Smooth Muscle Antibodies

What is the Smooth Muscle Antibodies (SMA) test?

The Smooth Muscle Antibodies (SMA) test is a blood test that detects autoantibodies directed against proteins found in smooth muscle cells. These antibodies are most commonly associated with autoimmune hepatitis, a condition where the immune system attacks liver tissue.

SMA testing is usually performed using immunological techniques such as immunofluorescence. The presence and titre (level) of antibodies provide important diagnostic information when assessing liver-related symptoms or abnormal liver function tests.

Why do I need a Smooth Muscle Antibodies test?

Autoimmune liver disease can be difficult to diagnose because symptoms are often non-specific or mild in early stages. SMA testing helps identify an autoimmune cause when routine liver tests are abnormal or when symptoms persist without a clear explanation.

You may need this test if you have:

• Persistently abnormal liver function tests (LFTs)
• Unexplained fatigue or weakness
• Jaundice (yellowing of skin or eyes)
• Abdominal discomfort or liver enlargement
• Suspected autoimmune hepatitis
• Other autoimmune conditions with liver involvement

Benefits of the Smooth Muscle Antibodies test

1. Supports diagnosis of autoimmune hepatitis
   One of the key antibodies associated with the condition.
2. Helps explain abnormal liver tests
   Identifies immune-mediated causes of liver inflammation.
3. Non-invasive blood test
   No imaging or biopsy required for initial assessment.
4. Guides specialist referral
   Supports hepatology or gastroenterology input.
5. Useful alongside other autoantibody tests
   Often interpreted with ANA, LKM, and AMA.
6. Detects disease even with mild symptoms
   Useful in early or atypical presentations.
7. Supports long-term disease monitoring
   Titres may change with disease activity.
8. Improves diagnostic confidence
   Adds objective evidence to clinical evaluation.

Step-by-step – How we offer this test

Option 1: Clinic-based blood test (UK-wide)

• Choose your nearest UK clinic
• Attend your appointment
• Blood sample taken by a clinician
• Sample analysed for smooth muscle antibodies

Option 2: Home or hotel visit (+£60, UK-wide)

• Qualified phlebotomist attends your location
• Blood sample taken at home or hotel
• No travel required
• Same laboratory analysis and reporting

Your results explained

Negative SMA result

No smooth muscle antibodies detected.

Typical UK interpretation:

• Negative or below laboratory cut-off

This makes autoimmune hepatitis less likely but does not completely exclude it.

Low-positive SMA result

Low levels of smooth muscle antibodies detected.

Typical UK interpretation:

• Low titre positivity

May be seen in early autoimmune hepatitis or occasionally in other liver or autoimmune conditions.

High SMA levels

High titres of smooth muscle antibodies detected.

Typical UK interpretation:

• Moderate to high titre positivity

Strongly supportive of autoimmune hepatitis, particularly when combined with abnormal liver enzymes and other autoantibodies.