blood transfusion

Compatibility Testing

Clinical Background

Procedure of providing compatible red cells for transfusion either by serological testing or electronic issue. The BT laboratory requires two group and save specimens taken a minimum of 30 minutes apart in order to provide group specific blood and blood products. When blood and blood components are requested for a patient the patient’s transfusion history including pregnancy, solid organ or bone marrow transplant must be taken into account.

Patients who have been pregnant or received a solid organ transplant, bone marrow transplant or transfusion in the last 3 months must have a blood specimen which is within 3 days (72 hours) to issue red blood cell products. Blood components such as platelets, plasma (fresh frozen plasma (FFP), Octaplas, and cryoprecipitate) as well as batch products can be issued on historical samples. Small volume replacement transfusion can be given repeatedly during the first 4 months of life without further serological testing. After 4 months of age compatibility testing should conform to the requirements of adults.

The presence of significant atypical antibodies in the plasma or a positive direct antiglobulin test (DAT) may reflect the presence of haemolytic disease of the fetus and newborn (HDFN) or an acute or delayed transfusion reaction (ATR, DTR). In those cases, further serological procedures, where appropriate, should be performed to allow selection of appropriate red cells for transfusion. A clinical history and involvement of a Haematology clinician may be required to ascertain the need for further serological procedures.

Sample Stability Short term storage: 24 hours at room temperature.
Long term storage: 7 days at 4-6°C
Transport requirements Sample should be transported to Laboratory Reception via hospital air-tube system or hand delivered to maintain storage conditions. Samples must not be subjected to extreme hot or cold conditions prior to testing.
Interpretation Types of compatibility testing: Serological testing – performed using the indirect antiglobulin test (IAT). It is used to detect ABO and non-ABO red cell antibody incompatibility between donor cells and patient plasma, by testing each donor unit against the plasma of the intended recipient. The (IAT) compatibility test is the default technique which should be used in the absence of functioning, validated IT or when electronic issue is contra-indicated. Generally patients with known alloantibodies or auto antibodies and neonates with maternal antibodies present require a serological IAT test.
Factors affecting result Incorrect specimen type received, clotted, haemolysed, icteric or lipaemic samples. Clotted samples may interfere with instrument pipetting and must not be used. Fibrin or particulate matter, clots, bubbles or scratches on the test cassette can interfere with reaction interpretations.