical Donors for AB type

Rh type of the recipient

It is the second most important consideration

Rh-positve recipients

They may receive either Rh-positive or Rh-negative units

avoid being sensitized to the D antigen

anti-D

Rh-negative recipients should only receive Rh-negative RBC to __________________________________. Rh-negative recipients may receive Rh-D positive RBC if it has been demonstrated that _____ is not present in the recipient.

Group O negative RBC

It is the component of choice for neonatal transfusion

• Group specific blood

• compatible

• _____________________ may be given if the mother and the infant are the same ABO type

• The donor RBC must be ___________ with the mother's serum

O negative ; group specific

compatibility testing

In emergency cases, if uncrossmatched blood is to be released, ___________ or __________ blood should be given and ____________________ should be performed as soon as possible

Crossmatch

an antibody test on the serum of the patient using the red cells of the donor as test cell

• cold ; 37°C

• saline suspended cells ; high protein molecule

Antibodies in the serum of the patient have different specificities, which are detected under a variety of different conditions:

• Some are best detected in the ____; others are incubated at _____

• Some work well against ____________________, while others require a ____________________ as:

  • 30% bovine albumin

  • Antiglobulin reagent

  • Enzymes

crossmatch

There have been thoughts of eliminating it entirely. However, to many blood bankers, it still has a definite role

crossmatch

a final check of ABO incompatibility between donor and patient

crossmatch

It may detect the presence of an antibody in the patient serum that will react antigens on the donor red cells but was not detected in antibody screening because the corresponding antigen was lacking from the screening cells

Major crossmatch

This consists of mixing the patient serum with donor red cells (PSDR)

Major crossmatch

This will ensure that the blood given does not contain antigens to which the recipient has antibodies

Major crossmatch

This is much more critical for ensuring safe transfusion test than the minor crossmatch

Minor crossmatch

This consists of mixing the donor's serum with patient's red cells (PRDS)

Minor crossmatch

This determine whether the donor contains an antibody, which will attack the recipient's red cells

Minor crossmatch

lf donor units are screened in advance for unexpected antibodies, it is not necessary

Immediate Spin Saline Crossmatch

Simplest Serologic Crossmatch

Immediate Spin Saline Crossmatch (Simplest Serologic Crossmatch)

Red cells for crossmatching are obtained from a segment or tubing from donor's blood bag.

The cells are washed to remove fibrin clots as they may interfere with interpretation of results.

The cells are then resuspended to a 2-4% concentration in saline

Immediate Spin Saline Crossmatch (Simplest Serologic Crossmatch)

Procedure: The patient's serum is mixed with saline-suspended red cells at room temperature and the tube is centrifuged immediately

Immediate Spin Saline Crossmatch (Simplest Serologic Crossmatch)

is designed to detect ABO incompatibilities between patient's serum and donor's red cells

Immediate Spin Saline Crossmatch (Simplest Serologic Crossmatch)

can be used as sole crossmatch method only if the patient has no present or previous clinically significant antibodies

Computer Crossmatch

It was indicated it can detect ABO incompatibility as safe as the immediate spin crossmatch

Computer Crossmatch

compares recent ABO serologic test results and interpretation on file for both the donor and the patient being matched and determine compatibility based on comparison

Abbreviated Crossmatch

Type and screen coupled with immediate spin crossmatch

Abbreviated Crossmatch

The type and screen is a policy in which the patient's blood sample is tested for ABO, Rh and unexpected antibodies, then stored in the blood bank for immediate crossmatching

Type and screen

a policy in which the patient's blood sample is tested for ABO, Rh and unexpected antibodies, then stored in the blood bank for immediate crossmatching

Abbreviated Crossmatch

ABO and Rh compatible blood can be safely released after an immediate spin or computer crossmatch only if the patient has no present or previous clinically significant antibodies

Antiglobulin Crossmatch

Begin in the same manner as the immediate spin crossmatch then continues with the 37C incubation and finishes with an antiglobulin test

Albumin

It is a general method used to enhance antigen-antibody rxns, which is added during incubation at 37 deg C to enhance reactivity of some abs

