Radiology – Page 7 – Emergency Medicine Literature of Note

Shared Decision-Making to Reduce Overtesting

Medicine, like life, is full of uncertainty. Every action or inaction has costs and consequences, both anticipated and unintended. Permeating through medical culture for many reasons, with the proliferation of tests available, has been a decreased tolerance for this uncertainty and the rise of “zero-miss” medicine. However, there are some tests that carry with them enough cost and risk, the population harms of the test outweigh the harms of the missed diagnoses. CTPA for pulmonary embolism is one of those tests.

In this study, these authors attempt to reduce testing for pulmonary embolism by creating a shared decision-making framework to discuss the necessity of testing with patients. They prospectively enrolled 203 patients presenting to the Emergency Department with dyspnea and, independent of their actual medical evaluation, attempted to ascertain their hypothetical actions were they to be evaluated for PE. Specifically, they were interested in the “low clinical probability” population whose d-Dimer was elevated above the abnormal threshold – but still below twice-normal the threshold. For these “borderline” abnormal d-Dimers, the authors created a visual decision tool describing their estimate of the benefit and risk of undergoing CTPA given this specific clinical scenario.

After viewing the benefits and risks of CTPA, 36% of patients in this study stated they would hypothetically decline testing for PE. Most of the patients (85%) who planned to follow-through with the CTPA did so because they were concerned regarding a possible missed diagnosis of PE, while the remaining hoped the CT would at least also provide additional information regarding their actual diagnosis. The authors conclude, based on a base case of 2.6 million possible PE evaluations annually, this strategy might save 100,000 CTPAs.

I think the approach these authors promote is generally on the right track. The challenge, however, is the data used to discuss risks with patients. From their information graphics, the risks of CTPA – cancer, IV contrast reaction, kidney injury and false positives – are all fair to include, but can be argued greatly regarding their clinical relevance. Is a transient 25% increase in serum creatinine in a young, healthy person clinically significant? Is it the same as a cancer diagnosis? Is it enough to mention there are false-positives from the CTPA without mentioning the risk of having a severe bleeding event from anticoagulation? Then, in their risk of not having the CTPA information graphic, they devote the bulk of that risk to a 15% chance of the CT identifying a diagnosis that would have otherwise been missed. I think that significantly overstates the number of additional, clinically important findings requiring urgent treatment that might be identified. Finally, the risks presented are for the “average” patient – and may be entirely inaccurate across the heterogenous population presenting for dyspnea.

But, any quibbles over the information graphic, limitations, and magnitude of effect are outweighed by the importance of advancing this approach in our practice. Paternalism is dead, and new tools for communicating with patients will be critical to the future of medicine.

“Patient preferences for testing for pulmonary embolism in the ED using a shared decision-making model”
http://www.ncbi.nlm.nih.gov/pubmed/24370071

The Latest Myth: Contrast-Induced Nephropathy?

Here’s the simple explanation for why none of our observed treatments to prevent contrast-induced nephropathy – acetylcysteine, hydration, sodium bicarbonate – reliably work: CIN is a myth.

There’s a lot of observational literature evaluating the incidence of mild acute-kidney injury after iodinated contrast exposure – either CT scans or vascular procedures – and every study shows some increase in serum creatinine in a small, but significant, proportion of patients. But, as this study suggests, is this just random effects, a confounder from co-occurring medical illness, or true dose-dependent renal injury?

This study, although retrospective, is almost precisely how I would have addressed the question. This is a single-center review of ten years of patients receiving CT scans. There were 116,694 contrast-enhanced scans and 40,446 non-contrast scans for whom before-and-after serum creatinine values were available. These CT scan events were compared by both risk-stratification as well as propensity score-matched subsets, as well as a counterfactual set of patients who had both independent contrast-enhanced and non-contrast CTs in their records. With every adjusted and unadjusted analysis, regardless of baseline renal insufficiency, there was no evidence of an excess of CIN following the contrast-enhanced events.

This is retrospective, so it’s hard to say whether there are undetected confounders – other comorbid illnesses, diagnosis disparities – that influenced these results despite the large numbers analyzed. However, it is absolutely reasonable to move forward with a prospective study design based on the hypothesis that intravenous contrast-enhanced CT scans do not increase risk of AKI. These results are not yet generalizable, however, to other interventional procedures in which higher volumes of contrast might be used.

This article was also covered by James Roberts in Emergency Medical News.

Addendum: Joel Topf argues this and related work is junk science at Precious Bodily Fluids.

“Intravenous Contrast Material-induced Nephropathy: Casual or Coincident Phenomenon”
http://www.ncbi.nlm.nih.gov/pubmed/23360742

Unlocking the Secrets of Atherosclerotic Plaques

In general, the best way to determine the cause of death is autopsy. Most of our patients, however, aren’t willing to undergo this procedure in order to guide preventative care. Thus, we are left using imprecise predictive instruments to prognosticate and prevent untimely demise.

