C1 Inhibitor Functional assay
Investigation : C1 Inhibitor Functional assay
Specimen type : Serum
Spec container : Serum Gel 
Volume required : 3ml
Turnaround : 16 days

Methodology: Enzyme immunoassay

Reference Range:
<40% is considered Abnormal
41 - 67 % is considered Equivocal
>68% is considered Normal


  1. In cases where angiodema is suspected to be due to hereditary or acquired C1 inhibitor deficiency, the most effective screening test is a C4 - this is invariably greatly reduced in untreated patients. Only then is it necessary to go on to measure C1 inhibitor.
  2. It is not necessary to test for C1 inhibitor defeciency in patients who only have urticaria.


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