RNP antibodies medical test is for the evaluation of patients with a possible connective-tissue disease such as lupus erythematosus (LE) and mixed connective-tissue disease (MCTD). The test is performed when the patient has signs and symptoms of MCTD or LE and tested positive for antinuclear antibodies.
RNP is a small nucleoprotein that contains three autoantigens - A, C, and 68 kD. Antibodies to RNP is detected in half the cases of connective-tissue diseases. But it should not be considered a diagnostic. A person may have high levels of RNP antibodies and still not show any clinical signs associated with the diseases.