C1 Esterase Inh,Func (QN)
Functional C'1 Esterase
Hereditary Angioedema Panel (3 tests)
Hereditary Angioedema, HAE
Diagnosing hereditary angioedema
Monitoring response to C1 esterase inhibitor replacement therapy
1. Immediately after specimen collection, place the tube on wet ice.
2. Centrifuge at 4 degrees C and aliquot serum into a 5-mL plastic vial.
3. Freeze specimen within 30 minutes.
This assay is a functional test and is dependent on correct sampling, storage, and shipping conditions.
Absent (or low) C1 esterase inhibitor function should be confirmed with a new serum specimen to confirm that inactivation has not occurred during shipping.
>67% normal (normal)
41-67% normal (equivocal)
<41% normal (abnormal)
The C1 esterase inhibitor (C1-INH) concentration assay can be used to distinguish type I hereditary angioedema (HAE), with low C1-INH concentration, from type II HAE characterized by normal or elevated concentration. Furthermore, serum C1q concentrations can be used to differentiate HAE from acquired angioedema (AAE) forms of angioedema as the latter is characterized by decreased C1q antigen concentration and autoantibodies against C1-INH. Genetic analysis for SERPING1 variants status may also help exclude HAE.
-Nonfunctional C1-INH results are consistent with HAE
-Patients with current attacks may also have low C2 and C4 concentrations due to C1 activation and complement activation of the classical pathway (consumption).
-Patients with acquired C1-INH deficiency have a low C1q concentration and/or function in addition to low C1-INH.