U1-nRNP Antibodies Test

Antibodies to ribonucleoprotein, RNP, are found often in very high levels in patients with a variety of systemic rheumatic diseases, including SLE, progressive systemic sclerosis and Mixed Connective Tissue Disease, a distinct disease entity with overlapping clinical features of SLE, scleroderma, polymyositis and rheumatoid arthritis. Antibodies to Ribonucleoprotein occur in approximately 50% of patients with lupus erythematosus and in patients with other connective tissue diseases, notably mixed connective tissue disease (MCTD). MCTD is characterized by high levels of RNP antibodies without detectable Sm or double-stranded DNA antibodies. Testing for RNP antibodies is not useful in patients without demonstrable antinuclear antibodies. There are no conditions under which this test should not be done. The test will be of very low yield if the patient has a negative Antinuclear Antibody (ANA).

No special preparation is needed for Extractable Nuclear Antibodies. Inform your doctor if you are on any medications or have any underlying medical conditions or allergies before undergoing Extractable Nuclear Antibodies. Your doctor depending on your condition will give specific instructions. While the detection of anti-RNP antibodies is consistent with MCTD (mixed connective tissue disease), it is not diagnostic; a patient may have high levels of anti-RNP and present with no clinical signs of disease.

Blood tests are usually useful in confirming clinically suspected diagnosis and monitoring the disease activity. Ribonucleoprotein Antibodies test is used to evaluate patients with signs and symptoms of a connective tissue disease in whom the test for antinuclear antibodies is positive. The positive test result with high pretest probability helps to make a diagnosis, and the negative test result with low pretest probability helps to rule out the diagnosis

A positive result for Ribonucleoprotein antibodies is consistent with a connective tissue disease. Although strongly associated with connective tissue diseases, RNP antibodies are not considered a 'marker' for any particular disease except in the following situation: when found in isolation, a positive result for RNP antibodies is consistent with the diagnosis of mixed connective tissue disease. The degree of positivity or the titer of anti-RNP antibody does not indicate the severity or duration of disease.