DIRECT COOMBS

DAT

Antihuman Globulin; Broad Spectrum Direct Coombs; Coombs Direct; DAT ;Polyspecific Direct Coombs

DAT RESULT;

Pink Tube (EDTA) 

1mL

Lavender Tube (EDTA)

Diagnosis and all medications received by the patient before and after admission to the hospital must be entered into the computer.

One Pink Tube

Room Temperature

Store at 1-6 °C if not tested immediately. Sample can be tested for up to three days after collection.

Specimen drawn in wrong tube; improperly labeled; quantity not sufficient for analysis .

Daily, 24 hours

1 hour

Drugs cause at least 16% of positive reactions, especially penicillin, Keflin«, other cephalosporins, Aldomet« (alpha methyldopa), quinidine, insulin, mefenamic acid, sulfonamides, tetracycline, Lanoxin«, and levodopa. Many positive direct antiglobulin tests are due to methyldopa. Methyldopa antibodies are IgG and have Rh specificity. Lead poisoning and reticulocytosis may cause positive reactions. Two percent to 4% of patients with clinical autoimmune hemolytic anemia have a negative direct Coombs' test.

Negative

Detects immunoproteins, IgG, or complement absorbed on red cells. Used to detect autoimmune hemolytic anemias caused by antibody and/or complement components being bound to patient's red cells (including drug induced), transfusion reaction and erythroblastosis fetalis (hemolytic disease of the newborn). Coated red cells are said to be "sensitized". Warm autoimmune hemolytic anemias may have IgG, complement, or both coating the patient's cells. Broad spectrum or polyspecific antisera contain both anti-IgG and anti-C3d antibodies, possibly with additional antibodies directed against other complement fractions. If positive, a direct Coombs' using anti-IgG will be performed to determine if the cells are coated with IgG and using anticomplement to determine if the cells are coated with complement. An indirect Coombs' test and, if indicated, antibody identification may be helpful in the work-up of a positive direct Coombs' test. In cases of autoimmune hemolytic anemia or hemolytic disease of the newborn, an eluate from the patient's red cells may be performed to determine if a specific antibody is involved. Positive tests are found in warm autoimmune hemolytic anemias, hemolytic disease of the newborn, autoantibodies of no clinical significance, cold agglutinin disease, paroxysmal cold hemoglobinuria, and patients treated with drugs listed under Limitations.