RA Blood Tests: What Lab Tests Show Rheumatoid Arthritis?

To diagnose rheumatoid arthritis there is no one test that can on its own reach a diagnosis. Instead, there are a number of criteria that must be established in order to reach a rheumatoid arthritis diagnosis.

As part of the criteria for diagnosing rheumatoid arthritis, doctors will order multiple blood tests. These blood tests look for specific indicators that support the possibility that the patient could have rheumatoid arthritis.

Rheumatoid Arthritis Blood Tests

The rheumatoid arthritis blood tests that doctors perform to help diagnose the disease include:

  • Rheumatoid factor (RF)
  • Cyclic Citrullinated Peptide (CCP)
  • Erythrocyte Sedimentation Rate (ESR)
  • C-Reactive Protein (CRP)
  • Antinuclear Antibody (ANA)

Rheumatoid Factor

Rheumatoid factor is a type of antibody found in an estimated 80% of rheumatoid arthritis patients. It’s an antibody that attacks healthy tissue and leads to joint inflammation potentially resulting in the development of rheumatoid arthritis symptoms.

A rheumatoid factor blood test determines the level of rheumatoid factor in a patient’s blood. Once the rheumatoid factor level reaches a certain range, the patient tests positive for rheumatoid factor.

Years ago, doctors used the positive result of rheumatoid factor in a patient’s blood to firmly diagnose them with rheumatoid arthritis. If a patient showed signs of joint inflammation and tested positive for rheumatoid factor, then rheumatoid arthritis generally became the clear diagnosis.

Since then, research has shown us that many people contain the rheumatoid factor antibody in their blood but that it can lead to different autoimmune or inflammatory conditions besides rheumatoid arthritis. This now makes the test considered less conclusive than it used to be.

This discovery blurred the lines about what does and doesn’t constitute a rheumatoid arthritis diagnosis. Today, doctors are more cautious about diagnosing a patient with rheumatoid arthritis if they test positive for rheumatoid factor. Although, it can still be a strong indicator in many patient cases.


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