Coombs test
The antibody screening test [A 1] or indirect Coombs test [A 2] is a blood serum test in which antibodies against specific characteristics of red blood cells (erythrocytes ) and demonstrated against certain infectious diseases.
Implementation
The blood serum of the patient (which is to be tested contains antibodies ) is reacted with the test antigen (so-called test cells from donor blood, in which the available antigens are known ) together.
If there are against the antigens IgM class antibodies in the serum, clotted the approach already in this step of the test and the test result is therefore positive.
If the test is negative up to this point, any remaining incomplete antibodies of the IgG class can be detected indirectly. In this step, in addition Coombs serum is added ( antihuman globulin ), so the rabbit antibody against human antibodies. Here means a clumping of a positive test result.
If a multiple antigens simultaneously performed antibody screening test has a positive result must be determined in further testing, which has the antigens caused the reaction ( differentiation).
Antibody detection tests for pregnancies and blood transfusions
Everyone has formed in the early months of pregnancy natural antibodies against antigens of foreign red blood cells. The antibody screening test is beyond irregular antibodies that may arise, for example, two to three days after the mixing of the mother and child during childbirth or after a blood transfusion. You can then lead to incidents on subsequent blood transfusions or pregnancies.
For antibody screening test the patient's serum is brought together with red blood cells which contain the test antigens. By default, a rhesus incompatibility is excluded, as well as the antigens of the Kell, Duffy and MNS system will be tested. In the great majority of cases the antibody test is negative, if positive results include the Rhesus antibodies to the most common found antibodies for differentiation.