Anti-dsDNA Ab (Farr Assay, RIA)

Test Code: 13
CPT Codes: 86225
Methodology: RIA
Specimen Requirements: 1 mL serum, ambient, refrigerated or frozen
Turn Around Time: 1 – 3 Days
Special Instructions: None
Clinical Utilities: 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 this predictive value.