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Test Code IGAS IgA Subclasses, Serum

Reporting Name

IgA Subclasses, S

Useful For

Investigation of immune deficiency due to IgA2 deficiency


Evaluating patients with anaphylactic transfusion reactions


Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Specimen Required


Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Ambient  7 days
  Frozen  7 days

Reference Values


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

≥18 years: 61-356 mg/dL



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

≥18 years: 50-314 mg/dL



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

≥18 years: 9.7-156.0 mg/dL

Day(s) and Time(s) Performed

Monday through Saturday; Continuously

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


82787 x 2-Immunoglobin subclasses

LOINC Code Information

Test ID Test Order Name Order LOINC Value
IGAS IgA Subclasses, S 87552-6


Result ID Test Result Name Result LOINC Value
IGA_ IgA 2458-8
IGA1_ IgA1 6886-6
IGA2_ IgA2 6939-3

Clinical Information

IgA, the predominant immunoglobulin secreted at mucosal surfaces, consists of 2 subclasses, IgA1 and IgA2. IgA1 is the major (approximately 80%) subclass in serum. IgA2 is the major subclass in secretions such as milk. Although IgA deficiency is a common defect (1 in 700), it is usually asymptomatic. IgA deficiency with or without IgG subclass deficiency, however, can lead to recurrent pulmonary and gastrointestinal infections. Some infections (eg, recurrent sinopulmonary infections with Haemophilus influenzae) may be related to a deficiency of 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 inactivated by certain bacteria, thus depleting the majority of the IgA. In the presence of a concurrent IgA2 deficiency, infection by these organisms results in an apparent IgA deficiency.


IgA deficiency is 1 cause of anaphylactic transfusion reactions. In these situations, IgA-deficient patients produce anti-IgA antibodies that react with IgA present in the transfusion product. While transfusion reactions typically occur in patients who have no detectable levels of IgA, they can occur in patients with measurable IgA. In these situations, the complete deficiency of 1 of the IgA subclasses may be the cause of the transfusion reactions.

Analytic Time

1 day

NY State Approved


Method Name

Nephelometry for Total IgA, IgA1, and IgA2