Direct antiglobulin test
This chapter describes the direct antiglobulin test (DAT) which is also known as Direct Coombs test (DCT). The test detects the presence of immunoglobulin G (IgG) or complement C3 and small amounts of IgG and complement are found on red blood cells (RBCs) of normal individuals. The DAT is mentioned to be useful in diagnosis of several situations that include: antibody identification, autoimmune hemolytic anemia, drug-induced hemolytic anemia and hemolytic diseases of the fetus and newborn. The detailed procedure of the test is discussed such as the specimen requirement, the methodology, evaluation of a positive DAT, eluate and panagglutinin. The clinical significance of a positive DAT is stated to be difficult to assess and among hospitalized patients, 0.7% have positive DATs, while 18% of AIDS patients have positive DATs. The significance of the DAT is assessed based on clinical and laboratory findings suggestive of decreased RBC survival, such as anemia, jaundice, hematuria and elevated lactate dehydrogenase. The false-negative DAT and false-positive DAT are further described.
