Serum/plasma substance concentration by immunoassay (e.g., anti-nuclear antibody)

What This Test Measures

The test looks for **antinuclear antibodies (ANA)**, which are proteins your immune system mistakenly produces against parts of your cells. These antibodies can be found in conditions like lupus, rheumatoid arthritis, or other autoimmune disorders. The test is typically performed on serum or plasma and uses an immunoassay method to detect their presence.

Why It’s Done

Your healthcare provider may order this test if you have symptoms like joint pain, unexplained fatigue, rash, or other signs of an autoimmune condition. It’s often used as a **first-line screening test** to check for conditions where the immune system attacks your own tissues.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it involves drawing blood. If you’re taking certain medications (e.g., steroids), let your provider know, as they may affect results.

What to Expect During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it’s usually over quickly. The blood sample is then sent to a lab for testing using an immunoassay method to detect antibodies.