1. 1
CHAPTER SEVEN
THE CROSS-MATCH
(COMPATIBILITY TESTING)

2. Content
2
7.1. Cross matching
7.2. Types of Cross Match
7.3. Steps for compatibility testing
7.4. Choice of Blood for cross-match
7.5. Procedure for cross-match
7.5.1.Standard cross matching
7.5.2. Emergency cross matching
7.5.3. Rapid slide crossmatching

3. Learning Objectives
3
At the end of this chapter, the student should be
able to:
 Understand the cross-match and its primary
purpose.
 Explain the constituents of the major and
minor cross match.
 Select appropriate blood for cross-match.
 Describe the types of antibodies that can be
encountered at various phases of a cross-
match.

4. 7.1 Cross-Matching
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 It is a procedure performed before transfusion to
select donor’s blood that will not cause any
adverse reaction, (hemolysis /agglutination)
 It helps the patient to receive maximum benefit
from the transfusion of red cells
 This is done by ensuring compatibility

5. Cross-Matching…
5
 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
 Detect ABO/Rh errors
Types of Cross Match
Two types
I. Major cross-match:
 Involves mixing recipient’s serum with the donor’s red cells.
 is much more critical for assuring safe transfusion than the minor
compatibility test.
 called major b/c the Abs in the recipient’s serum are most likely to

6. Types….
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II. Minor cross match:
 Involves mixing the donor’s serum with
patient’s red cells
 Called minor because
 any Ab in the donor’s serum will be diluted by the
large volume of the recipient’s blood
 the destructed RBCs of the patient may be
compensated by the transfused RBC of the donors

7. 7.3. Steps for compatibility testing
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 Accurate Patient Identification
 Proper sample collection and handling
 Review of the recipient’s past blood bank records
 Careful ABO/Rh determination
 Antibody screening of the recipient (cross matching of
the donor unit).
 In cases when the recipient possess a clinically
significant Antibody, donor units must be:
 Screened for the corresponding Ag and should be
negative
 Cross- matched

8. Steps for….
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 Finally, during the actual transfusion :
 careful observation of the recipient’s vital signs and
 post transfusion hematocrit and Heamoglobin levels
must be considered.

9. 7.4.Choice of Blood for cross-match
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 The blood selected for cross-match should be of the same ABO
and Rh (D) group as that of the recipient.
 However, Rh positive recipients may receive either Rh positive
or Rh negative blood.
 Whenever possible blood of the patients own blood group
should be given.
Otherwise the following rules should be applied.
Group A patient.
 Should receive group A blood, if not available group O
Group B patient.

10. Choice of…
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Group O patient.
 Can only receive group O blood
Group AB patient.
 Should receive from group AB, if not possible can receive
blood from group A,B, and O.
 When cross-matching is carried out, the serum is tested
against the cells.
 The serum should be fresh, that is not more than 48hours
old, to make sure that it contains complement.

11. Choice of…
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When deciding on methods for cross-matching, the
following conditions are required for Ag-Ab reactions.
 The right Temperature.
 Suitable surrounding medium
 Antigen-Antibody ratio etc..
 The safe cross-matching of blood requires that the
donor’s cells be mixed with the patient’s serum in three
separate tubes, using :
1. Saline
2. Albumin
3. Anti-human globulin reagents

12. 1. Saline tube
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 The red cells from the donor are suspended in
saline and mixed with the patient’s serum .
 show the presence of any complete antibodies
 Agglutination in the saline tube is usually caused
by:
 anti-A or anti-B antibodies and
 Occasionally by Lewis, MNSs, Lutheran and kell
antibodies.

13. 2. Albumin tube
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 The red cells from the donor’s suspended in
saline, are mixed with the patient’s serum,
and albumin is added.
 The tube is incubated at 370C
 shows the presence of any incomplete
antibodies
 the antibodies react in albumin or any other
protein medium
 Agglutination in the albumin tube is often
caused by:
 the rhesus antibodies,
 Lewis, MNSs, Lutheran and P antibodies, and
 occasionally by anti-kell.

14. 3. Anti-human globulin tube
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 A more concentrated suspension of red cells
is mixed with the patient’s serum and
incubated at 370C and then AHG is added.
 A positive test detects the presence of
antibodies of:
 rhesus, kell, kidd, S and Lewis
 Anti globulin is also essential for detection
anti-Duffy

15. 7.5. Procedure for cross-match
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7.5.1.Standard cross-match
 Is cross-match that is performed in three tubes
(Saline, albumin and AHG) within 45 to 60
minutes
Clinical significance
 detects unexpected (irregular) antibodies in the
recipient/ donor serum

16. Cross match (Standard)…
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Principle
 Serum of the recipient / donor is tested
against the red cells of the donor/ recipient
under different conditions in order to establish
their compatibility
Type of specimen
 Serum (plasma) not older than 48 hrs
 Washed cells (20-30% and 2-5%)

