Norm of Anti-Sm Test (Extractable Nuclear Antigen)
Usage of Anti-Sm Test (Extractable Nuclear Antigen)
Assists in differentiating the type of autoimmune disease occurring. The presence of antibodies specific against Sm is strongly suggestive of systemic lupus erythematosus (SLE) when other autoantibodies are negative. Increases in Sm antibody levels are seen in arthritis, heart-related diseases, Raynaud's phenomenon, and SLE.
Description of Anti-Sm Test (Extractable Nuclear Antigen)
An antinuclear antibody active against acidic nuclear proteins, present in autoimmune disease detected by an immunofluorescent procedure. Immunofluorescence results in characteristic staining patterns that help differentiate the type of connective tissue disease occurring. Anti-Sm antibodies are associated with a speckled pattern and occur in clients with mixed connective tissue syndrome and in about one fourth of clients with scleroderma, discoid lupus erythematosus, and SLE.
Professional Considerations of Anti-Sm Test (Extractable Nuclear Antigen)
Consent form NOT required.
- Tube: Red topped, red/gray topped, or gold topped.
- See Client and Family Teaching.
- Draw a 4-mL blood sample.
- Send the specimen to the laboratory for immediate spinning.
Client and Family Teaching
- Fast for 8 hours before sampling.
- Results may not be available for several days if testing is not performed on site.
Factors That Affect Results
- Reject hemolyzed, lipemic, or contaminated specimens.
- False-negative results may be caused by drug therapy with corticosteroids.
- Drugs that may cause false-positive results arising from a drug-induced syndrome resembling SLE include acetazolamide, aminosalicylic acid, carbidopa, chlorothiazide, chlorpromazine, clofibrate, diphenylhydantoin, ethosuximide, gold salts, griseofulvin microsize, griseofulvin ultramicrosize, hydralazine hydrochloride, hydroxytryptophan, infliximab, isoniazid, mephenytoin, methyldopa, methyldopate hydrochloride, methylthiouracil, methysergide maleate, oral contraceptives, penicillin, phenylbutazone, phenytoin, primidone, procainamide hydrochloride, propylthiouracil, quinidine gluconate, quinidine polygalacturonate, quinidine sulfate, reserpine, streptomycin sulfate, sulfadimethoxine, sulfonamides, tetracyclines, thiouracil, and trimethadione.
- There is a clinical association of this antibody titer with vasculitis.
- Not useful as a screening test for lupus because results must be interpreted in consideration of other antibody testing.