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Test Code FC1EQ C1 Esterase Inhibitor, Functional, Serum

Important Note

Patient should be fasting. 

After specimen collection, place the tube on ice and send to laboratory immediately.

Additional Codes

Epic Ordering Code LAB3040935
NBS code LBC13199
Service code 36933

Reporting Name

C1 Esterase Inhib, Functional, S

Specimen Type

Serum Red


Specimen Required


Patient Preparation:

Fasting: 8 hours, preferred but not required

Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL Serum

Collection Instructions:

1. Immediately after specimen collection, place the tube on wet ice and allow specimen to clot.

2. Centrifuge at 4° C and aliquot serum into a plastic vial.

3. Within 30 minutes of centrifugation, freeze specimen. Specimen must be placed on dry ice if not frozen immediately.

Note: If a refrigerated centrifuge is not available, it is acceptable to use a room temperature centrifuge, provided the specimen is kept on ice before centrifugation, and immediately afterward, the serum aliquoted and frozen.


National University Hospital-Singapore Note:

NUH Outreach Laboratories:
Specimen Requirements
Submit the following immediately:
Container: Red Top
Fasting: 8 hours, preferred but not required
Processing Requirements
Centrifuge at 4° C and aliquot serum into a plastic vial. Freeze immediately.
Specimen type: Serum
Volume: 1 mL
Storage/transport requirements: Frozen

Specimen Minimum Volume

Serum: 0.4 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Frozen 28 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus Reject
Heat-inactivated samples Reject

Method Name

Enzyme Immunoassay (EIA)

Day(s) Performed

Varies

Report Available

3 to 5 days
National University Hospital-Singapore Note:

Please note that this is a referral test requiring transport to the external testing facility and an additional 3-5 days is required.

Reference Values

>67% normal (normal)

41-67% normal (equivocal)

<41% normal (abnormal)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Diagnosing hereditary angioedema

 

Monitoring response to C1 esterase inhibitor replacement therapy

CPT Code Information

83520

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C1INF C1 Esterase Inhib, Functional, S 48494-9

 

Result ID Test Result Name Result LOINC Value
C1INF C1 Esterase Inhib, Functional, S 48494-9

Secondary ID

616906
National University Hospital-Singapore Note:

Mayo test code: C1INF 

Test Classification

This test has been cleared, approved, or is exempt by the US 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.
National University Hospital-Singapore Additional Information:

Last updated 06/07/2026