In the cardiovascular sciences, a large part of what we do is salvage – catheterization, stenting, and cardiovascular care units to minimize myocardial injury after infarction. These authors, however, believe they’ve identified a new paradigm in cardiovascular imaging: identification of individual high-risk atherosclerotic plaques.

In this observational cross-sectional study, the authors enrolled 40 patients immediately following myocardial infarction and 40 patients with known stable angina. All patients underwent combined PET and CT with radioactive tracers. In 37/40 post-MI patients, the culprit lesion had significantly higher radioactive uptake compared with all non-culprit lesions. Extending this observation to the 40 patients with stable angina, 18/40 had lesions associated with similar radioactive tracer uptake compared to background. Patients with these lesions underwent intravascular ultrasound, which confirmed high-risk features such as remodeling, microcalcifications, and necrotic cores.

This is light-years away from being validated, and then being further translated into routine care – but it is quite fascinating work. We’ve bemoaned the limitations of our non-invasive imaging, based on our inability to characterize lesion histology or adequacy of tissue perfusion from varying levels of stenosis, and this is a promising step for guiding management of a subset of high-risk patients.

“18F-fluoride positron emission tomography for identification of ruptured and high-risk coronary atherosclerotic plaques: a prospective clinical trial”
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(13)61754-7/abstract

Gorging Ourselves to Death on Healthcare

This Harvard Business School paper highlights the nonsensical nature of the United States healthcare system – every advance promises one step forward, yet inevitably results two steps backward.

This is a piece of observational operations research regarding radiology turnaround times. If you’re involved in your ED’s throughput initiatives in any fashion, I am certain this has been a recurring issue. Most conversations probably take the form “If only radiology were faster, patients would flow through the department like quicksilver.” So, what happened in a 100,000-visit academic ED and a 60,000-visit community ED when, through process improvement, an “inefficient” gatekeeping step was eliminated?

Initially, at the hospitals observed, ultrasounds were available only by radiologist approval after 5pm on weekdays and on weekends. Scans could be performed as needed from a technician on-call, but this inconvenient step alone added 10-15 minutes to the radiology turnaround time for these patients. After these hospitals added 24/7 technician coverage and eliminated the approval step, two things happened: length of stay for patients receiving an ultrasound on nights and weekends decreased (huzzah), and the number of ultrasounds ordered increased by 11.5% (oh hmm).

Unsurprisingly, as the number of patients receiving ultrasounds increased, the overall average LOS for a patient with an abdominal complaint went up by 26 minutes. And, with the extra ultrasounds for the radiologists to read, turnaround times for non-ultrasound radiology results were increased by 30 minutes. Furthermore, CT use in those same time windows also increased by 4.5%, while general CT use in both departments decreased by 10%. The authors hypothesize incidental findings on ultrasound were prompting subsequent CT use to follow-up suspicious reads, leading to even greater resource utilization. As you would expect, this congestion extended out to the waiting room, with a predicted increase in time-to-room as well.

So – more tests, more costs, longer waits – no detectable effect on outcomes.

‘Merica.

“Increased Speed Equals Increased Wait: The Impact of a Reduction in Emergency Department Ultrasound Order Processing Time”
http://hbswk.hbs.edu/item/7310.html

Watch & Wait For Stab Wounds

Thankfully, very few of us actually deal with these sorts of injuries on a regular basis – and even fewer of us are actually responsible for managing these injuries.

However, this is an important article out of USC pushing back against the trend towards utilizing CT for every traumatic injury possible. There certainly seems, universally in medicine, to be a regression in reliance on the clinical examination along with a corresponding increased use of technology. There are many reasons this occurs – convenience, patient satisfaction, and “zero-miss” mentality – and we’re just now fully accounting for the tremendous costs associated with this flawed evolution in practice.

In this study, all diagnostically equivocal abdominal stab wounds underwent a structured protocol including CT and observation. Over a two-year period, 177 stable patients qualified for this protocol. Overall, 87% were managed non-operatively – but, most importantly, clinical deterioration directed all necessary operative interventions, rather than CT findings. Of the 23 patients who underwent operative intervention, 4 patients underwent operative intervention based solely on CT findings – and all four detected no injury during exploration. The final test characteristics for CT were sensitivity of 31.3% and specificity of 84.2%.

I think these authors are entirely appropriate in describing the use of CT in abdominal stab wounds as inferior to clinical observation. They don’t specifically emphasize the false positives from CT in their discussion, but these findings lead to real patient harms – even just in their small cohort. One of the four CT-directed interventions underwent negative pericardial window for suspected hemopericardium – and suffered a peri-operative cardiac arrest due to complications from anesthesia.

Let’s try to avoid that.

