The Canadian C-Spine Rule for Radiography in Alert and Stable
Trauma Patients
Ian G. Stiell, MD, MSc, FRCPC; George A. Wells, PhD; Katherine L.
Vandemheen, BScN; Catherine M. Clement, RN; Howard Lesiuk, MD; Valerie J. De
Maio, MD, MSc; Andreas Laupacis, MD, MSc; Michael Schull, MD, MSc; R. Douglas
McKnight, MD; Richard Verbeek, MD; Robert Brison, MD, MPH; Daniel Cass, MD;
Jonathan Dreyer, MD; Mary A. Eisenhauer, MD; Gary H. Greenberg, MD; Iain
MacPhail, MD, MHSc; Laurie Morrison, MD, MSc; Mark Reardon, MD; James
Worthington, MBBS
Context High levels of variation and inefficiency exist in current
clinical practice regarding use of cervical spine (C-spine) radiography in
alert and stable trauma patients.
Objective To derive a clinical decision rule that is highly sensitive for
detecting acute C-spine injury and will allow emergency department (ED)
physicians to be more selective in use of radiography in alert and stable
trauma patients.
Design Prospective cohort study conducted from October 1996 to April
1999, in which physicians evaluated patients for 20 standardized clinical
findings prior to radiography. In some cases, a second physician performed
independent interobserver assessments.
Setting Ten EDs in large Canadian community and university hospitals.
Patients Convenience sample of 8924 adults (mean age, 37 years) who
presented to the ED with blunt trauma to the head/neck, stable vital signs, and
a Glasgow Coma Scale score of 15.
Main Outcome
Measure Clinically important
C-spine injury, evaluated by plain radiography, computed tomography, and a
structured follow-up telephone interview. The clinical decision rule was
derived using the 
coefficient,
logistic regression analysis, and 
2 recursive partitioning techniques.
Results Among the study sample, 151 (1.7%) had important C-spine injury.
The resultant model and final Canadian C-Spine Rule comprises 3 main questions:
(1) is there any high-risk factor present that mandates radiography (ie, age 
65 years, dangerous
mechanism, or paresthesias in extremities)? (2) is there any low-risk factor
present that allows safe assessment of range of motion (ie, simple rear-end
motor vehicle collision, sitting position in ED, ambulatory at any time since
injury, delayed onset of neck pain, or absence of midline C-spine tenderness)?
and (3) is the patient able to actively rotate neck 45° to the left and right?
By cross-validation, this rule had 100% sensitivity (95% confidence interval
[CI], 98%-100%) and 42.5% specificity (95% CI, 40%-44%) for identifying 151
clinically important C-spine injuries. The potential radiography ordering rate
would be 58.2%.
Conclusion We have derived the Canadian C-Spine Rule, a highly sensitive
decision rule for use of C-spine radiography in alert and stable trauma
patients. If prospectively validated in other cohorts, this rule has the
potential to significantly reduce practice variation and inefficiency in ED use
of C-spine radiography.
JAMA. 2001;286:1841-1848
More than 1 million patients with blunt trauma
and potential cervical spine (C-spine) injury are treated each year in US
emergency departments (EDs).1, 2 Among those patients
presenting with intact neurological status (arriving either walking or by
ambulance), the incidence of acute fracture or spinal injury is less than 1%.3-5 Due to concerns
about potentially disabling spinal injuries, most clinicians make liberal use
of C-spine radiography.6-9 Nevertheless, such
practice is inefficient
more than 98% of C-spine
radiographs are negative for fracture.10-16 Furthermore, there
is considerable practice variation among well-trained emergency physicians,
with radiography rates ranging as much as 6-fold.17 Cervical spine
radiography is an example of a "little ticket" item, a low-cost
procedure that significantly adds to health care costs due to its high volumes
of use.18, 19
There are no widely accepted guidelines that
have been shown to be both safe and efficient in guiding the use of C-spine
radiography. Recently, clinical decision rules have been developed to guide
physicians in making diagnostic or therapeutic decisionsfor example, the use of radiography for patients with ankle or
knee injuries.20-23 A clinical
decision rule may be defined as a decision-making tool that is derived from
original research and that incorporates 3 or more variables from the history,
physical examination, or simple tests.24, 25 The National
Emergency X-Radiography Utilization Study (NEXUS) low-risk criteria for C-spine
radiography were recently evaluated in a large study of EDs that found the
criteria to be 99.6% sensitive for clinically important injuries.26 However, the
specificity was only 12.9%, leading to concerns that use of the NEXUS criteria
would actually increase the use of radiography in some US jurisdictions and in
most countries outside of the United States.
We believe that the current inefficiency and
variability of clinical practice can be remedied with the development of an
accurate, reliable, and clinically sensible decision rule. Hence, the objective
of this study was to derive a clinical decision rule that would be highly
sensitive for detecting acute C-spine injury among patients sustaining blunt
trauma who are alert and stable but at risk for neck injury. This will
ultimately allow physicians to be more selective in their use of radiography
without jeopardizing patient care.
METHODS
Study Setting and Population
This prospective cohort study was conducted in 10 large Canadian community and
university hospitals and included consecutive adult patients presenting to the
ED after sustaining acute blunt trauma to the head or neck. We did not include
the many patients presenting with trivial injuries, such as simple lacerations
to the face.The treating physician's decision of whether to order radiography
had no bearing on the enrollment of patients into the study. Patients were
eligible for enrollment if they were at some risk for C-spine injury either because
they had neck pain from any mechanism of injury, or because they had no neck
pain but had all of the following: some visible injury above the clavicles, had
not been ambulatory, and had sustained a dangerous mechanism of injury. In
addition, patients had to be alert,
which was defined as a Glasgow Coma Scale (GCS) score of 15 (scale range,
3-15), and stable, defined as
normal vital signs (systolic blood pressure >90 mm Hg and respiratory rate
between 10 and 24/min).
Patients were excluded if they: (1) were younger
than 16 years; (2) had minor injuries, such as simple lacerations, and did not
fulfill the first 2 inclusion criteria above; (3) had a GCS score lower than
15; (4) had grossly abnormal vital signs; (5) were injured more than 48 hours
previously; (6) had penetrating trauma; (7) presented with acute paralysis; (8)
had known vertebral disease (ankylosing spondylitis, rheumatoid arthritis,
spinal stenosis, or previous cervical surgery), as determined by the examining
physician; (9) had returned for reassessment of the same injury; or (10) were
pregnant. Eligible patients transferred from other hospitals with suspected
C-spine injury were enrolled at the study sites with the proviso that
physicians complete the data form prior to reviewing radiographic films. Many
of these patients proved not to have C-spine injury. The research ethics
committees of the study hospitals approved the protocol without the need for
informed consent. Patients followed up had an opportunity to give verbal
consent during the telephone interview conducted by a study nurse.
Standardized Patient Assessment
All patient assessments were made by staff physicians certified in emergency
medicine or by supervised residents in emergency medicine training programs.
The physician assessors were trained with a 1-hour session to evaluate patients
for 20 standardized clinical findings from the history, general examination,
and assessment of neurological status. These potential predictor variables were
selected by a team of investigators at a planning consensus conference based on
a review of the existing literature and on results of a pilot study. Findings
were recorded on a data collection sheet prior to radiography. A subset of
patients, where feasible, were independently assessed by a second emergency
physician to judge interobserver agreement. An additional 5 demographic
variables were obtained from hospital records by study nurses.
Outcome Measures and Assessment
The primary outcome measure was clinically
important cervical spine injury, defined as any fracture,
dislocation, or ligamentous instability demonstrated by diagnostic imaging. Clinically unimportant cervical spine injuries
generally do not require stabilizing treatment or specialized follow-up and the
definition for this has been standardized based on the results of a formal
survey of 129 neurosurgeons, spinal surgeons, and emergency physicians at 8
tertiary care hospitals.27 All C-spine injuries
were considered clinically important unless the patient was neurologically
intact and had 1 of 4 injuries: (1) isolated avulsion fracture of an osteophyte
(2) isolated fracture of a transverse process not involving a facet joint (3)
isolated fracture of a spinous process not involving the lamina or (4) simple
compression fracture involving less than 25% of the vertebral body height.
