STANDARD OPERATING PROCEDURE (SOP): COMPATIBILITY TESTS

BLOOD CENTRE NAME

1.SCOPE & APPLICATION

This procedure is applied for compatibility testing of all patients requiring transfusion.

2.RESPONSIBILITY

It is the responsibility of the technician in the cross-matching laboratory to perform cross match and document the results. If any unexpected antibody is discrepancy, the Medical Officer in Charge of Crossmatching Laboratory is to be informed along with implicated blood samples.

3. REFERENCES

• Technical Manual of the American Association of Blood Banks 18th Edition, 2014.  Pages Method 3-1.
• Model Standard Operating Procedures for Blood Transfusion Service, WHO, New Delhi 2002

4. MATERIALS REQUIRED:

     EQUIPMENT:

• Refrigerator to store samples & reagents at 2-6 ◦C. 
• Tabletop centrifuge. 
• Microscope. 
• Incubator 

       SPECIMEN:

• Clotted blood sample of patient.
• Donor blood sample (segment of donor unit)

REAGENTS:

• Antisera (anti- A₁, anti- B, anti- AB and anti- D)
• Antihuman globulin reagent (AHG): polyspecific antiglobulin reagent 
• IgG sensitised control  check cells. 
• 0.9%  normal saline. 

            GLASSWARE:

• Glass tubes.
• Pasteur pipettes. 
• Glass slides

             MISCELLANEOUS:

• Rubber teats. 
• Disposal box. 
• Plastic beakers. 
• Wooden/ plastic blocks to hold micro tubes.
• Racks to hold serum and coombs’ tubes.

5. PROCEDURE

  PRINCIPLE:

The major crossmatch is used to detect unexpected blood group antibodies in patient’s serum against antigens on donor cells. Positive reaction in any test indicates incompatibility.

 SALINE TECHNIQUE (IMMEDIATE SPIN)

• Label tubes with patient/donor test identification.
• Add 2 drops of patient’s serum to the labelled tube.
• Prepare 5% cell suspension of donor unit segment using 0.9% normal saline.
• Add 1 drop 5% donor red cell suspension to the tubes containing patient’s serum. 
• Centrifuge the tubes at 1000 rpm for 1 minute.
• Gently resuspend the red cell button and examine for agglutination
• Read, interpret and record test results

   AHG CROSSMATCH 

• Label tubes with patient/donor test identification.
• Add 2 drops of patient’s serum to the labelled tube.
• Prepare 5% cell suspension of donor unit segment using 0.9% normal saline.
• Add 1 drop 5% donor red cell suspension to the tubes containing patient’s serum. 
• Centrifuge the tubes at 1000 rpm for 1 minute. Read and record the result
• Incubate at 37⁰C for 45 to 60 minutes. 
• Centrifuge and observe under microscope for hemolysis or agglutination. Grade and record the result
• Wash the red cell three times with normal saline solution and decant the final wash.
• Add one drop of AHG reagent to the red cell button
• Centrifuge the tubes at 1000 rpm for 1 minute. 
• Observe under microscope for hemolysis or agglutination. Grade and record the result
• Confirm the validity of negative result by adding IgG sensitised control cells
• Record test results. 
• Let a second technician check the results.

        INTERPRETATION:

• Hemolysis or agglutination in any test indicates incompatibility. 
• Absence of hemolysis / agglutination in all tests indicates compatibility.

        6. LIMITATIONS OF COMPATIBILITY TESTING

        Even a fully compatible transfusion cannot:

• Prevent isoimmunisation of the recipient
• Ensure normal red blood cell survival 
• Detect some weakly reactive antibodies

          7.DOCUMENTATION

• Enter results in crossmatch register and compatibility report form. All records are initialled by technician who performed the test and the technician who has checked the results.
• If there is incompatibility found,report it to resident I/C and faculty I/C of crossmatch lab.

           8. END OF DOCUMENT