Is 'Point of Care' Testing Worthwhile, or a Waste?


 
 

Howard Rodenberg, MD, MPH, Dip(FM) | | Tuesday, November 27, 2007


One of my favorite Saturday Night Live bits of all time is the sketch in which William Shatner tells a group of middle-aged, uniform-wearing, Spock-eared fans, "Get a life!" I don't think I'm alone in my generation in confessing a certain affection for Star Trek. My fascination with the show first surfaced in junior high school, with reruns of the original series; and although my interest was in abeyance during the "touchy-feely" reign of The Next Generation, Deep Space Nine and Voyager, it's now back with the advent of Enterprise. The common denominator between the original Star Trek and Enterprise is that while the "middle captains" (Picard, Sisko and Janeway) want to talk and think and diplomacize their way out of things, Captains Kirk and Archer have no problem blasting things out of the sky.

One innovation of the Starfleet Medical Corps was the tricorder, which allowed instant diagnostic testing of crew members affected by germs, or slimes, or plasma, or whatever was going to kill off a studio extra that week. We are approaching that era in prehospital care with the advent of "point-of-care" testing devices. Put simply, these handheld units allow paramedics to test a patient's blood for a variety of clinical parameters, both in the field and en route.

I had an opportunity to learn about many of these devices at a recent meeting and was quite impressed by the technology. Point-of-care testing can now be performed on hemoglobin and electrolytes. Cardiac markers, such as CPK-MB, tropoinin and myoglobin, may be assayed, and point-of-care screens for a wide spectrum of toxicologic agents, including methamphetamine, benzodiazepines, cocaine, opiates, PCP and cannaboids may be performed. B-type natriuretic peptide, a new marker for heart failure, may also be detected. In most cases, results are available in 15 minutes. Point-of-care testing is marketed as a way to speed up ED times by decreasing the turnaround times for laboratory work. But do these devices have utility in the EMS setting?

As with many prehospital issues, point-of-care testing is not an issue of what we can do, but what we should do. There is no question that current technology allows us to quickly uncover a lot of information. The question becomes one of efficacy. Will point-of-care testing help us take better care of our patients in the field?

To evaluate this question, we need to look at our reasons for doing a clinical test. Presumably we do so to acquire useful information. It's crucial to note that there's a difference between information and useful information. We are surrounded by billions of bits of data, but very few of these play a key role in our daily thoughts. I'm reminded of the line from the BBC comedy Blackadder, in which the lead character notes that he's perfectly happy to wear clothing, but has very little interest in where it came from. So while point-of-care testing might give us information, the real issue becomes the utility of that data.

I would contend that with some exceptions, the utility of the data available through current point-of-care testing is somewhat negligible in prehospital care. My reason for this statement is the nature of prehospital care itself. EMS is not focused on diagnosis, but on assessment. These two functions differ in a critical way. Diagnosis is the establishment of the root cause of the patient's problem, which leads to a focused, narrow intervention. Assessment determines the patient's status at a given moment in time, and directs broad interventions to return the patient to a stable condition.

With these operative definitions, it becomes fairly clear that point-of-care testing does not really help us in our assessment process. A hemoglobin value does not help us to identify hemorrhagic shock in the trauma victim or the patient with a GI bleed. A cardiac marker does not help us determine that the patient's pain may be reflective of angina, and a positive drug screen may not necessarily reflect the cause of a patient's altered level of conciousness. These values do not aid us in determining the stability of the patient, nor do they determine which patients require aggressive prehospital interventions. As always, a complete assessment, with special attention to the patient's history, exam and vital signs, leads the way to correct care.

Let me give you an example to demonstrate the point. You arrive on scene to find an unconscious 16-year-old male with a GCS of 6. He has a laceration on his scalp, and there are some beer cans nearby. This is an easy case: He gets intubated, oxygenated and transported to the nearest trauma center. Even a point-of-care drug screen that is positive for opiates and benzodiazepines won't change this patient's care. (We've discussed my feelings about naloxone and flumazenil in earlier columns.)

Let's take a more complex situation. Your service is doing point-of-care testing for cardiac markers, such as troponin and CK-MB (for the record, elevated levels of troponin are associated with myocardial ischemia, while CK-MB is released with the tissue damage of infarction). You also do ECG testing to look for signs of acute MI. Just to make it fun, we'll even say you have the ability to given thrombolytic therapy en route.

You are called to respond to a 72-year-old male complaining of chest pains. The 12-lead ECG is negative, so there are no indications for lysis. You place the patient on oxygen, administer an aspirin, spray some nitro under his tongue and give him two milligrams of morphine. Point-of-care testing for troponin and CK-MB are both positive. However, even with this result your care does not change. You continue your anti-anginal therapy and transport the patient to your facility of choice.

I've chosen this kind of case for a reason. Even though we can demonstrate no immediate advantage to point-of-care testing, do the positive cardiac markers mean anything to EMS at all? The answer is maybe, and it does hint at a use of point-of-care testing to determine optimal patient destinations. If we accept that patients with positive cardiac markers may have significant myocardial disease, perhaps these patients need to be routed to a specific cardiac center (that's a separate "hot item" discussion for another time). So although point-of-care testing in it's current incarnation probably has minimal therapeutic value in the field, it may have significant value as a triage tool for transport to specialty centers.

The one caveat one must keep in mind is the difference between urban and rural systems. With longer transport times, point-of-care testing may be more relevant in the latter regions. I would still contend that the impact of real-time clinical care would be minimal, but the longer transport times in rural settings do allow sufficient time for the results to be obtained without prolonging EMS times. This, in turn, may expedite the patient's ED time.

Point-of-care testing may hold traps for EMS crews. The availability of testing may lead to an over-reliance on test results to initiate clinical decisions. Waiting for a test result to confirm the need for action may prolong on-scene or transport times, and place the patient at risk from paramedic inactivity while waiting for the results. Similarly, once a test has been started it must be finished, so patient drop-off times in the ED may be extended in systems with very short transport times. On a more theoretical bent, I think that an emphasis on medical testing promotes an intellectual sloppiness. Given that in EMS, the fine gradations between disease states are often of less import than the need to maintain the patient's vital functions, extensive prehospital testing may not promote a correct mindset for paramedics and EMTs.

Point-of-care testing must be taken for what it is. It is not a tool that provides magical insights into patient status, nor can it be the premier guide to clinical care. Its real value is in decreasing patient care times in the ED, and it may have service as a triage tool. To the extent that point-of-care testing as performed by EMS crews may accelerate the entire patient care process, the use of this technology should be encouraged. I would not expect it to significantly change EMS practice, protocol, or patient care. Excellence in patient assessment, rather than in diagnostic testing, is still the key to EMS care.


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