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C1 Esterase Inhibitor, Functional
Test Code297
CPT Codes
86161
Preferred Specimen
1 mL serum collected in a red-top tube (no gel)
Minimum Volume
0.2 mL
Instructions
Freeze serum within one hour of time drawn.
Do not submit the sample in a glass tube. Do not thaw.
Do not submit the sample in a glass tube. Do not thaw.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days
Refrigerated: Unacceptable
Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Grossly lipemic • Serum separator tube (SST) • Received thawed
Methodology
Enzyme Immunoassay (EIA)
Setup Schedule
Monday-Saturday Afternoon Report available: Next Day
Reference Range
| ≥68 % | Normal |
| 41-67 % | Equivocal |
| ≤40 % | Abnormal |
Less than 40% of the reference functional activity indicates a likely diagnosis of hereditary angioedema or acquired C1 Inhibitor deficiency.
Clinical Significance
C1 esterase is decreased in angioedema. The inherited form is usually diagnosed in the first two decades of life. The acquired form affects primarily adults with autoimmune or lymphoproliferative disorders. Approximately 15% of patients with hereditary angioedema have a normal concentration of the protein but it is dysfunctional.
