C-Reactive Protein and Its Surprising Role in Rheumatoid Arthritis

Aging is a natural process that brings many changes to your body and mind. Some of these changes are expected, such as gray hair and wrinkles, but some are unexpected, such as joint pain, stiffness, and swelling. These symptoms are often from a medical condition called arthritis, which affects about 528 million people.¹ 

If you’ve recently been diagnosed with arthritis, you may have heard about a blood test to measure C-reactive protein (CRP) and wonder what this test has to do with your condition. 

In this article, we’ll explain what CRP is and discuss its link to arthritis. We’ll also share recent studies on aging, CRP, and arthritis, which have provided insights into the role of inflammation in aging.

What is C-Reactive Protein?

CRP belongs to a group of proteins known as acute-phase reactants. As a response to inflammation,² your liver produces CRP and releases it into the bloodstream.

The role of CRP is to activate certain parts of your immune system, specifically white blood cells called macrophages, to help clear foreign attackers and dying or dead cells from the body. 

Another function of CRP is to bind to the surface of some bacteria, making it easier for your immune system to recognize and destroy. 

CRP levels rise and fall with changing levels of inflammation in the body,³ making CRP an ideal marker for inflammatory conditions. Inflammatory markers, including CRP, are blood tests that detect inflammation in the body.

The Intriguing Link Between C-Reactive Protein and Arthritis

Evidence-based insights into the role of C-reactive protein and arthritis:

• CRP is a marker of inflammation. 
• CRP levels can help to diagnose and monitor rheumatoid arthritis,⁴ which is an autoimmune disease that causes chronic inflammation and joint damage.
• CRP levels can also identify the risk of comorbidities (when more than one disease or condition exists in your body simultaneously),⁴ such as cardiovascular disease, which is increased in people with rheumatoid arthritis due to chronic, systemic inflammation. 
• CRP levels help to determine the effectiveness of anti-inflammatory treatments for rheumatoid arthritis. 
• CRP levels vary based on several factors,³ including age, infection, obesity, smoking, and medical history. Doctors interpret CRP levels,  taking clinical and additional laboratory results into account. 

Can arthritis increase CRP levels? 

Arthritis, particularly rheumatoid arthritis, can cause high CRP levels due to systemic inflammation. 

Additionally, arthritis can indirectly influence CRP levels by affecting your overall health and well-being. It can limit your physical activity levels, cause weight gain, impair your sleep, and cause mental health conditions such as stress and depression. All of these factors can contribute to increased inflammation in your body and an elevated CRP level.³ 

Clinical Indicators: What Your CRP Levels Say About Rheumatoid Arthritis

Labs interpret CRP levels in either mg/dL or mg/L. Below is a chart showing standard lab values⁵ and what they indicate. 

Level	Elevation level	Possible Condition
Less than 0.3 mg/dL	Normal	Healthy
0.3 to 1.0 mg/dL	Normal or minor	Obesity, pregnancy, depression, common cold, periodontitis, gingivitis, cigarette smoking, sedentary lifestyle, or genetic polymorphisms
1.0 to 10.0 mg/dL	Moderate	Rheumatoid arthritis, lupus, other autoimmune diseases, cancer, myocardial infarction, bronchitis, or pancreatitis
More than 10.0 mg/dL	Marked	Acute bacterial infection, viral infection, systemic vasculitis, or major trauma
More than 50.0 mg/dL	Severe	Acute bacterial infection

What level of C-reactive protein indicates rheumatoid arthritis? A level between 1.0 to 10.0 mg/dL⁵ indicates systemic inflammation, such as rheumatoid arthritis.  

