Draft Manuscrpt - Society for Academic Emergency Medicine

Group 6: Comparative Effectiveness Research: Alternatives to Traditional CT Use
Background
Diagnostic imaging has been described as one of the top ten most important medical
developments in the last millennium (ref). Computed tomography (CT) has emerged as the
most utilized imaging test for many common emergency department (ED) complaints (ref),
as it can provide rapid and accurate diagnosis of many conditions.
However, the diagnostic value of CT has not always been accompanied by
measurable improvements in patient outcomes. (ref) The advantages of this powerful
diagnostic technique are tempered by cost, time considerations, and risks associated with
radiation exposure, contrast media reactions, and the discovery of incidental findings
leading to unnecessary further workup. There is concern that the risks of CT overutilization
may outweigh the benefits in some cases, or that other approaches may be equivalent or
better in specific clinical scenarios. Utilization of CT by Medicare patients in the US
increased at a compounding annual growth rate of 7.8% from 2000 to 2009. In 2010, 155
out of 1,000 fee-for-service Medicare beneficiaries received a CT in the ED.1
Reimbursement for “advanced diagnostic imaging” represents one of the highest areas of
growth in medical spending in the last two decades.2
Comparative effectiveness research is "designed to inform health-care decisions by
providing evidence on the effectiveness, benefits, and harms of different treatment
options".3 The 2015 Academic Emergency Medicine Consensus Conference, “Diagnostic
Imaging in the Emergency Department: A Research Agenda to Optimize Utilization,”
developed six groups to examine the various facets of emergency imaging. This group was
tasked with prioritizing research questions surrounding the comparative effectiveness of
alternatives to "traditional” CT use in the ED.
Methods
Beginning in the summer of 2014, a group of stakeholder experts comprised of emergency
physicians, radiologists, physicists and an industry expert was convened. A list of research
questions was solicited from group members and combined to avoid overlap. After
discussion, each question was rated using a 7-point Likert scale (with seven being the
highest for each domain) on areas of importance, feasibility, and relevance to the group.
Preliminary (first round) ratings for specific questions are included in this manuscript. This
modified Delphi approach will be repeated prior to the conference.
Results
Overlying considerations
Positives and negatives of CT use
While there is wide agreement that CT has vastly improved ED diagnosis and
patient care, there is also widespread agreement in the emergency medicine and radiology
communities that overutilization of CT may be an issue.4,5 The goal of this Consensus
Conference group is not to advocate against CT when it is an optimal test but to highlight
areas that warrant further study because current patterns of "traditional" CT use may not
be optimized. This does not mean that traditional CT may not be appropriate in certain
settings, even if another approach may be comparatively more effective by some
measures.6 However, this discussion necessitates a thorough understanding of the
advantages, disadvantages, and alternatives in order to weigh the trade-offs of CT use
compared to other diagnostic approaches.
Diagnostic accuracy and speed. CT has a high diagnostic sensitivity, specificity, and
reproducibility for a wide variety of conditions.7,8 Whether this uniformly results in
improved patient outcomes is unlikely and requires further study.9 While CT may decrease
ED length of stay, avoid unnecessary repeat visits, and lower unnecessary admissions,
inappropriate CT utilization may increase ED length of stay without improving patient
outcomes.10,11
Radiation risk. CT exposes patients to ionizing radiation. A single exposure to ionizing
radiation in excess of 100 millisieverts (mSv) has been shown to increase the risk of
cancer.12 Estimates of lifetime attributable cancer risk from CT are typically extrapolated
from populations who have been exposed to higher doses of ionizing radiation than those
experienced by patients getting CT, such as survivors of the atomic bomb in Hiroshima.
Some estimates of the potential morbidity from CT scanning seem alarming.13 However,
these estimates have been challenged based on uncertainties surrounding extrapolation of
radiation risk data to the lower doses used in diagnostic imaging.14 There are few studies
that directly link exposure to CT with increased risk of malignancy risk.15–17 Studies that
accurately and precisely characterize cancer risks of CT based on age, sex, body size, type of
CT and amount of radiation delivered will help to inform appropriate use of CT.
