Recent research found that patients with psoriatic arthritis (PsA) face delayed diagnoses or are misdiagnosed.
PsA can be elusive. Some patients with PsA may not have psoriasis, while others seem to have another similar or entirely different disease.
Knowing exactly what the symptoms are makes all the difference when it comes to determining a PsA diagnosis, but some experts may not be aware of the criteria.
Patients with psoriatic arthritis (PsA) face serious diagnostic issues, from delays to misdiagnoses, according to research presented recently at the Rheumatology Nurses Society annual conference.
A recent study also found that 1,134 PsA patients saw an average diagnostic delay of about 35.1 months. In fact, about one-third of patients wait over two years for a diagnosis. These findings suggest clinicians may not always know how to assess or diagnose PsA accurately. Here’s how you can better support your patients.
The differences between spondyloarthritis, psoriatic arthritis, and psoriasis
Spondyloarthritis (SpA) is a family of related diseases that affect 3.2 million adults in the U.S. and share common features, including inflammatory arthritis in the spine and other joints.
There are two subtypes of SpA, including axial spondyloarthritis, which is characterized by inflammatory pain and arthritis in the spine and hips— as in ankylosing spondylitis or non-radiographic axial spondyloarthritis—and peripheral spondyloarthritis, which is characterized by inflammatory pain and arthritis in joints and tendons other than the spine.
The latter category includes a few diseases, such as psoriatic arthritis. PsA symptoms include:
Inflammation, pain, and swelling of the smaller joints, including those in the hands, feet, wrists, knees, and ankles.
Psoriasis, which typically presents before arthritis.
Nail changes, including small indentations, lifting, and discoloration of the fingernails or toenails.
Inflammatory eye conditions.
Swelling of an entire finger or toe—dactylitis—causing a sausage-like appearance.
Back pain and stiffness.
Psoriasis (PsO), on the other hand, is an inflammatory skin disease that causes itchy, raised skin plaques. The key difference between PsO and PsA is the “largely irreversible nature of inflammatory joint changes in PsA, whereas cutaneous plaques in psoriasis completely heal,” according to a clinical rheumatological journal. It’s important to note that up to 30% of people with PsO also develop PsA.
Why is PsA misdiagnosed?
An October 2023 study published in Rheumatology International found several diagnostic delay factors at play, including lower levels of education, arthritis symptoms preceding skin manifestations, low back pain at the first visit, symptom onset age, and psoriasis subtype.
A main issue with diagnosing PsA?: “There is no blood test for it, and imaging is often unrevealing,” Stella Bard, MD, a New York–based rheumatologist, says.
Dr. Bard says that PsA is often misdiagnosed as enteropathic arthritis or reactive arthritis “because they have the same symptoms of joint and/or spine pain.”
Enteropathic arthritis (inflammatory arthritis with bowel issues) and reactive arthritis (inflammatory arthritis triggered by an infection) also fall under the spondyloarthritis subcategory “peripheral spondyloarthritis,” which is why this jump may be easy for clinicians to make.
PsA may also be misdiagnosed as osteoarthritis, rheumatoid arthritis, or gout, according to the Spondylitis Association of America (SAA).
PsA can be elusive, too. While many patients with psoriasis later develop PsA, some people who have PsA won’t have any psoriasis at all.
“[PsA] is a difficult diagnosis to make, especially when someone doesn't have the psoriatic arthritis rash,” Dr. Bard says. “A segment of patients with PsA will develop arthritis before the psoriasis rash. In fact, some people [with PsA] never develop the rash in their lifetime.”
While this is not common, it does happen. Sometimes, these patients have a family history of psoriasis or psoriatic arthritis.
On the flip side, it can take up to a decade for PsA to develop after a patient is diagnosed with psoriasis, according to findings from the aforementioned conference. These patients can sometimes fall through the cracks due to vague or ignorable symptoms like fatigue and stiffness.
Clinicians may even miss a PsA diagnosis if a patient’s rash doesn’t resemble the standard skin plaque. The conference’s findings state that other kinds of psoriasis, including guttate, inverse, or pustular psoriasis, may be overlooked, leading to a delayed PsA diagnosis.
How to diagnose PsA accurately: A step-by-step approach
“Timely diagnosis of PsA is crucial for effective management and improved outcomes…By identifying influential factors such as education level, arthritis symptoms preceding skin manifestations, initial visit symptoms, age of symptom onset, and psoriasis subtype, healthcare practitioners may create specific techniques to help in early detection and intervention,” authors write in Rheumatology International.
According to Anca Dinu Askanase, MD, Founder and Clinical Director of Columbia University’s Lupus Center and Director of Rheumatology Clinical Trials, healthcare providers should start by assessing a patient’s medical and family history and physical examination. “Most of the time, patients have or have had psoriasis of the skin or nail,” Dr. Askanase says. “The nails may have ridges and may be growing away from the nail bed.”
From there, you’ll want to “look for evidence of inflammatory arthritis in the joints, enteritis, and spine. Remember to check for dactylitis,” she says. Imaging can help in making a diagnosis; she adds: “X-ray the hands or feet to look for early damage and evidence of juxta-articular new bone formation. Consider ultrasound evaluations to look for subtle joint or enthesis involvement. MRI can also help diagnose early psoriatic arthritis.”.
According to the SAA, “In the early stages of the disease, standard X-rays usually don’t reveal signs of PsA and may not aid in diagnosis. In later stages, however, they may show characteristic changes that distinguish PsA from other rheumatic diseases. One of these is the “pencil-in-cup” phenomenon, in which the end of a bone gets whittled down to a sharp point where it enters a joint. Changes in the peripheral joints and spine, which also occur in later stages of disease, can also support a PsA diagnosis.”
While there’s no single lab test that can confirm PsA, blood tests can help rule out other diseases. “Rheumatoid factor and an anticyclic citrullinated peptide antibody test are expected to be negative in psoriatic arthritis,” Dr. Askanase says. “However, tests for inflammation could be positive.”
When assessing the skin, some patients may have tiny patches of psoriasis that they don’t even notice or aren’t bothered by Dr. Askanase stresses. You may want to consult a dermatologist as well.