How to Diagnose Psoriatic Arthritis

To diagnose psoriatic arthritis (PsA), a healthcare provider will take your medical history and examine you for signs of the condition. These may include joint swelling and tenderness, as well as red, scaly patches of skin. They also ordered tests and imaging studies to look for evidence of inflammation in the blood and joint abnormalities.

Still, the diagnosis of psoriatic arthritis is never really confirmed. Rather, it is determined by ruling out other possibilities.

This article explains the diagnostic process, how to perform a self-test at home, and when you may have similar symptoms. It also looks at the importance of family history and how ethnicity affects how PsA is experienced and diagnosed.

physical examination

Psoriatic arthritis gets its name from its two main components: psoriasis and arthritis.

Psoriasis causes damage to the epidermis, the outer layer of the skin, while arthritis is inflammation of the joints.

Given this, your healthcare practitioner will ask you about your symptoms and look for the following signs:

  • joint pain, swelling, especially in the fingers and toes
  • lower back, ankle and foot pain
  • Symptoms of psoriasis on the skin, including redness, dryness, flaking, and scaling
  • Symptoms of psoriasis on the nails, such as pitting and detachment from the nail bed
  • swollen fingers and toes
  • Pain in which connective tissue attaches to the bones in the heels, soles, elbows, and other areas (called enthesitis)

They will also ask where you were injured and what made your pain better or worse.

medical history

Be sure to tell your provider about any other diagnoses, especially psoriasis. Although PsA can occur on its own, it precedes psoriasis in about 85% of cases.

Also mention if you have a family history of PsA or psoriasis. PsA is more common if your family member has one or both of these conditions. In fact, you can get PsA without having psoriasis first.

Labs and Testing

There is no specific test to confirm a diagnosis of psoriatic arthritis. But blood tests that can detect signs of inflammation throughout the body could help support one. Some tests can also help rule out other forms of arthritis.

You may need the following blood tests:

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  • Rheumatoid factor (RF): About 80% of people with rheumatoid arthritis (RA) have RF, another inflammatory disease that affects the joints. Higher level RF points to RA. In contrast, no RF or low levels suggest PsA.
  • anti-cyclic citrullinated peptide (Anti-CCP) Antibodies: These immune system cells attack your joints. They are common in RA. Only about 5% of PsA patients test positive for anti-CCP.
  • Inflammatory markers: red blood cells Sedimentation rate (ESR) and C-reactive protein (CRP) can indicate systemic inflammation. Blood tests may show higher levels of PsA, but higher levels of RA.

These tests may be performed by a primary care physician or a rheumatologist (a doctor who specializes in arthritis and similar conditions). If you haven’t been diagnosed with psoriasis before, you may be sent to a dermatologist who specializes in skin diseases.

You may need to complete other tests, depending on other diagnoses your provider is exploring. These may include:

  • Urinalysis: People with PsA may have excess protein in their urine.
  • Biopsy: A sample of tissue (such as skin) is removed and examined under a microscope.
  • Bacterial Culture: This is done on skin lesions.
  • Antinuclear Antibody (ANA) Test: This blood test looks for proteins associated with autoimmune diseases.

Blood tests ordered by a rheumatologist

review

Your healthcare provider will begin the diagnostic process with a physical exam to look for signs of PsA. Tell them if you have a family history of PsA or psoriasis. Blood tests cannot detect PsA, but they can help the diagnostic process and rule out similar conditions.

imaging

X-rays and/or magnetic resonance imaging (MRI) are common in the diagnosis of PsA.

X-rays use electromagnetic waves to take pictures of the inside of your body. They show your bones and joints. MRI uses radio waves and strong magnetic fields to show soft tissue damage.

Findings pointing to PsA include:

  • enthesitis
  • Joints on one side of the body are affected but not on the other side (asymmetric joint involvement)
  • Only part of the spine is affected (asymmetric spine involvement)
  • Involvement of the finger and toe joints closest to the tip
  • “Pencil in a cup” deformity, where the bone in the finger becomes sharp (like the tip of a pencil) and wears down adjacent bones, making it look like a cup

About 77% of people with psoriatic arthritis have joint abnormalities on X-rays. Additionally, up to 47% of newly diagnosed patients experience bone wear within two years.

review

X-rays and MRI may help support the diagnosis of PsA. If you notice certain warning signs at home, make an appointment with your healthcare provider.

