RNP Autoantibodies Test

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.

Test for RNP antibodies is conducted just like any other blood test. Wearing a sleeveless shirt is recommended. Or you can just roll the sleeve up at the time of testing. No need to be anxious, just relax while the person responsible takes the blood sample.

The test does not demand any prior preparation or diet change. You can have your regular diet freely. Your doctor will guide you through the process and will inform you in case there are diet considerations. Although it’s recommended that you ask your doctor about whether fasting is needed before the test.

If the anti-RNP antibodies value is found to be negative then it indicates a normal value, effectively ruling out MCTD diagnosis. A rise in value correlates with the presence of connective-tissue disease.

Varying degrees of values mean varying diseases on the connective-tissue disease spectrum. Here’s how various values relate to various diseases:
95%-100% — MCTD
38%-44% — Systemic lupus erythematosus (SLE)
20%-30% — Discoid lupus erythematosus
20%-30% — Scleroderma
10% — Rheumatoid arthritis

Once again, we would like to stress that positive non-RNP antibodies values have been associated with MCTD, but the values per se do not diagnose MCTD.

Just like any other blood test, about 0.5mL or a couple of tablespoon blood will be taken from you. The doctor may conduct the test at the clinic or refer you to a nearby lab. The steps performed are as follows: A vein near the bend of your elbow will be marked An antiseptic liquid such as alcohol will be applied on the skin. Do not touch that area after the antiseptic is applied. A needle will be injected into your vein and sufficient sample will be taken The sample will be collected in sampling device and labeled with your information