Lab Test

Smith Antibody

Sm Antibody, Anti-Smith, Anti-Sm

Test Codes

EPIC: LAB6987, SOFT: SMTHA

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

A positive result for Smith antibody is consistent with a diagnosis of lupus erythematosus.

Clinical Utility

Smith antibodies are detected in approximately 30% of patients with lupus erythematosus. The levels of Smith antibodies remain relatively constant over time in lupus patients, and are commonly found in individuals that also have RNP antibodies. Testing for Smith antibodies is not useful in patients negative for antinuclear antibodies.

CPT Codes

86235
LOINC: 21523-6

Contacts

Last Updated

6/15/2021

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