Additionally, investigation of ways to encourage appropriate adoption and monitoring of
radiation dose with recommendations for utilization would be valuable.18
False positive and false negative diagnoses. False positive diagnoses can result in patient
harms through unnecessary anxiety, morbidity from unnecessary follow-up procedures,
and cost.19 In some cases, false positive imaging diagnoses may appear to contraindicate
the therapy for the true diagnosis (e.g., CT incorrectly interpreted as showing punctate
intracranial hemorrhage, when the true diagnosis is ischemic stroke warranting tPA
administration). While CT angiography has become the diagnostic test of choice for
pulmonary embolism, studies have suggested that small (subsegmental) PEs may be
clinically insignificant and the benefit of finding these may not exceed the long term risk of
anticoagulation.20
False negative diagnoses may result in harm, preventing discovery of correct
diagnoses and delaying appropriate treatment. Inappropriate investigation or treatment of
other diagnoses may cause patient injury, increase morbidity and increase patient costs. 19
Incidental findings. Incidental findings are unrelated to the reason the test was obtained
and are commonly encountered on CT.21,22 Sometimes, an incidental finding will result in
improved patient outcomes (e.g. a malignancy detected at a curable stage).23 However,
even when an incidental finding represents an early and previously unsuspected disease,
the benefit of early CT detection may be tempered by lead-time bias in which a diagnosis is
made earlier without lengthening survival.24 More frequently, incidental findings may lead
to other costly and invasive tests which may pose a greater risk of harm (secondary to
surgical complications, further radiation exposures, added financial costs) than benefit.25
Pediatrics. Use of CT in pediatric patients presents particular challenges. Prevalence and
nature of diseases, signs and symptoms of presentation, test characteristics, and radiation
risks differ significantly in younger patients. Areas where comparative effectiveness
research is needed in pediatric imaging include CT in pediatric trauma evaluation
(particularly when MRI or ultrasound is available and could or should be used); use of CT
in evaluation of pediatric headache (e.g. evaluation of ventriculoperitoneal shunt); and
evaluation of abdominal pain with concern for appendicitis, particularly when an initial
ultrasound is non-diagnostic.
Alternatives to traditional CT use.
With reference to the advantages and disadvantages of traditional CT use, it is valuable to
compare CT to the alternatives. These are addressed in the specific questions in the tables
below. Alternative imaging strategies include:
1) No imaging
There are specific and limited areas where clinical decision rules are supported by
adequate evidence to avoid CT imaging. Though some of these rules have had a large
impact on patient evaluation for conditions such as pulmonary embolus and head and neck
trauma, it would be of great clinical value to develop other evidence based clinical decision
rules to optimize imaging utilization. Specific rules will be discussed further under each of
their respective sections to follow.
2) Non-traditional CT
a. Low Radiation Dose CT
Compared to traditional CT doses initiated more than a decade ago, lower radiation dose
CT techniques are accurate for several emergent conditions, including kidney stone,
cervical spine injury, and appendicitis. Reduced dose techniques may be particularly
effective when coupled with technological advances that improve image quality at lower
dose (such as iterative reconstruction).26 However, some prior studies that report “reduced
dose” techniques have compared these techniques to high dose CT, and their “reduced
dose” techniques use similar doses to those used widely in the radiology community today.
Diagnostic accuracy at absolute CT dose levels needs to be determined to compare lower
dose CT with traditional CT. Low dose techniques appear to be infrequently used and there
is substantial dose variation between institutions.26 Moreover, several studies that have
investigated “reduced-dose” CT have evaluated the accuracy when used for specific
indications or diagnoses (e.g. detection of kidney stones) rather than the use of these
techniques for clinically undifferentiated presentations (e.g. abdominal pain).
b. Dual Energy and Dual Source CT
Dual energy CT (DECT) and dual source CT (DSCT) are emerging CT techniques that may
improve diagnostic accuracy, reduce radiation dose compared to traditional multi-detector
CT, and potentially reduce the need for follow-up of incidental findings.27 Higher speeds
may also reduce motion artifact and improve imaging applications such as cardiac CT.
Further research is needed to compare the impact of DECT compared to traditional single
energy CT on follow-up rates for incidental findings.
c. Use of Oral and Intravenous Contrast
A body of literature has emerged showing similar sensitivity and specificity of CT with or
without intravenous contrast for appendicitis, diverticulitis, and other common emergency
diagnoses.28 Moreover, use of oral contrast may be unnecessary for traumatic and nontraumatic abdominal disorders, offering opportunities to speed patient throughput, and
reduce costs.29 Recent studies have also questioned the causal relationship between
intravenous (IV) contrast use for CT and post-contrast acute kidney injury (AKI).30 More
research is warranted to compare the risk of AKI in patients who do and do not receive IV
contrast.
3) Radiography
In some circumstances in which CT is now used as the initial imaging investigation,
radiography may remain appropriate. For example, radiography may be appropriate for
low-risk of cervical spine injury and non-specific abdominal pain.31 More research is
needed to determine whether alternative imaging strategies can result in decreased rates
of CT, and determine the impact of algorithms that incorporate radiography on patientcentered outcomes.
4.) Ultrasound
Ultrasound is typically charged less than CT, can be performed efficiently at the bedside by
the treating provider in many cases, and does not expose the patient to ionizing radiation.
Ultrasound has been shown to safely reduce CT utilization for the assessment of blunt
abdominal trauma.32 More research is needed to compare algorithms that utilize
ultrasound instead of or supplementary to CT, the optimal order of imaging tests, and the
impact on patient-centered outcomes.
5. Magnetic Resonance Imaging (MRI)
Although often more expensive, more time consuming, and less available than CT, MRI does
not utilize ionizing radiation and is the reference standard for the diagnosis of a number of
acute conditions. Further research is needed to compare the use of CT with MRI for
suspected acute headache, spine trauma, and musculoskeletal injury with equivocal
radiography.
Methodologies and means of measurement
Research into the comparative effectiveness of imaging includes some particular
methodologic challenges. Although randomized-controlled trials are standard methods of
acquiring comparison data, it is difficult to randomize and blind the use of an imaging
study. Therefore, novel techniques using large observational data sets such as simple
pragmatic trials propensity scoring should be considered and given appropriate weighting
in the hierarchy of methodology.33 Access to large, de-identified observational databases
(“big data”) may help answer some of the needed questions. The ability to gather granular
data from CT reports (or even actual images) on a large scale, either through structured
reporting or natural language processing will improve the ability to measure diagnostic
performance. Prospective national registries, such as the American College of Radiology
Dose Index Registry, should be encouraged and funded.34
Initial
overall
average
Research questions involving overall considerations in comparative
response
effectiveness of CT use:
(Scale 1-7;
7 highest
priority)
Can (and how can) decision support improve the comparative
5.08
effectiveness of imaging approaches in the ED?
What is the long-term benefit/harm of incidental findings on CT and how
5.00
does that impact the comparative effectiveness of imaging approaches?
What is the incremental impact on comparative effectiveness of various
imaging approaches (standard CT, reduced dose CT, point-of-care or
5.00
radiology ultrasound, no imaging) for incidental findings in abdominal
imaging?
When can dual energy CT be used to improve the comparative
4.97
effectiveness of imaging in the ED population?
What is the actual harm of radiation from CT and how does that impact
4.95
the comparative effectiveness of CT use?
How can we improve the speed/ accessibility of MRI to improve
4.92
comparative effectiveness of imaging?
Does reduced dose CT provide a benefit or harm compared to regular CT
4.90
in terms of incidental findings identified?
Which uses of standard CT in the ED are most amenable to comparative
effectiveness research (in terms of overall utilization, harms of radiation,
4.83
practice variation)?
How do we best quantify the diagnostic benefit of CT (and other imaging
approaches) in terms of information gained for estimating comparative
4.67
effectiveness (can we standardize "bits of information gained")?
How do we change the culture of imaging to implement the most
4.67
comparatively effective approaches?
What is the most effective imaging approach for facilities with limited or
4.59
unavailable MRI (when MRI may be the most effective approach)?
Can (and how can) improved technical support (such as an on site
physicist, improved education, etc.) impact the adoption of
4.52
comparatively more effective approaches?
