Psoriatic arthritis is a painful joint condition associated with psoriasis that is diagnosed through imaging and blood tests when accompanying symptoms are present.
Psoriatic arthritis is a painful joint condition most commonly found in patients suffering from psoriasis. Delay in treatment may result in permanent deformity of the affected joints. Hence, early diagnosis and treatment are necessary.
Medical history and physical examination
The doctor will examine your skin and nails for psoriatic lesions. Psoriasis is present as silvery dandruff-like plaques on the skin, especially over elbows, soles, palms, knuckles, knees, legs, and the scalp. In addition, nails may show signs of pits and dents. The presence of psoriatic scales on the skin accompanied with joint pain often indicates psoriatic arthritis.
Your doctor will ask about your current symptoms and how long you’ve been experiencing them. Additionally, your doctor will examine your joints and body for other signs and symptoms, such as:
- Joint stiffness
- Joint swelling
- Tenderness over joints
- Swelling over the joints
- Swollen fingers or toes
- Patches of red, itchy skin
- Thick silver or gray, scaly areas (flakes) on the skin, especially on the joints
- Pitting of fingernails or toenails
- Redness and swelling in the eye
Your doctor will also ask you if any of your close family members have a history of psoriasis or psoriatic arthritis, since a family history of these two conditions puts you at a higher risk of psoriatic arthritis.
What blood tests indicate psoriatic arthritis?
There is no single blood test that can confirm a diagnosis of psoriatic arthritis; however, your doctor may order the following laboratory tests to rule out other joint conditions, such as rheumatoid arthritis, gout and osteoarthritis. Some of these tests are also used to monitor your response to psoriatic arthritis treatment.
- Rheumatoid factor (RF). RF is a protein detected in the blood of most people with rheumatoid arthritis. If your RF levels are high, then you more than likely have rheumatoid arthritis and not psoriatic arthritis.
- Uric acid levels. High levels of uric acid in the blood indicate gout.
- Erythrocyte sedimentation rate (ESR or sed rate). High ESR levels in the context of painful and swollen joints indicate an inflammatory joint condition. The ESR levels determine the severity of any type of inflammatory arthritis, such as psoriatic arthritis, in the body.
- C-reactive protein. C-reactive protein (CRP) is a protein in the blood that indicates inflammation in the body. Your doctor usually orders this test if your ESR levels are normal but you have a few or all of the signs and symptoms of psoriatic arthritis. A high CRP level indicates a diagnosis of any type of long-standing condition, such as arthritis.
- Anti-CCP antibody. A high level of anti-CCP antibody indicates rheumatoid arthritis.
- HLA-B27. About 60 to 70 percent of people with psoriatic arthritis-associated spine problems (spondylitis) are positive for HLA-B27.
- Joint fluid test. Your doctor inserts a needle into one of your affected joints (mostly likely the knee) to remove a small sample of fluid from the joint. The sample is sent to the laboratory where it is viewed under a microscope. The presence of uric acid crystals in the fluid indicates gout.
Your hemoglobin levels and number of red blood cells may decrease if you have psoriatic arthritis.
What imaging tests are used in the diagnosis of psoriatic arthritis?
The following imaging tests are used:
- X-rays. Plain X-rays of the affected joints may show changes that are typically found in psoriatic arthritis.
- Magnetic resonance imaging (MRI). An MRI uses radio waves and strong magnetic fields that give a detailed view of joints, ligaments and tendons in the body.
- Bone mineral density or BMD test (DEXA scan). Psoriatic arthritis and the medications used to treat the condition can cause an increased loss of bone. Your doctor may order this test to know the extent of bone loss. The result indicates your risk of fractures.