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SM and SM/RNP Antibodies
Test CodeSMRNQ
Alias/See Also
LAB13720
Anti-Ribonucleic Protein Antigen
Anti-ENA Antibody
ENA Antibodies
Anti-Smith Antibody,Ribonuclear Protein Antibody
RNP Antibody
CPT Codes
86235 (x2)
Preferred Specimen
1 mL serum
Minimum Volume
0.5 mL
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 4 days Refrigerated: 7 days Frozen: 30
days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Grossly
icteric
Methodology
Immunoassay (IA)
Setup Schedule
Mon-Sat a.m.
Report Available
Next day
Reference Range
Sm Antibody <1.0 AI Negative
Sm/RNP Antibody <1.0 AI
Negative
Clinical Significance
Antibodies to Sm are highly specific for systemic lupus erythematosus (SLE) and when present are considered a marker antibody. However, these antibodies are found in only 20% of patients with SLE.
RNP antibodies (also known as anti-u1 or ribonucleoprotein antibodies) are found in 45% of SLE patients but are also observed in numerous other disease states such as Sjögren's syndrome, scleroderma and polymyositis. Elevated levels of antibodies to RNP are seen in mixed connective tissue disease. In SLE, RNP antibodies have been associated with a relatively benign disease course with lower incidence of renal and central nervous system involvement. Patients may be considered positive for RNP antibodies when the RNP antibody result is significantly higher than the Sm antibody result.
RNP antibodies (also known as anti-u1 or ribonucleoprotein antibodies) are found in 45% of SLE patients but are also observed in numerous other disease states such as Sjögren's syndrome, scleroderma and polymyositis. Elevated levels of antibodies to RNP are seen in mixed connective tissue disease. In SLE, RNP antibodies have been associated with a relatively benign disease course with lower incidence of renal and central nervous system involvement. Patients may be considered positive for RNP antibodies when the RNP antibody result is significantly higher than the Sm antibody result.
Performing Laboratory
Quest Diagnostics Nichols Institute 14225 Newbrook Drive Chantilly, VA 20153
Last Updated: February 17, 2023