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Test Name:
Smooth Muscle Antibody


  • SBMF No:
    28151
  • Performance Lab Name:
    Immunology
  • Test Mnemonic:
    SMO MUS AB
  • ABN:
    Not required
  • CPT Code:
    86256
  • LOINC Code:
    5358-7
  • Also Known As:
    Antismooth Muscle Antibody
    ASMA
    SMA
  • Also See:
    28150 Antimitochondrial Antibody
  • Spec Type:
    Serum
  • Spec Container:
    Gold top (SST) or red top (serum) tube
  • Pref Vol:
    1.0 mL
  • Min Vol:
    0.5 mL
  • Fasting:
    No
  • Spec Collect:
    Routine venipuncture
  • Spec Process:
    Clot 30 minutes
    Promptly centrifuge 15 minutes
    Immediately transfer serum to separate plastic tube
    Properly centrifuged gel barrier tube sample does not require transfer of serum to separate tube
  • Spec Store Transport:
    Refrigerated
  • Spec Stability:
    5 days refrigerated (2-8°C)
    Greater than 5 days, freeze (-20°C) – Do not use frost-free units that undergo repeated freeze/thaw cycles
  • Spec Reject:
    Plasma sample
    Hemolyzed, lipemic, or turbid sample
  • Spec Remarks:
    Turbidity, hemolysis, visible bacterial growth or drugs capable of fluorescing may interfere with the performance and accuracy of the test.
  • Methodology:
    Indirect Fluorescent Antibody (IFA)
  • Use:
    Differential diagnosis of liver disease
    Antismooth muscle antibodies are found mainly in chronic active hepatitis
    The antibody is usually not seen in systemic lupus erythematosus
    Antismooth muscle antibodies are also seen in acute viral hepatitis and low tiers may be seen in primary biliary cirrhosis
  • Clinical Significance:

    Smooth muscle antibodies (SMA) may be demonstrated in patients with acute and chronic hepatitis, with the highest titers occurring in chronic active hepatitis (CAH). Various forms of chronic liver disease are associated with low SMA titers (less than 1:160), except for CAH, where titers may reach 1:640 or greater. In most cases, however, CAH titers range from 1:80-1:320 and persist for years. In viral hepatitis, the titers are generally below 1:80 and are transient. Both viral and autoantibody markers may be used to classify different sub-groups of CAH and it has been demonstrated that most HBV antigen-negative patients are SMA positive. Antinuclear antibodies (ANA), SMA, and anti-mitochondrial autoantibodies (AMA) occur in CAH and form the basis of distinguishing different groups of autoimmune hepatitis. CAH patients who are ANA and SMA positive have high titers that are readily demonstrable by immunofluorescent techniques.

    SMA tests have been helpful in confirming the diagnosis of approximately 70% of the cases of CAH. A positive SMA test helps to rule out systemic lupus erythematosus, as this disease usually tests negative for SMA. It is also found in approximately 50% of patients with primary biliary cirrhosis (titers are low; 1:10-1:40) and in up to 28% of patients with cryptogenic cirrhosis. A high incidence of SMA has also been reported in serum of patients with infectious mononucleosis. Diseases including carcinoma of the breast, malignant melanoma, and ovarian carcinoma have been reported to have SMA. SMA is rarely found (less than 2%) in patients with bile duct obstruction, alcoholic cirrhosis, and in the normal population.

  • Reference Range:

    Negative
    If positive, results are titered

    ASMA titers greater than 1:40 are significant

  • Day Run:
    Wed, Sat
  • Time Run:
    6:00 am
  • Time Reported:
    5:00 pm
  • Test Type:
    IMMUNOLOGY

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