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Also Known As: Anti-Ribonucleic Protein Antigen, Anti-ENA Antibody, ENA Antibodies, Ribonuclear Protein Antibody, Anti-Smith Antibody, RNP Antibody, sm rnp antibody

What Is A Sm RNP Antibodies Test?

Sm RNP Antibodies test is used to measure Sm and RNP antibodies in your bloodstream. It serves as a reliable and efficient way of confirming diagnosis related to SLE, i.e., systemic lupus erythematosus and MCTD, i.e., mixed connective tissue disease using a positive ANA result. These antibodies are also helpful for your doctor during the differential diagnosis related to other chronic, systemic, autoimmune rheumatic disorders such as systemic sclerosis, Sjogren syndrome, dermatomyositis, polymyositis, and other similar overlap syndromes.

The ANA test has been used as a screening method for such antibodies; however, it cannot indicate or specify the presence of any particular antibody. On the contrary, some antibodies to ENA do not indicate a positive ANA test as well. Therefore, at times, you might need to undergo another secondary confirmatory testing to detect antibodies to ENA.

The Sm antigen was acknowledged during 1966 as a saline, soluble, non-histone glycoprotein independent of the DNA or RNA for the antigenicity qualities. The antibodies to Sm are known as a specific serologic marker due to the presence with multiple rheumatic disorders like SLE, scleroderma, and even rheumatoid arthritis. High-tittered RNP antibodies are associated with overlap syndrome and MCTD.

What Is The Sm And RNP Antibodies Test Used For?

Doctors or healthcare professionals use the Sm And RNP Antibodies Test to measure the level of anti-ribonucleoprotein or RNP antibodies in your blood serum. RNP is a kind of antibody that is abundantly found in people with autoimmune disorders or autoimmune conditions. In such circumstances, the antibodies are produced by the immune system and attack the body's healthy cells and tissues.

Usually, autoimmune conditions are very hard to diagnose as they display similar symptoms to one another. Testing for different antibodies at once can help differentiate these antibodies and their characteristics. Elevated levels of RNP antibodies are often seen in people with connective tissue disorders such as lupus, scleroderma, and rheumatoid arthritis.

Your doctor or care provider will recommend this test as a follow-up test for positive antinuclear antibody or ANA test results. Depending on your health condition, age, and severity of symptoms, some other tests will also become mandatory in identifying the type of disorder you might be affected by.

Why And When Do You Need A Sm And RNP Antibodies Test?

Your doctor or health care provider will ask you to undergo the Sm And Sm/RNP Antibodies Test if you show symptoms of SLE, mixed connective tissue disease, rheumatoid arthritis, and scleroderma.

Symptoms of systemic lupus erythematosus include:

  • Joint pain and swelling
  • Chest pain while taking deep breaths
  • Fatigue
  • High fever
  • General discomfort or uneasiness
  • Hair loss
  • Weight loss
  • Mouth sores
  • Butterfly skin rash on cheeks and bridge of the nose
  • Swelling in legs
  • Abdominal pain
  • Nausea and vomiting
  • Headaches
  • Vision problems
  • Memory and personality changes

Early indications and signs/symptoms of mixed connective tissue disease include the following:

  • A general feeling of being unwell
  • Constant fatigue
  • Mild fever
  • Cold/numb fingers or toes
  • Swollen hands and fingers
  • Joint and muscle pain
  • Red or brown patches over the knuckles

What Kind Of Sample Is Required For The Test?

For Sm And Sm/RNP Antibodies Test, a doctor, healthcare provider, or lab technician will draw a blood sample, usually from a vein in your arm. During the procedure, the lab technician first cleans your arm with an antiseptic and then ties an elastic band around it to make the veins visible. They will then insert the needle to collect an adequate blood sample as per your doctor's recommendation. Once the sample is collected, it is sent to the laboratory for further analysis.

Do You Need To Prepare For sm rnp antibody?

Since Sm And Sm/RNP Antibodies Test is a standard blood test, you don't have to do anything special before the procedure. Suppose your doctor recommends other tests along with this test. In that case, you might need to fast for at least 8-10 hours and even stop using your routine medication, supplements, and vitamins to avoid misinterpretation of the results.

Are There Any Risks To sm rnp antibody? 

An Sm RNP Antibodies Test is one of the harmless, most common tests required for confirming the actual diagnosis. In rare cases, people might feel a bit dizzy, lightheaded, or even faint, but the symptoms do not last long.

What Do The Test Results Mean?

Because the normal and abnormal reference range for the Sm And Sm/RNP Antibodies Test depends upon your laboratory and its testing method. It is wise to see the results as per guidelines established by the lab running your sample. The antibodies to RNP are found in very high levels, i.e., in 95% of the patients with SLE and mixed connective tissue disease. Indeed, if your doctor finds a high titer of RNP in your ANA specificities and Sm And Sm/RNP Antibodies Test, it will be considered synonymous with SLE.

However, there remains a dispute as to whether SLE and MCTD are present as truly distinct diseases or merely as an overlap syndrome. In other rheumatoid syndromes, anti-RNP antibodies are often linked with antibodies to Sm proteins. The antibodies to RNP and Sm antigen are found in up to 20-30% of patients with SLE and up to 20-25% in patients with progressive systemic sclerosis.      

Related Tests: Antinuclear Antibody Panel (ANA Panel), ENA Antibody Panel.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on January 09, 2024. 


Anti-Sm and anti-RNP antibodies

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Anti-Sm-RNP activity in sera of patients with rheumatic and autoimmune diseases

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