Blood tests for rheumatoid arthritis: Understanding the basics

Rheumatoid arthritis: Your joint’s enemy

Rheumatoid arthritis (RA) is an autoimmune condition that affects your joints, joint linings and causes pain, swelling, and inflammation. An autoimmune disease is a health condition when your body’s immune system mistakenly identifies your own body cells as harmful foreign bodies and starts damaging them. RA affects small joints (like the wrist) first and later on, can include other large joints like elbow, knee, etc. Also, usually joints of both sides are involved. Though it chiefly affects your joints, it can show symptoms related to the eyes, skin, lungs, blood vessels, etc. 

Causes of rheumatoid arthritis

While the exact cause of RA is not known, various factors can increase the risk of developing RA, for example,

• Family history of RA
• Gender (women are at an increased risk of getting RA).

A few factors that may trigger the onset of RA include:

• Injury to bones or joints, such as a fracture, joint dislocation, or ligament tear
• Smoking
• Being overweight
• History of viral infections, such as the Epstein-Barr virus.

Diagnosing rheumatoid arthritis

It might not be possible through blood tests only to get a simple yes-or-no answer to whether you have RA. But, they are extremely important to guide your doctor around the diagnosis, and also give hints on how the disease is progressing or how helpful the treatment is after the diagnosis is confirmed.

Blood tests for rheumatoid arthritis

• Rheumatoid factor (RF) test: The RF test looks for rheumatoid factor (RF) antibodies present in the blood. These are the first autoantibodies collected in people with RA and found in tissue lining your joints. Autoantibodies are produced in autoimmune conditions like RA when the body starts attacking its own cells.
  
  The results of the RF test are reported as units per milliliter (u/mL). Normal levels of RF antibodies in your blood are less than 40 to 60 u/mL. A higher number indicates a positive RF result and points towards RA. However, the RF antibodies are not exclusive to RA, they can also show up if you have other autoimmune disorders. Such conditions can include hepatitis, leukemia, and lupus. Not all people with RF have RA. The test results need to be correlated with other clinical findings, other tests and validated thoroughly through an expert physician.  

• Erythrocyte sedimentation rate (ESR): Primarily, an ESR test measures how quickly the red blood cells in a blood sample settle at the bottom of a vertical tube. It is also called the sed rate. Inflammation or infection in the body can cause extra proteins to build up in the blood, which can cause to settle it faster and results in a high ESR. This increase in ESR may indicate inflammation in your joints.
   
• C-reactive protein (CRP): This test looks for CRP- a ring-shaped protein that may indicate inflammation in your joints. It is produced by the liver as a result of inflammation. Please note that the CRP test may be more sensitive than the ESR test, however, it does not confirm the diagnosis of RA. Just like the RF test. The CRP levels may rise in presence of any autoimmune response or bacterial infection. If you have a false negative on the RF test, the ESR or CRP test will indicate your doctor of RA.

• Complete blood count (CBC): The CBC test looks for different types of blood cells in the blood along with certain other blood parameters. Low hemoglobin and hematocrit values may be associated with RA.

Connecting the dots

Along with your blood test results, you can be asked to take radiological investigations like X-rays. They are aimed at identifying the damage caused to the bones in a more physical setup. Your doctor will combine the results of the RF antibodies test, ESR, CRP, and CBC tests, dig deeper into your joint pain symptoms (which bones are affected, symmetric joint pain or not), and/or analyze X-ray results to steer towards a diagnosis of RA. You may also be requested to undertake the blood tests for RA periodically as they will help monitor the progress of your disorder.

Do not ignore that morning stiffness in joints. It could be RA! Why wait further when you can get tested at the comfort of your home with Metropolis? Let modern diagnostic tools come to your rescue and help devise an effective treatment plan. Have happy and strong joints!