Sm and Sm/RNP Antibodies

Cassandra Greaves S, Test

NEW YORK DOH APPROVED: YES

CPT Code: 86235 (x2)
Order Code: 7448
Alternative Names: Anti-Ribonucleic Protein Antigen, Anti-ENA Antibody, ENA Antibodies, Ribonuclear Protein Antibody, Anti-Smith Antibody, RNP Antibody
ABN Requirement:
No
Specimen: Serum
Volume:  1.0 mL
Minimum Volume:  0.5 mL
Container: Gel-barrier tube (SST, Tiger Top)

Collection:

  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 5 times immediately after draw. DO NOT SHAKE.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge for 10 minutes.

Transport: Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.

Stability:

Ambient (15-25°C): 4 days
Refrigerated (2-8°C):
7 days
Frozen (-20°C):
30 days

Causes for Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits; gross hemolysis; gross lipemia; gross icterus

Methodology: Immunoassay (IA)

Turn Around Time:  2 to 3 days

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.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.