Pretransfusion Testing (Compatibility Testing)

11. Pretransfusion Testing (Compatibility Testing)

4. Test on Neonate

5. Identification of blood sample in the blood transfusion laboratory.

- Request Form

Transfusion request form must contain sufficient information for definite identification of the recipient. It should include:

- Name
- Age/Date of birth
- Sex
- Registration number (1.D.No.)
- Ward/Bed No.
- Address


For proper selection of blood and blood components; and for record maintenance, the request form should also provide information on:

• Type of requirement (Routine/Emergency/Group & Screen)
• Clinical diagnosis
• Obstetric history
• Indication for transfusion
• Number of units required
• Which component required
• Date and time when required
• History of previous transfusion and transfusion reaction
• Previous tests and unexpected antibody
• The blood sample alone with the request form should be signed by a doctor or a phelebotomist collecting the sample.
• Laboratory personnel should check the information on the request form with the sample and record the time of receiving the request form.

6. Storage of sample

- For 7 days at 2-6°C in sealed tubes

7. Checking previous transfusion records

• ABO & Rh(D) group
• presence of unexpected antibodies
• any problem in compatibility testing
• previous transaction
• any transfusion reaction

ABO and Rh (D) Grouping of Recipient

Perform ABO and Rh(D) grouping using a recommended technique. Any discrepancy must be resolved before blood is issued. In emergency situations, if time does not permit detailed testing, issue C group red blood cells.

If problem with Rh (D) typing, give Rh (D) negative blood.


Screening and identification of Unexpected Antibodies

* Unpooled C group cells should be used.
* C cells with known antigen profile preferred.
* Antibody identification if antibody screen positive.
* Selection of blood lacking corresponding antigen for compatibility testing.


Selection of Blood

ABO & Rh (D) grouping and screening for transfusion transmitted diseases must be done on all donor blood or blood component before the compatibility test is performed.

1. Whenever possible select ABO group specific blood or blood component for the recipient.

2. When group specific bipod is not available, use alternate ABO compatible blood or blood component.

Component	ABO group of recipient	Alternate compatible gorup
1. Whole blood	O,A,B,AB	None (only ABO group specific blood)
2. Red cell concentrate	O A B AB	None use only 0 group O O A,B or O
3. Plasma	O A B AB	A,B, or AB AB AB Note use only AB
4. Platelet concentrate	All ABO group	Compatible with red cells are preferred

3. Select blood of same Rh (D) type as that of recipient particularly in women of child bearing age.

4. If Rh(D) negative blood is not available, give Rh (D) positive blood followed by Rh (D) immunoglobulins.

5. Change over to group specific blood after administering group nonspecific blood.

6. If recipient’s serum contains unexpected antibodies, identify the antibody if possible before selecting the appropriate blood.

When this is not possible, perform compatibility testing by indirect antiglobulin technique with multiple (>10) ABO and Rh group specific donor units to find compatible blood.


Special Transfusion Requirement

1. Exchange transfusion in the newborn select <5 days old blood.

2. Massive transfusion (transfusion of blood equal to or more than the recipients blood volume within a period of 24 hours) select 10-14 days old blood.

3. Compromised heart and brain circulation select <10-14 days old blood.


Compatibility Testing (Major Crossmatch)

The function of a crossmatch is to detect in vitro incompatibilities between the donor’s cells and the patient’s serum.

If antibody screening of recipient’s serum is negative, an ABO immediate spin crossmatch (ISXM) is sufficient to check for errors that may have occured in ABO grouping of the recipient and the donor.

If antibody screening has not been done, perform crossmatch using antiglobulin technique.


Routine procedure for compatibility testing

• ABO and Rh (D) group
• Antibody screen
• Crossmatch
  • Saline RT 37”C
  • Albumin
    or
  • Enzyme
  • Antiglobulin test (using Broad Spectrum AHG)

Techniques of compatibility test

Immediate spin technique (Saline technique)


Reagents required

1. 2-5% suspension of donor’s red cells.
2. Recipient’s serum.


