A 23-year-old female presented with jaundice and pallor for 2 months. Her peripheral blood smear shows the presence of spherocytes. The most relevant investigation to arrive at a diagnosis is;
Correct Answer: Coombs test
Description: Ans. c. Coombs test (Ref: Robbins 9/e p643-644; Chandrasoma and Taylor 3/e p401)History of jaundice in a 23-year old female with pallor and spherocytes in peripheral blood points towards the diagnosis of autoimmune hemolytic anemia (AIHA). The diagnostic test for AIHA is the antiglobulin test (Coombs' test).Autoimmune hemolytic anemia (AIHA):Onset is very often abrupt and can be dramatic.The hemoglobin level can drop, within days, to as low as 4g/dL; the massive red cell removal will produce jaundice, and often the spleen will be enlarged. When this triad is present, the suspicion of AIHA must be high.The diagnostic test for AIHA is the antiglobulin test (Coombs' test).AIHA is diagnosed by detection of autoantibodies with the direct antiglobulin (direct Coombs') test.IgG is present in warm antibody hemolytic anemia, and C3 (C3b and C3d) in cold antibody disease.Reticulocyte count is increased in both hereditary spherocytosis and AIHA.Osmotic Fragility Test is used to evaluate hemolytic anemia, especially hereditary spherocytosis, and immune hemolytic states.Test for PNH:PNH will present with hemoglobinuria.Blood tests in PNH show changes consistent with intravascular hemolytic anemia:Low hemoglobinRaised LDHRaised reticulocytes (immature red cells released by the bone marrow to replace the destroyed cells)Raised bilirubin (a breakdown product of hemoglobin)Decreased levels of haptoglobinThe direct antiglobulin test (DAT, or direct Coombs' test) is negative, as antibodies do not cause the hemolysis in PNH.Warm antibody hemolytic anemiaCold antibody hemolytic anemia* Antibodies here bind with antigens (on RBC) at body temperature (37deg C)* These antibodies are called warm antibodies and are nearly IgGQ* Antibodies here bind with antigens (on RBC) better at temperature lower than 37degC* These antibodies are called reactive antibodies and are usually IgM* Rarely IgG antibodies e.g. The Donath Landsteiner antibody of Paroxysmal cold hemoglobinuria)QCausesCauses1. Idiopathic2. Lymphomas: CLLQ, Non-Hodgkins etc.3. SLEQ and other Collagen Vascular DiseasesQ4. Drugs:* Alpha-MethyldopaQ* Penicillin type (stable pattern)* Quinidine type (unstable pattern)1. Acute: Mycoplasma InfectionQ, Infections mononucleosisQ2. Chronic: IdiopathicQ, Lymphoma3. Paroxysmal cold hemoglobinuriaQ IgGMechanism of HemolysisMechanism of Hemolysis* Human red cells cooled with IgG are trapped by splenic macrophages leading to red cell destructionQ* Antibodies of IgM type bind on red cell surface and cause agglutination* Hemolytic effect is mediated through fixation of C3 to RBC surfaceQ.DiagnosisDiagnosis* Positive direct Coomb's test, at 37degC for presence of warm antibodies on surface of Red cell.* Positive Indirect Coomb's test at 37degC for presence of large quantities of warm antibodies in serum.Q* Positive direct Coomb's test for detection of C3 on the red cell surface, but IgM responsible for coating on red cells is not found.Q
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