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Smooth Muscle Antigen (Serum) – Mass Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the presence of antibodies directed against smooth muscle proteins, often used to evaluate conditions affecting the gastrointestinal tract or reproductive organs.

Quick summary

["This test helps diagnose conditions like autoimmune disorders or certain infections that may affect smooth muscle tissues."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
31629-9
Short code
Smooth muscle Ab Ser-aCnc
Synonyms
Smooth muscle Ab Ser-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

The test detects antibodies that target smooth muscle proteins found in organs such as the stomach, intestines, or uterus. These antibodies can be produced by the immune system in response to inflammation, infection, or autoimmune processes.

Why It’s Ordered

A healthcare provider may order this test if you have symptoms like abdominal pain, nausea, vomiting, or irregular menstrual cycles. It can also be used to investigate unexplained organ dysfunction or autoimmune conditions.

Common Conditions Linked to Positive Results

Positive results may suggest conditions such as autoimmune hepatitis, polycystic ovary syndrome (PCOS), or certain infections like viral hepatitis. However, false positives can occur, so results should be interpreted by a medical professional.

Sample Collection and Preparation

A blood sample is drawn from a vein, typically in your arm. The sample is sent to a lab for analysis. You may be asked to fast for a few hours before the test, depending on lab protocols.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Smooth Muscle Antibody (Serum)

Frequently asked questions

What does a positive result mean?
A positive result indicates the presence of smooth muscle antibodies, which may suggest an underlying condition like autoimmune hepatitis or other smooth muscle-related disorders. However, further testing and evaluation by a healthcare provider are needed to determine the exact cause and appropriate treatment.
If your results are abnormal, your healthcare provider will review them in the context of your medical history, symptoms, and other test results. They may recommend additional tests, such as liver function tests, imaging studies, or further antibody testing to narrow down the diagnosis and develop a treatment plan.
While lifestyle changes like a balanced diet, stress management, and avoiding known triggers (such as certain medications or infections) may support overall health, they may not directly address the underlying cause of positive antibody results. Always follow your healthcare provider’s advice for managing any diagnosed condition.
The frequency of retesting depends on your symptoms, medical history, and ongoing treatment. Your healthcare provider will determine whether repeat testing is necessary, typically based on clinical judgment rather than a fixed schedule.
Blood tests like this are generally safe. The most common side effect is mild bruising, swelling, or discomfort at the injection site. Rarely, there may be a slight reaction to the needle or blood draw, but serious complications are uncommon.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy