Think you have an iodine allergy? You may want to reconsider. [PODCAST]

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“Iodine-based contrast agents are widely used for CT and other X-ray studies. They light up blood vessels and enhance perfusing tissue. These agents are essential for diagnosing everything from clots, to tumor, to bleeding. Unfortunately, many patients do not get contrast studies they may benefit from, due to unnecessary confusion about allergies.

The most important step to avoiding confusion is to start calling contrast agents by their names, as you would do for any other drug, and to remove ‘iodine’ from your allergy vocabulary. Like antibiotics, there is more than one kind of contrast agent. Radiologists routinely dictate the name of the agent used in their study reports, so if a reaction occurs, the information is readily available. The problem comes when we do not distinguish one agent from another. Most patients with a prior reaction were never told the name of the drug they received, and they incorrectly assume that an allergy to one means allergy to all. Not so, just like with other classes of medications.”

Cullen Ruff is a radiologist and author of Looking Within: Understanding Ourselves through Human Imaging.

He shares his story and discusses his KevinMD article, “Think you have an iodine allergy? You may want to reconsider.”

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Hosted by Kevin Pho, MD, The Podcast by KevinMD shares the stories of the many who intersect with our health care system but are rarely heard from.

Transcript

Kevin Pho: Hi, and welcome to the show, where we share the stories of the many who intersect with our health care system but are rarely heard from. My name is Kevin Pho, founder and editor of KevinMD. Today on the show we have Cullen Ruff. He is a radiologist, and he wrote the KevinMD article “Think you have an iodine allergy? You may want to reconsider.” And he’s the author of the book Looking Within: Understanding Ourselves through Human Imaging. Cullen, welcome to the show.

Cullen Ruff: Thank you for having me, Kevin.

Kevin Pho: So we’ll get into your article and book in a little bit, but first off, can you share your story and your journey to where you are today?

Cullen Ruff: Sure. I am a radiologist. I’m in a private practice outside of Washington, D.C., in Northern Virginia, and I also have an adjunct position as an associate professor with the Virginia Commonwealth University school. We have medical students at our hospital, and so we’re involved in teaching them as well.

Kevin Pho: Excellent. So we’re talking the second week of December, and we’re on the cusp of another wave of the COVID-19 pandemic. Now, from a radiology standpoint, what are some radiological findings that you’re seeing that could teach us primary care clinicians what to look out for when we’re ordering a chest X-ray, for instance?

Cullen Ruff: There are. We’ve seen plenty, as most people have nationwide, unfortunately. There is a typical pattern that a lot of the people with the COVID-19 pneumonia do have, which is this sort of streaky, hazy infiltrate on the chest radiograph.

One thing that I have also noticed, and I don’t know if it’s been put in print so much, but we’ve noticed this, is that when people have comparisons, and it’s always a great idea to compare to old studies, the lung volumes do not seem quite so inflated when the people are sick, when they have comparisons that were taken previously when they were healthier. So for whatever reason, some of these people can’t seem to just take a breath. And then, of course, the CT scans that are prevalent on the web show that same type of ground-glass, hazy pneumonia.

Kevin Pho: Are there any specific radiologic findings that could portend a bad prognostic indicator going forward?

Cullen Ruff: That’s a good question. I mean, when we see CT, first of all, there are other complications. As you know, people have increased thrombosis, and we’ve seen pulmonary emboli, strokes, and different complications. But we are seeing people who get chronic lung scarring. It almost looks like the people with UIP, or idiopathic pulmonary fibrosis. It’s obviously different, but it’s quite rapid in its onset. I mean, within a couple months after the initial pneumonia, some of these people have really bad-looking lungs, as if they may need a transplant someday.

Kevin Pho: All right. So let’s transition now to your KevinMD article, “Think you have an iodine allergy? You may want to reconsider.” Now, for those who haven’t read that article, can you just walk my audience through it and maybe share the story of why you decided to write it?

Cullen Ruff: Absolutely. I found that there tends to be a lot of misunderstanding, and I hear the same questions over and over again from different care providers, students, and doctors in the emergency room when patients have a little bit of an ambiguous allergy history. And here’s what I mean. Of course, a small percentage of people can be allergic to the iodine-based contrast that we inject for CT and other X-ray studies. And that contrast is very useful because it will show everything from helping detect tumors to blood clots and active bleeding. So there are a lot of studies where you want to give it, depending on the situation.

Some people can be allergic to it, but the iodine-based contrast is a drug class. There are different kinds. The analogy I mentioned in the article was, if somebody’s allergic to penicillin, you would put that they’re allergic to penicillin in their records. You would never say that the person is allergic to antibiotics. It would definitely never occur to you to say, “Well, even though carbon is not really what they’re allergic to, it’s a component of penicillin, so why don’t we just say that they’re allergic to carbon?” That sounds crazy, and yet, unfortunately, that is exactly what has happened with the IV contrast.

