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Blood Test for Rheumatoid Arthritis: How It’s Done

Published:
Sep 2, 2020
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Updated:
Jun 4, 2021
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Contributor:
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14 minutes
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Medically reviewed by

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Kevin Deane, MD, Ph.D
Kevin Deane, MD, Ph.D
Associate Professor & Rheumatologist
Dr. Deane’s clinical activities include the evaluation and treatment of a wide variety of rheumatic & autoimmune diseases, with a special focus on rheumatoid arthritis. Dr Deane is world renowned for his RA research which is cited in a significant number of scientific papers.
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Rheumatoid arthritis (RA) is an autoimmune disorder that primarily affects your joints, causing aching, swelling, and pain. According to the review of the National Arthritis Data Workgroup, roughly 1.3 million people in the US are affected by rheumatoid arthritis.

RA occurs when your body erroneously launches an immune attack where subsequent inflammation gradually destroys tissue in the lining of your joints, and in some cases other parts of the body such as the lungs, blood vessels and heart.

In early RA, joint symptoms of pain, stiffness and swelling may come and go; however, for most people with RA, over time, symptoms are present every day. Importantly, if RA is left untreated it can ultimately lead to joint damage, deformity and loss of function. 

Like most autoimmune disorders, there currently is no cure; however, your health-care provider can recommend treatments to keep RA well-managed.

Diagnosis and Screening for Rheumatoid Arthritis

One of the most important parts of managing RA is making a diagnosis early, and getting on appropriate treatment. Diagnosing rheumatoid arthritis can prove to be a difficult task for rheumatologists and doctors, particularly in its early stages. That’s because the early symptoms and signs of RA resemble those of a variety of other conditions and disorders - and symptoms may not even be present every day. For example, if you experience pain and morning stiffness in symmetrical joints, you may have rheumatoid arthritis. However, other conditions such as a very common form of arthritis called ‘osteoarthritis’, or forms of arthritis such as psoriatic arthritis and gout may be present and cause similar symptoms.

Health-care providers can distinguish between forms of arthritis based on your symptoms as well as joint examination findings. However, often tests including blood tests and imaging tests (such as x-rays) need to be done to help identify if RA is present. 

RA Imaging Tests

Your health-care provider may recommend certain imaging tests to check for joint damage. These tests can help determine:

  • If joint symptoms are caused by inflammation that is characteristic of RA
  • If your joints have been damaged in a pattern that suggests that RA is the cause
  • The severity of the joint damage

There are many types of imaging tests including x-rays, computed tomography (CT), ultrasound and magnetic resonance imaging (MRI). To evaluate RA, often X-ray tests are done first, enabling doctors to see clearly if there is joint damage. However, in some cases ultrasound and MRI tests are recommended to identify if joint inflammation is present, as well as to check how severe the damage is in your body.

However, many times imaging tests are not enough to determine if RA is present - especially in early RA when there might not be much joint inflammation or damage. That’s where blood tests come in handy. 

 

RA Blood Tests

Health-care providers use blood tests in several ways in the diagnosis and management of RA:

  • Diagnosis of RA
  • Predicting ‘prognosis’ of RA or how RA may behave over time
  • Following effectiveness of therapy
  • Monitoring for side-effects of medications 

Fortunately, you don’t have to make a long trip to the doctor’s office to start with an effective RA blood test. Our at-home RA test makes the whole process easy, painless and hassle-free to begin testing in order to provide you with results designed to enable you to engage a physician sooner.

Common Blood Diagnostic Tests for Rheumatoid Arthritis

Your physician will leverage numerous blood tests ⁠— usually combined with imaging tests ⁠— to help diagnose you with RA. Most of these blood tests are done with a simple blood test and results are available within a few days.

The tests to diagnose RA are grouped into the following general categories:

  • Autoantibody tests which can measure if your immune system is making specific factors that can be seen with RA
  • Inflammation tests that can help with the diagnosis of RA, as well as in the monitoring of success of therapy
  • Additional tests to evaluate your general health

Anyone with RA normally has high levels of C-reactive protein (CRP) or elevated erythrocyte sedimentation rate (ESR), both of which are signs of inflammatory activity in the body.

 

Pre-Rheumatoid Arthritis

Before taking a close look at each primary blood diagnostic test for RA, it’s important to highlight a stage of RA that can occur before you become symptomatic. It is now known that anti-CCP and RF antibodies (discussed below) may be present in the blood on average 3-5 years prior to the first onset of joint inflammation in RA. This period can be called ‘Pre-RA’. 

