Anti Smith (Anti Sm) Antibody

An Anti-Smith antibody test indicates the presence of chronic diseases like systemic lupus erythematosus (SLE). It is an autoimmune disorder with many different symptoms, like rashes on the skin and overlapping syndromes. 

The Anti-Smith antibody test is also helpful in detecting mixed connective tissue disease.

Anti-Smith (Anti-Sm) Antibody Test - Overview

Autoimmune disorders show several minor and significant symptoms. Therefore, it is essential to test the parameters accurately and start the treatment on time. Mostly, antibodies are responsible for immune disorders, and there are specific hallmarks of SLE and MCTD. 

Anti-Sm is an important ribonucleoprotein that indicates the presence of lupus in individuals. The antibody is present in 20% of people who have lupus. However, it is also helpful in ruling rheumatic diseases in healthy individuals because the antibody is rarely present in them. 

The techniques like hemagglutination, immunodiffusion and ELISA help find the presence of anti-Sm antibodies. These tests also indicate the concentration of antibodies in the blood that determines the adversity of the illness. 

Another test named anti-RNP is performed along with anti-Sm to confirm the presence of lupus in patients. This is an antibody that is very prominent in patients having SLE. Approximately 25% of people with lupus have this antibody in the blood. However, anti-RNP does not indicate SLE alone. These are also present in individuals who have rheumatoid arthritis, systemic sclerosis, and polymyositis. 

Hence, both these tests can quickly confirm or rule out the presence of autoimmune system disorder. Many results suggest that the level of anti-RNP keeps fluctuating, but it has nothing to do with symptoms of the condition. 

Other examinations like anti-histone antibody tests and serum tests help give accurate results about the condition. A concrete diagnosis helps in starting accurate chemotherapy to manage the disorder. 

Who Should Get Tested? 

SLE can arise in young adults and reach its peak during 37-40 years. The symptoms can include fatigue, fever, skin lesions, joint stiffness, chest pain, and memory loss. 

If a person has skin lesions that aggravate sun exposure, they might need a quick anti-Sm antibody test. These rashes also accompany a fever, fatigue, and constant ache in different body parts. 
 

Medically reviewed by Dr. S K Sahoo, Senior Consultant, General Physican/Internal Medicine, Apollo Hospitals Sector 26, Noida.