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Immunoglobulin G (IgG) Subclasses

Immunoglobulin G Subclasses (1, 2, 3, 4)

Test Codes

Antrim #30941, EPIC: LAB6464, SOFT: IGSUB

Department

Special Chemistry

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 4.0 mL)

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Do not refrigerate or freeze collection tube. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F) within 12 hours of collection. (Minimum serum: 0.5 mL)

Preparation for Courier Transport

Transport: Serum aliquot, refrigerated (2-8 °C or 36-46 °F). (Minimum serum: 0.5 mL)

Rejection Criteria

• Plasma specimens.
• Hemolyzed specimens.
• Severely lipemic specimens.
• This test is not suitable for the measurement of samples containing rheumatoid factor, paraproteins, or other circulating immune complexes.

In-Lab Processing

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Do not refrigerate or freeze the collection tube. Transfer serum to a plastic transport tube prior to refrigeration. Room temperature is acceptable for a maximum of 12 hours. (Minimum serum: 0.5 mL)

Storage

Specimen Stability for Testing:

Centrifuged SST tubes and Microtainers^®
Room Temperature (20-26°C or 68-78.8°F): 12 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 12 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Special Testing Laboratory

Performed

Monday, Wednesday, Friday.
Results available in 1-3 business days.

Reference Range

Age	Subclass 1 mg/dL	Subclass 2 mg/dL	Subclass 3 mg/dL	Subclass 4 mg/dL
0-4 months	56-215	0-82	7.6-82.3	0-19.8
5-8 months	102-369	0-89	11.9-74.0	0-20.8
9-14 months	160-562	24-98	17.3-63.7	0-22.0
15-23 months	209-724	35-105	21.9-55.0	0-23.0
2-3 years	158-721	39-176	17.0-84.7	0.4-49.1
4-6 years	209-902	44-316	10.8-94.9	0.8-81.9
7-9 years	253-1019	54-435	8.5-102.6	1.0-108.7
10-12 years	280-1030	66-502	11.5-105.3	1.0-121.9
13-15 years	289-934	82-516	20.0-103.2	0.7-121.7
16-17 years	283-772	98-486	31.3-97.6	0.3-111.0
greater than equal to 18 years	341-894	171-632	18.4-106.0	2.4-121.0

 

Test Methodology

Nephelometry.

Interpretation

Increased IgG1 levels are seen in patients with multiple sclerosis.

Increased IgG2 and IgG3 levels are seen in cystic fibrosis patients with chronic Pseudomonas aeruginosa infections.

Increased IgG4 levels are associated with patients with atopic dermatitis, food allergies, chronic exposure to environmental antigens (e.g., bee-keepers, pigeon breeder's), asthma, cystic fibrosis, some parasitic diseases, and in allergic individuals under hyposensitization regimens.

Decreased IgG1 levels are associated with end-stage renal failure, nephotic syndrome, and common variable immunodeficiency.

Decreased IgG2 levels are associated with bronchial asthma in children, idiopathic thrombocytopenia purpura, HIV, IgA deficiency, otitis media, recurrent sinopulmonary infections, bronchiectasis, alcoholic liver disease, ataxia teleangiectasia, bowel surgery and nephrotic syndrome.

Decreased IgG3 levels are associated with bronchial asthma in children, systemic lupus erythematosus, and recurrent sinopulmonary infections.

Decreased IgG4 levels are associated with idiopathic thrombocytopenia purpura, systemic lupus erythematosus, HIV, IgA and IgM deficiency, Wiskott-Aldrich's disease, alcoholic liver disease, ataxia teleangiectasia, and recurrent sinopulmonary infections.

Clinical Utility

Quantitation of the IgG subclasses helps to determine the immune status of patients with normal total IgG levels. Patients with a normal serum level of total IgG may have a clinically important deficiency of one or more IgG subclasses. Deficiencies in one or more IgG subclasses are associated with sinusitis, recurrent otitis media, asthma, respiratory tract infections, and impaired lung function with or without IgA deficiency.

Clinical Disease

IgG subclass deficiency occurs when there is an imbalance of the IgG subclasses with one or more subclasses being deficient. The etiology is unknown. These patients may be healthy but most have a history of frequent ear and sinus infections, bronchiectasis, and pneumonia. These infections are often caused by encapsulated bacteria such as Haemophilus influenzae, and Streptococcus pneumoniae, especially in the case of IgG2 deficiency.

CPT Codes

82787 x 4, 82784.
LOINC:  G1 2466-1, G2 2467-9, G3 2468-7, G4 2469-5

Contacts

Last Updated

1/11/2023