Evaluating patients with signs and symptoms of a connective tissue disease in whom the test for antinuclear antibodies is positive
Testing for Sm antibodies is not useful in patients without demonstrable antinuclear antibodies.
For more information see Connective Tissue Disease Cascade.
Multiplex Flow Immunoassay
Anti-Smith (Sm) Antigen
Autoantibodies to Sm (Smith)
Sm (Anti-Sm) (Smith)
Sm (Smith) Autoantibodies
Smith Antigen
SmRNP Autoantibodies
Smth
For more information see Connective Tissue Disease Cascade.
Serum
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.
0.35 mL
Gross hemolysis | Reject |
Gross lipemia | Reject |
Gross icterus | OK |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum | Refrigerated (preferred) | 21 days | |
Frozen | 21 days |
Evaluating patients with signs and symptoms of a connective tissue disease in whom the test for antinuclear antibodies is positive
Testing for Sm antibodies is not useful in patients without demonstrable antinuclear antibodies.
For more information see Connective Tissue Disease Cascade.
Sm (Smith) is a small nuclear ribonucleoprotein composed of several protein autoantigens designated B, B1, D, E, F, and G, which range in size from 11 kD to 26 kD. Sm antibodies are specific for lupus erythematosus (LE) and occur in approximately 30% of LE patients. The levels of Sm antibodies remain relatively constant over time in patients with LE and are usually found in patients that also have RNP (ribonucleoprotein) antibodies.(1,2)
Sm is 1 of 4 autoantigens commonly referred to as extractable nuclear antigens (ENA). The other ENA are RNP, SS-A/Ro, and SS-B/La. Each ENA is composed of 1 or more proteins associated with small nuclear RNA species (snRNA) ranging in size from 80 to approximately 350 nucleotides. Antibodies to ENA are common in patients with connective tissue diseases (systemic rheumatic diseases) including LE, mixed connective tissue disease, Sjogren syndrome, scleroderma (systemic sclerosis), and polymyositis/dermatomyositis.
For more information see Connective Tissue Disease Cascade.
<1.0 U (negative
> or =1.0 U (positive
Reference values apply to all ages.
A positive result for anti-Sm antibodies is consistent with a
1. Homburger H, Larsen S: Detection of specific antibodies. In
2. Kotzin B, West S: Systemic lupus erythematosus. In Clinical
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, Hercules, CA 11/2011)
Monday through Saturday
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
86235
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
SM | Sm Ab, IgG, S | 18323-6 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
SM | Sm Ab, IgG, S | 18323-6 |