Coombs test indirect

The direct Coombs test detects the presence of antibodies on red cells, whereas the indirect test detects the presence of circulating antibodies to antigens present on red cells. 

Blood transfusions Should the need for transfusion arise in a patient receiving methyidopa, perform both a direct and indirect Coombs test. 

Perform both direct and indirect Coombs test if blood transfusion needed. If indirect Coombs test positive, interference may occur with crossmatch. Positive direct Coombs test will not interfere... 

During penicillin treatment the erythrocytes are normally coated with penicillin, thereby forming a penicilloyl bond on their surface (49). A drug-specific IgG antibody is directed against the complete antigen, that is the penicU-lin-erythrocyte complex, and can be shown in direct and indirect Coombs tests. Clinical hemolysis therefore requires both sufficient coating of erythrocytes and high anti-penicilloyl IgG titers. 

Antiglobulin tests, also called Coombs tests, indicate hemolytic anemia caused by an immune response. A direct Coombs test detects antibodies bound to erythrocytes, whereas an indirect Coombs test measures antibodies present in the serum. A positive finding in a direct Coombs test is usually indicative of antibody-mediated hemolysis. 

An indirect Coombs test can identify antibodies in a patient s serum. This test is performed by combining the patient s serum with normal RBCs, then subjecting them to the direct Coombs test. Antibodies that have attached to the normal RBCs wiU be identified. This process is important in blood bank procedures. 

Figure 2.4-2 Illustration of Coombs test direct antiglobulin and indirect antiglobulin tests. Courtesy of Zarandona JM, et al. CMAJ 2006 174 305-307.

The indirect Coombs test measures free anti-RBC antibodies in serum. If fresh blood was not collected or could not be collected, an alternative is to evaluate serum if available. The indirect Coombs test is not commonly used to diagnose IMHA. However, when plasma or serum samples are saved from animals with suspected IMHA, they can be used for additional evaluation of potential reactivity with the drug or development of an assay for screening similar drugs in developmental process. More frequently, in humans, the indirect assay is used to determine whether an individual might have a reaction to a blood transfusion. 

The drug is readily attached to RBCs, which are then either directly agglutinated by antidrug antibody or, if the antibody is weak, it is revealed by a positive indirect Coombs test, e.g., penicillin. 

Hematologic A 10-year-old boy with acute leukemia developed an immune hemolytic anemia after taking co-trimoxazole for 3 days for Pneumocystis jirovecii prophylaxis [117 ]. A direct antiglobulin (Coombs ) test was strongly positive for IgG and C3, and an indirect antibody test was strongly positive in the presence of co-trimoxazole and trimethoprim, but not sulfamethoxazole alone trimethoprim-dependent erythrocyte antibodies were detected by flow cytometry. 

One test of this approach is to calculate the rate coefficient under the limiting conditions in terms of the concentrations of the aromatic substrate and the nitronium ion as in (26). The concentration of nitronium ions in the reaction medium cannot be measured directly, but an indirect estimation is possible from the fact that nitric acid is entirely converted to nitronium bisulphate in 90% sulphuric acid and the assumption that the change in reaction rate with the concentration of sulphuric acid comes essentially from the change in the position of the nitric acid-nitronium ion equilibrium. Then, from the rate coefficient for the nitration of mesitylene in 68.3% sulphuric acid (2.1 mol-1 s 1 dm3) (Coombes et al., 1968), the rate coefficient for the nitration of the phenyltrimethylammonium ion in 90.1% sulphuric acid (3.5 x 10 2 mol-1 s dm3) (Gillespie and Norton, 1953), and the relative reactivity of mesitylene and the phenyltrimethylammonium ion (a factor of 1.0 x 109) (Table 6 see also Gastaminza et al., 1969) it is possible to calculate that the concentration of nitronium ions in 68.3% sulphuric acid is less than the stoichiometric concentration of nitric acid by a factor of ca. 6 x 10 8. The value of the rate coefficient for mesitylene in (26) then becomes 3.5 X 107 mol-1 s dm3. This is... 

Coomb s test direct indirect D-Dimer test... 

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