Lowionic strength solution (LISS) and polyethylene glycol (PEG)

These 2 are general methods used to enhance antigen-antibody rxns, which is added in place of albumin to facilitate formation of ag-ab complexes

AHG ; anti-IgG ; anti-complement

For greatest sensitivity, an ____ containing both ________ and ______________ is added in the final phase of the crossmatch

Autocontrol

Consists of the patient's own cells and serum and may be tested in parallel with the crossmatch (PSPR)

Autocontrol

Current AABB standards no longer require it, but blood bankers still find it useful

Antibody Panel

Indirect Antiglobulin Test

Antibody Panel

Identily specificity of alloantibady and autoantibody

Direct Antiglobulin Test

Assess presence of antibody ar complement coated RBC

Antibody Panel

Mix patient serum + panel of 10 reagent RBC containing all commonly significant antigens

→AlloAb → IAT → Crossmatch ABO/Rh compatible donor lacking the corresponding antigen →Tranfuse compatible blood

→AutoAb → DAT → Crossmatch ABO/Rh compatible donor blood → Transfuse least incompatible bload

Direct Antiglobulin Test

To diagnose DHTR or AIMA

IAT

Alloantibody

DAT

Autoantibody

ALLOAb → IAT

Crossmatch ABO/Rh compatible donor lacking the corresponding antigen

AUTOAb → DAT

Crossmatch ABO/Rh compatible donor blood

compatible blood

Alloab → IAT → Crossmatch ABO/Rh compatible donor lacking the corresponding antigen →transfuse _________________

least compatible blood

AutoAb → DAT → Crossmatchg ABO/Rh compatible donor blood → transfuse ______________________

Antibody Screen

IAT

Determine red cell alloantibodies and autoantibodies in patient serum

Immediste Spin Bload Type

Determine the patient ABO/Rh phenotype

+

-

Cause of agglutination: Antibody reacts with antigen on screening cells but not on donor cells

Antibody screen = ?

Crossmatch = ?

-

+

Causes of agglutination:

• Antibody reacts with a low incidence antigen

• Donor cells have a positive DAT

• Technical error - REPEAT

Antibody screen = ?

Crossmatch = ?

+

+

Cause of agglutination: Antibody reacts with an antigen on donor cells and screening cells

Antibody screen = ?

Crossmatch = ?

-

-

Cause of agglutination: No Ab detected

Antibody screen = ?

Crossmatch = ?

Possibly phenotype donor to confirm compatibility

Antibody screen = +

Crossmatch = -

Compatible for Transfusion?

No

Antibody screen = -

Crossmatch = +

Compatible for Transfusion?

No

Antibody screen = +

Crossmatch = +

Compatible for Transfusion?

Yes

Antibody screen = -

Crossmatch = -

Compatible for Transfusion?

• Repeat ABO grouping

• Verify identity of the sample

Remedy for Incorrect ABO grouping of the patient or donor (2)

Perform antibody identification studies on patient serum and repeat crossmatch using blood units negative for the corresponding antigen

Remedy for an alloantibody in the patient's serum reacting with the corresponding antigen or donor red cells?

• Repeat autoadsorption of patient's serum to remove autoantibodies

• Perform antibody identification, then repeat the crossmatch using autoadsorbed serum

Remedy for an autoantibody being present in the patient's serum (2)

use saline replacement technique

Remedy for Rouleaux formation

Rouleaux formation

It due to:

• Imbalance of A/G ratio of patient serum as in diseases, such as myeloma and macroglobulinemia

• Presence of highly molecular weight dextrans or other plasma expanders

• Contaminants

(-) Ab screen, Autocontrol

(+) Major crossmatch

May be caused by:

• Error in ABO grouping of donor and patient

• Donor unit with a positive DAT

• Donor with an alloantibody to a low incidence antigen

(+) Ab screen

(-) Autocontrol

(+) Major crossmatch

May be caused by a patient alloantibody to an antigen on donor cells

(+) Ab screen, Autocontrol, Major crossmatch

May be caused by

• Recipient autoantibody

• Recipient alloantibody to recently transfused RBC

• Rouleax formation (which is usually seen at 37°C)