Anti-RNP-Sm Antibody
Anti-RNP-Sm Antibody
Patients suffering from Mixed Connective Tissue Disease (MCTD) show very high levels of antibodies to ribonucleoprotein (RNP). MCTD is a very rare autoimmune disease in which the body’s immune system attacks the cells, considering them to be foreign substances. This condition has overlapping clinical features similar to those of systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis, and polymyositis.
This test is done to detect anti-RNP antibodies (alone) in cases of MCTD or together with anti-Sm (Smith) antibodies in cases of Lupus disease. Anti-Sm is very rarely found alone in the body.
Anti-RNP-Sm antibody test is also known as Anti-RNP, Anti-Ribonucleoprotein, Anti-SmRNP
Symptoms of Mixed Connective Tissue Disease and Lupus
Some of the symptoms common to both MCTD and Lupus are mentioned below
Fever
Persistent fatigue
Muscle pain
Joint swelling
Skin rash
Hair loss
Who should get tested?
A person who has a positive ANA test
Woman over 50 years who has a high risk of MCTD
A person suffering from autoimmune diseases such as lupus
Test preparation
No special preparation is needed for this test.
Interpretation of the Test Results
Negative test result: A negative test result means that the person does not have RNP and Sm antibodies in the body. In other words, he or she does not have that condition (MCTD/Lupus) and may be experiencing the above-mentioned symptoms for any other condition that needs to be diagnosed.
Positive test result: A positive anti-RNP result is observed in 95-100% of the cases with mixed connective tissue disease (MCTD). Similarly, a positive Anti-Sm indicates lupus, as seen in nearly 30% of the cases. This is a very specific antibody marker for this disease
FAQs
How is the sample collected for this test?
A sample of blood is drawn from a vein in the arm and collected into a sterilized vial or test tube using a fine, small needle. The process gets over very quickly, within 5 minutes
What is the turnaround time (TAT) for this test?
The results can be obtained within 72 hours from the time the sample was taken. However, sometimes this can get delayed
Does the Anti RNP-Sm antibody test involve any risk?
No, this test is quite safe to conduct. The only discomfort that a person might feel is after the sample has been collected by inserting a fine needle. The area of injection may show slight swelling or bruising due to needle insertion. This usually gets resolved on its own within a couple of minutes
Is it possible to get false-negative results for Anti RNP Sm test?
Yes, it is possible to get false-negative test results even if you are positive for lupus. At times, one may have lupus, which is due to the presence of other antibodies, such as anti-dsDNA, apart from anti-Sm. In such conditions, the test results will be shown as false-negative
What are some of the common markers for identifying autoimmune disorders?
Anti centromere antibody (ACA) or antinuclear antibody (ANA) are some of the most important markers for identifying autoimmune disorders. Other than these, Anti RNP-Sm antibody test is a specific marker that is useful in diagnosing diseases such as systemic lupus erythematosus
Related tests
Tests At Lupin Diagnostics