Assay

C1 esterase inhibitor (antigenic)

Key Words

C1 esterase inhibitor (C1INH)

Specimen Collection

Serum (Brown)

Turnaround time

5 days

This test is referred to another centre:

Department of Clinical Chemistry and Immunology

Level 4

Addenbrooke’s Hospital NHS Trust

Hills Road

Cambridge

CB2 2QQ

01223 217215

Test indications

This protein regulates spontaneous complement activation via the classical pathway.  Inherited or acquired defects usually result in severe angioedema that is a painless, non-itchy swelling of sub-dermal tissues and is life threatening if the larynx is affected.  Low levels are found in 85% of cases of Hereditary Angioedema, the remaining 15% of cases are associated with a non-functioning protein which gives normal results in immunochemical assays and for which a functional assay is available. Normal C4 levels during an acute attack of angioedema excludes C1 INH deficiency. However low normal C4 levels during asymptomatic periods may rarely be seen in patients with C1 inhibitor deficiency. Therefore in such cases both immunochemical and functional C1 inhibitor levels should be measured. C1 inhibitor concentrate or Fresh Frozen Plasma is used to treat acute attacks. Clinical assessment by an Immunologist is strongly recommended where this diagnosis is suspected.

Methodology

Nephelometric

Interferences

Contact referral centre

Reference Range

0.19-0.39 g/L

Analytical error

Contact referral centre

Reference change value

N/A