Anti-Smith (Sm) antibody Test

An anti-Sm antibody test is a confirmatory test for lupus. It is recommended to people who present with System lupus symptoms and show positive for the presence of autoantibodies in a preliminary blood test. This is because a preliminary blood test usually does not differentiate between various autoimmune disorders and need further tests to find out the specific disorder.

Symptoms of lupus commonly include:

• Joint pain
• Fatigue and tiredness
• Swelling around eyes or in hands and legs
• Fever and headache
• Pain in the chest while breathing deeply
• Sensitivity to sunlight or any fluorescent light

Anti-Sm antibody test can also be used:

• To establish a baseline at the time of diagnosis and determine how the condition will progress
• To assess the efficacy of the treatment and guide the doctor about modulation of the therapy

You do not require any specific preparation for this test. Before the doctor orders the test, they may need to know your detailed medical history. Please inform the doctor if any family members have had a similar disorder. Also, give the doctor all the information about your symptoms, as it can help with the diagnosis. You must also let the doctor know if you are on any medications.

The procedure followed for blood sample collection is usually easy and painless and involves the following steps: 

• A nurse or technician may first tie a tourniquet (elastic band) around your upper arm. This helps in easy detection of a vein for blood collection
• With a sterilised needle, he/she will draw blood from the vein. You may feel a stinging sensation from the prick of the needle. The discomfort will, however, disappear soon
• The blood sample will be collected in a tube and sent to a lab for further analysis.

Normal results:

Anti-Sm antibodies are found in less than 1% healthy individuals. Therefore, a normal test result is usually negative for the presence of anti-Sm antibodies. 

Abnormal results:

Abnormal results are when anti-Sm antibodies are detected in the blood sample of a person. The test result is then said to be positive. Generally, the presence of these antibodies confirms the disease condition. However, everyone affected with systemic lupus may not necessarily have anti-Sm antibodies in their blood. It is known that anti-Sm antibodies are found only in 20% of people affected with this disorder. The doctor may, therefore, order further tests or may need to repeat the same test at intervals to confirm the diagnosis.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.