Establishing a Diagnosis of Irritable Bowel Syndrome

A comprehensive review of an irritable bowel syndrome (IBS) diagnosis, including the various subtypes of disease.

Mark Pimentel, MD: Let’s shift gears to the diagnostic work-up. What do we need to do in these patients? How do we work them up? We really have to start with the diagnostic challenges. What’s the challenge for you, in your clinic, in terms of making the diagnosis of IBS [irritable bowel syndrome]? It’s a problem for our group because we’re all tertiary care. So everybody comes in with a stack of records like this. They’ve already had everything. So we’re not starting with the patient walking in the door on the first day. But there is a lot to be said, and Brennan could definitely chime in on this. The sooner you make a diagnosis from the time the patient walks in the door on day 1 to the diagnosis, the more money you save in health care. Plus, a patient’s quality of life improves, likely, because they feel as if they’ve been identified. So what’s the best approach for the clinician in the community?

Anthony J. Lembo, MD: I think what you said is absolutely right. Making the diagnosis, a diagnosis early, and confidently convincing yourself and convincing the patient that you have the correct diagnosis is essential. We know from previous studies that patients undergo multiple tests—sometimes unnecessary procedures, and even operations—to come to the diagnosis of IBS. And so we need to do a better job of getting that diagnosis earlier.

The concern is obviously the uncertainty that exists among the patient and the doctor. If you follow the criteria, and if you look for the alarm features that Brennan spoke about earlier, and you look at the chronicity of symptoms—oftentimes patients have had symptoms for quite some time—you could make a very confident diagnosis just by doing limited testing. We’ll talk about that in a few minutes. But I think that making that confident diagnosis and convincing the patient, and yourself, that they have IBS and that doing it early is the most essential thing.

Mark Pimentel, MD: Can you comment on the health economics of early diagnosis for disease?

Brennan Spiegel, MD: Sure. The diagnostic test we’re talking about can range from inexpensive, like a CBC [complete blood count], to quite expensive, like doing CT [computed tomography] scans, and colonoscopies, endoscopies, and even sphincter of Oddi manometries. It goes on and on and on. So at some point, you’ve got to sort of make the diagnosis and not keep paying out this promise that there’s another diagnosis. “If we just look hard enough and long enough, we’re going to find it.” And sometimes that’s true. I don’t want to say we should stop and be satisfied with a diagnosis of IBS if somebody is not feeling better or the treatments aren’t working.

But in the absence of alarm features, particularly if they’re under the age of 45 or 50 years for colon cancer screening, the use of all these procedures just adds to the bill. And it also undermines the diagnosis, to some degree. I think that’s maybe even a more important point. It takes away from this notion that you really do have a condition. Think about something like depression. I don’t need to do an MRI [magnetic resonance imaging] scan of the brain to diagnose depression. Psychiatrists aren’t ruling out 20 other things before they say somebody is depressed. They just say, “You meet these criteria, and you’re depressed.” And they’re OK with starting to manage it. So I think we can learn a little bit from that paradigm, but we have to be careful, too, not to miss things. Maybe we can discuss this a bit.

Mark Pimentel, MD: The Rome criteria identified the D, the mixed, and the C, and sort of transitioning from this to that, we already talked a little bit about the subcategories. But I think what drives some of this disappointment in my patients is maybe they were identified as IBS, they don’t have the red flags, but then the treatment doesn’t really work. In the patient’s mind, they say, “Well, that didn’t work. That didn’t work. Maybe the doctor is wrong. Maybe it’s not IBS. Maybe it’s something else. Maybe I need to do another colonoscopy.” How do we frame these different subcategories? And by subcategorizing, are we doing better in treatment? Can you reflect on that?

William D. Chey, MD: This really gets to the point that, at the current time, the best mechanism that we have to decide on how to work a patient up and how to choose treatment is by their symptoms. Unfortunately, we don’t have the degree of precision necessary to really be able to parse out patients on the basis of their underlying physiology. The best that we have right now is symptoms, which is reasonably good, but it’s certainly not perfect. I think that we would all agree that there are probably a number of different reasons why somebody might develop abdominal pain and diarrhea, or abdominal pain and constipation.

The good news is, as all of you have pointed out, if you meet criteria—the Rome criteria, for example—and you have no warning signs or alarm features, we can safely go down a path of minimizing diagnostic tests and choosing therapy. But it dooms us, to a certain degree, to response rates in the range of 40% to 50% because of that imprecision. The good news is, it’s not dangerous to do it that way, but I can totally understand why it would be frustrating for the patient and the doctor sometimes.

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