Test Overview
Test Methodology


Test Usage

Diagnosis of hereditary angioedema and monitoring levels in response to therapy. Abnormally low results are consistent with a heterozygous C1 inhibitor deficiency. Normal (or elevated) levels with a nonfunctional protein are detected in 15% of hereditary angioedema patients (detection of these patients requires the functional assay).

Reference Range *

19 - 37 mg/dL

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

The assay measures total antigenic C1EI (both biologically active and inactive). The patient may have normal amounts of C1EI by this method, but it may be functionally inactive and therefore abnormal. (See C1 Esterase Inhibitor, Functional Assay). If decreased by this method, functional C1EI need not be ordered.

Test Details
Days Set Up
Monday - Friday
Analytic Time

2 - 6 days

Soft Order Code
MiChart Code
C1 Esterase Inhibitor, Antigen
  • C1 Esterase Inhibitor Quantitative
  • Complement C1 Esterase Inhibitor, Antigen
  • HAE (Hereditary Angioedema)
  • Hereditary Angioedema (HAE)
  • C1ES
Reference Laboratory
Mayo C1ES (8198)
Special Testing
Specimen Requirements
Collection Instructions

Collect blood in a red top or SST tube. A fasting speciment is preferred but not required (12 hour fast). Centrifuge, aliquot serum into a plastic vial and freeze immediately. Thawed specimens or those stored at room temperature are unacceptable. Do not refreeze thawed specimens; may be refrigerated up to 3 days.

Fasting Specimen
A fasting specimen is preferred but not required.
Normal Volume
1.0 mL serum
Minimum Volume
0.5 mL serum
Additional Information

C1 esterase inhibitor blocks the activation of the proenzyme C1 to its active form. The deficiency of C1 esterase inhibitor results in the inappropriate activation of C1 and the subsequent release of an activation peptide from C2 with kinin-like activity. This kinin-like peptide enhances vascular permeability. C1 esterase inhibitor deficiency results in hereditary angioedema. This disease is autosomal dominant and exhaustion of the low levels of C1 esterase inhibitor results in C1 activation, breakdown of C2 and C4, and subsequent acute edema of subcutaneous tissue, the gastrointestinal tract, or the upper respiratory tract. The disease responds to attenuated androgens. Test sent to Mayo Medical Laboratories.

CPT Code
Fee Code