Would understanding the cumulative radiation doses that a patient has
4.13
received previously help improve comparative effectiveness of CT use?
Specific scenarios
Trauma
Using the classification system developed by the National Center for Healthcare Statistics,
trauma accounts for between 18-35% of all ED visits.35,36 Although CT scanning for ED
trauma evaluation rose more than four-fold between 2000 and 2007, outpacing overall CT
growth in the ED, it has not been accompanied by an increase in the diagnostic prevalence
of life-threatening conditions.35,36 CT scanning for trauma occurs disproportionately in
younger patients who may be more susceptible to radiation. For these reasons the use of
CT in trauma has emerged as an area requiring further research.
Panscan
Use of whole body CT for trauma (a.k.a. "panscan"), which usually involves CT of the head,
cervical spine, chest, abdomen/pelvis, with reconstruction of thoracic and lumbar spine
images, has increased over the last two decades.37 Several reports of this approach have
concluded that it minimizes missed diagnosis.37,38 Also, there is a decrease in patient
radiation exposure by elimination of overlap scanning which would occur if these anatomic
areas were scanned separately rather than as a panscan. A recent meta-analysis of panscan
use found no conclusive evidence of a mortality benefit, though ED length of stay was
reduced. The authors stated, they "…eagerly await the results of randomized clinical trials
[and] data on cost and radiation exposure will be needed before definitive conclusions can
be made."39 Some studies outside of the United States, including a recent meta-analysis,
have demonstrated a mortality benefit, although there are significant flaws in design,
particularly their adjustment for injury severity.40 Inclusion criteria for these positive
studies included significantly altered mental status and/or high injury severity score, a
relatively small subset of all traumas. Further studies comparing the benefits of “panscan”
versus targeted imaging of body regions are needed that take into account morbidity,
mortality, radiation exposure, expense, cost, and potential for incidental or clinically
insignificant findings.22,41
Specific body areas in trauma
Head trauma
CT remains an excellent first-line imaging test for significant head trauma. Decision rules
such as the Canadian and New Orleans criteria have been validated in adults to avoid
unnecessary CT imaging in “minor” head trauma.42 A similar rule for pediatric patients has
been developed by the Pediatric Emergency Care Applied Research Network (PECARN),
though further research may define when MRI instead of CT may be indicated.43 Studies
regarding CT head in the elderly, particularly with very minor trauma in the presence of
blood thinners, may be warranted.
Spine trauma
Tools such as the Canadian and NEXUS cervical spine rules have been validated to safely
avoid unnecessary imaging in suspected injury. Observational studies have shown an
increased sensitivity for CT compared to radiography in patients with elevated risk for
cervical spine injury, however there is limited data on when a patient should undergo CT
rather than radiography.7 More data are needed to evaluate the indications and scan
parameters for CT of the cervical spine in elderly and pediatric patients.44 There is a dearth
of data that evaluates the need for thoracic, lumbar, and whole spine CT imaging for
trauma.
Torso trauma
CT is superior to chest radiography in detecting injuries, particularly blunt aortic injury,
but further research is needed to determine when chest CT is necessary in trauma.45 The
thoracic portion of the extended focused assessment with sonography in trauma (EFAST)
exam, when performed by an appropriately trained and experienced provider, is more
accurate than chest radiograph for pneumothorax or hemothorax, and might be used in
combination with a clinical score to help optimize use of chest CT in trauma.46
Initial
overall
Research questions involving comparative effectiveness of CT in trauma:
average
response
In which blunt trauma patients is it beneficial to obtain whole body CT
6.06
imaging as compared to selective use of CT?
In pediatric patients with minor head injury and/or headache, is rapid
MRI brain as effective a diagnostic approach to standard, non-contrast
5.70
CT?
What is the optimal use of CT in pediatric blunt abdominal or chest
5.68
trauma (compared to history and physical, radiography, ultrasound,
MRI)?
When should CT (vs. MRI or plain radiography) be used in suspected
5.68
cervical spine injury?
How does pan scan impact: operative intervention, mortality, incidental
findings, ED length of stay, resource utilization and availability, radiation
5.65
exposure, etc.?
What is the optimal use of CT chest in blunt chest trauma in conjunction
5.56
with clinical signs, symptoms, radiography, and ultrasound?
