Tuesday, November 29, 2011

Ankylosing Spondylitis – overcoming myths

Yesterday we have been talking about inflammatory back pain, now we want to come to a diagnosis. Classificatory criteria may lead to the diagnosis, but these criteria weren’t put together to serve this purpose.
To come to a diagnosis you will need a couple of pieces to put together in the diagnostic puzzle. You already have inflammatory back pain and some features of spondyloarthropathies like dactylitis, enthesitis, psoriatic lesions, arthritis, Crohn’s, acute anterior uveitis, positive family history, inflammatory bowel disease, and good response to NSAIDs. Much depends now on how experienced you are making a diagnosis axial spondylitis or ankylosing spondylitis, to name two. With three features out of the ASAS set you already come to definte axial arthritis. If you are experienced, you have some options on how to continue. You don’t have MRI at hand but X-ray. X-ray changes take long to develop, but if you find typical changes of the iliosacral joints, you are very close to the diagnosis of ankylosing spondylitis, though you have been contacted too late. You need a clinical exam of the patient to make sure that function is impaired (metrology). If you come earlier into play and/or if X-ray are inconclusive or negative, you go on with HLA B27. If it’s positive you might come to the conclusion that you patient suffers from probable axial spondyloarthritis. If you didn’t find any of the features of spondyloarthropathies, but the patient tested positive for HLA B27, you need to get an MRI to reach the diagnosis of definite axial spondyloarthritis.
As you might imagine there are still lots of white areas on this map. Space , which later will be occupied by other gene predispositions and so on.
What of physicians, not being experienced in the field of spondyloarthropathies? Should we train the GPs or orthopedic colleagues to be able to make the diagnosis? If you you think that this would be feasible, well then we have created a new myth. No they don’t have to make a diagnosis, but we have to empower them to know the red flags, when to send someone to a rheumatologist. They have to screen low back pain patients for inflammatory back bain and send these patients for further diagnostic procedures. They could even leave the expensive HLA B27 test to the rheumatologist.
Read more in: M Rudwaleit, D van der Heijde, M A Khan, J Braun, J Sieper: How to diagnose axial spondyloarthritis early. Ann Rheum Dis 2004;63:535–543. doi: 10.1136/ard.2003.011247

To be continued …

1 comment:

  1. Great Article, Dr. Kirsh.

    If the GPs are trained to differentiate between routine low backache & inflammatory backache (the red flags); it would help a lot of patients have an early diagnosis.

    The flowchart in the article you mentioned gives a good snapshot of the diagnostic algorithm (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1754994/figure/F1/).

    The most important fact the GPs & the Orthos need to be told is to avoid basing their diagnosis on HLA-B27 report alone.