Test Overview
Test Methodology

Immunoturbidimetric

Test Usage

C4 is decreased when classical pathway of complement is hyperactivated. It is usually decreased in hypergammaglobulinemia, cryoglobulinemia, inborn C4 deficiency, active SLE, serum sickness, SBE, chronic active hepatitis, acute glomerulonephritis and rheumatoid arthritis, as well as in hereditary angioneurotic edema.

Reference Range *

Adult: 13-60 mg/dl

Test Details
Days Set Up
Daily, 24 hrs
Analytic Time

2 hours

Soft Order Code
C4
MiChart Code
C4 Complement
Synonyms
  • C4
  • B1E
  • C4
  • Complement C4
  • Fourth Component of Complement
  • C4 COMPLEMENT
Laboratory
Chemical Pathology
Section
Automation
Specimen Requirements
Collection Instructions

Collect specimen in an SST tube. Centrifuge, aliquot serum into a plastic vial and refrigerate up to 48 hours.

Alternate Specimen
Red top tube, Green top tube (heparin). [rev 8/03]
Yellow Top Tube
Normal Volume
0.5 mL serum
Minimum Volume
0.25 mL serum
Additional Information

C4 comprises approximately 20% of the complement system. C4 is utilized only by the classical pathway, so that it is decreased only when this arm is hyperactivated. In diseases activating the alternate pathway alone, C4 levels will be normal. Total hemolytic activity (CH50), C3, and C4 are frequently decreased in a variety of conditions relating to immune complex formation. While many complement components are depressed with uremia, C4 is an exception and is elevated with uremia.

Billing
CPT Code
86160
Fee Code
21944
LOINC
4498-2
NY State Approved
No