After the clinical examination, patients
underwent plain radiography of the C-spine according to the judgment of the
treating physician, not according to any preset guidelines. Radiographs were
interpreted by qualified staff radiologists who were blinded to the contents of
the data collection sheet. The reliability of the radiography interpretations
was assessed by having all abnormal radiographs and 1% (randomly selected) of
normal radiographs reviewed by a second radiologist who was blinded to the
first interpretation. Radiography consisted of a minimum of 3 views. Patients
also underwent flexion-extension views and computed tomography of the C-spine
at the discretion of the treating physician.
Because not all patients with blunt trauma
routinely undergo C-spine radiography at the Canadian study sites, we could not
ethically mandate universal radiography for all eligible patients.
Consequently, all enrolled patients who did not have radiography underwent the
structured 14-day proxy outcome measure administered by telephone by a
registered nurse. Patient telephone numbers were verified by the treating
emergency physician. According to this tool, patients were classified as having
no clinically important C-spine injury if they met all of the following 4
explicit criteria for 14 days: (1) neck pain rated as none or mild, (2)
restriction of neck movement rated as none or mild, (3) use of a cervical
collar not required, and (4) neck injury has not prevented return to usual
occupational activities. The assessment of these criteria was made by
registered nurses who were unaware of the patient's status for the individual
predictor clinical variables. Patients who did not fulfill the criteria were
recalled for clinical assessment and radiography. Patients who could not be
reached were excluded from the final study analysis. These criteria have been
previously shown to identify all C-spine injuries in a substudy that applied
the telephone follow-up questionnaire to a sample of 389 study patients
(including 66 with clinically important C-spine injury) who had all undergone
radiography.28
Data Analysis
The interobserver agreement for each variable was measured by calculating the coefficient,
the proportion of potential agreement beyond chance, along with 95% confidence
intervals (CIs).29, 30 Values were not calculated for variables collected from
medical records (eg, age or mechanisms of injury). Univariate analyses were
used to determine the strength of association between each variable and the
primary outcome to aid selection of the best variables for the multivariable
analyses. The appropriate univariate techniques were chosen according to the
type of data. For nominal data, the 2 test with continuity correction was used; for ordinal
variables, the Mann-Whitney U test; and for continuous variables, the unpaired
2-tailed t test, using pooled or
separate variance estimates as appropriate.
Those variables found to be both reliable (>0.6) and
strongly associated with the outcome measure (P<.05)
were combined using either recursive partitioning or logistic regression. The
objective was to find the best combinations of predictor variables, ie, those
highly sensitive for detecting the outcome measure while achieving the maximum
possible specificity. Building of the regression model proceeded with forward
stepwise selection until no variables met the criteria for entry (P<.05) or removal (P>.10) for the significance levels of
the likelihood-ratio test. Recursive partitioning was performed as an
alternative technique using KnowledgeSEEKER, version 3.1 (Angoss Software
International, Toronto, Ontario).31, 32 Our experience
suggested recursive partitioning may be more suitable than logistic regression
when the objective is to correctly classify one outcome group at the expense of
the other (ie, where high sensitivity is more important than overall accuracy).
The derived decision rule was cross-validated by
comparing the classification of all patients to their actual status for the
primary outcomes allowing estimates, with 95% CIs, of the sensitivity and
specificity of the rule. In addition, we conducted a statistical validation
using a jackknife nonparametric estimate of bias for the sensitivity,
specificity, and overall accuracy of the rule.33, 34 The a priori sample
size was estimated to be 8000 patients and 120 injury cases, based on the
desired precision of 100% sensitivity for clinically important C-spine injury
with 95% confidence limits of 97% to 100%.
