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Interpretive Handbook

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Test 9008:
Direct Coombs, Blood

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

IgG antibody or complement components secondary to the action of IgM antibody may be present on the patient's own RBCs or on transfused RBCs.

Useful For Suggests clinical disorders or settings where the test may be helpful

Demonstrates in vivo coating of RBCs with IgG or the complement component C3d in the following settings:

-Autoimmune hemolytic anemia

-Hemolytic transfusion reactions

-Drug-induced hemolytic anemia

Interpretation Provides information to assist in interpretation of the test results

Negative: no IgG antibody or complement (C3d) detected on the surface of the red cell.

 

Positive: IgG or complement (C3d) is present on the surface of the red cell.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Autoimmune hemolytic anemia can occasionally occur with a negative direct Coombs test.

 

The direct Coombs test can be positive in some apparently healthy individuals.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

If positive, reaction is graded (micro positive to 4+).

Clinical References Provides recommendations for further in-depth reading of a clinical nature

Technical Manual. American Association of Blood Banks, 16th edition 2008, pp 499-519