Immune Complexes, C3d Circulating

CPT: 86332
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Test Details

Synonyms

  • C3d
  • Complement c3d
  • Complement c3dg
  • Complement ic3b
  • Raji cell, Quantitative

Use

For the measurement of C3d-bound circulating immune complexes (CIC) present in human plasma or serum.

Limitations

False-positives occur when antilymphocyte antibodies are present. This assay does not detect noncomplement fixing CIC. Occasionally, positive specimens may not confirm. Nonconfirming specimens may be due (among other reasons) to contaminated or heat-inactivated specimens or specimens containing human IgG antibodies that bind to mouse IgG. Such specimens, however, are not necessarily negative for CIC. The material causing the apparent false-positive result may mask concomitantly occurring CIC that, if they were present alone, would otherwise yield a confirmable positive CIC result.

Methodology

Enzyme immunoassay (EIA)

Reference Interval

• Normal: <15.1 μg Eq/mL

• Equivocal: 15.1−19.9 μg Eq/mL

• Positive: >19.9 μg Eq/mL

Additional Information

The importance of circulating immune complexes, and their relationship to various diseases, has been the subject of study for many years. Formation of immune complexes is a protective and usually benign process of a normally functioning immune system. CIC are removed from circulation by a number of complex biochemical, enzymatic, and cellular processes. Key to all of these, however, is the complement system.

In certain disease states, immune complexes may initiate complement-mediated damage of various organs and tissues. This activation of complement may begin a series of potentially destructive events, including cell lysis, the production of anaphylatoxins, leukocyte stimulation, and activation of macrophages. Major tissue damage can also occur with IC fix to cell membranes as in some cases of glomerulonephritis.

More than 40 assays have been developed to measure CICs, many of these require multiple complex steps and sophisticated equipment. Since the characteristics of CIC vary widely, none of these assays has been accepted as standard. In fact, in a comprehensive study, the WHO determined that no single method was appropriate to measure CIC in all disease states and that a combination of two different methods and techniques be used.

Specimen Requirements

Specimen

Serum or plasma, frozen

Volume

1 mL

Minimum Volume

0.1 mL

Container

Red-top tube or gel-barrier tube; lavender-top (EDTA) tube is also acceptable.

Collection

Transfer specimen to a plastic transport tube before freezing. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Freeze at -70°C or store on dry ice within six hours of collection. Specimen is stable for 14 days if stored at -70°C. Storage of specimens at -20°C will yield erroneous results.

Causes for Rejection

Specimen not received frozen on dry ice

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
123014 C3d Immune Complexes 123015 C3d Immune Complexes ug Eq/mL 10864-7

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