“Prospective Evaluation of the Role of Computed Tomography in the Assessment of Abdominal Stab Wounds”
http://www.ncbi.nlm.nih.gov/pubmed/23824102

CTCA Is Better Than Wishing & Hoping

CT coronary angiograms have infiltrated the Emergency Department, with trials such as ACRIN-PA, CT-STAT, and ROMICAT II demonstrating their utility – primarily sensitivity – for the rapid detection of coronary artery disease. It comes as a surprise to no one that an angiogram demonstrating a total absence of coronary artery disease confers an excellent short-term prognosis. The downside, of course, is cost, contrast, radiation, and the suggestion that low-risk patients might be harmed by additional, unnecessary testing. However, enthusiasm for the procedure abounds.

This is an observational study from Thomas Jefferson University looking at consecutive Emergency Department patients referred for CTCA, prospectively collecting variables to calculate TIMI and GRACE risk scores. No clearly defined primary outcome is provided, but it seems these authors aimed to demonstrate that CTCA would correctly detect severe coronary disease (>70% stenosis) and better prognosticate adverse outcomes than the TIMI and GRACE risk scores. They enrolled 250 patients, lost 29 to follow-up, and reported six adverse cardiovascular events within 30 days – 2 MIs, 2 ACS, and 2 revascularizations. All six were TIMI 1 or 2, had relatively middling GRACE scores, and had extensive CAD detected on CTCA. Overall, 17 patients had significant CAD (>50% stenosis) detected, and increasing TIMI and GRACE scores did not correlate with its presence or absence. Therefore, these authors feel CTCA is an appropriate diagnostic study and is superior to clinical assessment and risk scores. They even go so far as to disparage Rita Redberg’s editorial in the New England Journal of Medicine that questioned whether any cardiovascular imaging was indicated before low- and intermediate-risk chest pain patients left the Emergency Department.

They seem, unfortunately, to turn a blind eye to their inability to appropriately select patients for imaging, with only a 6.8% yield for significant stenosis, fewer than half of whom even progressed to a cardiac outcome. I also take issue with the 2 patients they classified as ACS – they didn’t receive revascularization and didn’t have an MI – so what were they? Either way, we’re looking at great expense in a cohort with only 1.4-2.4% incidence of positive cardiac outcome within 30 days. Additionally, the comparison to TIMI and GRACE is a straw-man comparison to instruments proven to have poor predictive value in Emergency Department populations.

This is simply another trip down the quixotic zero-miss path to destruction, even going so far as to fearmonger with liability claim cost statistics. Rather, it’s clear we’re simply doing a terrible job searching for the needle in the haystack – and the vast majority of these patients are safe for appropriate follow-up after initial Emergency Department assessment. Rather than use this article to justify admission for CCTA, I would present this data to your patients in the context of shared decision-making and educate them regarding the high costs, abysmal yield, and poor specificity of the test used in this context.

“Cardiac risk factors and risk scores vs cardiac computed tomography angiography: a prospective cohort study for triage of ED patients with acute chest pain”
http://www.ncbi.nlm.nih.gov/pubmed/24035047

Local Variation in CT Use

Tell me if this sounds like your department – some folks, every time you receive sign-out, the radiologist has billed for a new BMW. Other times, there’s an uncomfortable disuse of CT, even in the ticking time bombs of the elderly. We all have that anecdotal feel for the variation in practice, and these authors have gone ahead and quantified it.

This is a descriptive, observational study of a single-center in Virginia evaluating individual physician CT scan use. Overall, the department performed CT scans on 23.8% of the nearly 200,000 patient visits during the study period. Across the 49 Emergency Physicians tracked during the study period – yes, the variation is exactly as one would expect. The most frequent utilizers ordered CTs on nearly one third of patients, while the least frequent users only 1 in 8.

There are a couple individually coded information graphics embedded in the paper that demonstrate some extremely striking variation. For example, as coded by chief complaint – a few physicians ordered CT scans on >60% of headache patients, while an even greater number ordered zero. 60% vs. zero! While some practice variation is obviously acceptable in evolving practice and heterogenous patient substrate, this clearly reflects some element of underlying low-quality care.

As poorly implemented as they may be, the conception behind prior quality measures for CT use certainly has merit. Quality measures aimed at increasing testing yield – ideally coupled with liability protections for Emergency Physicians – are likely to have increasing roles moving forward.

“Variation in use of all types of computed tomography by emergency physicians”
http://www.ncbi.nlm.nih.gov/pubmed/23998807

“Distracting”, But Not Distracting

Cervical spine clearance is always a fun topic. Once upon a time, it was plain radiography, clinical re-assessment, and functional testing with dynamic radiography. Now, a zero miss culture has turned us mostly to CT – and, beyond that, even some advocate for MRI.

