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HelpTest Code LAB850 C1 Esterase Inhibitor Antigen, Serum
Reporting Name
C1 Esterase Inhibitor Antigen, SUseful For
Diagnosis of hereditary angioedema
Monitoring levels of C1 esterase inhibitor in response to therapy
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumSpecimen Required
Patient Preparations: Fasting preferred but not required.
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Immediately after specimen collection, place the tube on wet ice.
2. Centrifuge and aliquot serum into plastic vial.
3. Freeze specimen within 30 minutes.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Frozen (preferred) | 28 days | |
| Refrigerated | 28 days | ||
| Ambient | 72 hours |
Reference Values
19-37 mg/dL
Day(s) Performed
Monday through Friday
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
83883
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| C1ES | C1 Esterase Inhibitor Antigen, S | 4477-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| C1ES | C1 Esterase Inhibitor Antigen, S | 4477-6 |
Clinical Information
C1 esterase inhibitor blocks the activation of C1 (first component of the complement cascade) 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 or acquired angioedema. This disease is an autosomal dominant inherited condition, in which exhaustion of the abnormally 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.
Because 15% of C1 inhibitor deficiencies have nonfunctional protein, some patients will have abnormal functional results (FC1EQ / C1 Esterase Inhibitor, Functional Assay, Serum) in the presence of normal (or elevated) antigen levels.
Interpretation
Abnormally low results are consistent with a heterozygous C1 esterase inhibitor deficiency and hereditary angioedema.
Fifteen percent of hereditary angioedema patients have a normal or elevated level but nonfunctional C1 esterase inhibitor protein. Detection of these patients requires a functional measurement of C1 esterase inhibitor; FC1EQ / C1 Esterase Inhibitor, Functional Assay, Serum.
Measurement of C1q antigen levels; C1Q / Complement C1q, Serum, is key to the differential diagnoses of acquired or hereditary angioedema. Those patients with the hereditary form of the disease will have normal levels of C1q, while those with the acquired form of the disease will have low levels.
Studies in children show that adult levels of C1 inhibitor are reached by 6 months of age.
Cautions
Quantitation of specific proteins by nephelometric means may not be possible in lipemic sera due to the extreme light scattering properties of the specimen. Turbidity and particles in the specimen may result in extraneous light scattering signals, resulting in variable specimen analysis.
Clinical Reference
1. Willrich MAV, Braun KMP, Moyer AM, Jeffrey DH, Frazer-Abel A: Complement testing in the clinical laboratory. Crit Rev Clin Lab Sci. 2021 Nov;58(7):447-478. doi: 10.1080/10408363.2021.19072972
2. Drouet C, Lopez-Lera A, Ghannam A, et al: SERPING1 variants and C1-INH biological function: A close relationship with C1-INH-HAE. Front Allergy. 2022 Mar 31;3:835503. doi: 10.3389/falgy.2022.835503
3. Tangye SG, Al-Herz W, Bousfiha A, et al: Human inborn errors of immunity: 2022 update on the classification from the International Union of Immunological Societies Expert Committee. J Clin Immunol. 2022 Oct;42(7):1473-1507. doi: 10.1007/s10875-022-01289-3
4. Brodszki N, Frazer-Abel A, Grumach AS, et al: European Society for Immunodeficiencies (ESID) and European Reference Network on Rare Primary Immunodeficiency, Autoinflammatory and Autoimmune Diseases (ERN RITA) Complement Guideline: Deficiencies, Diagnosis, and Management. J Clin Immunol. 2020 May;40(4):576-591. doi: 10.1007/s10875-020-00754-1
5. Patel G, Pongracic JA: Hereditary and acquired angioedema. Allergy Asthma Proc. 2019 Nov 1;40(6):441-445. doi: 10.2500/aap.2019.40.4267
6. Longhurst HJ, Tarzi MD, Ashworth F, et al: C1 inhibitor deficiency: 2014 United Kingdom consensus document [published correction appears in Clin Exp Immunol. 2015 Dec;182(3):346]. Clin Exp Immunol. 2015;180(3):475-483. doi:10.1111/cei.12584
Method Description
C1 esterase inhibitor complement antigen (C1ES) is measured by immunonephelometry. Antiserum to C1ES is mixed with patient serum, the light scatter resulting from the antibody interaction with C1ES is measured, and the signal is compared to standard concentrations of C1ES.(Instruction manual: Siemens Nephelometer II Operations. Siemens, Inc; Version 2.4, 07/2019; Addendum to the Instruction Manual 2.3, 08/2017)
Report Available
2 to 5 daysSpecimen Retention Time
14 daysReject Due To
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Gross icterus | OK |
NY State Approved
YesMethod Name
Nephelometry