Smith (Sm) Antibodies, IgG, Serum
Use
Evaluating patients with clinical features suggestive of antinuclear antibody associated connective tissue disease and the confirmation of a diagnosis of systemic lupus erythematosus. Testing for Smith antibodies is not useful in patients without demonstrable antinuclear antibodies. The presence of antibodies to Sm is specific for SLE with a sensitivity of 5% to 30%. Based on classification criteria for SLE, patients positive for anti-Sm antibodies already fulfil 60% of the criteria required for SLE classification. However, anti-Sm antibodies may occur together with ribonucleoprotein antibodies in certain ANA-associated connective tissue diseases. In routine clinical practice, a variety of immunoassays are used for the determination of anti-Sm antibodies.
Special Instructions
Not provided.
Limitations
The presence of antibodies to Sm is specific for SLE but has limited sensitivity, observed in only 5% to 30% of the cases. Immunoassays for detecting anti-Sm antibodies differ in their analytical characteristics, which may affect diagnostic performance. It is also noted that there might be ethnic variability in the prevalence of positive anti-Sm antibody. The solid-phase immunoassays might include a mixture of Sm antigens that can affect the results depending on their composition.
FDA ApprovedNew York Approved
Methodology
Immunoassay (Multiplex Protein Panel)
Biomarkers
Smith Antigen
Protein
LOINC Codes
- 18323-6 - ENA SM IgG Ser-aCnc
- 18323-6 - ENA SM IgG Ser-aCnc
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
0.5 mL
Minimum Volume
0.35 mL
Container
Serum gel (preferred) or Red top
Collection Instructions
Centrifuge and aliquot serum into a plastic vial.
Causes for Rejection
Gross hemolysis, Gross lipemia, Heat treated
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 21 days |
| Frozen | 21 days |