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Lupus Renal Activity Profile (RDL)

CPT: 83520; 86160(x2); 86225

Test Includes

Anti-dsDNA Ab by Farr; C3 & C4 Complements; Anti-C1Q Ab, IgG


Expected Turnaround Time

14 - 21 days


Specimen Requirements


Specimen

Serum


Volume

1 mL


Minimum Volume

0.3 mL (Note: This volume does not allow for repeat testing.)


Container

Red-top tube or gel-barrier tube


Collection

Separate serum from cells within one hour of collection. Transfer to a plastic transport tube before shipping. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.


Storage Instructions

Refrigerate or freeze.


Stability Requirements

Temperature

Period

Room temperature

2 days

Refrigerated

8 days

Frozen

8 days


Causes for Rejection

Grossly hemolyzed; bacterial contamination; lipemic specimen; icteric specimen; non-serum specimen types


Test Details


Use

Serial testing shows that increasing amounts of IgG anti-C1q predict renal flares in SLE patients. Elevated serum titers of anti-C1q antibodies tend to be associated with proliferative forms of lupus, glomerulonephritis and subendothelial deposits of immune complexes.

The Farr method detects the high-affinity anti-dsDNA antibodies. The Farr assay is the most specific method for detecting dsDNA auto antibodies. Significant elevations in dsDNA autoantibody concentrations confirm the diagnosis of systemic lupus erythematosus (SLE). Serial studies of elevated values of dsDNA auto antibodies are useful for predicting activity of SLE and for measurement of serum C3 or C4 concentrations. Absence of dsDNA auto antibodies does not exclude the diagnosis of SLE. Doubling of dsDNA auto antibody concentrations or increases greater than 30 IU/mL in less than 10 weeks are reliably predictive of exacerbations of SLE. A simultaneous decrease in serum C4 complement enhances ths predictive value. Measurement 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, post-streptococcal and membranoproliferative glomerulonephritis, and others.

Measurement of C4 in serum 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, post-streptococcal and membranoproliferative glomerulonephritis, and others.


Limitations

This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.


Methodology

Enzyme-linked immunosorbent assay (ELISA), RIPA, Enzyme Immunoassay (EIA)


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