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PTD - 327

Test Directory - IgG Subclasses

Clinical Indications

IgG1, IgG3 & IgG4 immunoglobulins are predominantly directed against protein antigens, while IgG2 antibodies are directed towards bacterial polysaccahrides and IgG2 deficiency may be associated with increased risk of infection with Streptococcus pneumoniae, Haemophilus influenzae type b. and Staph. aureus.

The clinical importance of IgG subclass deficiency is controversial. Persons with chromosomal deletions of some IgG subclasses have been reported to be healthy, and the demonstration of a low IgG subclass level is not sufficient to diagnose antibody deficiency. Patients with deficiencies involving IgG2 display the highest frequency of infectious complications, generally of the respiratory tract.

Test Includes

IgG1, IgG2, IgG3 and IgG4

Request Form

Combined Pathology Blood form (Yellow/Black)

Availability

Referred test: Analysed by Protein Reference Unit, Sheffield, if specific criteria met.

Specific Criteria

None

Turnaround Time

Two weeks

Specimen

Serum

Volume

2 ml

Container

Yellow top (SST) tube.

Causes for Rejection

Unlabelled sample.

Reference Ranges

Age

IgG1 g/L

IgG2 g/L

IgG3 g/L

IgG4 g/L

0 - 6 months

1.5 - 3.0

0.3 - 0.5

0.1 - 0.6

< 0.5

6 - 24 months

2.3 - 5.8

0.3 - 3.9

0.1 - 0.8

< 0.5

2 - 5 years

2.3 - 6.4

0.7 - 4.5

0.1 - 1.1

< 0.8

5 - 10 years

3.6 - 7.3

1.4 - 4.5

0.3 - 1.1

< 1.0

10 - 15 years

3.8 - 7.7

1.3 - 4.6

0.2 - 1.2

< 1.1

Over 15 years

3.2 - 10.2

1.2 - 6.6

0.2 - 1.9

< 1.3

Reference; Protein Reference Unit Handbook, 9th Edition 2007

Interpretation

It is important to note that normal total IgG and subclass IgG levels do not exclude significant humoral immunodeficiency. Individuals can have normal levels of immunoglobulins but still be unable to mount an adequate immune response to an invading pathogen. Patients can have low or absent IgG subclasses but normal total immunoglobulin concentrations.

Low IgG1 can be seen in primary or secondary immunodeficiency but often does not occur in isolation. Low IgG2 concentration may be observed in individuals susceptible to bacterial infections. The clinical significance of low/absent IgG3 and IgG4 is uncertain.

Lab. Handling

Processing:  Aliquot (MPA) and store at 4C in separating fridge (CB39). Referral: GSUB and send or BPRO and save at -20C in separating freezer (CB40).


Version 1.0 / November  2014                                                                                                 Approved by: Consultant Biochemist