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Test ID: IGGS4 Immunoglobulin Subclass IgG4, Serum

Reporting Name

Immunoglobulin Subclass IgG4, S

Useful For

Supporting the diagnosis of IgG4-related disease

Clinical Information

The most abundant immunoglobulin (Ig) isotype in human serum is immunoglobulin G (IgG). IgG immunoglobulins are comprised of 4 subclasses designated IgG1 through IgG4. Of total IgG, approximately 65% is IgG1, 25% is IgG2, 6% is IgG3, and 4% is IgG4. Each IgG subclass contains structurally unique portions of the constant region of the gamma heavy chain.

 

IgG subclass 4-related disease is a recently recognized syndrome of unknown etiology most often occurring in middle-aged and older men. Several organ systems can be involved and encompasses many previous and newly described diseases such as type1 autoimmune pancreatitis; Mikulicz disease and sclerosing sialadenitis; inflammatory orbital pseudotumor; chronic sclerosing aortitis; Riedel thyroiditis, a subset of Hashimoto thyroiditis; IgG4-related interstitial pneumonitis; and IgG4-related tubulointerstitial nephritis. Each of these entities is characterized by tumor-like swelling of the involved organs with infiltrative, predominately IgG4-positive, plasma cells with accompanying "storiform" fibrosis. In addition, elevated serum concentrations of IgG4 are found in 60% to 70% of patients diagnosed with IgG4-related disease.

 

The diagnosis of IgG4-related disease requires a tissue biopsy of the affected organ demonstrating the aforementioned histological features. It is recommended that patients suspected of having an IgG4-related disease have their serum IgG4 level measured.

Interpretation

Elevated levels of IgG4 are consistent with, but not diagnostic of, IgG4-related disease.

Analytic Time

Same day/1 day

Day(s) and Time(s) Performed

Monday through Saturday; Continuously

Clinical Reference

1. Cheuk W, Chan JK: IgG4-related sclerosing disease: a critical appraisal of an evolving clinicopathologic entity. Adv Anat Pathol 2010;17(5):303-332

2. Zen Y, Nakanuma Y: IgG4-related disease: a cross-sectional study of 114 cases. Am J Surg Pathol 2010;34(12):1812-1819

3. Bateman AC, Deheragoda MG: IgG4-related systemic sclerosing disease-an emerging and under-diagnosed condition. Histopathology 2009;55(4):373-383

Method Name

Nephelometry

Specimen Type

Serum


Advisory Information


This test only quantitates the IgG4 protein. If quantitation of all IgG subclass types is wanted, order IGGS / IgG Subclasses, Serum.



Specimen Required


Patient Preparation: Fasting preferred but not required

Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Ambient  14 days
  Frozen  14 days

Reference Values

0-<5 months: ≤19.8 mg/dL

5-<9 months: ≤20.8 mg/dL

9-<15 months: ≤22.0 mg/dL

15-<24 months: ≤23.0 mg/dL

2-<4 years: 0.4-49.1 mg/dL

4-<7 years: 0.8-81.9 mg/dL

7-<10 years: 1.0-108.7 mg/dL

10-<13 years: 1.0-121.9 mg/dL

13-<16 years: 0.7-121.7 mg/dL

16-<18 years: 0.3-111.0 mg/dL

≥18 years: 2.4-121.0 mg/dL

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
IGGS4 Immunoglobulin Subclass IgG4, S 2469-5

 

Result ID Test Result Name Result LOINC Value
IGGS4 Immunoglobulin Subclass IgG4, S 2469-5
Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Neuroimmunology, mml-CNS-Infections