Lab Test

C1q Complement, Functional Assay

Test Codes

MAYO: C1QFX, EPIC: LAB6233, SOFT: XC1QF

Department

Send Outs

Instructions

It is preferred that the patient be fasting 8 hours prior to specimen collection, but not required.

Specimen Collection Criteria

Collect: One plain Red-top tube.

Do not use Serum Separator Tubes.
Critical frozen. Transport specimen the the Laboratory, on ice, immediately after collection.

Physician Office/Draw Specimen Preparation

Critical frozen. Let specimen clot then immediately centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and freeze (-20°C/-4°F or below) immediately.

Preparation for Courier Transport

Transport: 1.0 mL serum, frozen (-20°C/-4°F or below). (Minimum: 0.5 mL)

Rejection Criteria

  • Serum Separator (SST) tubes.
  • Specimens not collected and processed as indicated.

Inpatient Specimen Preparation

Critical frozen. Transport specimen to the Laboratory immediately, on ice, for processing.

In-Lab Processing

Critical frozen. Let specimen clot then immediately centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and freeze (-20°C/-4°F or below) immediately.

Transport: 1.0 mL serum, frozen (-20°C/-4°F or below). (Minimum: 0.5 mL)

Laboratory

Sent to Mayo Medical Laboratories, Rochester, MN.

Performed

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

Reference Range

34-63 U/mL.

Test Methodology

Automated Lyposome Lysis Assay.

Interpretation

Low levels of complement may be due to inherited or acquired deficiencies or to complement consumption (e.g., infectious, autoimmune process). The measurement of C1q activity is an indicator of the amount of C1 present. An absent C1q level in the presence of normal C3 and C4 values is consistent with C1 deficiency. A low C1q level in the presence of low C4 but normal C3 may indicate the presence of an acquired inhibitor (auto antibody) to C1 esterase inhibitor.

Clinical Utility

  • C1q Complement, Functional Assay is useful for:
    • Diagnosis of C1 deficiency.
    • Investigation of a patient with absent CH50.
  • An absent C1q functional level in the presence of a normal C1q antigen level should be repeated to confirm that C1q inactivation did not occur during shipping.

CPT Codes

86161
LOINC:  87722-5

Contacts

Last Updated

7/7/2021

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