Fibrillarin (U3 RNP) Antibody, IgG
| Label Mnemonic: | U3FIB |
| Epic code: | LAB8877 |
| Downtime form: | A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery |
Commercial Mailout Laboratory
6240-8 RCP
356-8593
6240-8 RCP
356-8593
Specimen(s):
Serum
Collection Medium:
 |
| Red top tube 5 mL (Clot Activator) |
Minimum:
Preferred Minimum: 1 mL serum in red top tube
Absolute Minimum: 0.5 mL serum
Absolute Minimum: 0.5 mL serum
Rejection Criteria:
Grossly hemolyzed or severely lipemic.
Turn Around
Time:
1-4 days upon receipt at reference laboratory.
Reference Range:
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.
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.
Comments:
This test is 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.
Methodology:
Qualitative Immunoblot
CPT Code:
86235