Key takeaways
- Diagnosing PsA requires a comprehensive approach, including physical exams, blood tests, and imaging to differentiate it from other conditions such as rheumatoid arthritis and gout. Rheumatologists may use the CASPAR criteria, assigning points based on factors like current psoriasis, family history, and nail issues, to assist in diagnosis.
- Various tests, like X-rays, MRI scans, CT scans, and ultrasounds, enable doctors to inspect bones and joints for changes typical of PsA. Blood tests, including ESR and CRP, may indicate inflammation, while others help exclude different conditions.
- Although no single test definitively diagnoses PsA, early detection and treatment are vital to slowing disease progression and preventing joint damage. Lifestyle modifications, like diet and exercise, may also help manage the condition.
Doctors typically diagnose psoriatic arthritis (PsA) using a variety of tests that help them rule out other causes of your symptoms. It may take multiple appointments to receive a diagnosis and begin a treatment plan. They may need to rule out other diagnoses, such as:
- rheumatoid arthritis
- reactive arthritis
- gout
- ankylosing spondylosis
If you experience persistent joint stiffness, pain, or swelling, it’s best to talk with a medical professional so they can determine the cause and start treatment.
Read on to learn how a diagnosis of psoriatic arthritis is made.
In about 80% of cases, PsA develops after psoriasis is diagnosed. PsA primarily affects joints, which can be in any part of your body. The main symptoms include:
- fatigue
- joint pain, swelling, and stiffness
- reduced range of motion
To determine whether you have PsA, a doctor such as a rheumatologist will likely use:
Symptoms and family history
PsA is known to have a strong genetic connection. One 2020 study suggests that about
In the study, those with a family history of PsA had a higher risk of developing deformities from PsA but a lower risk of developing plaque psoriasis, the scaly skin patches that are a common symptom of psoriasis.
Researchers are still examining the specific genes associated with PsA. The main challenge is distinguishing the genes responsible for psoriasis from those responsible for PsA.
Identifying genes that lead to PsA may help researchers develop gene therapy for treating PsA in the future.
CASPAR criteria for diagnosis
Diagnosing psoriatic arthritis relies on markers in an established system called the Classification Criteria for Psoriatic Arthritis (CASPAR).
The criteria are each assigned a point value. Each one is worth 1 point except for current psoriasis, which is worth 2 points.
The criteria include:
- current psoriasis flare-up
- personal or family history of psoriasis
- swollen fingers or toes, known as dactylitis
- nail problems, like separation from the nail bed
- bone growths near a joint that are visible on an X-ray
- absence of rheumatoid factor (RF)
A person must have at least 3 points based on the CASPAR criteria to be diagnosed with psoriatic arthritis.
Repeated flare-ups
People with PsA usually experience periods of increased disease activity called flare-ups. Symptoms of a flare-up include muscle and joint pain. You may also have tendonitis and bursitis.
In psoriatic arthritis, fingers and toes may swell up. This is called dactylitis. You may also experience pain and swelling in your:
- wrists
- knees
- ankles
- lower back
Repeated flare-ups are one indicator of a PsA diagnosis. Sometimes, psoriasis flare-ups coincide with psoriatic arthritis flare-ups.
Common triggers for psoriatic arthritis flare-ups include:
- exposure to cigarette smoke
- infections or skin wounds
- severe stress
- cold weather
- alcohol misuse
- taking certain medications and foods
Psoriatic arthritis can’t be diagnosed with any single test. A doctor typically orders multiple tests and examines all of the evidence to make a diagnosis.
The tests they order can not only help diagnose or rule out PsA but also rule out other conditions. This can include:
- blood tests to help rule out gout and rheumatoid arthritis (RA)
- a blood test to show mild anemia, which may point toward the possibility of PsA or RA
- a blood test for rheumatoid factor RF, which can mean you have RA
Imaging tests for psoriatic arthritis
Imaging tests can help your doctor closely examine your bones and joints. Some of the imaging tests your doctor may use include:
- X-ray scan: X-rays aren’t always helpful in diagnosing early stage psoriatic arthritis. As the disease progresses, your doctor may use imaging tests to see changes in the joints characteristic of this type of arthritis.