Could reduced dose or dual energy CT be as effective an approach in
5.54
trauma imaging as standard CT?
What is the optimal use of abdominal CT in blunt abdominal trauma
5.54
based on clinical signs and symptoms, radiography, and ultrasound?
What is the comparative effectiveness of clinical assessment,
radiography/ CT/ MRI for suspected traumatic thoracic and/or lumbar
5.48
spine injury?
What is the optimal approach to the diagnosis of suspected pediatric
5.44
cervical spine injury?
When should MRI, scintigraphy, or follow-up radiography be used instead
of CT when there is a suspicion for traumatic musculoskeletal injury with
4.95
equivocal radiography (e.g. spine, hip, tibial plateau, scaphoid, foot)?
Are there biomarkers that are as effective as CT in the evaluation of
4.79
traumatic brain injury?
Atraumatic headache; neurologic signs or symptoms
CT head is the most commonly obtained CT examination in the emergency department.47
While CT head may be obtained in trauma, it is also obtained in headache (particularly if
subarachnoid hemorrhage is suspected), in new onset seizure, and in the evaluation of
focal neurologic complaints including suspected stroke. Focal neurologic signs or
symptoms represent about 1% of all ED presentations, and CT imaging is obtained in more
than half of these presentations, a higher percentage than any other "reason for visit".35
Due to speed and availability, non-contrast CT head is often performed initially in patients
presenting with focal neurologic complaints. However, it is not sensitive for early or small
stroke or transient ischemic attack, with MRI and CT potentially having a role in
management decisions, particularly in patients who may benefit from thrombolysis. The
approach to imaging in these patients varies widely, and research into optimal pathways
that reduce duplicative imaging are needed.
Initial
overall
average
Questions: Atraumatic headache
response
In pediatric patients with minor head injury and/or headache, is rapid MRI
5.70
brain as effective a diagnostic approach as standard, non-contrast CT?
What is the optimal diagnostic imaging strategy in patients with clinical
concern for stroke presenting within the window for thrombolytic
5.41
therapy?
What is the optimal diagnostic imaging strategy in patients with clinical
5.13
concern for atraumatic subarachnoid hemorrhage?
What is the optimal diagnostic imaging strategy in patients with clinical
4.86
concern for transient ischemic attack with resolution of symptoms?
What is the optimal diagnostic imaging strategy in patients with clinical
4.71
concern for central vertigo or suspected posterior circulation ischemia?
Does rapid MRI or reduced-dose CT provide a comparatively more
effective approach than standard CT in the evaluation of
4.68
ventriculoperitoneal shunt malfunction?
In what situations is imaging comparatively more effective than symptom
control in patients with headache, absent neurologic symptoms, and
4.59
concern for intracranial mass?
Chest CT: pulmonary embolism, acute aortic disease, coronary artery disease,
pneumonia
Chest pain and shortness of breath together account for more than 9% of ED visits, and
more than one in ten of these patients received a CT in 2007.35 Several decision rules have
focused on when CT can be avoided in suspected PE using clinical signs, symptoms, and D-
dimer testing. This includes when a D-dimer is not indicated (as false positive results may
lead to unnecessary imaging). It was felt by the group that the use of CT for suspected
pulmonary embolism remains variable and likely over-utilized and warrants further
research. Recent evidence suggests that the use of coronary CT angiography (CTA) for
suspected acute coronary syndrome (ACS) may reduce ED length of stay and be more costeffective than traditional evaluation.8,48 However, when patients present with
undifferentiated chest pain, a “triple rule out” CTA may be performed. This is a relatively
recent development and comparative effectiveness research is lacking. While CT is typically
not necessary to diagnose pneumonia, further research may be indicated when chest
radiograph is negative or equivocal in high-risk groups.
Initial overall
Research questions involving comparative effectiveness of CT in non-
average
traumatic chest pain and/or dyspnea:
response
(1-7 scale)
Would age- or situation-specific D-dimer cutoffs (i.e. in pregnancy) help
5.46
optimize appropriate CT imaging in suspected pulmonary embolism?