Right now there are no known methods to treat those with ‘Pre-RA’ to prevent future development of full-blown RA. As such, if you have ‘Pre-RA’ your health-care provider may just watch you carefully and only treat you once you develop clear joint inflammation. However, there are several ongoing research studies and it may mean in the near future that people who are in the Pre-RA period will be treated to prevent future RA.

 

Rheumatoid Factor (RF) Test

How RF is Used

Better known as an RF test, this is a common RA blood test, and it checks for the level of the autoantibody called ‘rheumatoid factor’ in your blood.

RF is a kind of protein that your body generates when your own immune system attacks healthy cells and tissue. It’s often linked to autoimmune disorders, especially rheumatoid arthritis.

There are several versions of the RF test. The most typical forms of RF that are tested in RA are immunoglobulin (IgM),  immunoglobulin A (IgA) and sometimes immunoglobulin G (IgG). Many versions of the RF test identify these types of RF specifically; however, there is also a version of RF that tests for a combination of these types of RF. 

An RF test is often used along with other autoantibodies and imaging tests  to determine a diagnosis of rheumatoid arthritis. 

 

Interpreting RF Results

RF tests will be reported in 2 ways: 

  • A level; for example, 50 units
  • negative/positive (or normal/abnormal)

 

Often, health-care providers just use the ‘positive/negative’ result; however, the higher the levels of RF in your blood, the greater your chances that you have rheumatoid arthritis. However, RF antibodies are found in other autoimmune disorders too.

 

What Do RF Test Results Mean?

Overall, in patients with clinical signs and symptoms of RA, the presence of rheumatoid factor shows that it’s highly likely that they have the disorder. However, RF is only abnormal in approximately 70-80% of people with rheumatoid arthritis. Another way to think about that is that 20-30% of people with RA will have a negative/normal RF test. Because of that, the RF test often needs to be performed along with other tests such as the anti-CCP test discussed below.

If RF is present, in some individuals, higher levels of RF may correspond with more severe RA, although this isn’t always the case. 

 

Other Conditions That May be Related to RF

It is important to note that while RF can be present in RA, there are other conditions that also can have a positive RF. These include lupus, chronic infections such as hepatitis C, and some rare blood cancers.  

In some cases, an abnormal RF may mean that you have Sjogren syndrome. This is an autoimmune condition that causes dry mouth and dry eyes.

Because of these other conditions that are associated with RF, if you have an abnormal level, your health-care provider may also test for these other conditions.

Anti-Cyclic Citrullinated Peptide (anti-CCP) Test

How Is ACPA or Anti-CCP Used?

This test measures an autoantibody to a protein that has undergone a modification called ‘citrullination’. Because of this, the test is called ‘anti-cyclic citrullinated peptide (or protein) antibody (anti-CCP) although sometimes similar tests are called ‘anti-citrullinated peptide/protein antibodies’, or ACPA. Similar to RF, anti-CCP is a kind of protein that your body generates when your own immune system attacks healthy cells and tissue. 

People with anti-CCP often have RA, but not everyone with RA tests positive for this antibody. That’s why doctors order an anti-CCP test after or alongside an RF (rheumatoid factor) test to help rule out or confirm a diagnosis.

Interpreting Anti-CCP Test Results

Like RF, anti-CCP tests will be reported in 2 ways: 

  • A level; for example, 50 units
  • negative/positive (or normal/abnormal)

Often, health-care providers just use the ‘positive/negative’ result; however, the higher the levels of anti-CCP in your blood, the greater your chances that you have rheumatoid arthritis. 

 

What Do the Test Results Mean?

Overall, in individuals with clinical signs and symptoms of RA, the presence of anti-CCP shows that it’s highly likely that they have the disorder. In comparison with the RF test, anti-CCP is much more accurate for RA. In particular, anti-CCP is over 90% specific for RA, while RF is only 70-80% specific. In other words, anti-CCP is rarely seen in other conditions - while RF can be seen in several other conditions that are discussed above. 

Importantly, like RF, anti-CCP is only abnormal in approximately 70-80% of people with rheumatoid arthritis. Another way to think about that is that 20-30% of people with RA will have a negative/normal RF test. Because of that, the anti-CCP test is often performed along with other tests such as the RF test. 

If anti-CCP is present, in some individuals, higher levels may correspond with more severe RA, although this isn’t always the case. 

