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Test ID 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

 

Specimen Type

Serum


Specimen Required


Container/Tube:

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

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

≥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

≥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

≥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

82784-IgA

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.

Interpretation

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

Analytic Time

1 day

Method Name

Nephelometry for Total IgA, IgA1, and IgA2