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Test Code C1ES C1 Esterase (C1ES) Inhibitor Antigen, Serum

Reporting Name

C1 Esterase Inhibitor Antigen, S

Useful For

Diagnosis of hereditary angioedema

 

Monitoring levels of C1 esterase inhibitor in response to therapy

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Fasting preferred but not required.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 14 days
  Ambient  72 hours
  Refrigerated  72 hours

Reference Values

19-37 mg/dL

Day(s) and Time(s) Performed

Monday through Saturday; Continuously until 3 p.m.

Test Classification

This test has been cleared or approved by the U.S. 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.

Clinical Reference

1. Frank MM: Complement deficiencies. Pediatr Clin North Am 2000;47(6):1339-1354

2. Gelfand JA, Boss GR, Conley CL, et al: Acquired C1 esterase inhibitor deficiency and angioedema: a review. Medicine 1979;58(4):321-328

3. Rosen FS, Alper CA, Pensky J, et al: Genetically determined heterogeneity of the C1 esterase inhibitor in patients with hereditary angioneurotic edema. J Clin Invest 1971;50(10):2143-2149

4. Frigas E: Angioedema with acquired deficiency of the C1 inhibitor: a constellation of syndromes. Mayo Clin Proc 1989;64:1269-1275

5. Soldin SJ, Hicks JM, Bailey J, et al: Pediatric reference ranges for estradiol and C1 esterase inhibitor. Clin Chem 1998;44(6s):A17

Analytic Time

1 day

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross reject

Icterus

Mild OK; Gross OK

Other

NA

Method Name

Nephelometry