CRP and Different Types of Arthritis

• C-reactive protein (CRP) levels in rheumatoid arthritis can help doctors diagnose and determine the effectiveness of treatment. However, while it is a marker of systemic inflammation, CRP level is not useful as an independent⁵ test to confirm a diagnosis of rheumatoid arthritis. CRP levels vary depending on various factors, including age and medical history. Therefore, doctors should use CRP levels in combination with clinical and other laboratory findings to diagnose rheumatoid arthritis. 
• Osteoarthritis is a degenerative disease that doesn’t usually cause significant inflammation or elevated CRP levels unless there is an associated trauma or infection. However, CRP levels in osteoarthritis may be elevated in more severe cases where there is significant synovial membrane inflammation.⁶  

The Aging Factor: How CRP and Arthritis are Connected As We Grow Older

Understanding the role of inflammation as you get older is essential for treating and preventing many age-related diseases. 

Inflammation is a natural defense mechanism that helps your body fight infections and heal injuries. However, as you get older, your immune system becomes more prone to chronic, low-grade inflammation that damages your cells and tissue. This type of age-related inflammation is known as inflammaging.⁷ It is associated with almost all age-related diseases, including arthritis, type 2 diabetes, cardiovascular disease, cancer, and dementia.

Recent studies on aging, CRP, and arthritis have provided some insights into the role of inflammation, including:

• CRP levels increase with age.⁵
• CRP levels reflect the local and systemic inflammation in osteoarthritis⁶ and rheumatoid arthritis⁴ and may be linked to the severity and progression of these diseases. 

Treatment Based on CRP Levels

C-reactive protein levels between 1.0 and 10.0 ml/dL are moderately elevated and signal systemic inflammation in the body, such as rheumatoid arthritis.

CRP levels above 10 ml/dL are markedly elevated and may indicate severe infection or trauma. 

CRP levels above 50 ml/dL⁵ are considered severely elevated and are often associated with a bacterial infection that requires immediate medical attention. 

If you have rheumatoid arthritis, your doctor may order a simple blood test to check your CRP level and other inflammatory markers such as erythrocyte sedimentation rate (ESR) and rheumatoid factor. 

They may also order a specific CRP test, hs-CRP, to assess your risk of cardiovascular disease. 

Depending on the results of these tests, your doctor may recommend anti-inflammatory medications, including non-steroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs), or biologics to reduce inflammation and lower your CRP levels.⁵ 

Regular monitoring of your CRP levels can help doctors evaluate the effectiveness of your treatment plan. Changes in CRP levels may warrant a tweak in your treatment plan. 

Prevention and Management: Steps for Healthy Aging

Making simple lifestyle changes can help to manage your CRP levels and arthritis. Some tips for a healthy lifestyle include:

• Eating a balanced diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats minimizes inflammation. Limiting or avoiding foods that trigger inflammation, including red and processed meats, added sugar, fried foods, and trans fats, also minimizes inflammation. 
• Regularly exercising at a moderate intensity reduces inflammation and improves your joint mobility and function. 
• Quitting smoking and limiting or avoiding alcohol reduces inflammation. 
• Managing your stress and getting enough quality sleep. Stress and lack of sleep can trigger inflammation and impair your immune system. Learning relaxation techniques such as deep breathing, meditation, or yoga can help you cope with stress. Improving your sleep routine so that you get at least 6 to 8 hours of quality sleep per night helps to decrease inflammation and maintain a healthy immune system.  

If you have arthritis, checking in with your doctor regularly for checkups and bloodwork can help monitor the effectiveness of your treatment plan. If your doctor finds irregularities in your exam or bloodwork, they can make necessary changes to your medication to help manage your arthritis more effectively and improve your quality of life. 

Takeaway

C-reactive protein is a marker of inflammation that can aid in diagnosing and monitoring arthritis, particularly rheumatoid arthritis. It can also help indicate your risk of cardiovascular disease, which increases with rheumatoid arthritis. 

If you have arthritis, it’s important to regularly consult with your doctor for monitoring to determine the effectiveness of your arthritis treatment plan and make changes as needed. 

Prioritizing a healthy lifestyle, including a balanced diet, regular exercise, stress management, and quality sleep as you age, can help to improve your quality of life and minimize the burden of arthritis.