Iodine itself is a mineral that we all need to live. It’s part of our thyroid hormone, which regulates cellular metabolism, and no one, by definition, can be allergic to that. In fact, it’s so important that we all have it that it’s put into our salt supply so that we don’t have the iodine deficiency goiters that were more common decades ago. Iodine therefore can’t be an allergen. It is a component of the different contrast agents, but the iodine itself is not what people are actually allergic to.

The problem comes when you use “iodine” as a slang, informal term, because people use it to mean at least three different and unrelated possible allergens. People can be allergic to iodine-based soap, which is totally unrelated to contrast. And for some reason I’ve never quite understood, some people use the term “iodine allergy” to refer to shellfish. Most food allergies are protein allergies, whether it be dairy or peanuts, or, in the case of shellfish, there’s a muscle protein called tropomyosin that’s believed to be the allergen. All of these are unrelated. So people can have an allergy to shellfish, and it has nothing to do with IV contrast.

And yet when people use this informal term, “iodine,” to refer to any of that, there’s a lot of confusion. And so sometimes people will not get the study that they need, or they may get a steroid prep to premedicate and lower their likelihood of having a reaction, which takes time to give, when maybe they don’t need to have that at all.

Kevin Pho: So one of the things that you wrote in your article is that people are very hesitant to remove allergies once they’re permanently embedded in a medical record. Now, let’s say you had a patient who was supposed to have some type of contrast study, and you saw that they had an allergy to iodine. Now, what’s normally your next step in terms of investigating whether this is a true allergy or not?

Cullen Ruff: Well, I’ll gladly answer that, but you’ve reminded me that if there’s anybody listening who’s involved in the structure of medical records, or electronics specifically, I would ask that you please remove the word “iodine” as an option under the allergy selections. It makes no more sense to say that someone’s allergic to iodine than it does to say they’re allergic to oxygen or carbon, and it really shouldn’t be a choice. If someone has that from a prior entry, then future visits could allow for a drop-down selection of what’s actually accurate, whether it be iodine-based soap, shellfish, or a contrast agent. And the most important thing to know is what specific agent they were allergic to.

So how do I go about that? I first just start asking the questions. And if you determine that someone did indeed have an injection of an iodine-based, iodinated contrast and they had an allergic reaction, you try to find out, one, do they know the name? There’s a study that I submitted or presented at a meeting this fall. The paper is still under review, so I won’t go into too much of the specifics, but the study that we did found that almost no patients with a bona fide allergy to an iodine-based contrast can tell you what they’re allergic to. They don’t know the name. There’s a miscommunication, or a lack of communication, between the technologists and the patient and the radiologist, and then the physicians taking care of them.

If you know when the reaction occurred, if it was before 1985 for sure, or before the early 1990s, it was probably the old stuff that is not typically used anymore. Because again, iodine-based contrast is not a single agent. It’s a class of drugs, and there were older agents that were more allergenic than the stuff we use now. But once somebody gets it in their head that they’re allergic to that stuff that they inject, you’re right, people are reticent to remove an allergy from the record. And so you have to ask these questions and then try to get the information as best as you can.

Kevin Pho: Now, people do have true contrast-related allergies when it comes to radiologic studies, is that correct?

Cullen Ruff: Absolutely. There are people who have genuine allergies. Most of the time it’s mild. They may have a rash or hives. Some people can get into trouble with breathing, and, uncommonly but seriously, people can have an anaphylactoid reaction. So it is a serious thing, and that’s why it’s important for people to know what they’re allergic to. And I try to encourage people, to make sure patients understand, to know this by name.

People used to carry cards around in their wallets. Now people can actually put this on their smartphones, so that if someone finds this down, without knowing the password to the phone, you can just swipe and find whom to call in the event of an emergency, and a brief medical history the person has entered onto their phone. It’s a really smart thing for people to do.

But when somebody presents, it’s important for us to know certain things more than others. We really want to know what medications somebody takes, if they’ve had cancer, if they’ve had surgery, and you want to know what somebody can’t take, i.e. what they’re allergic to. So yes, it is a potential allergy, but there are a lot of people who think they’re allergic, or who might think they might be allergic, when they’re really not.

Kevin Pho: Now, it’s been a while since I studied this, but can you briefly outline the basic contrast materials that are currently being used?

Cullen Ruff: Oh, I think there are other people who are more qualified than I am for that, but I’ll give you the basics. So if you’re talking about X-ray studies, or CT, which actually uses X-ray, but of course in a different technology, it’s iodine-based. It’s intravenous; it’s injected. That’s different than, say, if you’re having an MRI, which is gadolinium-based. That’s another point of confusion. If people happen to have an allergy to that, and that’s even less common, those are unrelated as well.

Kevin Pho: And you mentioned there are premedication protocols if we have to give contrast and there’s a supposed allergy to that contrast. Can you just outline typically what the protocol is if we had to do that?

Cullen Ruff: Yes. Some of the best references, one of them is the American College of Radiology Manual on Contrast Media. It’s available online, and there are plenty of other articles online. But what we typically do is we give several doses of prednisone, or prednisone-equivalent steroids, as well as Benadryl, so many hours in advance, to diminish the likelihood of having a reaction.

