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Complement C1q

Test Codes

MAYO: C1Q, EPIC: LAB6244, SOFT: XCC1Q

Department

Send Outs

Instructions

The patient should be fasting for 8 hours prior to specimen collection.

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 a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Preparation for Courier Transport

Transport: 1.0 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

Grossly lipemic 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 a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Transport: 1.0 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 21 days
Refrigerated (2-8°C or 36-46°F): 28 days
Frozen (-20°C/-4°F or below): 28 days

Specimen Storage in Department Prior to Disposal:

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

Laboratory

Sent to Mayo Medical Laboratories, Rochester, MN.

Performed

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

Reference Range

12-22 mg/dL.

Test Methodology

Nephelometry.

Interpretation

• C1, the first component of complement, comprises 3 subunits (C1q, C1r, C1s). C1 binds to immunoglobulin-antigen complexes and initiates the complement cascade. A congenital deficiency of C1 is associated with an increased incidence of autoimmune diseases such as SLE and polymyosits.
• An undetectable C1q together with absence of CH₅₀ activity and normal C2, C3, and C4 suggests congenital C1 deficiency. In contrast, a low C1q together with a low C1 inhibitor and low C4 suggests an acquired C1 inhibitor deficiency.

Clinical Utility

• Complement C1q (antigen assay) is useful for:
  • Assessment of a patient with undetectable CH₅₀ level.
  • Investigation and diagnosis of congenital C1 deficiency.
  • Investigation and diagnosis of acquired C1 inhibitor deficiency.
• The C1q Binding Assay was used to investigate circulating immune complexes. This is no longer available.

CPT Codes

86160
LOINC:  4478-4

Contacts

Last Updated

7/7/2021