Also Known As
SMA
Anti-Smooth Muscle Antibody
ASMA
Actin Antibody
F-Actin Antibody
ACTA
Formal Name
Smooth Muscle Antibody
This article was last reviewed on
This article waslast modified on
June 12, 2018.
At a Glance
Why Get Tested?

To help diagnose autoimmune hepatitis and distinguish it from other causes of liver injury

When To Get Tested?

When you have hepatitis that your healthcare practitioner suspects may be due to an autoimmune-related process

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Smooth muscle antibodies (SMA) are autoantibodies, proteins produced by the body's immune system that recognize and attack its own actin, a protein found in smooth muscle and other tissues, especially the liver. This test detects and measures the amount (titer) of SMA (or antibody against actin) in the blood.

The production of smooth muscle or actin antibodies is strongly associated with autoimmune hepatitis. It may also sometimes be seen in other forms of liver disease, such as primary biliary cholangitis (PBC), but usually at lower antibody titers.

Autoimmune hepatitis occurs when the immune system attacks the body's liver cells. It presents as an acute or chronic inflammation of the liver that is not due to another cause, such as a viral infection, exposure to a drug or toxin, a hereditary disorder, or alcohol abuse. It can lead to liver cirrhosis and, in some cases, to liver failure. Autoimmune hepatitis can affect anyone at any age, but about 80% of patients are women. In the United States, more than 70% of people with this disorder will have SMA or actin antibodies, either alone or along with antinuclear antibodies (ANA).

The majority of smooth muscle antibodies produced with autoimmune hepatitis is specifically directed against a protein called actin or F-actin. Testing is available for specific actin autoantibodies, but it is not available in every laboratory. Tests for actin antibodies detect more cases of autoimmune hepatitis but, in some studies, give more false-positive results than tests for smooth muscle antibodies.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

Accordion Title
Common Questions
View Sources

Sources Used in Current Review

Aizawa, Y. and Hokari, A. (2017 January 19). Autoimmune hepatitis: current challenges and future prospects. Clin Exp Gastroenterol. 2017; 10: 9–18. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5261603/. Accessed on 02/18/17.

Wolf, D. and Raghuraman, U. (2016 February 18, Updated).Autoimmune Hepatitis. Medscape Drugs and Disease. Available online at http://emedicine.medscape.com/article/172356-overview. Accessed on 02/18/17.

(© 1995–2017). Smooth Muscle Antibodies, Serum. Mayo Clinic Mayo Medical Laboratories. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/6284. Accessed on 02/18/17.

Sloan, J. et. al. (2014 March 4, Updated). Anti-Smooth-Muscle Antibody. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/2086774-overview. Accessed on 02/18/17.

Starkebaum, G. (2015 January 20, Updated). Anti-smooth muscle antibody. MedlinePlus Medical Encyclopedia. Available online at https://medlineplus.gov/ency/article/003531.htm. Accessed on 02/18/17.

Slev, P. and Tebo, A. (2016 December Updated). Autoimmune Hepatitis - Hepatitis, Autoimmune. ARUP Consult. Available online at https://arupconsult.com/content/autoimmune-hepatitis. Accessed on 02/18/17.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO. Pp 92-93.

Beuers, U. and Rust, C. (2005 October 27). Overlap Syndromes. Medscape, from Semin Liver Dis. 2005; 25(3): 311-320. [On-line information]. Available online at http://www.medscape.com/viewarticle/512463.

Stone, C. (2004 November 10, Updated). Autoimmune liver disease panel. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003328.htm.

Peng, S. (2005 April 20). Anti-smooth muscle antibody. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003531.htm.

(© 2005). Smooth Muscle Antibody, IgG with Reflex to Titer. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_203b.jsp#3219875.

Strassburg, C. and Manns, M. (2003 January 9). Autoantibodies and Autoantigens in Autoimmune Hepatitis. Medscape from Semin Liver Dis 22(4): 339 -351, 2002 [On-line journal]. Available online at http://www.medscape.com/viewarticle/445619.

Czaja, A. and Freese, D. et. al. (2002 August). Diagnosis and treatment of autoimmune hepatitis. National Guideline Clearinghouse [On-line information]. Available online through http://www.guideline.gov.

(© 2005). F-Actin (Smooth Muscle) IgG by Enzyme. ImmunoassayARUP's Guide to Clinical Laboratory Testing [[On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_a254.jsp#5444091.

(© 2003). Actin (Smooth Muscle) Antibody. LabCorp [On-line test information]. Available online at http://www.labcorp.com/datasets/labcorp/html/chapter/mono/se018700.htm.

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 96-97.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 272.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition: Saunders Elsevier, St. Louis, MO. Pp 990-991.

Lee, S. (Updated 2007 May 27). Anti-smooth muscle antibody. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003531.htm. Accessed 1/29/09.

(2008 April). Autoimmune Hepatitis. NDDIC [On-line information]. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/autoimmunehep/. Accessed 1/29/09.

Dugdale, D. (Updated 2008 November 2). Autoimmune liver disease panel. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003328.htm. Accessed 1/29/09.

Hill, H. et. al (Updated 2008 September). Hepatitis, Autoimmune – AIH. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/GastrointestinalDz/AIH.html#. Accessed 1/29/09.

Sloan, J. and Feyssa, E. (Updated 2012 December 20). Anti-Smooth-Muscle Antibody. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2086774-overview#showall. Accessed February 2013.

Longstreth, G. (2012 October 8). Autoimmune hepatitis. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000245.htm. Accessed February 2013.

Makover, M. (Updated 2011 February 10). Anti-smooth muscle antibody. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003531.htm. Accessed February 2013.

Tebo, A. (Updated 2012 August). Primary Biliary Cirrhosis – PBC. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/PBC.html?client_ID=LTD#tabs=0. Accessed February 2013.

(Updated 2012 February 16). Autoimmune Hepatitis. National Digestive Diseases Information Clearinghouse [On-line information]. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/autoimmunehep/. Accessed February 2013.

(© 1995–2013). Smooth Muscle Antibodies, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/6284. Accessed February 2013.

Shaffer, E. (Reviewed 2009 June) Laboratory Tests of the Liver and Gallbladder. Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merckmanuals.com. Accessed February 2013.

Slev, P. and Tebo, A. (Updated 2013 February). Hepatitis, Autoimmune – AIH. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/AIH.html?client_ID=LTD#tabs=0. Accessed March 2013.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 99-100.

Bogdanos DP. Autoimmune liver serology: Current diagnostic and clinical challenges. World J Gastroenterol. 2008 June 7; 14(21): 3374–3387. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2716592/. Accessed April 2013.

(June 2010) Manns M, et al. Diagnosis and Management of Autoimmune Hepatitis. AASLD Practice Guidelines, Hepatology. PDF available online at http://www.aasld.org/practiceguidelines/Documents/AIH2010.pdf. Accessed April 2013.

Ask a Laboratory Scientist

 

Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, the American Society for Clinical Laboratory Science (ASCLS). Click on the Contact a Scientist button below to be re-directed to the ASCLS site to complete a request form. If your question relates to this web site and not to a specific lab test, please submit it via our Contact Us page instead. Thank you.

Contact a Scientist