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HelpTest Code C1INF C1 Esterase Inhibitor, Functional, Serum
Specimen Required
Patient Preparation: Fasting, preferred but not required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
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. After sample has clotted on wet ice, centrifuge at 4° C and aliquot serum into a plastic vial.
3. Freeze specimen within 30 minutes of centrifugation. Sample must be placed on dry ice if not frozen immediately.
NOTE: If a refrigerated centrifuge is not available, it is acceptable to use a room temperature centrifuge, provided the specimen is kept on ice before centrifugation and immediately afterward, the serum aliquoted and frozen.
Useful For
Diagnosing hereditary angioedema
Monitoring response to C1 esterase inhibitor replacement therapy
Method Name
Enzyme Immunoassay (EIA)
Reporting Name
C1 Esterase Inhib, Functional, SSpecimen Type
Serum RedSpecimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Frozen | 28 days |
Reference Values
>67% normal (normal)
41-67% normal (equivocal)
<41% normal (abnormal)
Interpretation
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.
Table. Laboratory Features Consistent with Hereditary and Acquired Angioedema Subtypes
|
|
Type I hereditary angioedema |
Type II hereditary angioedema |
Acquired angioedema |
|
C1 esterase inhibitor (C1-INH) concentration |
Low |
Normal/high |
Low |
|
C1-INH function |
Low |
Low |
Low/normal |
|
C4 concentration |
Low |
Low |
Low |
|
C1q concentration |
Normal |
Normal |
Low |
|
Anti-C1-INH antibodies |
Absent |
Absent |
Present |
|
C3 concentration |
Normal |
Normal |
Normal |
|
Family history |
Yes |
Yes |
No |
Clinical Reference
1. Stoppa-Lyonnet D, Tosi M, Laurent J, Sobel A, Lagrue G, Meo T. Altered C1 inhibitor genes in type I hereditary angioedema. N Engl J Med. 1987;317(1):1-6. doi:10.1056/NEJM198707023170101
2. Frigas E. Angioedema with acquired deficiency of the C1 inhibitor: a constellation of syndromes. Mayo Clin Proc. 1989;64(10):1269-1275. doi:10.1016/s0025-6196(12)61290-7
3. Frazer-Abel A, Sepiashvili L, Mbughuni MM, Willrich MA. Overview of laboratory testing and clinical presentations of complement deficiencies and dysregulation. Adv Clin Chem. 2016;77:1-75. doi:10.1016/bs.acc.2016.06.001
Day(s) Performed
Varies
Report Available
3 to 5 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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
83520
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| C1INF | C1 Esterase Inhib, Functional, S | 48494-9 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| C1INF | C1 Esterase Inhib, Functional, S | 48494-9 |