Test Details
Methodology
Radioimmunoassay (RIA) Farr Technique
Result Turnaround Time
7 - 10 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Use
The Farr method detects the high avidity 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 autoantibodies does not exclude the diagnosis of SLE. Doubling of dsDNA autoantibody 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.
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.
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 Instructions
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.
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 7 days |
Refrigerated | 14 days |
Frozen | 60 days |
Freeze/thaw cycles | Stable x1 |
Storage Instructions
Refrigerate or freeze.
Causes for Rejection
Grossly hemolyzed; bacterial contamination; lipemic specimen; icteric specimen; non-serum specimen types
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 520059 | Anti-dsDNA Ab by Farr (RDL) | 47299-3 | 520060 | Anti-dsDNA Ab by Farr(RDL) | IU/mL | 47299-3 |
| Order Code | 520059 | |||||
| Order Code Name | Anti-dsDNA Ab by Farr (RDL) | |||||
| Order Loinc | 47299-3 | |||||
| Result Code | 520060 | |||||
| Result Code Name | Anti-dsDNA Ab by Farr(RDL) | |||||
| UofM | IU/mL | |||||
| Result LOINC | 47299-3 |