Differential diagnosis

The term differential diagnosis is a medical term that means “something else”.

Because there is no test to confirm PsA, it is important to test for similar conditions so they can be ruled out. These conditions and their salient features include:

  • Rheumatoid Arthritis: Positive blood test for RF factor, X-ray damage to the hand, joints affected on both sides of the body
  • Reactive Arthritis: Soft tissue swelling, mostly in weight-bearing joints
  • ankylosing spondylitis: MRI showing symmetrical inflammation of the sacroiliac (SI) joint (at the base of the spine) and the ilium (bone that forms the upper part of the pelvis)
  • Osteoarthritis: Negative for inflammatory markers, excessive wear of the central part of the bone on X-ray (“gull wing deformity”)
  • Gout: Uric acid crystals in joint fluid
  • Lupus: Diagnosed by ANA test and skin or kidney biopsy
  • Fibromyalgia: tender point examination to check for widespread pain or questionnaire based on symptoms and severity
  • Mycobacterial tenosynovitis: Laboratory cultures show bacterial infection
  • nodular dactylitis: A complication of the inflammatory disease sarcoidosis, which results in clumps of cells called granulomas; X-rays show bone cysts, and tissue biopsy detects granulomas

Several rounds of testing may be required before the cause of symptoms can be identified. This process can be frustrating, but it’s the only way to ensure a proper diagnosis and determine the right treatment.

Psoriatic Arthritis and Lupus

Racial Differences in PSA

There are serious racial disparities in the severity and treatment of psoriatic arthritis. For example, black people tend to have more severe:

  • skin involvement
  • psychological impact
  • impaired quality of life

Still, they were less likely than whites to take immunosuppressants — the treatment of choice for PsA.

Studies have shown that psoriatic arthritis is diagnosed less frequently:

  • Black person
  • Asian people
  • Latins

For PsA patients in these groups, the difference means higher disease burden and lower quality of life.

Several studies have shown that there is an implicit and often unconscious bias against people of color across the healthcare community. This is thought to negatively impact treatment decisions and outcomes.

Some agencies found that poverty played a role. However, when comparing blacks and whites of the same socioeconomic status, the results for blacks were still worse.

The researchers called for more investigation into these differences and their impact, And better education to eliminate prejudice.

Representation in textbooks

Dark-skinned people are often underrepresented in rheumatology textbooks and professional references. This can make it impossible for healthcare providers to recognize skin conditions in people of color, such as psoriasis.

generalize

The PsA diagnosis process includes a review of your medical and family history, a physical exam, blood tests, and imaging. No test alone can diagnose PsA. Conditions with similar symptoms must first be ruled out.

If you suspect you have PsA, see a healthcare provider. If you are a person of color, know that there are documented differences in PsA treatment. Seek another healthcare practitioner if you feel you are not getting the care you need.

Symptoms of Psoriatic Arthritis

VigorTip words

Psoriatic arthritis is a chronic progressive inflammatory arthritis. If not treated properly, PsA can lead to permanent joint damage and disability.

Don’t put off seeing your healthcare provider for a diagnosis. Early treatment can improve your long-term outcomes.

Frequently Asked Questions

  • What type of healthcare provider can diagnose and treat psoriatic arthritis?

    PsA is diagnosed and treated by dermatologists and rheumatologists. Dermatologists treat skin conditions, while rheumatologists treat underlying autoimmune diseases and joint pain.

  • Are there blood tests to check for psoriatic arthritis?

    yes and no. No one specific test can diagnose PsA, but multiple blood tests are needed to confirm the diagnosis. These include:

    • Rheumatoid factor (RF)
    • Anti-cyclic citrullinated peptide (anti-CCP) antibody
    • Erythrocyte sedimentation rate (ESR or sed rate)
    • C-reactive protein (CRP)
  • Which labs find abnormality in psoriatic arthritis?

    Blood tests that measure markers of inflammation, such as ESR and CRP, are often elevated in people with psoriatic arthritis.

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