Complement C3, Serum

Methodology: 
Immunologic
Performed: 
Monday - Friday
Use: 
Quantitation of C3 is used to detect individuals with inborn deficiency of this factor or those with immunologic disease in whom complement is consumed at an increased rate. These include lupus erythematosus, chronic active hepatitis, certain chronic infections, as well as poststreptococcal and membranoproliferative glomerulonephritis, in addition to others.
 

Limitations

This test detects both biologically active and inactive C3.
Specimen Requirements: 

Type: Serum

Container/Tube: Red-top tube, gel-barrier tube or green-top tube (heparin)
  • Remove serum from the specimen and transfer it to a plastic transport tube within 45 minutes of collection. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Sample Volume:

  • Adult: 1 mL
  • Pediatric: 0.5 mL

Minimum Volume: 0.3 mL (Repeat testing is not possible with this specimen volume.)

Storage: Refrigerate specimens immediately after collection.

Stability (collection to time of analysis/testing):
  • Ambient: 2 days
  • Refrigerated: 3 days
  • Frozen: 7days
  • Freeze/Thaw Cycles: Stable (x 3)
Rejection Criteria:
  • Excessive lipemia (>1500 mg/dL) significantly increases the apparent C3 concentration.
Reference Values: 
Adults: 90−180 mg/dL
CPT Code (s): 
86160
Notes: 

UFHPL Test #: 68065

UFHPL Epic order code: LAB152

C3 comprises about 70 percent of the total protein in the complement system and is central to activation of both the classical and alternate pathways. Increased levels are found in numerous inflammatory states as an acute phase response. CH50 (total complement hemolytic activity), C3 and/or C4 may be decreased in cases of systemic lupus erythematosus, especially in cases with lupus nephritis, acute and chronic hypocomplementemic nephritis, subacute bacterial endocarditis, DIC, and partial lipodystrophy (with associated nephritis-like activity in serum.) In cases of disseminated intravascular coagulation, plasmin attacks C3 directly, and C3 levels have been found low in the hemolytic uremic syndrome form of disseminated intravascular coagulation (DIC). Cases of hereditary C3 deficiency, while rare, have been reported and are characterized clinically by recurrent infections (eg, pneumonia, meningitis, paronychia, impetigo). Pathogenic bacteria causing infections in these cases have included both gram-positive and gram-negative organisms. C3 levels have also been found deficient in cases of uremia, chronic liver diseases, anorexia nervosa, and celiac disease.
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