But the issue with knowing what you’re allergic to is this: If you know the specific drug, it’s actually more effective to just get a different contrast agent than what you had before. And it makes sense, right? If somebody’s allergic to penicillin, again, as an antibiotic, and you need another antibiotic in the future, what would you rather do? Would you rather take penicillin with steroids to diminish the likelihood of a reaction, or would you rather just take a different antibiotic that you’re probably less likely to react to? And that would be what we would do in radiology in an ideal world. If we knew what people were allergic to by name, then we could select a different agent.

Kevin Pho: Sure. So if I’m a patient and I’ve always thought I had an iodine allergy, or if I’m a primary care physician and I saw iodine allergy in the allergy sections of the EMR, what’s your bottom-line advice? What’s the next thing that we should do if we’re in that situation?

Cullen Ruff: The first question I have is, what does that mean to you? Because, again, the term “iodine allergy” is nonsensical, and it means different things to different people. So I would ask them, “Have you ever had a contrast injection?” If they say, “No, I’ve never had that,” well, then you automatically know that they’re not definitely allergic to contrast at all. So then you find out: Was it a topical iodine soap? Was it shellfish, or some food allergy that’s totally unrelated? And then you just try to get down to the specifics.

If they’ve had a contrast reaction, then you ask, what were the symptoms? Patients are good at remembering what symptoms they had if they had a reaction. But as our study that’s still under review found, they’re not as good at remembering where they had the test done or when it was done, which limits the ability to look up records and to determine if it was an older or a newer agent.

Kevin Pho: So if a patient had a reaction to, say, just topical iodine or iodine soap, they’re OK to proceed with the contrast?

Cullen Ruff: Yes, that’s unrelated.

Kevin Pho: OK, great. So we’re talking to Cullen Ruff. He is a radiologist, and he wrote the KevinMD article “Think you have an iodine allergy? You may want to reconsider.” Cullen, you’re also the author of the book Looking Within: Understanding Ourselves through Human Imaging. Can you briefly share with our audience a little bit about your book?

Cullen Ruff: Gladly. And I want to thank you again. You, on KevinMD, allowed me to have one of my first excerpts, a short chapter, posted after the book released earlier this year. There have been some wonderful books written by a lot of different physician authors, but to my knowledge, there had not been one looking at the human perspective by way of looking into our bodies. And so I wanted to just share some stories that I had accumulated over the years of patients who had had an imaging study where some discovery was made, and it really may have changed their life, or may have just opened everyone’s eyes to the wonders and the mystery of our bodies, and of life in general, by way of looking inside of ourselves.

Kevin Pho: And can you share a particularly poignant anecdote from the book?

Cullen Ruff: Oh, there are so many. I’ve got trauma, I’ve got tumors and stroke, of course, but not everything is ominous. One is the story about a woman who had simply never been imaged before. She had an ultrasound that thought her spleen was enlarged, and they had trouble finding her gallbladder, and so they recommended a CT scan as a workup. And it turns out she had a normal-sized set of spleens, more than one, but they were on the right side, not the left. What they thought was her enlarged spleen was her liver, on the left side, not the right. And they couldn’t find her gallbladder because they didn’t know where to look for it. It was also on the left side, not the right, where it’s typically seen. And she simply did not know, having made it into her 30s, that she had what’s called situs inversus, where she had a mirror image, of sorts, of her anatomy development.

And I thought it was just an interesting opportunity for us to all realize that we’re all different. There’s this mind-body-spirit connection that we all try to understand as we go through life, because we need our bodies to live the lives we live, and yet our personalities and our essence are not necessarily related to our body. And so I don’t mean to get too esoteric, because it’s not an overtly spiritual book, but there are things that we can all reflect on and just learn from other people’s experiences. I’ve got stories of what it’s like to diagnose child abuse for the first time, and other forms of domestic abuse, drug abuse, and criminal activity. There are a lot of different types of stories in there.

Kevin Pho: And what has the response to your book been?

Cullen Ruff: It’s been good so far. Now, I don’t expect this to be the next Da Vinci Code, but it has been doing well, especially for a book that unfortunately got launched right as the pandemic shutdown set in. So the live events that I was planning on doing all got canceled except for the very first two, and then everything screeched to a grinding halt. But fortunately, it’s been well received, and currently the e-book, the Kindle version, is an Amazon bestseller. So I’m very pleased with the support that I’ve gotten.

Kevin Pho: Great, and best wishes with that. Now, my final question, Cullen: What’s your take-home message that you want to leave with the KevinMD audience?

Cullen Ruff: Let’s get back to the subject of this contrast allergy. Remember the most important thing: Know your allergies by name. Call them by name. Don’t use slang terms like “iodine,” which mean different things to different people and really are nonsensical. And if you can’t determine what people are allergic to, just dig a little deeper. Try to get the old records, and try to use the proper terminology going forward to prevent these areas of confusion from happening and persisting.

Kevin Pho: Well, thank you so much for sharing your time and insight, and thanks again for being on the show.

Cullen Ruff: It was my pleasure. Thank you for having me.

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