Diagnosis of nr-AxSpA: X-Ray Imaging

Transcript: Sergio Schwartzman, MD: Do you think that if you suspect nonradiographic axial spondyloarthritis that every patient should have x-rays first?

Atul Deodhar, MD, MRCP: Yes. X-rays are cheaper. X-rays would give you some of the ideas and, strangely, CT [computed tomography] scans are better than MRI [magnetic resonance imaging]. But x-rays can show changes in erosions. To get into a little more detail, the cortical bone on the MRI scan is black, and the joint space is also black, and both on the T1- and T2-weighted images are black. The edge of the bone can be a little difficult to find. But I would definitely do the plain x-ray in patients who see me.

It might change. The low-dose CT scan is being touted as 1 of the things to come, and we might just bypass the x-ray and straightaway go to the low-dose CT scan. I don’t think we are there yet. Just like with the MRI, we don’t know false positivity of the low-dose CT. When the MRIs came and we started jumping on that if there is bone marrow edema, that has to be inflammation. Then we ran into the trouble. We discovered that there are other reasons why one can have bone marrow edema.

We do not know the specificity of low-dose CT yet. In 2020, we do an x-ray, and then we will go to MRI scan if the x-rays are not very definitive for the diagnosis of nonradiographic axial spondyloarthritis.

Sergio Schwartzman, MD: Philip, any comments on that?

Philip J. Mease, MD: We do x-rays because insurance companies require that we do an x-ray before they will approve an MRI. We say to the patient that we’re most likely not going to find anything on the plain x-ray, but we’re doing it because we have to. I actually think it’s worthwhile to have somewhere in the patient’s history that we’ve done an x-ray, just for classification purposes if nothing else.

It’s very quick and easy to do. We do a single shot, a single view of the pelvis. We don’t do all the angle views because that requires too much radiation. I also find myself most often wanting to have an MRI scan as well partly because it gives different information from the x-ray. Even if I have a patient with flagrant changes on their sacroiliac joints, I often find myself desiring an MRI just to look at activity, the degree of light up. It’s always possible that the patient has had damage on their SI [sacroiliac] joints but may not have a lot of active inflammation on current MRI. We end up usually doing both but explaining to the patient that, most likely, the x-ray will be normal.

Atul Deodhar, MD, MRCP: Sergio, I just want to jump in here quickly. Our musculoskeletal radiologists definitely want an x-ray. It’s not just the insurance company. I think the plain x-ray of the sacroiliac joint is comparable to gold. I would go to that extent. One has to have x-ray. The MRI does not tell you everything you want to know. We go back and forth between the x-ray, MRI, and the T1-weighted image and speculate, “What does the x-ray show? This is being shown on the T1 image. Let’s go back to the x-ray.” X-ray is still pretty important. X-ray and MRI complement each other.

Sergio Schwartzman, MD: I agree with you, Atul and Philip, in terms of having it as a baseline. But the reason I raised the question was 2-fold. The first is, if your suspicion is that the patient has nonradiographic axial spondyloarthritis, by definition that’s not going to be a likely finding on an x-ray that you do. That was 1 reason I raised the question. The other reason I raised the question is the CT scan. The CT is great for erosions and structural damage. That’s the strength. I was raising that point supportive of what you said, Atul—that ultimately, once we know a little more about it, that it may replace the x-rays.

Atul Deodhar, MD, MRCP: Let me challenge you a little. What is my clinical suspicion that this person has nonradiographic axial spondyloarthritis versus ankylosing spondylitis [AS]? The idea of nonradiographic axial spondyloarthritis is based on x-ray. There is no difference clinically. I’ve seen somebody who has inflammatory back pain, uveitis, and has got peripheral arthritis. Perhaps I know only the HLA-B27. If I don’t have the x-ray, my diagnosis is this person has axial spondyloarthritis. Nonradiographic axial spondyloarthritis and clinical suspicion of ankylosing spondylitis is not especially different. By definition, the x-ray differentiates nonradiographic axial spondyloarthritis and AS.

Sergio Schwartzman, MD: I think you’re correct in terms of classification criteria. But where I would challenge you is for someone who’s had 6 months to a year of symptoms and someone who has had that short period of time. Would I predict that I would see something on the x-ray? The answer is that it is unlikely, but that’s the only reason.

Atul Deodhar, MD, MRCP: We find patients who have got fused spine, and they said they don’t have backache. If I’m suspecting it, the x-ray will tell me whether there is a AS or not. Several times, I will be surprised as to, “Wow, they already have this condition.” I recently saw a patient who was a young lady of Indian descent who was a doctor here at my university. Within 6 months of her getting what was thought to be reactive arthritis, which she caught after getting a diarrheal illness when she visited India, she actually has classic changes of ankylosing spondylitis.

Sergio Schwartzman, MD: But that’s the exception rather than the rule.

Atul Deodhar, MD, MRCP: Sure, I agree with you.

Transcript Edited for Clarity