Interpreting blood tests for rheumatoid arthritis: functional ranges, diagnosis, and more

Written by Samantha Odake | Last updated:

Understanding rheumatoid arthritis involves interpreting blood tests—a crucial step in managing this complex condition. In this blog post, we explore the basics of interpreting lab testing for rheumatoid arthritis, including functional ranges and key diagnostic markers.

What is rheumatoid arthritis?

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that predominantly affects the joints, causing inflammation, pain, and tissue damage. While RA primarily targets the joints, it can also harm other parts of the body and lead to complications outside the joints, such as heart disease, nerve problems, and infections.

Rheumatoid arthritis affects about 1% of people around the world. It affects more than 1.3 million people in the United States.

Rheumatoid arthritis symptoms & signs

Rheumatoid arthritis usually affects small joints in the hands and feet. Identifying the symptoms of rheumatoid arthritis is crucial for early diagnosis and effective management. Here are some common signs to watch out for:

  • Symmetrical joint pain and tenderness (not to be confused with osteoarthritis, which can be asymmetrical)
  • Heat and swelling in the affected joints
  • Joint stiffness
  • Fatigue

People living with this condition often report periods when symptoms worsen, referred to as “flares”, which can be triggered by stress, too much movement, or a change in medication.

What causes rheumatoid arthritis?

The exact triggers of rheumatoid arthritis remain uncertain, although a genetic influence is strongly suggested. Certain genes may increase an individual’s susceptibility to reacting to environmental factors that may trigger the disease.

Genes involved in this condition may influence:

Rheumatoid arthritis often appears between the ages of 40 and 60, with a higher prevalence among women. When left untreated, RA typically results in reduced quality of life and potentially a shortened lifespan.

Read our blog for 40+ strategies to manage rheumatoid arthritis.

Lifestyle and environmental factors such as cigarette smoking and obesity are also thought to influence rheumatoid arthritis.

How to test for rheumatoid arthritis: Genetic & blood tests for rheumatoid arthritis

To effectively diagnose and treat rheumatoid arthritis, health practitioners often rely on various laboratory tests. These tests provide valuable insights into a patient’s condition and help guide treatment plans.

Healthcare professionals may choose from a variety of tests to provide an accurate assessment for their clients, including blood tests, genetic analysis, and imaging procedures.

Blood test for rheumatoid arthritis

Blood tests play a crucial role in the diagnosis of rheumatoid arthritis. Below are some of the tests health practitioners may order for their clients:

  • Rheumatoid Factor
  • Cyclic Citrullinated Peptide (CCP) Antibody (IgG)
  • hs-CRP
  • Erythrocyte sedimentation rate (ESR)
  • Antinuclear antibody (ANA)

Rheumatoid Factor

Rheumatoid factor (RF) is an autoantibody produced by the immune system. It mostly appears as an IgM antibody and primarily targets IgG antibodies.

Although healthy individuals can produce beneficial forms of rheumatoid factors as a part of the body’s normal defense against bacterial toxins (lipopolysaccharides) and viruses, people with rheumatoid arthritis often have persistently high levels.

RF is valuable in diagnosing and gauging the progression of rheumatoid arthritis. Elevated levels can precede symptoms by many years and persist in the early stages of the disease. However, it’s not exclusive to rheumatoid arthritis and may also be detected in other autoimmune diseases, chronic infections, cancer, liver disorders, and parasitic infections.

Rheumatoid Factor increases with age, and healthy adults (50 years and older) may test positive for rheumatoid factor.

Name Range
Rheumatoid Factor
  • Optimal: 0 – 14 IU/mL
  • High: >14 IU/mL

Cyclic Citrullinated Peptide (CCP) Antibody (IgG)

Citrulline is naturally produced in the body, but individuals with rheumatoid arthritis tend to have higher levels within their joints. This surplus of citrulline can interact with proteins, subsequently provoking an immune response.

CCP is rarely elevated in people without rheumatoid arthritis, and it’s more likely to detect early disease — however, about 30% of people with RA test negative for CCP antibodies.

In rare cases, CCP antibodies can be positive in people with other inflammatory diseases and conditions, including:

  • Psoriatic arthritis
  • Other autoimmune diseases, such as lupus and Sjorgen syndrome
  • Hepatitis B and C infection
  • Tuberculosis
Name Range
CCP Antibody (IgG)
  • Optimal: 0 – 20 U
  • Suboptimal: 20 – 40 U
  • High: 40 – 59 U
  • Critical high: > 59 U


C-reactive protein is produced by the liver as a response to injury, infection, and inflammation. This protein binds to damaged tissue or microbes, effectively marking them for elimination by the immune system.

