Complement, C3

Complement, C3

Alternate Test Name

C3

Epic Mnemonic
Sunquest Mnemonic

LAB152
C3

Category

Chemistry

Methodology

Immunoturbidimetric

Test Performance Schedule

Sunday - Saturday

Result Availability

Within 24 hours

Container

Gold top (SST), Red top (serum), or Green top (lithium heparin) tube

Volume

Pref. Vol.: 1.0 mL serum
Min. Vol.:0.5 mL serum

Collection Instructions

• Routine venipuncture

• Immediately after collection, gently invert tube 5-10 times

• Clot 30 minutes

• Promptly centrifuge 10 minutes

• If no gel barrier is present immediately transfer serum or plasma to a plastic tube and refrigerate

• Properly centrifuged gel barrier tube does not require transfer of serum or plasma to separate tube

Transportation Instructions

Refrigerated

Stability

• Room Temperature: 4 days

• Refrigerated: 5 days

CPT Codes

86161

Effective/Revised

03/22/2017

Activation of the complement system takes place via a classical and an alternative route. The two pathways come together in a joint terminal path. As complement factor C3 is a factor common to both pathways, the concentration of C3 and its degradation products (including C3c) can be evaluated as a parameter for activation of the complement system.

Lowered values are indicative of activation. Additional differentiation can be made by determining C4. If the C4 level is normal, then activation of the alternative route is likely. Depressed values are observed in a number of inflammatory and infectious diseases. Primary causes are systemic lupus erythematosus (SLE), rheumatoid arthritis, subacute bacterial endocarditis, viremia, parasitic infections or bacterial sepsis. A considerable decrease in C3 can be found in patients with partial lipodystrophy or membranoproliferative glomerulonephritis when the C3-nephritis factor is present.

As an acute phase protein, C3 is produced to an increased extent during inflammatory processes. It is elevated in systemic infections, non-infectious chronic inflammatory conditions (primarily chronic polyarthritis) and physiological states (pregnancy). The elevation rarely exceeds twice the normal value and can mask a reduction in the current consumption.