Extractable Nuclear Antigen Antibodies

Included Tests

Sm (Smith) IgG Autoantibodies; RNP Antibodies

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 patient, but are also observed in numerous other disease states such as Sjogren'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.

Specimen Requirements

1.0 mL Serum in a SST Gold Top Tube

Transport And Storage

8 hrs Ambient 
2 days Refrigerated
28 days Frozen

Do not use frost free units that undergo repeated freeze/thaw cycles
Do not transport Frozen.
Specimen to be transported Refrigerated to PRMC within 48 hours of collection to be frozen by Immunology department to maintain specimen integrity until testing occurs.

Collection Instructions

 

Minimum Volume

0.5 mL

Neonatal Volume

Reference Range:

Smith Antibody
< 1.0 AI Negative
Smith/Ribonucleoprotein Antibody
< 1.0 AI Negative

Methodology:

• Enzyme Immunoassay (EIA)

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 patient, but are also observed in numerous other disease states such as Sjogren'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.

CPT Coding

86235 x 2