The Various Ways to Diagnose PTSD
Michael Roy, MD, Col. (Ret.) talks about the various means to diagnose PTSD from evaluations and checklists, which rely totally on a person's self-report, to functional MRI imaging and psychophysiological techniques.
[Dr. Michael Roy] For PTSD first of all, how do we diagnose PTSD? The sort of gold standard today is the clinician-administered PTSD scale or CAPS. It's a detailed interview. It's actually 17 pages long. So an experienced clinician—usually a psychologist or perhaps a social worker— who has been trained in administering this instrument, spends about an hour with the patient going through, asking them these questions over the course of an hour or so. We have more brief measures. I guess the briefest is a four-item questionnaire. The patient answers four questions. It's called the PC PTSD scale— I think it stands for primary care PTSD. If you're in a busy setting, and you just want to do something brief, you can ask these four questions. If they have two or more positive responses, it's probably the best correlation with having PTSD. In the military, we actually use that for everybody returning from combat. If you're deployed, you have to do the PC PTSD— those four questions. A kind of next step up from that, which we often use is called the PTSD checklist. This is a 17-item questionnaire. Again it's self-administered. It takes a minute or two for a patient to do that, as opposed to the hour or so with the clinician. It has a pretty good correlation with the CAPS. Now all of those rely on the report of the patient. So say they've had a TBI— they may not remember things as well, or there are a variety of reasons why somebody might not be completely truthful. Service members are afraid of stigma—that if they acknowledge symptoms of PTSD it might affect their promotion— it might affect their career assignments— things like that. So they might not tell you all their symptoms. So that's where—I think—we're moving into the arena where we're developing more confidence in truly objective measures— not just self-report. So one of those is the functional MRI— like I talked about—as I said— there are several areas of the brain where there are definitely reproducible differences in those who have PTSD versus those who don't— even if they've been exposed to the same sort of trauma. That's a potentially good way, but it's pretty expensive. A functional MRI costs upwards of a thousand dollars— so probably not practical for us to administer that to every service member when they return from deployment. Another measure that we've used is psychophysiology. So exposing somebody to stimuli— you probably are familiar with Pavlov's dog. Pavlov—more than a hundred years ago— he had a dog and he would basically present it with food, and he did these experiments where he would—say—ring a bell and the present the food. The dog would learn "Whenever I hear the bell, I'm going to get the food." So he would start to salivate just with hearing the bell. So we can do the same sort of thing. There's a lot of different ways to do that kind of experiment. The one that we use is we actually show some certain shapes and colors on a computer screen. So one pattern of shapes and colors will be followed by a loud noise. Then we hook up some tubes, and we have a tube hooked to an oxygen tank that provides a powerful puff of air right here—right at the front of the throat. That's not absolutely painful, but it's definitely uncomfortable. Anybody reacts to that puff of air at the front of the throat. So blood pressure tends to go up. Heart rate goes up. You sweat more. You blink your eyes faster and more. So we can measure all of those things—measure that response. Basically, the same thing— when they see this pattern of shapes and colors, they know this is going to happen. They start reacting to those shapes and colors on the screen even before they get that puff of air. If they see a different pattern of shapes and colors, they get the loud noise but not the puff of air. So we can look at this in people with PTSD and those who don't have PTSD. We see definite differences. Typically we get a greater reaction overall in those with PTSD. They sweat more. Their heart rate goes up more—things like that. We tend to even see a greater reaction when they get the safety cues— when they see those shapes and colors where they don't get the puff of air. It's almost like they're not really trusting what they're seeing. They're not trusting what's presented to them, and they react more to those. Where they learn the association between the shapes and colors and those different types of stimuli— that's what we call fear acquisition. They learn what they should be afraid of— what's going to be the danger cue, and what's the safety cue. Then we do—after that—we have a period where we call it fear inhibition. So we present them with a mix of shapes and colors. So they get one that's associated with a danger and one that's associated with a safety. So then there is uncertainty. We don't give them the puff of air then, but it's kind of confusing. Like, "Wait a minute—you told me one set —one set meant danger—one set meant safe— what does this stuff together mean? That mixes me up." We tend to see greater responses across the board in those who have PTSD— in that—what we call—fear inhibition phase. Then we do a fear extinction. Now we don't show them that confusing set of symbols again. We go back to the danger cues and the safety cues. But no matter what cue they get, there is no air blast. It's safe. We ask them—actually we have them right after they see the thing on the computer—the shapes—before they actually get the puff of air or just the noise—we ask them to press a button saying either they think it's going to be danger— they think they're going to get the air blast— or they think it's going to be safe or they're not sure. What we see is that those who have PTSD in that fear extinction phase— where there's nothing else— there are no more air blasts—no more danger— both those with and without PTSD will tell you cognitively it's okay now. I'm going to get safety. I'm not getting hit with that air blast anymore But physiologically, we see big differences. So those with PTSD—their heart rate goes up more. They sweat more. Their eyes are blinking more. So it's a really profound difference. This is—doing the physiology like that— it takes maybe an hour to do the whole experiment. So it takes some time, but maybe it costs more like a hundred dollars or hundred fifty or something, rather than a thousand for the scan.
Posted on BrainLine May 28, 2013.
Michael Roy, MD, Col. (Ret.) is professor of Medicine and director of the Division of Military Internal Medicine at Uniformed Services University and director of Recruitment for USU's Center for Neuroscience and Regenerative Medicine.
Produced by Victoria Tilney McDonough, Justin Rhodes, and Erica Queen, BrainLine.