ARUP's Laboratory Test Directory

0050470: RNP (U1) (Ribonucleic Protein) (ENA) Antibody, IgG

Test Mnemonic: RNP
Methodology: Multi-Analyte Fluorescent Detection

Performed: Sun-Sat

Reported: 1-2 days

Specimen Required:  
Collect: One 4 mL SST.

Transport: 1 mL serum at 2-8°C. (Min: 0.5 mL)  Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 0.15 mL serum at 2-8°C.

Remarks: Separate serum from cells ASAP.

Unacceptable Conditions: Plasma and other body fluids.  Severely lipemic, contaminated, and hemolyzed specimens.

Stability: After separation from cells: Ambient: 2 days; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)

Reference Interval:
29 AU/mL or less: Negative
30-40 AU/mL: Equivocal
41 AU/mL or greater: Positive

Interpretive Data:
RNP antibody is seen in 95-100% of mixed connective tissue disease and is considered specific for this syndrome if other antibodies are negative; RNP is also present in 20-30% of systemic lupus erythematosus and 15-25% of progressive systemic sclerosis.



Note:
RNP antigens also contain epitopes which are immunologically identical to free Smith antigens.  The Smith antibody response must be considered when interpreting RNP results.

CPT Code(s):
86235

 

 

 
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