Anti-IgA Antibodies, IgG Class, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Anaphylactic transfusion reactions induced by IgG anti-IgA antibodies may occur in IgA-deficient patients. Anaphylactic and anaphylactoid reactions are mediated by activation of complement with generation of vasoactive anaphylatoxins (C3a, C4a, and C5a). These reactions are characterized by urticaria, hypotension, and respiratory distress with bronchospasm or stridor.
Patients with IgA deficiency who require blood or blood component transfusions should receive IgA-free blood products. Patients with a history of a severe transfusion reaction with signs of anaphylaxis, who are known to be IgA deficient, should be tested for the presence of IgG anti-IgA antibodies prior to the anticipated need for blood or blood components. This will allow time for preparation of IgA-free blood products, if indicated.
Evaluation of patients with a history of a severe transfusion reaction with signs of anaphylaxis
Identification of patients who require IgA-free blood products
Positive results occur in IgA-deficient patients who have experienced an anaphylactic reaction associated with transfusion of blood or blood components that contain plasma.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Negative test results do not conclusively rule out the possibility of future anaphylactic transfusion reactions:
-Antibodies to other plasma proteins may be associated with release of vasoactive mediators.
-Testing performed on sera drawn immediately after a reaction may be falsely negative due to transfused IgA, which may deplete anti-IgA antibodies. Serum should be drawn a minimum of 10 days after the reaction.
The presence of IgG antibodies to IgA interfere analytically with detection of other anti-IgA isotypes (eg, IgE anti-IgA).
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: < or =52.0 U
Positive: >52.0 U
Pediatric reference ranges are not established.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Homburger HA, Smith JR, Jacob GL, et al: Measurement of anti-IgA antibodies by a two-site immunoradiometric assay. Transfusion 1981;21:38-44
2. Davenport RD, Mintz PD: Transfusion medicine. In Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st edition. Edited by RA McPherson, MR Pincus. Philadelphia, Saunders Elsevier, 2006, pp 707-708
3. Vassalo RR: Review: IgA anaphylactic transfusion reactions. Part I. Laboratory diagnosis, incidence, and supply of IgA-deficient products. Immunohematology 2004;20(4):226-233
4. Sandler SG, Zantek ND: Review: IgA anaphylactic transfusion reactions. Part II. Clinical diagnosis and bedside management. Immunohematology 2004;20(4):234-238