Lab Test

Complement, C4

C4, C4 Complement

Test Codes

Antrim #30210, EPIC: LAB6457, C4

Department

Chemistry

Specimen Collection Criteria

Collect: One Gold-top SST tube.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube within twelve hours of collection.

Preparation for Courier Transport

Transport: Centrifuged collection tube, refrigerated (2-8 °C or 36-46 °F). (Minimum: 0.5 mL)

Rejection Criteria

  • Grossly lipemic specimens.
  • Hemolyzed specimens
  • Plasma specimens.
  • Specimens that have gross bacterial contamination.
  • Specimens not collected and processed as indicated.

In-Lab Processing

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 12 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gel
Room Temperature (20-25°C or 68-77°F): 12 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 12 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Dearborn Chemistry Laboratory

Royal Oak Automated Chemistry Laboratory

Performed

Sunday – Saturday, 24 hours a day.
Results available within 24 hours.

Reference Range

10-43 mg/dL.

Test Methodology

Immunoturbidimetric.

Interpretation

  • Concomitant reduction of C4, C3 and CH50 is suggestive of complement activation and involvement of the classical pathway. Increased C4 levels are seen in various infections and inflammation.
  • Decreased C4 levels are seen in hypergammaglobulinemia, congenital C4 deficiency, acute glomerulonephritis, bacterial endocarditis, P. falciparam and P. vivax malaria, severe chronic liver disease, active systemic lupus erythematosus with renal involvement, mixed cryoglobulinemia, and hereditary angioedema.

Clinical Utility

C4 measurements should be performed whenever a complement activating disease is suspected or whenever hyposynthesis due to inherited deficiency is a possibility. C4 is the second most abundant complement protein in serum. C4 is only used in the classical pathway. Conditions affecting only the alternate pathway will not affect C4 levels. Individual assays for C3 and C4 are most useful in monitoring patients with immunologic diseases. Functional assays (e.g., the CH50 test) measure the activity of the entire complement cascade and are more likely to detect inherited deficiencies.

CPT Codes

86160
LOINC: 26931-6

Contacts

Last Updated

5/5/2021

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