Vikas Majithia, MD, and Abhijeet Danve, MD, on Diagnosing AxSpA: Part 2

Drs Majithia and Danve continue their podcast with a discussion of the importance of a detailed patient history in distinguishing between axial spondyloarthritis and mechanical back pain.

Vikas Majithia, MD, is chair of the Division of Rheumatology and a senior associate consultant in the Department of Medicine at Mayo Clinic-Florida in Jacksonville. Abhijeet Danve, MBBS, MD, is an associate professor of rheumatology and director of the Spondyloarthritis Program at Yale University.

Welcome back for part two of this podcast with doctors Abhijeet Danve And Dr. Vikas Majithia as they continue their conversation on diagnosing axial spondyloarthritis. Today, they're going to discuss additional testing that can be done to help make the diagnosis.

Dr Majithia:

You already mentioned additional testing which needs to be done in these patients, especially if a clinician feels that their back pain may be inflammatory. And what additional testing is needed and how do you make that diagnosis when you see these patients who may have been referred to you with inflammatory back pain.

Dr Danve:

That was a loaded question. So before going to the labs and imaging, I would take us back to clinical part because history is the most important component of diagnosis of axial SpA. So once we know that patients have inflammatory back pain, usually longstanding because these patients are not referred to rheumatology as quickly, there are some other musculoskeletal features that we need to inquire about, and they include peripheral inflammatory arthritis, which is typically intermittent and involves joints of lower extremities, then there is dactylitis that can happen in patients with axial SpA as well as psoriatic arthritis as we know. Enthesitis, common enthesitis including plantar faciitis, achilles tendonitis, tennis elbow, are quite common. Anterior chest wall pain is one of the lesser known but relatively common clinical feature of axial SpA. So I would ask the patient about these in addition to the inflammatory back pain questions.

And then there are some extra-articular features, most common being acute anterior uveitis. So we typically ask patients about history of uveitis in the past, history of inflammatory bowel disease, either Crohn's disease or ulcerative colitis and skin psoriasis. About 10% of the patients with axial SpA tend to have IBD, 10% tend to have psoriasis, and about 20 to 25% of the patients will develop uveitis either before or after the onset of back pain. A. few other features to find if the patient's back pain is from axial SpA to ask about family history because this condition tends to run in the family, cluster in the family. So if there is families to have spondyloarthritis like uveitis, inflammatory bowel disease, psoriasis or ankylosing spondylitis, that is quite helpful to know. And once you have enough suspicion, then I would go and do labs, mainly C-reactive protein that is inflammation marker relatively specific to AS we don't rely so much on sedimentation rate for axial SpA, we basically do CRP, which is a nmlmore useful test.

And in the right patient population I would get HLA-B27 gene test. So the diagnosis of axial SpA is not based on the lab tests or imaging. It's a diagnosis made by clinician-based judgment. So gold standard for diagnosis of axial SpA is clinicians' judgment. So I would like to know if the patient has got chronic back pain, if there is inflammatory back pain, whether that responds well to NSAIDs, if they have other musculoskeletal features or family history of spinal arthritis. On examination in someone with longstanding spinal inflammation and radiographic progression, one may be able to find limited range of movements at the cervical spine or lumbar spine or clinical findings of hip arthritis. In the right patient population, one may be able to identify peripheral inflammatory arthritis or uveitis, typically colonoscopies done by a gastroenterologist and they may find inflammatory bowel disease.

Sometimes patients may present with plantar fasciitis or ocular tendonitis; more or less, examination of the spine is not as helpful to make the diagnosis. It is more helpful to find if the patient is limited because of the long-standing condition. So in other words, in nonradiographic axial SpA, physical examination of the spine may not yield much. So lab tests-wise, CRP is elevated in about 50% of the patients, so remaining 50% may have the condition, but their CRP may not be elevated. And HLA-B27 is typically present in about 80 to 90% of patients with AS, and close to 70 to 80% patients with nonradiographic axial SpA. If you take 100 people with positive HLA-B27, only 5 will have AS. But if you take 100 patients with AS, only 5 will not have positive HLA-B27. So HLA-B27 is a helpful test, but not a confirmatory test as we know.

Imaging-wise, typically we like to order X-ray of the pelvis AP view, and if you want get more information, you could order x-ray of the pelvis, Ferguson view, and AP view. These are done to look for sacroiliitis, radiographic sacroiliitis, and in the right patient population. If the x-ray is inconclusive, you could go ahead and order MRI of the pelvis without contrast to look for sacroiliac joint inflammation and structural changes. Heart process, history-taking, and interpretation of the imaging and lab tests go into the diagnosis of axial SpA, but ultimately the diagnosis is based on the clinician's best judgment and not on one single test.

Don't miss part three of this podcast on diagnosing axial spondyloarthritis when Doctors Danve and Majithia will discuss some additional tools that are available to help confirm the diagnosis.