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Fibrillarin (U3 RNP) Antibody, IgG
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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.
Qualitative Immunoblot
Tue, Thu, Sat
1-4 days
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
Negative
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.
Compliance Statement D: For laboratory tests using a manufactured RUO kit. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.
86235
| Component Test Code* | Component Chart Name | LOINC |
|---|---|---|
| 2012174 | Fibrillarin (U3 RNP) Ab, IgG | 49963-2 |
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