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Fibrillarin (U3 RNP) Antibody, IgG
Copy Utility
Ordering Recommendation
Recommended for the diagnosis of systemic sclerosis in patients negative for centromere, Scl-70, or RNA polymerase III antibodies. May predict skeletal muscle involvement and pulmonary arterial hypertension.
Mnemonic
Methodology
Qualitative Immunoblot
Performed
Tue, Thu, Sat
Reported
1-4 days
New York DOH Approval Status
Specimen Required
Serum separator tube.
Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.5 mL)
Refrigerated. Also acceptable: Frozen.
Grossly hemolyzed or severely lipemic.
After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year
Reference Interval
Negative
Interpretive Data
The presence of fibrillarin (U3-RNP) IgG antibodies in association with an ANA IFA nucleolar pattern is suggestive of systemic sclerosis (SSc). In SSc, these antibodies are associated with distinct clinical features, such as younger age at disease onset, frequent internal organ involvement (pulmonary hypertension, myositis and renal disease). Fibrillarin antibodies are detected more frequently in African American patients with SSc compared to other ethnic groups. Strong correlation with ANA IFA results is recommended.
In a multi-ethnic cohort of SSc patients (n=98), U3-RNP antibodies detected by immunoblot had an agreement of 98.9 percent with the gold standard immunoprecipitation (IP) assay. Approximately 71 percent (5/7) of the borderline U3-RNP results with ANA nucleolar pattern in this cohort were IP negative.
This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.
Laboratory Developed Test (LDT)
Note
Hotline History
CPT Codes
86235
Components
| Component Test Code* | Component Chart Name | LOINC |
|---|---|---|
| 2012174 | Fibrillarin (U3 RNP) Ab, IgG | 49963-2 |
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