Diagnosing Lupus: Autoantibody Tests

Blood Tests for Lupus Diagnosis

vials of blood for testing and paperwork
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Lupus is a tricky disease to diagnosis because its signs and symptoms mimic those of so many other diseases. When diagnosing the disease, doctors take in many factors, including a patient’s medical history, routine lab test results and specialized tests focused on immune status. Here's what you should know about autoantibody blood tests for lupus diagnosis.

ANA Test for Diagnosing Lupus

A common test that is often performed is the anti-nuclear antibody (ANA) blood test, which screens for several autoimmune diseases by determining whether autoantibodies are present in a person’s bloodstream.

Autoantibodies are like antibodies, but instead of helping the body fight off harmful viruses or bacteria, they attack the cells of the body.

Additional Autoantibody Blood Tests for Lupus

If the ANA test comes back positive, and the patients is showing signs and symptoms common to lupus, the doctor may order a number of follow-up tests to detect specific autoantibodies, many that are specific to people with lupus. Not that not all people with lupus have the same antibodies. The autoantibody tests include

  • Antibodies to double-strand DNA (anti-dsDNA):These antibodies are present in half of people with lupus. They attack DNA, which is the genetic material inside the nucleus of the cell.
  • Antibodies to Sm: Thirty to 40 percent of people with lupus have this antibody present in their bodies, and having this antibody means it is very likely that you have lupus.
  • Antibodies to phospholipids (aPLs): Almost 30 percent of people with lupus test positive for these antibodies, which can cause narrowing of blood vessels, contributing to blood clots in the legs or lung, heart attack, miscarriage or stroke. It is the same antibody present in syphilis, which is why many people with lupus have false-positive test results for  syphilis.
  • Antibodies to Ro/SS-A and La/SS-B: People with Sjogren's syndrome, which commonly accompanies lupus. It's typically found in people with cutaneous lupus, which affects the skin and causes a rash that is very sensitive to the sun.
  • Antibodies to histone: Some people with lupus have this antibody in their body. It's most common in people with drug-induced lupus, caused by certain medications, and usually goes away once a person has come off the drug. Histone is a protein that surrounds the DNA molecule, and antibodies to histone attack the protein.
  • Antibodies to RNP (Anti-RNP): These antibodies are usually at very high levels in people whose symptoms combine features of more than one disease, including lupus. Anti-RNPs attack ribonuceloproteins, which are responsible for controlling chemical activities of cells. Anti-RNP is also an indicator of mixed connective tissue disease, a condition with symptoms like lupus.

Other Tests for Lupus

Autoantibody tests are not the only way to diagnose lupus. Other commonly-used tests include"

For more information about diagnosing lupus, be sure to read these other helpful articles:

Lupus Lab Tests and Diagnostic Tests

Lupus Signs and Symptoms, An Introduction

What Is Lupus Anticoagulant? This Antibody Puts Patients At Risk for Blood Clots

Sources:

Handout on Health: Systemic Lupus Erythematosus. National Institute of Arthritis and Musculoskeletal and Skin Diseases. August 2003.

Laboratory Tests. Lupus Foundation of America. January 2008.

Lupus Foundation of America. (2013, July 8). What are the laboratory tests for lupus? Retrieved March 06, 2016.

Mayo Clinic. (n.d.). Lupus tests and diagnosis. Retrieved March 06, 2016.

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