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Complement C1 Esterase Inhibitor, Functional

CPT: 86161
Updated on 09/22/2020
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  • C1 Esterase Inhibitor
  • C1 Inactivator
  • C1 Inhibitor
  • Esterase Inhibitor
  • Hereditary Angioneurotic Edema Test

Test Includes

Enzyme immunoassay (EIA) to measure functional activity. This method provides C1 esterase function activity as a percentage of mean normal activity.

Expected Turnaround Time

2 - 5 days

Related Documents

Specimen Requirements


Serum or plasma, frozen


0.5 mL

Minimum Volume

0.1 mL (Note: This volume does not allow for repeat testing.)


Red-top tube or lavender-top (EDTA) tube


Separate serum or plasma from cells and transfer to a plastic transport tube before freezing. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Freeze (A serum sample should not be stored at room temperature [15°C to 30°C] for longer than six hours. EDTA plasma may be held at room temperature for 24 hours.)

Causes for Rejection

Plasma other than EDTA; thawed or nonfrozen sample

Test Details


Esterase inhibitor is decreased in hereditary angioneurotic edema. Functional level will be decreased when concentration of inhibitor is decreased or inhibitor is nonfunctional.


Enzyme immunoassay (EIA)

Reference Interval

% of mean normal activity:

• Abnormal: <41%

• Equivocal: 41% to 67%

• Normal: >67%

Additional Information


Donaldson VH, Evans RR. A biochemical abnormality in hereditary angioneurotic edema. Absence of serum inhibitor of C1-esterase. Am J Med. 1963; 35:37-44. 14046003
Gelfand JA, Boss GR, Conley CL, et al. Acquired C1 esterase inhibitor deficiency and angioedema: A review. Medicine (Baltimore). 1979; 58(4):321-328. 449665
Kerr MA, Yeung-Laiwah AAC. C1-inhibitor deficiency and angioedema. In Whaley K, ed. Complement in Health and Disease. MTP Press Limited; 1979:53.
Ratnoff OD, Pensky J, Ogston D, et al. The inhibition of plasmin, plasma kallikrein, plasma permeability factor, and C1r subcomponent of the first component of complement by serum C1 esterase inhibitor. J Exp Med. 1969; 129(2):315-331. 4178758
Rosen FS, Alper CA, Pensky J, et al. Genetically determined heterogeneity of C1 esterase inhibitor in patients with hereditary angioneurotic edema. J Clin Invest. 1971; 50(10):2143-2149. 4107267
Travis J, Salvesen GS. Human plasma proteinase inhibitors. Annu Rev Biochem. 1983; 52:655-709 (review).6193754


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
120220 C1 Esterase Inhibitor, Func 48494-9 120221 C1 Est.Inhib.Funct. %mean normal 48494-9

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