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HelpOrder Code SM Smith (Sm) Antibodies, IgG, Serum
Additional Codes
| Mayo Test ID |
|---|
| SM |
Reporting Name
Sm Ab, IgG, SUseful For
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.
Specimen Type
SerumSpecimen Required
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.35 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 21 days | |
| Frozen | 21 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | OK |
| Heat treated | Reject |
Reference Values
<1.0 U (negative)
≥1.0 U (positive)
Reference values apply to all ages.
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Day(s) Performed
Monday through Saturday
Method Name
Multiplex Flow Immunoassay
CPT Code Information
86235
Special Instructions
Method Description
Affinity-purified Sm antigens are bound to polystyrene microspheres, which are impregnated with fluorescent dyes to create a unique fluorescent signature. Sm antibodies, if present in diluted serum, bind to the Sm antigens on the microspheres. The microspheres are washed to remove extraneous serum proteins. Phycoerythrin (PE)-conjugated antihuman IgG antibody is then added to detect IgG anti-Sm bound to the microspheres. The microspheres are washed to remove unbound conjugate, and bound conjugate is detected by laser photometry. A primary laser reveals the fluorescent signature of each microsphere to distinguish it from microspheres that are labeled with other antigens, and a secondary laser reveals the level of PE fluorescence associated with each microsphere. Results are calculated by comparing the median fluorescence response for Sm microspheres to a 4-point calibration curve.(Package insert: Bioplex 2200 ANA Screen. Bio-Rad Laboratories; 02/2019)