How Psoriatic Arthritis Is Diagnosed
- Updated on: 2021-06-27
- Read original article here
The diagnosis of psoriatic arthritis involves a review of 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).
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.1
Psoriatic arthritis can be well managed with certain medications, but treatments used for other types of arthritis are not effective for treating psoriatic arthritis. This is why getting an accurate diagnosis is so important.
At-Home Screening
There are no at-home tests that can definitively diagnose psoriatic arthritis. With that being said, you should seek medical attention if you develop signs and 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
Symptoms of Psoriatic Arthritis
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.2 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.3 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).
Blood Tests Ordered by Rheumatologists
Imaging
You might have diagnostic images, including X-ray and magnetic resonance imaging (MRI). X-rays can detect areas of bone resorption (bone mineral breakdown), while 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 fo 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.
Differential Diagnoses
Because there are no tests that definitively confirm that you have psoriatic arthritis, exclusion of other possible conditions can be an important part of your diagnostic process. This can include tests to rule out conditions that may cause the same symptoms and signs that you have.
Some of the more common differential diagnoses include:
RA, differentiated with an RF factor blood test, hand X-rays, and symmetrical joint involvement
Gout, differentiated by the presence of uric acid crystals in synovial joint fluid
OA, differentiated by normal levels of ESR and CRP or a "gull-wing deformity" on X-ray (the central portion of a bone is worn down due to erosive OA)
Ankylosing spondylitis, differentiated by the inflammation of the sacroiliac joint and the ilium on MRI. Psoriatic arthritis can also cause sacroiliitis but it tends to be asymmetric, while ankylosing spondylitis causes symmetric inflammation
Reactive arthritis, differentiated by soft tissue swelling, mainly on weight-bearing joints
Mycobacterial tenosynovitis, a bacterial infection differentiated by lab cultures
Sacroid dactylitis, a complication of sarcoidosis differentiated by the appearance of bone cysts on X-ray and granulomas (granular deposits) on tissue biopsies
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 doctor so you can start treatment as soon as possible. Early treatment improves the outcome.4
If left untreated, joint damage may be irreversible and may eventually require invasive treatments, such as surgery.
