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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Smith Ab

Test Code(s): Smith / HCSMITH

CPT Code(s): 86235

Test Description: Included In: ENA Ab

Methodology: Enzyme Immunoassay

Clinical Significance: Antibodies to extractable nuclear antigens (SSA, SSB, RNP, Sm) are found in many connective tissue diseases including SLE (SSA, SSB, RNP, SM), mixed connective tissue disease (high titer RNP), Sjogren's syndrome (SSA, SSB) and scleroderma (SSA, RNP). Sm is very specific for SLE, but not sensitive (30%). Mixed connective tissue disease is almost always (90%) associated with high titer RNP and is associated with antibodies to the 70kd protein by Western blot. SSA is found in approximately 70% of patients with Sjogren's syndrome, whereas SSB is found in 30% of patients. Scleroderma is typically associated with centromere or Scl-70 antibodies, but RNP and SSA are found in a small proportion of patients.

Days Performed: Mon-Fri, dayshift - day varies.

Turnaround Time: Routine: 5 working days.


Specimen Requirements

Specimen: Blood

Collection Container: Preferred: Red top
Also Acceptable: Red cap with yellow ring (SST)

Collection Volume: Preferred: 3 mL
Pediatrics: 1 mL

Sample Analyzed: Serum

Volume Required: Preferred: 1 mL
Pediatrics: 0.3 mL

Specimen Processing: Centrifuge. Transfer cell-free serum to clear plastic vial. Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from UWHC Satellite lab location.

Unacceptable Criteria: Hemolyzed, grossly lipemic/turbid and icteric specimens are not acceptable.

Stability: Ambient: 8 hours
Refrigerated: 7 days
Frozen: No limit at-20C or lower. Note: Avoid repeat freeze and thaw.


Interpretation

Normal Smith Ab (0 days and up):  Negative

Anti-Smith antibodies, Anti Sm, Smith antibodies

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