By Mary Anne Dunkin | 12 June 2022

Diagnostics rheumatoid arthritis (RA) may take time. Like other types of arthritis, a diagnosis is based largely on the results of a medical examination and your symptoms. These may include joint pain, tenderness and swelling affecting the same joint or joints on both sides of your body (such as both wrists or both knees); fatigue and fever. Lab tests and imaging tests can help your doctor make the diagnosis.

Diagnostic laboratory tests

Signs of RA can be seen in the blood, so blood tests play an important role in making a diagnosis. The following are some of the tests your doctor may order.

• Erythrocyte sedimentation rate (ESR or sed rate). The ESR can measure how much inflammation there is in your body by measuring how quickly red blood cells (erythrocytes) separate from other cells in the blood and collect as sediment at the bottom of a test tube. Because inflammation can be caused by conditions other than RA, the results must be considered along with the results of other tests when making an RA diagnosis.
• C-reactive protein (CRP). This measures levels of CRP, a protein produced by the liver that signals inflammation. High CRP levels are common in RA and other inflammatory forms of arthritis. Because a high CRP can be present with many diseases and conditions, a high CRP by itself does not mean you have arthritis or identify which form you may have. The results must be interpreted in the context of your symptoms as well as the results of other tests.
• Rheumatoid factor (RF). Rheumatoid factor is a protein made by the immune system that can attack healthy tissue. High levels of rheumatoid factor can help your doctor make a diagnosis of RA. However, RF levels can also be high in other autoimmune diseases, so an RF test alone cannot be used to diagnose RA.
• Anti-CCP antibody test (ACCP or CCP). This test is for a type of autoantibody called cyclic citrullinated peptide (CCP) antibodies, which can be found in the blood of 60% to 80% of people with rheumatoid arthritis. The test is often performed in conjunction with an RF test.
• Antinuclear antibody test (ANA). Antinuclear antibodies (ANA) are a type of autoantibody, a protein that attacks your body’s own tissue. The presence of ANAs may indicate an autoimmune condition, including RA.

Diagnostic imaging tests

Imaging tests along with the physical examination and laboratory tests can help identify RA. These imaging tests can be used to diagnose RA.

• X-ray. X-rays can show bone damage, characteristic of RA, where they meet at the joints. They are a common tool in diagnosis; however, because damage from inflammation develops over time and may not be visible via X-ray early on, it may not be useful in diagnosing early RA.
• Magnetic resonance imaging (MRI). MRI is a procedure in which radio waves and a powerful magnet attached to a computer are used to create 3D images of structures inside the body. MRI can show changes in cartilage and bone that are indicative of RA.
• Ultrasound. Ultrasound, or sonography, uses sound waves to create images of structures inside the body. This can be used to see changes in bone and cartilage that suggest RA before changes show up on X-rays. Other advantages of ultrasound include its relatively low cost and the fact that it does not expose the body to radiation, like X-rays.
• Computed tomography (CT) scan. A CT scan is an imaging procedure that combines a series of X-ray images to create cross-sectional images of parts of the body. Studies show that CT scans can be effective in seeing early bone erosion that occurs with RA.

Supervision of laboratory tests

Some of the same laboratory and imaging tests used to diagnose RA are also used to monitor disease progression and response to treatment. Your doctor may order other tests to check for side effects of medications used to treat RA or effects of the disease itself. Your doctor may order some of these lab tests during your treatment.

• Erythrocyte sedimentation rate (ESR or sed rate). A reduced sed rate is an indication that inflammation is being controlled.
• C-reactive protein (CRP). As with the sed rate, lower levels of CRP indicate that inflammation is being controlled.
• The MBDA test (Vectra DA). This blood test checks for 12 proteins, hormones and growth factors. It gives your doctor a single disease activity score that can indicate how aggressive your disease is, how likely you are to have a flare-up when you stop medication, and which drug combinations may work best for you.
• Complete blood count (CBC). Although the CBC doesn’t necessarily tell your doctor how active your disease is, components of the test can help if you have complications from RA or its treatment. For example, low levels of red blood cells indicate anemia, which is common in people with RA. Low white blood cell counts, which are needed to fight infection, and low platelets, which are needed to make blood clots, can sometimes occur in people taking biologics.
• Liver enzyme (SGOT, SGPT, bilirubin, alkaline phosphatase). Measuring levels of enzymes in your blood can help your doctor determine whether you have liver damage that may be related to RA treatment, an associated autoimmune condition, or RA itself.
• Hematocrit (HCT) and hemoglobin (Hgb). These tests measure your number and quality of red blood cells. Lower red blood cell counts may mean that medications, such as NSAIDs or corticosteroids, are causing gastrointestinal bleeding.
• Lipid panel. Because some RA medications, such as interleukin inhibitors and JAK inhibitors, can cause increases in your triglyceride and cholesterol levels, your doctor may check these levels during RA treatment and, if necessary, prescribe medications to lower lipid levels.
• Kidney function test. Laboratory tests performed on your blood and urine can tell your doctor how well your kidneys remove waste products from the body. Kidney damage can occur from RA itself or medications used to treat it, including nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs), corticosteroids, and biologics.

Supervision Imaging tests

A number of imaging tests can be used to monitor joint damage from inflammation. They may be the same as those used to diagnose RA, including

• X-ray
• Magnetic Resonance Imaging (MRI)
• Ultrasound
• CT scan