RESULTS
Between October 1996 and April 1999, 12 782
eligible patients were examined at the study sites. Of these, 8924 patients
were enrolled and assessed for the primary outcome measure, clinically
important C-spine injury, and thus made up the final study group (Table 1).
Not included in this study group were 3281 eligible patients examined but not
enrolled by the treating physicians. All characteristics of these nonenrolled
patients were very similar to those of the patients enrolled except for
slightly higher rates of arrival by ambulance (61% vs 54%), transfer from
another hospital (10% vs 4%), and incidence of C-spine injury (3.2% vs 2.0%).
Finally, 577 eligible patients were also not included in the final study group
because they did not undergo C-spine radiography and could not be reached for
the proxy outcome measure. This latter group were much less severely injured:
only 32% arrived by ambulance, 0.2% were transfers from other hospitals, and
only 0.9% were admitted to hospital. Of the patients in the final study group,
6185 (68.9%) underwent C-spine radiography and the remaining 31.1% underwent
the structured 14-day telephone proxy outcome measure administered by a
registered nurse. Of all study patients, 151 (1.7%) were determined to have a
clinically important C-spine injury. The radiologists showed 100% agreement in
diagnosing C-spine injury. An additional 28 (0.3%) patients were judged to have
a clinically unimportant C-spine injury, primarily avulsion fractures. No
patient contacted for the proxy outcome measure was later determined to have a
C-spine injury.
Table 2
and Table 3
show the association between the predictor variables and clinically important
C-spine injury as determined by univariate analyses. Overall, we evaluated 25
primary predictor variables (20 from the physician's form and 5 from the chart)
as well as another 8 created by combination or cutpoints. Table 2
also shows the interobserver agreement for the primary clinical variables from
those patients (n = 150) examined by 2 physicians.
Logistic regression analysis (Table 4)
provided a model with good overall accuracy for discriminating cases with
clinically important C-spine injury (area under the receiver operating
characteristic curve, 0.91; P =
.94 for the Hosmer-Lemeshow goodness-of-fit test). We also conducted
recursive-partitioning analysis, which ultimately resulted in a more clinically
acceptable model. The predictor variables in this latter statistical model were
then combined into a simple algorithm, the "Canadian C-Spine Rule" (Figure 1).
This clinical decision rule asks 3 basic questions and establishes the safety
of evaluating active range of motion by identifying high-risk and low-risk
factors.
The potential classification performance of the
Canadian C-Spine Rule for identifying 151 cases with clinically important
C-spine injury reveals a sensitivity (95% CI) of 100% (98%-100%) and a
specificity of 42.5% (40%-44%) (Table 5).
From the jackknife statistical analysis, we calculated the bias-corrected
estimates for sensitivity to be 100% and those for specificity to be 42.63%;
the bias for overall accuracy was estimated to be 2.12%. We estimate a
potential C-spine radiography rate of 58.2% in this cohort, a relative
reduction of 15.5% from 68.9%. The rule also would have identified 27 out of 28
patients with clinically unimportant C-spine injury. One 63-year-old patient
not identified had a small C3 osteophyte avulsion fracture and was discharged
from the ED with a cervical collar.
COMMENT
This represents the largest derivation study yet
conducted of patients having potential C-spine injury, evaluating the accuracy
and reliability of 25 clinical variables and enrolling 8 times more patients
than any previous derivation study. We developed a highly sensitive clinical
decision rule that, if prospectively validated, will allow physicians to
rationally order C-spine radiography for alert and stable trauma patients who
are at risk for neck injury. This will lead to more timely and efficient use of
resources without jeopardizing patient care. This new Canadian C-Spine Rule
identifies those trauma patients who require C-spine radiography based on 3
simple clinical questions. First, patients judged to be at high risk due to
age, dangerous mechanism of injury, or paresthesias must undergo radiography.
