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Extractable Nuclear Antibodies (ENA)

ENA, anti-Sm/RNP, Anti-Smith (Anti-Sm), Antibodies to Extractable Nuclear Antigens (ENA)

Test Codes

Antrim #30141, EPIC: LAB5756, SOFT: ENA

Department

Special Chemistry

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 2.0 mL)

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube within two hours of collection. (Minimum Serum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged collection tube, refrigerated (2-8 °C or 36-46 °F). (Minimum Serum: 0.5 mL)

Rejection Criteria

Plasma specimens. 

Severely hemolyzed, lipemic or icteric specimens.   

In-Lab Processing

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Room temperature is acceptable for a maximum of two hours. (Minimum Serum: 0.5 mL)

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers^® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers^® without Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 2 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Special Testing Laboratory

Performed

Monday – Friday.
Results available within 2 business days.

Reference Range

Negative: Less than 100 AU/mL.
Equivocal: 100-120 AU/mL.
Positive: Greater than 120 AU/mL.

Test Methodology

Multiplex Bead Immunoassay.

Interpretation

ENA assay includes: Anti-Sm (Smith antigen) and RNP (ribonucleoproteins).

Smith antibody is specific for systemic lupus erythematosus (SLE) but only occurs in 30-35% of cases. Smith autoantibodies are often associated with renal disease in SLE.

Sjogren SSA Antibody, Sjogren SSB Antibody, Scleroderma (SCL-70) Antibody (IgG), and Jo-1 Antibody, IgG are also extractable nuclear antigens. However, these autoantibody assays must be ordered individually.

Antibodies to RNP are seen in 95-100% of mixed connective tissue disease and are specific for this syndrome if other antibodies are negative; RNP antibody is also present in 20-30% of SLE and 15-25% of progressive systemic sclerosis.

CPT Codes

86235

Contacts

Last Updated

4/8/2024