C1 Inhibitor, Functional

Last Modified: 1/25/2019 6:28:27 AM

Medical Necessity Documentation:  
Client Notes:  
Patient Preparation:  
Specimen Requirements:

1.0 mL Frozen Serum from a Red Top Tube in a Plastic Vial

Collection Instructions: Freeze serum within 1 hour of time drawn
Minimum Volume: 0.2 mL Serum
Transport & Storage: Temperature/Stability: 30 days Frozen
Rejection Criteria: Lipemia • Received thawed • Received room temperature • Received refrigerated • Serum Separator Tube (SST®) • In Glass tubes • CSF
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.
Critical Ranges:  
Test Comments: limitations: Fifteen percent of patients with the inherited form of the disease will test within range.
Methodology: Immunoassay
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.

Custom Panel: No


Turn Around Time: 2 to 3 days
Days Performed: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday
Sites Performed: Quest - Chantilly
PHL Test Code: MSOT
EPIC Test Code:
Send Out Test Code: 297
Alternate Test Names: C1 Esterase; Functional C1-Inhibitor
Included Tests:  
CPT Coding: 86161

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