Procedure

1. Label 1 tube for each donor sample to be crossmatched.

2. Add 2 drops of recipient’s serum to each tube.

3. Add 1 drop of 2-5% saline suspension of donor red cells from each donor unit to appropriate tube.

4. Spin tubes at 1000 rpm for 1 minute.

5. Look for agglutination.

6. No agglutination should occur if the donor’s and recipient’s blood are compatible.


Do not proceed further if agglutination occurs since it indicates ABO mismatch. Regroup the recipient and the donor.

If no agglutination occurs in the immediate spin crossmatch and no antibody screening has been performed, proceed to the antiglobulin crossmatch.


Enzyme technique

Reagents required

1. 1% papain-cystein solution
2. Recipient’s serum.


Procedure

1. Mix 2 drops of patient’s serum with 1 drop of papain-cystein enzyme and 1 drop of 2-5% washed saline suspension of donor’s red cells.

2. Incubate at 37°C for 45 minutes.

3. Read results after centrifugation at 1000 rpm for 1 minute.


Interpretation

Agglutination indicates that the unit is incompatible and absence of agglutination indicates a compatible unit. Antiglobulin technique


Reagents required

1. Anti-human globulin reagent (Al-IC)

2. Recipient’s serum.


Procedure

1. Mix and incubate the tubes from step 6 of immediate spin test for 45 minutes at 3 7°C.

2. Spin and look for agglutination. Record the results.

3. Proceed to IAT.


Enhancing techniques e.g. albumin, enzyme and LISS can be used with AI-IG test to increase the sensitivity.

It is recommended to use two enhancing techniques for increasing the sensitivity of compatibility test.

Interpretation

No agglutination should be seen at any stage in compatibility testing. Blood is compatible if no agglutination occurs.


Use of low ionic strength saline (LISS) solution

Use of LISS allows reduction in incubation time with relatively little loss of sensitivity. Instead of suspending cells in saline, make to the correct strength suspension using LISS. The serum to cell ratio must be kept to unity. Increasing the serum to cell ratio reduces the sensitivity of LISS tests.

LISS may be used with Albumin, Enzyme or IAT. When incubation time is reduced, the second stage of haemagglutination must be assisted by gentle centrifugation. Great care must be exercised in reading the tests to distinguish between true agglutination and aggregation.


Minor Crossmatch

Minor crossmatch using patient’s red cells and donor’s serum is not essential, if every donor serum is screened for irregular antibodies at least with pooled 0 cells by saline and enzyme techniques.


Precautions

Use the attached tubing with the blood bag for obtaining donor red cells in major crossmatch.

Always place the sample from the segment of tubing from the blood bag into a prelabelled test tube and match the donor unit no on the bag and the test tubes.


Pretransfusion Testing in Special Situations

1. Emergency transfusion

During an emergency it is best to do as much as the time allows.

After the blood has been issued, full routine procedure should be adopted.


Minimum testing

. Rapid ABO grouping of patient and donor unit

. Immediate spin crossmatch (ISXM) technique


2. Massive transfusion

a. When time does not allow for compatibility testing, issue C Rh (D)-negative blood.

b. Do ABO & Rh (D) grouping of the patient and change over to the ABO and Rh (D) group-specific blood as soon as possible. Issue the blood after doing an immediate spin crossmatch.

c. After the emergency has been dealt with, antibody screening on pretransfusion samples may be performed. If negative, additional units can be issued after immediate spin crossmatch.

d. If antibody screening detects presence of antibody, additional compatibility testing may be done using AHG technique.


3. Infants

a. Determine ABO and Rh (D) group of the infant. Only cell grouping is necessary in infants less than 6 months.
b. Perform a direct antiglobulin test (DAT) on baby’s cells.
c. Screen maternal serum for expected antibodies.
d. If baby’s DAT and maternal antibody screening are negative:

* For neonates, select group ‘C’ Rh type specific blood using mother’s (if ABO compatible) or baby’s serum for compatibility testing. Transfusing group ‘C’ blood will also ensure compatible blood in ABO-HDN without any additional tests.
* For infants, select ABO and Rh group specific blood for compatibility test using infant’s serum.
* If baby’s DAT and maternal antibody screening are positive.
* Identify the antibody in the maternal serum.
* Alternatively perform compatibility testing with multiple ABO and Rh specific donor units by the AI-IG technique against maternal and infant’s serum.