CPT CODE:

USEFUL FOR:

Investigation of immune deficiency due to IgA2 deficiency
Evaluating patients with anaphylactic transfusion reactions

SPECIMEN REQUIRED:

Draw blood in a plain, red-top tube(s) or a serum gel tube(s). Spin down and send 1 mL of serum refrigerated.

TRANSPORT TEMPERATURE:

Refrig\Ambient OK\Frozen OK

CLINICAL INFORMATION:

IgA, the predominant immunoglobulin secreted at mucosal surfaces,consists of 2 subclasses, IgA1 and IgA2. IgA1 is the major (approximately80%) subclass in serum. IgA2 is the major subclass in secretions suchas milk. Although IgA deficiency is a common defect (1 in 700), it isusually asymptomatic. IgA deficiency with or without IgG subclassdeficiency, however, can lead to recurrent pulmonary and gastro-intestinal infections. Some infections (eg, recurrent sinopulmonaryinfections with Haemophilus influenzae) may be related to a deficiencyof IgA2 in the presence of normal total IgA concentrations.
Paradoxically, bacterial infections may also cause IgA deficiency.For example, IgA1 (but not IgA2) can be cleaved and inactivatedby certain bacteria, thus depleting the majority of the IgA. In thepresence of a concurrent IgA2 deficiency, infection by theseorganisms results in an apparent IgA deficiency.
IgA deficiency is 1 cause of anaphylactic transfusion reactions.In these situations, IgA-deficient patients produce anti-IgAantibodies that react with IgA present in the transfusion product.While transfusion reactions typically occur in patients who haveno detectable levels of IgA, they can occur in patients withmeasurable IgA. In these situations, the complete deficiencyof 1 of the IgA subclasses may be the cause of the transfusionreactions.

CLINICAL INTERPRETATION:

Low concentrations of IgA2 with normal IgA1 levels suggest anIgA2 deficiency.
Elevated concentrations of IgA2 with normal or low amounts ofIgA1 suggest a clonal plasma cell proliferative disorder secretinga monoclonal IgA2.
Increased total IgA levels also may be seen in benign disorders(eg, infection, inflammation, allergy), hyper IgD syndrome withperiodic fever and monoclonal gammopathies (eg, myeloma,monoclonal gammopathies of undetermined significance[MGUS]).

REFERENCE VALUES:

IgA

      0-<5 months:  7-37 mg/dL

      5-<9 months:  16-50 mg/dL

      9-<15 months:  27-66 mg/dL

      15-<24 months:  36-79 mg/dL

      2-<4 years:  27-246 mg/dL

      4-<7 years:  29-256 mg/dL

      7-<10 years:  34-274 mg/dL

      10-<13 years:  42-295 mg/dL

      13-<16 years:  52-319 mg/dL

      16-<18 years:  60-337 mg/dL

      > or =18 years: 61-356 mg/dL

IgA1

      0-<5 months:  10-34 mg/dL

      5-<9 months:  14-41 mg/dL

      9-<15 months:  20-50 mg/dL

      15-<24 months:  24-58 mg/dL

      2-<4 years:  16-162 mg/dL

      4-<7 years:  17-187 mg/dL

      7-<10 years:  21-221 mg/dL

      10-<13 years:  27-250 mg/dL

      13-<16 years:  36-275 mg/dL

      16-<18 years:  44-289 mg/dL

      > or =18 years: 50-314 mg/dL

IgA2

      0-<5 months:  0.4-5.5 mg/dL

      5-<9 months:  1.5-6.2 mg/dL

      9-<15 months:  2.8-7.0 mg/dL

      15-<24 months:  3.9-7.7 mg/dL

      2-<4 years:  1.3-31.1 mg/dL

      4-<7 years:  1.1-39.1 mg/dL

      7-<10 years:  1.4-48.0 mg/dL

      10-<13 years:  2.6-53.4 mg/dL

      13-<16 years:   4.7-55.1 mg/dL

      16-<18 years:  6.6-54.3 mg/dL