What is an antibody screen?

What is an Antibody Screen?

An antibody screen is a laboratory test that detects unexpected antibodies in a patient's serum or plasma against red blood cell antigens, performed before blood transfusion to prevent hemolytic transfusion reactions. 1, 2

Purpose and Clinical Application

The antibody screen serves as a critical pretransfusion safety measure that identifies clinically significant antibodies that could cause transfusion reactions. The test is designed to detect antibodies against common red blood cell antigens including C, D, E, c, e, M, N, S, s, P1, Lea, Leb, K, k, Fya, Fyb, Jka, and Jkb. 3

• The antibody screen is 99.99% effective in preventing transfusion of incompatible blood when properly performed 1, 2
• This test is particularly important in multitransfused patients, where alloimmunization rates are higher 4, 5
• In general hospital populations, the overall alloimmunization rate is approximately 0.49%, with antibodies against the Rh system being most frequent (64.1%) 5

Testing Methodology

The antibody screen uses reagent red blood cells that possess specific antigens to detect whether the patient has developed antibodies against these antigens. 3

• Screening reagent red blood cells can detect approximately 96% of clinically significant antibodies 1
• The test is performed using techniques such as microcolumn gel technology or tube methods 4
• Both serum and plasma samples can be used for antibody screening 3

Clinical Context: Type and Screen

The "type and screen" approach combines ABO/Rh typing with antibody screening and serves as a safe alternative to routine crossmatching for surgical procedures that rarely require transfusion. 1, 2

• If the antibody screen is negative, blood can be rapidly provided when needed without full crossmatching 2
• If the antibody screen is positive, specific antibody identification must be performed to find compatible blood units 4, 5
• The immediate spin crossmatch procedure should still be performed before releasing blood in emergency situations to verify ABO compatibility and detect high-titer antibodies against low-frequency antigens 2

When Antibody Screening is Required

Antibody screening should be performed at each transfusion visit in multitransfused patients, as new antibodies can develop between transfusion episodes. 4

• The most common alloantibodies identified are anti-E (37.2%), followed by anti-D (19.2%) 5
• Antibodies against Rh and Kell blood group antigens are the most frequent, suggesting that provision of Rh and Kell matched red cells may provide protective value 5
• The risk of clinically significant hemolytic transfusion reactions when rare antibodies are missed is approximately 1 in 500,000 to 1 in 1 million transfusions 3

Important Distinctions

The antibody screen differs from other antibody testing contexts:

• For transfusion medicine: The antibody screen detects red blood cell antibodies to prevent hemolytic reactions 1, 2, 3
• For autoimmune disease: Antibody screening refers to detecting autoantibodies like ANA, with indirect immunohistochemistry or immunofluorescence being the preliminary screening method 6
• For neurological conditions: Antibody screening involves testing for neuronal surface antibodies using cell-based assays with patient serum or CSF 6