 

Other Conditions That May be Related to anti-CCP

Because anti-CCP is very accurate for RA if the test shows high numbers of anti-CCP antibodies, it is quite accurate for RA. That said, if you do have an abnormal anti-CCP, your health-care provider may look into some other conditions that may include some other autoimmune diseases.

 

Other Autoantibodies in RA

RF and anti-CCP are the main autoantibody tests that are used in RA. However, there are several others including antibodies to carbamylated proteins (antiCarP), anti-mutated citrullinated vimentin (anti-MCV) and several others. In addition, when an individual initially develops RA, their health care provider may perform other tests that can be related to other autoimmune conditions that can be similar to RA. These tests include anti-nuclear antibodies (ANAs) and several others. If you have abnormalities of these other tests, please ask your health-care provider for more information. 

Tests for general inflammation in RA 

Autoantibody tests including RF and anti-CCP are the mainstay of diagnosis in RA. However, other tests that measure general inflammation in the body are also used in the following ways in RA:

  • Help in diagnosis
  • Monitoring response to therapy

There are two tests that are most commonly used to diagnose RA: the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP).

Erythrocyte Sedimentation Rate (ESR) Test

How Is ESR Used?

ESR is a non-specific yet cheap and simple blood test for RA. Erythrocyte sedimentation rate refers to the hourly rate at which red blood cells (RBCs) form clumps and fall to the bed of a special glass tubing. Some doctors may call this a sed rate, Sedimentation Rate Wintrobe, Westergren Sedimentation Rate, or simply ESR.

An ESR test is designed to help doctors figure out the level of inflammation in your body. The faster the sedimentation rate, the greater the inflammation, showing that you are more likely to have an autoimmune disorder and that your body is inflamed. 

 

Interpreting ESR Test Results

The results of your ESR test are normally presented in the following ways:

  • A level; for example, 50
  • negative/positive (or normal/abnormal)

However, normal ESR varies depending on age and gender. There also may be variations in what is considered normal based on the laboratory that the test was performed in. 

 

What Do the Test Results Mean?

Healthy people usually have low ESR. 

A positive or ‘elevated’ ESR result can be used in conjunction with obvious clinical signs and symptoms, as well as other blood tests, especially RF and CCP tests.

If the clinical findings and ESR match, the doctor might be able to rule out or confirm suspected rheumatoid arthritis.

When monitoring RA, a rising ESR may be an indication of increasing inflammation or a poorer treatment method. Decreasing or normal ESR, on the other hand, may show that you are responding to medication.

 

Other Conditions You May Have

High ESRs are usually an indication of inflammation in the body, but they can’t pinpoint any specific inflammatory condition. It could point towards many other conditions including other autoimmune diseases, infections and some cancers. Because of that, if you have a positive ESR test, your health-care provider may obtain additional tests.

 

C-Reactive Protein (CRP) Test

How Is CRP Used?

Better known as CRP, C-reactive protein is a ring-like protein that your liver produces when inflammation occurs. A CRP test checks for the presence and levels of this protein in your blood.

C-reactive protein cannot be used on its own to confirm rheumatoid arthritis diagnosis. Instead, doctors request this test to determine the severity of the disease.

Even though more expensive, the CRP test is usually more sensitive and accurate than an ESR test.

 

Interpreting CRP Test Results

Like the ESR test, the results of a CRP test are typically presented as both a level, and a positive/negative result. 

The level of C-reactive protein is usually low, but the results can vary from one lab and person to another.

 

What Do the Test Results Mean?

In individuals without inflammation, CRP levels are often very low.

If your CRP levels are abnormal, this is typically an indication of inflammation, injury, or the presence of an autoimmune condition. 

Additionally, doctors use ongoing CRP tests to monitor disease activity and to know the progress or efficacy of medication.

 

Other Conditions You May Have

While the CRP test can help diagnose RA, bacterial infection and any autoimmune condition can raise your levels of CRP. Because of that, if you have a positive ESR test, your health-care provider may obtain additional tests.

Summary

RF, anti-CCP, ESR and CRP are the four most common blood tests doctors order to determine if you may have rheumatoid arthritis. These tests can help in a diagnosis, as well as provide information as to the severity of RA, and response to therapy. However, keep in mind that a single blood test may not confirm or rule out RA diagnosis. Because of that, you may be asked to have additional blood tests, or imaging of your joints (e.g. x-rays, ultrasound or magnetic resonance imaging (MRI)) to help with diagnosis.

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