C1Q BINDING ASSAY

Code
000.0000
Name
C1Q BINDING ASSAY
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
Circulating Immune Complex Detection by C1q Binding
CPT Codes
86332
Site
SBMF
Reference Test
44042
ATLAS Test Code

Specimen Information

Type

Red, Plain

Volume

1.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Frozen

CRITICAL FROZEN – Separate samples must be submitted when multiple tests are ordered

Fasting Required?
False
Patient Instructions

Reference Range

C1Q Binding Assay
Less than 4 µgE/mL is considered negative for circulating complement binding immune complexes

Methodology

Enzyme-Linked Immunosorbent Assay

Clinical Significance

A variety of diseases are associated with circulating immune complexes (CIC). CICs are formed by the interaction of antibodies with specific antigen. This normal process of the immune response results in the rapid clearance of CICs by the reticuloendothelial system. However, in some cases there is deposition of CICs in tissues with associated inflammatory-mediated damage. Elevated CICs have been detected in a variety of autoimmune diseases (e.g., systemic lupus erythematosus [SLE], rheumatoid arthritis [RA], etc.), certain cases of glomerulonephritis, infectious diseases (e.g., Lyme disease, chronic HBV infection, HIV infection, endocarditis, etc.), and some malignancies. Some authors believe that immune complex determinations may be useful in monitoring disease activity in certain autoimmune disorders, particularly RA and SLE. A positive CIC assay, however, does not necessarily implicate immune complexes in disease pathogenesis, nor does it necessarily correlate well with disease activity. Circulating immune complexes may be found without any evident pathology and positive results do not necessarily implicate the immune complex in a disease process. There are two general categories of CICs: antigen-specific (e.g., to HBsAg) and antigen-nonspecific. In most clinical circumstances the nature of the specific antigen is unknown. Therefore, most assays are designed to detect antigen-nonspecific CICs. These include Raji cell, C1q binding, conglutinin, and anti-C3 assays. C1q is a normal component of the C1 factor molecular complex and possesses multiple recognition sites for the heavy chain of the immunoglobulin (Ig) molecules. Assays for CICs target C1q and its ability to bind Ig. In general, however, C1q assays are the least sensitive and specific for CICs.

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