Second, patients with any 1 of 5 low-risk characteristics may safely undergo
assessment of active range of motion. Third, patients who are able to actively
rotate their neck 45° to the left and to the right, regardless of pain, do not
require C-spine radiography. The Canadian C-Spine Rule was derived according to
strict methodological standards and provides a very tight CI around the estimated
sensitivity of 100% for detecting injury. Future studies will further evaluate
the rule for accuracy and reliability, acceptability to clinicians, and actual
impact on patient care.
We believe that current use of C-spine
radiography for alert and stable trauma patients is very inefficient and highly
variable.12, 15, 16 Most patients in the
United States undergo radiography regardless of their clinical presentation.
While Canadian practice is more selective, we have shown that there is very
large variation among hospitals and physicians in their use of C-spine
radiography.17 This 2-fold
variation among hospitals and 6-fold variation among certified attending
emergency physicians persisted even after using multivariable analysis to
control for differences in severity of trauma. There is considerable
controversy among emergency physicians, neurosurgeons, and trauma surgeons
regarding indications for C-spine radiography. Some firmly maintain that all
trauma patients should undergo radiography.3, 7, 35-37 For example, in
its Advanced Trauma Life Support Course, the American College of Surgeons
recommends that " . . . C-spine films should be attained on every patient
sustaining an injury above the clavicle and especially a head injury."38 Other trauma
clinicians agree that a selective approach is ideal but do not give clear
recommendations.39-41 Most authors
suggest that radiography may not be required in alert patients with no pain or
tenderness of the neck.42-46 Such an approach
is still very conservative, but only a few authors are willing to suggest that
radiography may be withheld in alert patients with neck pain if there is no
midline bone tenderness of the neck.47, 48 According to Neifeld
and colleagues,13 "the real
difficulty exists in patients who are awake, alert, have normal physical
examination findings and have minimal or no symptoms." This latter group
represents the largest group of blunt trauma patients and the greatest
potential for improved efficiency of radiography. Our own surveys have shown
that most Canadian physicians and those in the United States disagree with guidelines
for universal C-spine radiography and support evidence-based guidelines if they
are shown to be accurate and reliable.49
A number of studies have been conducted in
recent years by emergency physicians, trauma surgeons, and radiologists to
identify a group of trauma patients who do not need C-spine radiography.
Unfortunately, these studies have great variability in design and none could be
considered robust according to methodological standards for the development of
clinical decision rules. An exception are the US-based NEXUS criteria, which
have recently received prominent attention after the publication of a huge
validation study incorporating more than 34 000 patients.26, 48, 50 These guidelines
state that no C-spine radiography is required if patients satisfy all 5
low-risk criteria: absence of midline tenderness, normal level of alertness, no
evidence of intoxication, no abnormal neurological findings, and no painful
distracting injuries. We have concerns about the sensitivity, specificity, and
reliability of these criteria. The authors' own calculated specificity of 12%
is very low and may actually lead to an increase in the use of C-spine
radiography in most countries outside of the United States. Clinicians in Canada
have found 2 of the criteria ("presence of intoxication" and
"distracting painful injuries") to be poorly reproducible. We
recently attempted a retrospective validation of the NEXUS criteria based upon
our database of 8924 patients and found that the criteria failed to predict 10
of 148 clinically important injuries, yielding a sensitivity of only 93%.51 We believe that the
NEXUS criteria should be further evaluated, prospectively and explicitly, for
sensitivity, specificity, and interobserver agreement in multiple sites before
they can be accepted for widespread clinical use.
One strength of our study was the strict
adherence to methodological standards for the derivation of clinical decision
rules.24, 25, 52-54 The primary
outcome measure, clinically important C-spine injury, was clearly defined and
was assessed in a blinded fashion. In addition, the clinical findings used as
predictors were standardized and collected without knowledge of the outcome
measure. The reproducibility of the predictor findings was assessed by having a
subset of patients examined by 2 physicians. The study subjects were selected
without bias and based on preset criteria rather than on the subjective
decision of individual physicians to order C-spine radiography. These patients
represented a wide spectrum of clinical characteristics and geographic sites,
hence increasing generalizability. The mathematical techniques for deriving the
rule were explicit and appropriate. We believe that the format of the rule, a
simple list of questions, makes it clinically sensible for the intended
audience of busy emergency physicians. Furthermore, the rule appears to be
highly sensitive for the clinically important outcome, making its use safe for
patient care. In addition, it is relatively specific, making it an efficient
tool. The true impact of the Canadian C-Spine Rule, however, can only be
determined in a prospective study to evaluate the accuracy, interobserver
agreement, clinician acceptability, and potential radiograph ordering rates in
a new patient population.
