There’s no one definitive test.
Psoriatic arthritis—an inflammatory and chronic type of arthritis—affects up to 30 percent of people with psoriasis, according to the National Psoriasis Foundation (NPF). If you have psoriasis, it’s a good idea to be aware of the symptoms of psoriatic arthritis (PsA), because catching it early, if it does develop, may improve treatment outcome.
If you do notice the telltale signs of PsA, such as pain and stiffness in the joints, what’s the next step? Unfortunately, there’s no single test that can diagnose PsA with a yes-or-no answer. Instead, a combination of different exams can help doctors form a PsA diagnosis, according to Leah Anon, MD, rheumatologist at Harlem Health Center and Queens Health Center in New York City.
Here are the factors doctors consider before diagnosing with PsA:
The patient’s symptoms, including when they started, where the stiffness is occurring, and how much it impacts daily life
Personal history of psoriasis
Family history of psoriasis
A physical exam
An X-ray or MRI to check for inflammation or damage to the joints
And blood tests to rule out other conditions.
Other Conditions to Rule Out
Many health conditions can cause joint pain, and psoriatic arthritis can mimic some of them. In particular, doctors need to rule out other types of arthritis like rheumatoid arthritis and gout, according to NPF. Many blood tests used to diagnose PsA are actually meant to rule out these similar conditions.
A blood test that evaluates the “rheumatoid factor” checks for a certain antibody that is typically present in someone with rheumatoid arthritis, but not PsA. (It’s possible, but rare, to have both rheumatoid arthritis and PsA.)
Since PsA usually affects the distal joints close to the nails in the fingers and toes, pain in the toe could be mistaken for gout. To rule out gout, doctors test joint fluid for elevated levels of serum uric acid—a possible sign of gout.
Although symptoms of the different conditions are similar, they have some key differences:
Joint pain caused by gout will usually strike a single joint—often the big toe—very suddenly. Gout causes intense pain.
If there is no swelling in the joints, it is likely osteoarthritis instead of PsA. Another sign of osteoarthritis is pain after activities, whereas PsA causes stiffness and pain in the mornings.
If joint pain is symmetrical and affects the same joints on both sides of the body, it is likely rheumatoid arthritis. PsA joint pain is usually asymmetrical.
PsA also has unique symptoms, such as skin lesions, nail changes, and dactylitis, which is when fingers and toes become swollen and take on a sausage-like appearance.
If you think you have PsA—or any of the related conditions—it’s best to visit your doctor for a professional diagnosis. The sooner you begin treatment for psoriatic arthritis, the more likely you are to avoid permanent joint damage and improve your quality of life.
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When it comes to diagnosing
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it's important to know there's not one
single test that instantly tells you.
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Because psoriatic arthritis can
look similar to other conditions,
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we will often do certain tests
to try to rule those out.
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We ask patients to tell
us about their symptoms,
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how they started where in your
body you're having pain or
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stiffness, and how your symptoms
effect your daily activities.
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We will do a physical exam, and might
order x-rays to look for inflammation and
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damage in the joints.
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We can test joint fluid
to try to rule our gout.
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If a single joint becomes swollen and
extremely painful almost overnight,
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it's probably gout,
not psoriatic arthritis.
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We'll do a blood test to check for
something called rheumatoid factor and
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They're present in people
with rheumatoid arthritis,
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but less commonly in psoriatic arthritis.
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Certain symptoms can also help
us rule out other conditions.
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If you have little or no joint swelling,
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there's a good chance you have
osteoarthritis, not psoriatic arthritis.
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People with psoriatic arthritis tend
to wake up feeling stiff or in pain.
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Doctors can also test for
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a gene that can be related to psoriatic
arthritis involving the spine.
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There are some symptoms that tend to
be unique to psoriatic arthritis.
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Skin lesions, nail problems and
specific patterns of inflammation
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usually let us differentiate
it from other conditions.
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If your fingers or
toes are completely swollen,
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that's another likely sign
it's psoriatic arthritis.
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This is called dactylitis or
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If you are at all concerned
that your skin issues, pain,
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or other symptoms could potentially be
psoriatic arthritis, please see a doctor.
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Starting treatment early can
help prevent joint damage, and
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improve your symptoms and quality of life.
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About psoriatic arthritis. Portland, OR: National Psoriasis Foundation. (Accessed on August 27, 2018 at https://www.psoriasis.org/about-psoriatic-arthritis#symptoms.)
Gout. Portland, OR: National Psoriasis Foundation. (Accessed on August 27, 2018 at https://www.arthritis.org/about-arthritis/types/gout/.)
Psoriatic arthritis. Atlanta, GA: American College of Rheumatology. (Accessed on August 27, 2018 at https://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Psoriatic-Arthritis.)
Psoriatic arthritis. Portland, OR: National Psoriasis Foundation. (Accessed on August 27, 2018 at https://www.psoriasis.org/psoriatic-arthritis.)