How Psoriatic Arthritis Is Diagnosed

Diagnosis involves a process of elimination

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To diagnose you with psoriatic arthritis, healthcare providers use your medical history, a physical examination, and X-rays or other imaging studies.

Blood tests and synovial fluid analyses may help rule out other types of arthritis, such as gout, rheumatoid arthritis (RA), or osteoarthritis (OA).

Doctor reviewing x-ray with patient
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Psoriatic arthritis is a type of inflammatory arthritis that belongs to a group of conditions known as spondyloarthropathies. It is a progressive autoimmune disease that affects the joints and skin.

If it's not adequately treated, it may lead to permanent joint damage and disability. 

Psoriatic arthritis can be well managed with certain medications. But treatments for other types of arthritis aren't effective against psoriatic arthritis. That makes getting an accurate diagnosis extremely important.

At-Home Screening

No at-home tests can definitively diagnose psoriatic arthritis. You should seek medical attention if you develop symptoms of psoriatic arthritis.

Warning signs include:

  • Painful, swollen joints, typically affecting the ankle, knee, fingers, toes, or lower back
  • Joint stiffness, especially in the early morning or after a period of rest (similar to other inflammatory joint diseases)
  • Reduced range of motion
  • Swelling of the tips of the fingers (similar to gout)
  • Sausage-like fingers or toes (dactylitis), typically occurring along the entire length of the fingers or toes
  • Tendon or ligament pain (enthesitis), often occurring at the Achilles tendon, the bottom of the foot (plantar fasciitis), or elbow (tennis elbow)
  • Skin plaques that are characteristically dry, thick, red, and covered with silvery-white scales
  • Nail changes, including dents, ridges, lifting (onycholysis), thickening (hyperkeratosis), crumbling, and discoloration
  • Persistent fatigue
  • Eye problems, including uveitis and conjunctivitis (pink eye), caused by inflammation of the eye
  • Eyelid inflammation, including episcleritis and scleritis, caused by eyelid inflammation
  • Psoriatic flares, in which disease symptoms spontaneously appear or worsen—and resolve just as suddenly

Psoriatic arthritis has two main components: psoriasis and arthritis.

  • Psoriasis is autoimmune damage to the epidermis (the outer layer of the skin).
  • Arthritis is inflammation of the joints.

While psoriatic arthritis can occur on its own, around 85% of cases are preceded by psoriasis. Rarely, joint symptoms precede the skin symptoms.

Labs and Tests

Blood tests are primarily used to rule out other types of arthritis, especially RA, and there are no specific results that confirm a diagnosis of psoriatic arthritis.

Tests your rheumatologist may order include:

  • Rheumatoid factor (RF): RF is found in around 80% of people with RA. A negative or low RF blood level is consistent with psoriatic arthritis. Low levels are present in 5% to 16% of people with psoriatic arthritis.
  • Anti-cyclic citrullinated peptide antibodies (anti-CCP): Once thought to be specific to RA, anti-CCP is present in about 5% of people with psoriatic arthritis.
  • Inflammatory markers: Blood tests like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are signs of systemic (whole-body) inflammation. These may be elevated with psoriatic arthritis (but to a far lesser degree than RA).

Imaging

You might have diagnostic images, including X-ray and magnetic resonance imaging (MRI) as part of the diagnostic process.

X-rays can detect areas of bone resorption (bone mineral breakdown). MRIs are more useful for characterizing soft tissue damage, including cartilage loss or buildup of fibrous tissues (pannus) around a joint.

MRIs may also identify enthesitis (inflammation of the connective tissue between a tendon or ligament and bone).

Characteristic features of psoriatic arthritis observed on X-ray or MRI include:

  • Asymmetric joint involvement, as opposed to symmetrical joint involvement with RA
  • Distal joint involvement (the joints closest to the nail) of the fingers or toes
  • Entheseal involvement
  • Asymmetrical spinal involvement, as opposed to the symmetrical involvement of ankylosing spondylitis
  • "Pencil-in-a-cup deformity" in which the tip of the finger looks like a sharpened pencil and the adjacent bone has been worn down into a cup-like shape

Around 77% of people with psoriatic arthritis have joint abnormalities that are seen on X-ray. Moreover, 47% of those who are newly diagnosed will develop bone erosions within two years.

