Domain based approaches to diagnosing PsA
Dr Nicola Gullick, Consultant Rheumatologist, University Hospitals Coventry and Warwickshire NHS Trust, talks about how she differentiates between Rheumatoid Arthritis and Psoriatic Arthritis in real-life clinical practice.
Psoriatic Arthritis (PsA) can be a difficult condition to distinguish and can be misdiagnosed for Rheumatoid Arthritis (RA). Although it is easy to assume that a PsA patient would present equally with both psoriasis and arthritis, I regularly find that due to the fact that psoriasis presents mildly in some patients, it is often ignored or goes unnoticed. With this in mind, I think it is very important to think beyond the psoriasis and the joints alone – this is where the Six Domains are very useful in ensuring an accurate and timely diagnosis of PsA.
I often find in patients who are referred to me, particularly those who are seronegative for rheumatoid factor, it is assumed they do not have an inflammatory arthritis and referral has been delayed. In some cases they have had years of symptoms before being referred as the connection between joint pain or enthesitis and skin disease has not been made. Dactylitis and enthesitis symptoms are often missed. I have also seen a number of patients with established seronegative RA who have clear features of PsA, including skin lesions which have been missed in the past.
In my clinic, rheumatoid factor negative patients with inflammatory sounding pain are assessed in detail using the Six Domains approach. We consider the wider symptoms that the patient is experiencing and apply the Six Domains to their assessment – for example looking for nail disease, asking the patient to remove their socks/shoes, and considering the presence of even mild skin lesions or enthesitis. In taking this wider approach, and in particular looking at the patient’s feet, we can identify the domains responsible for some of the symptoms experienced. For example, in patients with vague aches and pains, this may indicate presence of enthesitis which raises the suspicion of PsA.
My advice to anyone who is sitting with a patient who has been shown to be negative for rheumatoid factor is to always think outside the joints and consider the Six Domains in their assessments. I would also recommend downloading the GRAPPA app for further guidance about PsA management.