For patients with negative or inconclusive chest radiography performed for
pneumonia, does a regular or reduced dose CT of the thorax improve
5.37
patient-centered outcomes to identify occult pneumonia?
In patients with clinical concern for ACS what is the comparative
effectiveness of coronary CT in relation to: serial troponin, provocative
testing, and/or cardiac catheterization?
5.33
Is there a benefit to using dual energy CT in suspected pulmonary
5.11
embolism/ aortic dissection/ acute coronary syndrome?
Could the use of D-dimer and/or bedside ultrasound help improve the
comparative effectiveness of CT angiography for suspected thoracic aortic
4.70
dissection?
Abdomen/pelvis CT
After trauma and upper respiratory complaints, abdominal pain is the next most common
reason for ED evaluation - accounting for over 6% of ED visits - and nearly a third of these
patients received a CT in 2007.35 Abdominal CT is an excellent test for undifferentiated
abdominal pain, and is indicated in the elderly who harbor a higher prevalence of disease.
However, women with lower abdominal pain (particularly pre-menopausal) may be at
higher risk from radiation. This population in particular may benefit from ultrasound first
to evaluate uterine or adnexal conditions that could obviate the need for CT. Pediatric
patients are also at potentially more risk from radiation, and ultrasound is recommended
as the first imaging test for suspected appendicitis in children, though there are limited
data evaluating the comparative effectiveness of further imaging, including MRI, CT, or no
testing, following a non-diagnostic or equivocal ultrasound.
Kidney stones will afflict 1 in 11 people in their lifetime. While recent research has
demonstrated that ultrasound first is a reasonable approach49, CT remains a first line
investigation and is obtained in more than 40% of patients presenting with flank pain. 35
Disadvantages to this approach include the often high and variable radiation doses
associated with renal stone CT as well as the high frequency of incidental findings.21,50 A
recent objective clinical prediction rule (the “STONE score”) has been derived and
validated in a single site51 but further research into the optimal combination of clinical and
point-of-care testing results, ultrasound, and CT, including reduced dose CT is warranted.
Initial overall
Research questions involving comparative effectiveness of CT in nonaverage
traumatic abdominal and flank pain:
response
In suspected appendicitis what is the comparative effectiveness of
different diagnostic approaches compared to standard CT in different
populations (i.e. by age and sex)? I.e. how do history, physical,
5.86
laboratory, point-of-care ultrasound, radiology ultrasound, focused
and/or reduced dose CT or MRI as a first approach compare?
What is the optimal diagnostic approach to suspected pediatric
5.83
appendicitis with non-diagnostic ultrasound?
In suspected kidney stone, what is the optimal diagnostic imaging
strategy using clinical prediction rules, point-of-care or radiology
5.73
ultrasound, and reduced dose CT compared to standard, non-contrast
CT?
How does reduced dose CT affect diagnostic accuracy for common
abdominal conditions (i.e. appendicitis, bowel obstruction,
diverticulitis) in various patient populations (i.e. by age, sex, and size)
5.68
and how does this affect the comparative effectiveness of diagnostic
approaches?
In patients with suspected bowel obstruction what is the best imaging
approach? Is there a role for radiography and/or ultrasound? What is
5.49
the optimal use of contrast?
How does ultrasound first performed by emergency providers
compared to standard CT with respect to accuracy, length of stay and
5.43
cost for renal, pelvic, cardiac and biliary indications?
What is the optimal diagnostic imaging strategy for premenopausal
women with undifferentiated, acute lower abdominal/pelvic pain that
5.32
may be due to gastroenterological or gynecological pathology?
Can dual energy CT be as effective an approach to acute, atraumatic
4.97
abdominal pain as standard CT?
Discussion/ conclusion
CT is a powerful diagnostic technology, but its many advantages are accompanied by
potential harms, including high cost, radiation exposure, contrast risks, and incidental
findings. Research is needed to refine the indications for CT and to identify the scenarios in
which alternatives to traditional CT are most appropriate. Further characterizing the
benefits and harms of CT is a necessary first step. Future research should prioritize not
only diagnostic advantages of CT, but also patient-centered outcomes resulting from use of
CT, and when CT can be avoided without adversely impacting these outcomes.
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