C1 Esterase Inhibitor, Protein

C1 Esterase Inhibitor Antigen, C1 Inhibitor Level, C1 Esterase Inhibitor Quantitative, C-1-Esterase Inhibitor Antigen (C1ES), Serum

Test Codes

EPIC: LAB1232044, Beaker: C1ESTPROTEIN, Quest: 298

Department

Send Outs

Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube.

Also acceptable: One Gold-top SST tube.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: 1.0 mL serum, room temperature (20-26°C or 68-78.8°F). (Minimum: 0.5 mL)

Rejection Criteria

• Grossly lipemic specimens.
• Grossly hemolyzed specimens.
• Grossly icteric specimens.
• Specimens not collected and processed as indicated.
  

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F).

Transport: 1.0 mL serum, room temperature (20-26°C or 68-78.8°F). (Minimum: 0.5 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 8 days
Frozen (-20°C/-4°F or below): 1 year

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Quest Diagnostics, Wood Dale, IL.

Performed

Monday – Saturday.
Results available in 2-4 days.

Reference Range

21-39 mg/dL

Test Methodology

Nephelometry

Interpretation

By report.

Clinical Utility

C1 Esterase Inhibitor, Protein – The C1 esterase inhibitor protein is a normal constituent of serum which functions as a serine proteinase inhibitor of the serpin family. The C1 esterase inhibitor inhibits the complement proteases C1r and C1s, as well as the proteases Kallikrein, factor XIa, XIIa and plasmin of the blood clotting system. The concentration of C1 esterase inhibitor protein is reduced to 10-30% of normal in patients with angioedema secondary to C1 esterase inhibitor deficiency (85% of patients with hereditary angioedema (HAE)); in 15% of patients with HAE, the concentrations of the inhibitor protein is normal but function is markedly reduced.

CPT Codes

86160

Contacts

Last Updated

12/17/2025