If there are no psoriatic arthritis findings present on the X-rays, your doctor can order additional tests to rule out other conditions, like rheumatoid arthritis and gout since both can cause joint pain and inflammation similarly to psoriatic arthritis. This is helpful in situations where people have less severe forms of psoriatic arthritis that aren’t easily detected on X-rays.
To rule out gout, your doctor can perform a joint fluid test. By using a needle to extract a small amount of fluid from a swollen, tender, or stiff joint, your doctor can look for the presence of uric acid crystals, which indicates that you may have gout.
Blood tests cannot positively identify psoriatic arthritis, but they can still be helpful for ruling out other types of inflammatory arthritis. Some blood tests can identify inflammation in the body, for example, one test looks for C-reactive protein, a blood marker of inflammation14. The presence of C-reactive protein may help support a psoriatic arthritis diagnosis.
Nearly everyone who is evaluated for psoriatic arthritis will have their blood tested for rheumatoid factor (RF), a protein produced by the immune system that attacks healthy joints. People with rheumatoid arthritis will often test positive for the RF antibody. People with psoriatic arthritis generally test negative for the RF antibody. (It’s not a guarantee, though: about 20 percent of people who do have rheumatoid arthritis test negative for RF15.) To test for RF, a health care worker will take a vial of blood using a small needle—you don’t have to do anything to prepare, and it usually only takes a few minutes.
Sometimes, physicians ask people to complete screening tests to assess the patient’s risk for developing psoriatic arthritis. For example, people with psoriasis may be asked to complete16 these tests, which are self-reported questionnaires covering topics like joint pain and morning stiffness. These can help physicians refer people to a rheumatologist for further psoriatic arthritis testing and possible diagnosis. Screening tests aren’t perfect— they’re most likely only moderately accurate—but they may help doctors identify early-stage disease, which is easier to treat.
Psoriatic arthritis diagnostic criteria
Finally, in order to confirm a psoriatic arthritis diagnosis, your doctor can use a criteria checklist. Since 2006, doctors have used a test designed by a group of rheumatologists known as the CASPAR—classification criteria of psoriatic arthritis— for this purpose. The CASPAR test assigns point values to different symptoms and signs, as follows:
- The presence of skin psoriasis (2 points, 1 point for having it previously or having a family history but not having it yourself)
- Nail lesions, pitting, or pulling away from the nail bed (1 point)
- Swollen toe or nail (1 point)
- RF negative (1 point)
- Juxta-articular bone formation (in other words, a bone formation near a joint) (1 point)
People who score at least three points are considered to have psoriatic arthritis.
Psoriatic arthritis treatment
Psoriatic arthritis treatment is highly variable, depending on the severity of your case, how many joints are affected by the condition, whether you have psoriasis, and your personal preferences. “The treatment is very individualized,” Dr. Gupta says. Treatment can both help ease the severity of symptoms and prevent the disease from getting worse. Usually, doctors will recommend medication combined with lifestyle treatment for the best symptom management.
Psoriatic arthritis medication
Psoriatic arthritis medication functions like a ladder: If the first treatment doesn’t combat your symptoms, you stop taking it and climb up to the next rung. People with mild cases of psoriatic arthritis might just treat symptoms as they occur. Then, if those don’t work, you may be prescribed a more powerful drug. Here are the commonly used psoriatic arthritis medications: