U3RNP Fibrillarin Ab
Test Mnemonic
U3RNP
CPT Codes
- 86235 - QTY (1)
Aliases
- Fibrillarin Ab
Includes
- Fibrillarin (U3 RNP) Ab, IgG
Performing Laboratory
ARUP
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | SST (Gold) | Refrigerated | Transfer 1 mL serum into standard aliquot tube. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.5 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | After separation from cells: 48 hours |
| Refrigerated | After separation from cells: 2 weeks |
| Frozen | After separation from cells: 1 month (avoid repeated freeze/thaw cycles) |
Days Performed
Tue, Thu, Sat
Turnaround Time
2 - 5 days
Methodology
| Name | Description |
|---|---|
| Immunoblot (IB), Qualitative |
Reference Range
Special Info
Grossly hemolyzed or severely lipemic specimens will be rejected. This test is New York DOH approved.
Clinical Info
This test is recommended for the diagnosis of systemic sclerosis in patients negative for centromere, Scl-70, or RNA polymerase III antibodies. It may predict skeletal muscle involvement and pulmonary arterial hypertension. 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% with the gold standard immunoprecipitation (IP) assay. Approximately 71% (5/7) of the borderline U3-RNP results with ANA nucleolar pattern in this cohort were IP negative.