- MRI scans: An MRI alone can’t diagnose psoriatic arthritis, but it may help detect problems with your tendons, ligaments, or sacroiliac joints.
- CT scans: Doctors use these scans primarily to examine joints deep in the body that are not easily seen on X-rays, such as in the spine and pelvis.
- Ultrasounds: These tests can help determine the progression of joint involvement and pinpoint the location. They can also identify enthesitis, inflammation that’s typical of psoriatic arthritis.
Blood tests for psoriatic arthritis
Blood tests alone cannot confirm a PsA diagnosis. Doctors usually order these tests to determine the presence of inflammation and to rule out other conditions.
Read on to learn what types of blood tests may be given to diagnose a PsA.
- Erythrocyte sedimentation rate (ESR, also called sed rate): This gauges your body’s degree of inflammation, though not specifically for PsA. It measures the amount of red blood cells that settle in a vial of blood, which is greater when you have inflammation.
- C-Reactive protein (CRP): Your doctor may order this test to check for an elevated C-reactive protein (CRP) level. This test is not specific for PsA, but it does indicate the presence of inflammation.
- Rheumatoid factor (RF): The presence of this antibody in your blood indicates rheumatoid arthritis (RA). Its presence means you don’t have PsA.
- Anti-cyclic citrullinated peptide test: These antibodies usually indicate RA. However, their presence can occur in other forms of arthritis.
- Human leukocyte antigen B27 (HLA-B27): This protein is found on the surface of white blood cells in some people with PsA.
- Serum uric acid: Your doctor may take a fluid sample from your joints to check for uric acid crystals. Elevated uric acid in the blood or crystals in bodily fluids usually indicates gout.
Bone density scan
In a bone density scan, X-rays measure the density of calcium and other minerals in a particular portion of your bones. The higher the density, the stronger and more healthy your bones.
PsA is associated with low bone density. Therefore, this test indicates possible osteoporosis and risk of fracture, which can be managed to lower the risk of fracture.
Like other tests for PsA, a bone density scan does not provide the basis for a definitive diagnosis. Low bone density can also result from other conditions and from the use of certain medications called corticosteroids.
Iron deficiency
Chronic inflammation associated with PsA can cause anemia, or a reduction of healthy red blood cells.
Low hemoglobin, or red blood cell count, can be another indication of PsA. Low hemoglobin can also result from iron deficiency.
Since there is no single test for psoriatic arthritis, a definitive diagnosis may take time. If you have psoriasis and joint pain, a doctor or dermatologist may refer you to a rheumatologist.
A rheumatologist is a doctor who specializes in diagnosing and treating arthritis and autoimmune diseases.
Be prepared to list all your symptoms, give a complete medical history, and tell your doctor if you’ve been diagnosed with psoriasis.
The rheumatologist will likely conduct a physical exam. They may also ask you to perform simple tasks that demonstrate your range of motion. They may order tests to rule out other forms of arthritis, including:
They may look for an elevated ESR or CRP level, which indicates some amount of inflammation. Your rheumatologist may also order various imaging tests to look for joint damage.
Once they confirm the cause of your symptoms, they can recommend a treatment plan.
Medications and surgery aren’t the only treatment options for psoriatic arthritis. Certain lifestyle choices can make the condition more tolerable.
These include changes in diet, specifically adding in more omega-3s, and adopting a safe exercise regimen.
Other lifestyle choices that may help include:
- maintaining a healthy-for-you weight
- taking steps to protect your joints
- avoiding your flare-up triggers
Psoriatic arthritis, when treated, can usually be slowed down to prevent further joint damage.