Smith and Smith/RNP (ENA) Antibodies, IgG
Also known as: SMITH_RNP
Use
Useful for confirming a diagnosis of systemic lupus erythematosus (SLE) or mixed connective tissue disease (MCTD) following a positive ANA result. Antibodies may be useful in the differential diagnosis of other systemic autoimmune rheumatic diseases such as systemic sclerosis, Sjögren syndrome, polymyositis, dermatomyositis, and overlap syndromes. Smith antibody is highly specific for SLE but only occurs in a minority of SLE cases. The presence of antibodies to Smith/RNP has variable associations with clinical manifestations of mixed connective tissue disease and SLE.
Special Instructions
This test is New York state approved.
Limitations
Antibodies targeting the Smith/RNP antigenic complex also recognize Smith antigens, therefore, the Smith antibody response must be considered when interpreting results. False positives may occur in patients with other autoimmune diseases. The methodology deployed, while highly specific, may not detect all potential autoantibodies in these syndromes.
New York Approved
Methodology
Immunoassay (ELISA)
Biomarkers
LOINC Codes
- 18323-6
- 33983-8
- 18323-6
- 33983-8
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
ARUP standard transport tube
Collection Instructions
Separate from cells ASAP or within 2 hours of collection.
Storage Instructions
Refrigerated. After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 month (avoid repeated freeze/thaw cycles)
Causes for Rejection
Plasma or other body fluids. Contaminated, hemolyzed, or severely lipemic specimens.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 48 hours |
| Refrigerated | 2 weeks |
| Frozen | 1 month |