17. Cross match (Standard)…
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Equipments and reagents
 Test tubes
 Centrifuge
 Microscope
 Microscopic slide
 Normal saline
 20% albumin
 AHG (Coombs reagents)

18. Procedure
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1. Take 3 small tubes mark them 1,2 and 3, and add to
each the following
Tube 1 1volume of patient’s serum
1volume of 3-5% donor’s red cells
Tube 2 1 volume of 20% bovine albumin
1volume of patient’s serum
1volume of 3-5% donor’s red cells
Tube 3 3 volume of patent’s serum
1volume of 20-30% suspension of
donor’s cells

19. Cross match (Standard)…
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2. Incubate tube 1 and 2 for 30 minutes at 370C.
Incubate tube 3 for 15 minutes at 370C.
3. After incubation, remove tube 3 and wash the
cells three times with clean saline to make
sure that all the globulins are removed
from the cells.
4. And make a 3% saline suspension of the
washed cells in a tube.

20. Cross match (Standard)…
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5. To one volume of red cell deposit add 2
volumes of fresh diluted antiglobulin (coombs)
Reagent.
6. Remove tube 1 and 2 and centrifuge with
tube 3 for one minute at 1000 rpm
7. Examine the tube for heamolysis
macroscopically and microscopically for
agglutination.

21. Cross match (Standard)…
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Results
 No hemolysis or agglutination is seen in tube
1, 2 or 3
 the blood is compatible and can be issued with the
completed cross-match label.
 If there is agglutination or hemolysis in any of
the tubes
 the blood is incompatible, and must not be issued
for the patient.

22. Incompatibility investigation
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ABO incompatibility (anti A and Anti-B.)
 Saline tube ………………….Shows strong
agglutination
 Albumin tube ………………. Shows agglutination
 Anti- globulin tube ………… show no agglutination
Rhesus incompatibility (anti-D ,c, e)
 Saline tube …………………….does not usually show
agglutination
 Albumin tube …………………. Shows agglutination
 Anti- globulin tube ……………. Shows agglutination

23. Cross match (Incomp. Invest.)…
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Anti- Duffy and anti- kidd incompatibilities
 Saline tube …… Does not usually show agglutination
 Albumin tube … does not usually show agglutination
 Anti- globulin tube ……………. Shows agglutination
Anti- Lewis incompatibility
 Saline tube …………………….. Shows agglutination
 Albumin tube ………………….. Shows agglutination
 Anti- globulin tube ……………. Shows agglutination

24. 7.5.2 Emergency cross match
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 Performed when there is no enough time to perform the
standard cross match
 Takes about 25 to 30 minutes and
 Does not include antiglobulin test.
Principle
 Serum of the recipient / donor is tested against the red
cells of the donor/ recipient in saline and albumin medium
in order to establish their compatibility
Type of specimen
 Serum (plasma) not older than 48 hrs
 Washed cells (2-5%)

25. Cross match (Emergency)…
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Equipments and reagents
 Test tubes
 Centrifuge
 Microscope
 Microscopic slide
 Normal saline
 20% albumin

26. Procedure:
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1. Take 2 small tubes, mark them 1 and 2 and
add to each the following
Tube 1 1volume of patient’s serum
1volume of 3-5% donor’s red cells
Tube 2 1volume of patient’s serum
1volume of 3-5% donor’s red cells.
1volume of 20% bovine albumin

27. Cross match (Emergency)…
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2. Leave tube 1 at room temp for 15 minutes
incubate tube 2 for 15 minutes at 370C.
3. Centrifuge both tubes for one minute at 1000
rpm/min
4. Examine the tubes macroscopically for
hemolysis and microscopically for agglutination.

28. Cross match (Emergency)…
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Results
 If no hemolysis or agglutination is seen in either
tube 1 or 2
 the blood is compatible and can be issued with the
emergency cross match.
 If agglutination or hemolysis is seen in either of
the tubes
 the blood is incompatible and must not be issued for the
patient.

29. 7.5.3. Rapid direct slide cross match
(Request for un cross matched blood )
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 Takes only 3 or 4 minutes
 Plasma is used instead of serum.
 Not safe and must only used in extreme emergencies
 Standard cross match should be carried out while the
transfusion is in progress.
Procedures
1. Take 2 volume of patient’s plasma on a slide
2. Add 1 volume of donor’s whole blood of the same
group as the patient and mix.
3. Leave for 2 minutes and examine microscopically
for agglutination
Results. If the cells show agglutination the blood must
not be given and will usually indicate that the wrong
ABO group blood is being cross marched.

30. Cross match (Rapid)…
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Sources of errors in cross-matching
 Rouleaux
 Auto agglutinins
 Infected donor cells
 Anti- A1
 Over centrifugation
 Dirty glass wares etc..

31. Review Questions
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1. What is cross-matching?
2. What is the purpose of cross-matching?
3. List the types of cross-match with their
constituents
4. List the stages of cross-match and their
respective importance in antibody detection.