Conversely, our study has potential limitations
that warrant discussion. Some may be concerned about our use of clinically
important C-spine injury as the primary outcome. Our definition has, however,
been well accepted by Canadian academic neurosurgeons, spine surgeons, and
emergency physicians. We believe that this represents a pragmatic and very safe
approach to patient care. The priority of diagnostic imaging for these trauma
patients should be to identify C-spine injuries that require treatment and
follow-up. Clinically unimportant C-spine injuries, according to the academic
surgeons in our survey, require neither stabilizing treatment nor specialized
follow-up and are unlikely to be associated with long-term problems.
Furthermore, the Canadian C-Spine Rule has also proven to be very sensitive for
the clinically unimportant injuries, missing only 1 small avulsion fracture
that required treatment with a cervical collar only.
Another potential limitation is that not all
study patients underwent C-spine radiography. The Canadian clinicians in our
study often withhold diagnostic imaging for trauma patients whom they consider
to be at low risk for injury. Consequently, we could not ethically insist upon
universal radiography for all patients. Patients were only classified as having
no clinically important injury if they satisfied all criteria on the structured
14-day telephone proxy outcome tool. Patients who could not fulfill all
criteria were recalled for radiography and patients who could not be reached
were excluded from the final analysis. The proxy outcome tool has been
validated and shown to be very accurate in identifying patients with clinically
important injuries. In addition, we acknowledge that not all eligible patients
were enrolled in the study. However, this is not unusual for a clinical study
and we are confident that there was no selection biasthe characteristics of patients not enrolled were very similar to
those of the patients who were enrolled.
The Canadian C-Spine Rule encompasses many
variables that have previously not been prominently considered in guidelines
for the use of C-spine radiography. We found that patients 65 years or older
and those experiencing paresthesias were at considerable risk of C-spine
injury, and that all such patients should undergo radiography. In addition, our
data clearly demonstrate that particular mechanisms of injury are associated
with substantially increased risk of important injury and that patients with
such injuries should not be further examined prior to radiography. Furthermore,
our results demonstrate that 5 factors put the patient at very low risk of
injury and allow safe assessment of range of motion: simple rear-end motor
vehicle collision, found to be in the sitting position in the ED, ambulatory
status at any time after the injury, delayed onset of neck pain, and absence of
midline C-spine tenderness. The final common pathway of the Canadian C-Spine
Rule requires patients to successfully demonstrate an ability to rotate the
neck actively left and right a minimum of 45°, regardless of pain. This
assessment mirrors clinical practice in Canada but would appear to be a
relatively uncommon approach in US sites that have adopted the NEXUS criteria.
There are 2 potential implications of a decision
rule or guideline for the use of C-spine radiography in alert and stable trauma
patients. First, patient management would become standardized and more
efficient. The great variation of current practice and the extremely low yield
of radiography suggest a need for accurate and reliable guidelines. A sensitive
and specific decision rule would reduce the unnecessary use of radiography and
would allow much more rapid triage and evaluation of patients brought to the ED
by ambulance stretcher. Such patients often languish for hours on an
uncomfortable backboard before their C-spine is judged free of injury.
Second, an accurate decision rule could lead to
significant savings for our health care systems. The current variation in
practice and very low yield of C-spine radiography among alert and stable
trauma patients would suggest significant potential for reducing the use of
this radiography. Our survey of emergency physicians in 5 North American and
European countries clearly indicates a willingness to adopt a decision rule for
C-spine radiography.55 Based on our studies
that show large reductions in the use of ankle radiography after the
implementation of the Ottawa Ankle Rules,20, 21 we estimate that a
25% to 50% relative reduction in the use of C-spine radiography could be safely
achieved.
