How is PsA diagnosed?
Psoriatic arthritis (PsA) is usually diagnosed from your symptoms and a physical examination. There is no single test that can confirm that you have PsA. However, your doctor may order blood tests or imaging, such as x-rays, to help reach a diagnosis.
About 1 in 3 people with psoriasis will develop PsA. Symptoms usually appear between the ages of 30 and 50. If you have psoriasis and start to develop joint pain, stiffness and swelling, you should let your GP or dermatologist (skin specialist) know without delay. Early referral to a rheumatologist (a specialist doctor in arthritis) is important to confirm diagnosis and start treatment. Early diagnosis and treatment can prevent the joint damage that PsA can cause.
Your rheumatologist will:
- Talk to you about your symptoms, including where and when you feel joint pain.
- Check your skin and nails for signs of psoriasis.
- Ask about any family history of skin problems.
- Examine your hands, feet, spine and other joints for swelling, heat or tenderness.
- Order blood tests to check for inflammation and to help rule out other conditions such as rheumatoid arthritis
- Send you for imaging tests, such as x-rays, if required.
Difficulties diagnosing PsA
PsA is often under diagnosed or misdiagnosed. Some studies have found that more than half of people with PsA wait over two years for a diagnosis.
PsA can be difficult to diagnose for several reasons:
- PsA has many different symptoms
PsA is a complex disease that can present in different ways. Symptoms can also be similar to other types of arthritis, such as rheumatoid arthritis (RA), ankylosing spondylitis (AS) and gout. Some symptoms, such as pain in the heel or sole of the foot, can have other more common causes as well, so PsA may not be suspected.
- Not everyone with PsA has psoriasis
Most people with PsA will have psoriasis symptoms first. However, more than one in ten people with PsA will have arthritis symptoms first. In these cases, a family history of psoriasis can help to diagnose PsA.
In addition, some people may not realise they have psoriasis. They may have a small area behind their ear or on their scalp that itches, around their belly button or between their buttocks but they may not realise it is psoriasis. Without obvious signs of psoriasis, doctors may not think you have PsA, even if you have joint pain.
- Blood tests are not conclusive
Blood tests can help to rule out other conditions, but they are not conclusive. PsA and RA often have similar symptoms. PsA is considered “seronegative”. This means that people with PsA don’t usually have markers in the blood, such as rheumatoid factor (RF), that are common in people with RA. However, some people with RA are also seronegative and some people with PsA do have these markers. This can cause confusion between PsA and RA.
- PsA is not well recognised
People with PsA symptoms may delay talking to their doctor about their joint pain. This could be because they are not aware of PsA or they may think their symptoms are due to other conditions. GPs may also not recognise the symptoms of PsA or may diagnose a more common condition with similar symptoms.
People with psoriasis often see a dermatologist (specialist skin doctor). However, dermatologists may not know all the signs or symptoms of arthritis. So even though you may have PsA you may not be referred to a rheumatologist, who can look for signs of arthritis.
Given these factors, it is common for people with PsA to have their symptoms attributed to other conditions first. Some health issues that can have symptoms similar to PsA include:
If you are having any aches and pains and you think or know you have psoriasis, don’t write off your symptoms. The same applies if you are being treated for any of the conditions listed above but the condition is not getting better or keeps coming back. Instead, ask your doctor to refer you to a rheumatologist, which is the best type of healthcare provider to determine if you have PsA or another condition.
It may be helpful to complete the Psoriasis Epidemiology Screening Tool (PEST) and take it to your doctor if you are concerned. PEST is a simple tool which can help to identify people with psoriasis who should be referred to a rheumatologist for assessment.