Access to Care Challenges

Serious racial disparities exist when it comes to access to care, both when it comes to psoriatic arthritis and in general.

Studies show differences in psoriatic arthritis based on skin color and race. For example, Black people tend to have more severe:

  • Skin involvement
  • Psychological impact
  • Impaired quality of life

Despite that, they're less likely than White people to be put on immunosuppressive drugs.

Furthermore, according to 2021 research, psoriatic arthritis is diagnosed less often in:

  • Black people
  • People of Asian descent
  • Latinx people

People in these groups who have psoriatic arthritis often have a higher disease burden and lower quality of life because of disparities in care.

Some studies show implicit, often unconscious biases against people of color throughout the healthcare community. This is believed to have negative effects when it comes to treatment decisions and outcomes.

Some facilities have looked at disparities in their own patients. They found that poverty plays a role. But when comparing Black and White people of the same socioeconomic status, it became clear that outcomes remained worse for Black people.

Researchers call for more investigation into the impacts and disparities caused by bias in the medical profession and better education aimed at eliminating these issues.

Representation in Textbooks

People with dark skin are often underrepresented in rheumatology textbooks and professional reference materials. This can leave healthcare providers unable to recognize skin-based symptoms such as psoriasis in people of color, including Blacks, Native Americans, and Asian Americans.

Differential Diagnoses

The term differential diagnosis is medical jargon for "other things it could be."

Because no tests can definitively confirm psoriatic arthritis, it's important to exclude other possible conditions. You may be tested for conditions with signs and symptoms similar to yours.

Other possible conditions and how they're differentiated for psoriatic arthritis include:

  • RA: RF factor blood test, hand X-rays, and symmetrical joint involvement
  • Gout: Uric acid crystals in synovial joint fluid
  • OA: Normal levels inflammatory markers, "gull-wing deformity" on X-ray (the central portion of a bone is worn down)
  • Ankylosing spondylitis: MRI shows symmetrical inflammation of the sacroiliac (SI) joint and the ilium (Psoriatic arthritis can involve asymmetric SI joint inflammation.)
  • Reactive arthritis: Soft tissue swelling, mainly on weight-bearing joints
  • Mycobacterial tenosynovitis: Lab culture shows bacterial infection
  • Sacroid dactylitis: Complication of sarcoidosis, X-ray shows bone cysts, tissue biopsy detects granulomas (granular deposits)

A Word From Verywell

Psoriatic arthritis is a painful, progressive illness, and, without proper treatment, it affects quality of life and can lead to disability.

If you think you may have psoriatic arthritis, speak to your healthcare provider so you can start treatment as soon as possible. Early treatment improves the outcome.

If left untreated, joint damage may be irreversible and may eventually require invasive treatments, such as surgery.

Frequently Asked Questions

  • What type of healthcare provider diagnoses and treats psoriatic arthritis?

    Healthcare providers who diagnose and treat psoriatic arthritis can be rheumatologists or dermatologists. A dermatologist treats the skin condition, while a rheumatologist treats the underlying autoimmune disease and joint pain. 

  • How do you get tested for psoriatic arthritis?

    Psoriatic arthritis is diagnosed by blood work and imaging tests. Blood tests are used to rule out other conditions, such as rheumatoid arthritis and ankylosing spondylitis. Imaging tests, such as X-rays and MRIs, help differentiate psoriatic arthritis from other joint disorders. 

  • Is there a blood test to check for psoriatic arthritis?

    Yes and no. There is no one specific test used to diagnose psoriatic arthritis. But there are several blood tests involved in pinpointing a diagnosis. These include:

    • Rheumatoid factor (RF)
    • Snti-cyclic citrullinated peptide antibodies (anti-CCP)
    • Erythrocyte sedimentation rate (ESR)
    • C-reactive protein (CRP) 
  • What labs are abnormal with psoriatic arthritis?

    Blood tests that measure inflammatory markers, such as ESR and CRP, are usually elevated in patients with psoriatic arthritis.

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9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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