High CRP levels are common in rheumatoid arthritis.

A standard CRP test primarily detects very high elevations occurring in severe infections, inflammatory disorders, or autoimmune conditions. To gauge chronic low-grade inflammation within the body, the highly-sensitive CRP (hs-CRP) test is required.

Name Range
  • Optimal: 0 – 1 mg/L
  • Suboptimal: 1 – 3 mg/L
  • High: 3 – 5 mg/L
  • Critical high: > 5mg/L

Erythrocyte sedimentation rate (ESR)

Erythrocyte sedimentation rate (ESR) is a blood test that checks for chronic inflammation. It measures the rate at which erythrocytes, or red blood cells, sink to the bottom of a sample tube. When there is more inflammation, red blood cells stick together and sink faster

Higher ESR can be found in conditions such as:

  • Infections
  • Inflammatory and autoimmune disorders
  • Anemia
  • High blood cholesterol (hyperlipidemia)
  • Thyroid disorders
  • Heart, liver, or kidney disease

Other factors that may increase ESR include inflammation, age, and pregnancy.

Name Range
Erythrocyte sedimentation rate (ESR)
  • Optimal: 0 – 6 mm/hr
  • Suboptimal: 6 – 20 mg/L
  • High: 20 – 100 mg/L
  • Critical high: > 100 mg/L

Antinuclear antibody (ANA)

Antinuclear antibodies are autoantibodies, a group of antibodies that attack the body’s healthy cells, causing inflammation, pain, and fatigue.

A positive ANA test result indicates the presence of antinuclear antibodies in the blood. Nevertheless, it’s crucial to consider a person’s medical history, signs, symptoms, and other test results when assessing this finding, as up to 50% of healthy individuals may exhibit slightly elevated ANA levels.

Name Range
Antinuclear antibody (ANA)
  • Positive
  • Negative (optimal)

Need extra help deciding which lab tests to order for rheumatoid arthritis? SelfDecode Pro’s Suggested Labs feature identifies the top recommended lab markers based on your client’s genetic predispositions and health concerns.

An example of SelfDecode’s recommended labs for Bone, Joint & Muscle Health

Genetic testing for rheumatoid arthritis

Rheumatoid arthritis is a complex autoimmune condition that involves a combination of both genetic and environmental factors. While traditional blood tests are important for diagnosing and monitoring this condition, genetic testing has introduced a new dimension in understanding and tailoring more effective treatment strategies.

Variations in certain genes can influence how a client responds to treatment. By understanding these genetic markers, health practitioners can make more informed decisions about the most suitable treatment options for their clients.

An example of SelfDecode’s genetic predisposition score

Beyond treatment, individuals who are genetically predisposed to rheumatoid arthritis can be informed about their risks and encouraged to adopt healthier lifestyles that can potentially delay symptoms. This holistic approach not only enhances patient care but also underlines the critical role of genetics in the management of rheumatoid arthritis.

A tool such as SelfDecode Pro can help health practitioners streamline the implementation of genetic testing and analysis in their practice.

With over 600 DNA reports, including Bone and Joint Health, SelfDecode equips health practitioners with genetic predisposition scores and tailor-made recommendations. These insights are finely tuned according to each client’s unique genetic profile, lab results, and lifestyle, empowering practitioners to deliver more precise and effective care.

Example of the SelfDecode Joint Inflammation report – Recommendations

In addition, SelfDecode also provides a dedicated platform where practitioners can analyze and monitor lab results, reinforcing a holistic approach to healthcare.

Example of the SelfDecode Hs-CRP Lab Results Page

Other tests for rheumatoid arthritis

In addition to the tests mentioned earlier, health practitioners may also recommend additional imaging tests to gain a comprehensive understanding of a patient’s rheumatoid arthritis status, including:

  • X-rays
  • Ultrasounds
  • Magnetic resonance imaging (MRI) scans

By incorporating these tests for rheumatoid arthritis, practitioners can form a more comprehensive diagnosis and tailor their treatment strategies effectively.


This guide is tailored to empower healthcare practitioners, providing a deeper understanding of the nuances of interpreting blood tests for rheumatoid arthritis. By incorporating these insights into your practice, you can enhance patient care and contribute to more informed decision-making.

It’s important to keep in mind, however, that every patient is unique, and healthcare practitioners should determine the most appropriate tests on an individual basis, taking into consideration other factors such as a person’s genetic predispositions, lifestyle, and other lab results.

Schedule a demo call with us to discover how SelfDecode Pro can help you streamline your clinical practice!


About the Author


1 Star2 Stars3 Stars4 Stars5 Stars
(1 votes, average: 5.00 out of 5)

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Articles View All