There is currently much controversy in the
literature and much variation and inefficiency in clinical practice regarding
the use of C-spine radiography for alert and stable trauma patients. Our study
has developed the highly sensitive Canadian C-Spine Rule to identify a large
group of patients for whom C-spine radiography is unnecessary. If prospectively
validated in other cohorts, this rule has the potential to standardize and
improve efficiency in the use of C-spine radiography in EDs.
Author/Article Information
Author Affiliations: Division of
Emergency Medicine (Drs Stiell, Greenberg, Reardon, and Worthington),
Department of Medicine (Drs Stiell, Wells, and Laupacis), Department of
Epidemiology and Community Medicine (Drs Stiell and Wells), Division of Neurosurgery
(Dr Lesiuk), and Clinical Epidemiology Unit (Drs Stiell and De Maio, and Mss
Vandemheen and Clement), University of Ottawa, Ottawa, Ontario; Department of
Emergency Medicine, Queen's University, Kingston, Ontario (Dr Brison); Division
of Emergency Medicine, University of Toronto, Toronto, Ontario (Drs Schull,
Verbeek, Cass, and Morrison); Division of Emergency Medicine, University of
Western Ontario, London (Drs Dreyer and Eisenhauer); Division of Emergency
Medicine, University of British Columbia, Vancouver (Drs McKnight and
MacPhail).
Corresponding Author: Ian G.
Stiell, MD, MSc, FRCPC, Clinical Epidemiology Unit, F6, Ottawa Health Research
Institute, 1053 Carling Ave, Ottawa, Ontario, Canada K1Y 4E9 (e-mail: [log in to unmask]).
Author Contributions: Study concept and design:
Stiell, Wells, Vandemheen, Lesiuk, Laupacis, McKnight, Verbeek, Brison, Dreyer,
Eisenhauer, Greenberg, MacPhail, Reardon.
Acquisition of data: Stiell, Vandemheen, Clement, McKnight, Verbeek, Brison, Cass,
Dreyer, Eisenhauer, Greenberg, MacPhail, Morrison, Worthington.
Analysis and interpretation of
data: Stiell, Wells, De Maio.
Drafting of the manuscript: Stiell, Schull.
Critical revision of the manuscript
for important intellectual content:
Stiell, Wells, Vandemheen, Clement, Lesiuk, De Maio, Laupacis, Schull,
McKnight, Verbeek, Brison, Cass, Dreyer, Eisenhauer, Greenberg, MacPhail,
Morrison, Reardon, Worthington.
Statistical expertise: Stiell, Wells, De Maio.
Obtained funding: Stiell, Wells, Vandemheen, Lesiuk, Laupacis.
Administrative, technical, or
material support: Stiell, Vandemheen,
Schull.
Study supervision: Vandemheen, Clement,
Funding/Support: This study was funded by peer-reviewed grants from the Medical
Research Council of Canada (MT-13700) and the Ontario Ministry of Health
Emergency Health Services Committee (11996N). Drs Stiell and Laupacis hold
Investigator Awards from the Canadian Institutes of Health Research.
Acknowledgment: We thank the following for their much appreciated assistance:
study nurses Erica Battram, RN, Kim Bradbury, RN, Teresa Cacciotti, RN, Pamela
Sheehan, RN, Taryn MacKenzie, RN, Kathy Bowes, RN, Karen Code, RN, Virginia
Blak-Genoway, RN, Debbie Karsh, RN, Sharon Mason, RN, Percy MacKerricher, RN,
and Jan Buchanan, RN; My-Linh Tran and Emily Moen for data management; Irene
Harris for manuscript preparation; and all the physicians, nurses, and clerks
at the study sites who voluntarily and patiently assisted with case
identification and data collection.
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