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Test Code IGAS IgA Subclasses, Serum

Important Note

ASANTE order is IGAS

Epic/Beaker order is LAB5521

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

IgA Subclasses, S

Specimen Type


Specimen Required


Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Reject Due To


Mild OK; Gross OK


Mild OK; Gross reject


Mild OK; Gross OK



Specimen Stability Information

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

Specimen Minimum Volume

0.5 mL

Day(s) and Time(s) Performed

Monday through Saturday; Continuously

Specimen Retention Time

7 days

Analytic Time

1 day

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

Useful For

Investigation of immune deficiency due to IgA2 deficiency


Evaluating patients with anaphylactic transfusion reactions


Method Name

Nephelometry for Total IgA, IgA1, and IgA2

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

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.


Low concentrations of IgA2 with normal IgA1 levels suggest an IgA2 deficiency.


Elevated concentrations of IgA2 with normal or low amounts of IgA1 suggest a clonal plasma cell proliferative disorder secreting a monoclonal IgA2.


Increased total IgA levels also may be seen in benign disorders (eg, infection, inflammation, allergy), hyper IgD syndrome with periodic fever and monoclonal gammopathies (eg, myeloma, monoclonal gammopathies of undetermined significance [MGUS]).

Clinical Reference

1. Schauer U, Stemberg F, Rieger CHL, et al: Establishment of age-dependent reference values for IgA subclasses. Clin Chim Acta 2003;328:129-133

2. Saulsbury FT: Hyperimmunoglobulinemia D and periodic fever syndrome (HIDS) in a child with normal serum IgD, but increased serum IgA concentration. J Pediatrics 2003:127-129

3. Popovsky MA: Transfusion Reactions. American Association of Blood Banks, Third edition, 2007

Method Description

The assay is performed on a Siemens NII nephelometer. Nephelometry is based on the increase in light scatter that occurs when antibody binds to antigen. The increase in light scatter is proportional to the amount of antigen present in the sample. The assay uses immune reagent sets from The Binding Site.(Package insert: Human IgA Subclass Liquid Latex Reagent Kits. The Binding Site)