But, as far as clinical clearance of the cervical spine goes, we usually use the NEXUS criteria or the Canadian C-Spine criteria. One of the elements of the NEXUS criteria that is, essentially, subjectively defined is the presence of “distracting injury”. Many have questioned the inclusion of this element.

These authors looked at cervical spine clearance in the presence of “distracting injury”, which, for the purpose of research protocols, was essentially a fracture somewhere, an intracranial injury, or an intra-abdominal organ injury. They found, when assessing a GCS 14 or 15 trauma patient, even in the presence of these other injuries, clinical examination picked up 85 of 86 cervical spine injuries. One patient did not report midline cervical spine tenderness – with humerus and mandible fractures, as well as frontal ICH – and had a 2nd vertebrae lateral mass fracture.

So, clinical examination is mostly reliable in the presence of a “distracting injury”. I think the best interpretation of this study is “distracting injury” has to be determined on a case-by-case basis – one patient might be a reliable reporter in the presence of long-bone fracture, while another might need such a high level of pain control for initial management they are no longer aware of their cervical spine injury. It’s fairly clear it is reasonable to remove the cervical collar and forgo imaging for most patients who can be adequately clinically assessed.

“Clinical clearance of the cervical spine in patients with distracting injuries: It is time to dispel the myth”
http://www.ncbi.nlm.nih.gov/pubmed/23019677

“NEXUS Chest” Decision Instrument

Low-yield radiography in the setting of trauma is pervasive and costly, but, unfortunately guidance regarding appropriateness is poor. The NEXUS group previously derived a chest imaging decision instrument, and this newly published article describes the validation study.

The good: 98.8% (CI 98.1-99.3%) sensitivity for any thoracic injury on imaging, and 99.7% (CI 98.2-100%) sensitivity for injuries of major clinical significance.

The really, really bad: 13.3% (CI 12.6-14.1%) specificity for thoracic injury or 12.0% (11.3-12.6%) specificity for major significance.

And, these numbers are probably subject to some limitations, considering about half the patients only received chest x-ray, rather than chest CT. That said, the injuries missed by x-ray are not likely of major clinical significance – and the patients selected for x-ray alone in the run of standard practice were likely selected for a low pretest probability of serious injury, regardless.

The authors suggest their instrument, despite it’s terrible specificity, still represents a valuable rule-out option, theorizing that even the small reduction in imaging this rule represents is beneficial. However, as we’ve covered before, one-way decision instruments are subject to cognitive bias and use as two-way rules, which may paradoxically increase imaging – although, in trauma, it’s hard to imagine a way to order more. Careful adoption of this instrument will be required – perhaps only after clinical evaluation as a screening decision-support question in the CPOE, asking one last time if the patient possibly meets this very-low-risk criteria prior to ordering.

The exclusion from very-low-risk criteria, by the by:

Older than 60 years
Rapid deceleration mechanism (fall >20 ft, MVC >40mph)
Chest pain
Intoxication
Abnormal mental status
Distracting painful injury
Tenderness to chest wall palpation

“NEXUS Chest – Validation of a Decision Instrument for Selective Chest Imaging in Blunt Trauma”
http://www.ncbi.nlm.nih.gov/pubmed/23925583

Observation of Minor TBI Prevents Harms

This study regarding the observation of children following minor traumatic brain injury is a little bit oddly spun by its authors and the medical news.

As we all know, most children presenting to the Emergency Department for minor head trauma do not have a clinically significant injury. Regardless, a significant portion of these children receive non-therapeutic cranial radiation to further assure parents and clinicians alike. The PECARN group, a few years back, published a rough decision instrument to help classify ~50% of these patients as “very low risk” (<0.05% risk of TBI) to give clinicians a tool to obviate CT scanning.

This group at Boston Children’s prospectively evaluated clinicians’ use of immediate CT scanning versus delayed CT scanning (observation). They find, of course, that observing children in the ED for a short period, rather than making an immediate decision regarding CT use, resulted in decreased use of CT. Thusly, the press releases state “Waiting and Watching Can Reduce Use of Brain Scans for Kids in the Emergency Department“.

But, watching and waiting doesn’t benefit the children in this cohort – other than preventing avoidable harms. The eight children who had CT scans showing clinically important injuries were easily identified by clinicians as requiring immediate CT. The period of observation doesn’t change the short-term clinical outcome of any of the patients – it only “treats” the risk-aversion of clinicians and parents. “Watching and waiting” may reduce scans – but discharging the entire observation cohort immediately would have reduced scans even further, without missed cTBI (although the study is underpowered to truly detect all events down to an appropriate “zero-miss” threshold).

While I agree this is an important clinical problem to address, I simply find an odd discordance between the patient-oriented features and the resource utilization-oriented outcome measured.

“Effect of the Duration of Emergency Department Observation on Computed Tomography Use in Children With Minor Blunt Head Trauma”
www.ncbi.nlm.nih.gov/pubmed/23910481