Stiell IG, Clement CM, Rowe BH, Schull MJ, Brison R, Cass D, Eisenhauer MA, McKnight RD, Bandiera G, Holroyd B, Lee JS, Dreyer J, Worthington JR, Reardon M, Greenberg G, Lesiuk H, MacPhail I, Wells GA. Comparison of the Canadian CT Head Rule and the New Orleans Criteria
in Patients With Minor Head Injury. JAMA. 2005;294(12):1511–1518. doi:10.1001/jama.294.12.1511
Author Affiliations: Department of Emergency
Medicine (Drs Stiell, Worthington, Greenberg, and Reardon), Department of
Epidemiology and Community Medicine (Dr Wells), Division of Neurosurgery (Dr
Lesiuk), and Clinical Epidemiology Program (Ms Clement), University of Ottawa,
Ottawa, Department of Emergency Medicine, University of Alberta, Edmonton
(Drs Rowe and Holroyd), Division of Emergency Medicine, University of Toronto,
Toronto (Drs Schull, Cass, Lee, and Bandiera), Department of Emergency Medicine,
Queen’s University, Kingston (Dr Brison), Division of Emergency Medicine,
University of Western Ontario, London (Drs Eisenhauer and Dreyer), and Division
of Emergency Medicine, University of British Columbia, Vancouver (Drs McKnight
and MacPhail), Canada.
Context Current use of cranial computed tomography (CT) for minor head injury
is increasing rapidly, highly variable, and inefficient. The Canadian CT Head
Rule (CCHR) and New Orleans Criteria (NOC) are previously developed clinical
decision rules to guide CT use for patients with minor head injury and with
Glasgow Coma Scale (GCS) scores of 13 to 15 for the CCHR and a score of 15
for the NOC. However, uncertainty about the clinical performance of these
Objective To compare the clinical performance of these 2 decision rules for detecting
the need for neurosurgical intervention and clinically important brain injury.
Design, Setting, and Patients In a prospective cohort study (June 2000-December 2002) that included
9 emergency departments in large Canadian community and university hospitals,
the CCHR was evaluated in a convenience sample of 2707 adults who presented
to the emergency department with blunt head trauma resulting in witnessed
loss of consciousness, disorientation, or definite amnesia and a GCS score
of 13 to 15. The CCHR and NOC were compared in a subgroup of 1822 adults with
minor head injury and GCS score of 15.
Main Outcome Measures Neurosurgical intervention and clinically important brain injury evaluated
by CT and a structured follow-up telephone interview.
Results Among 1822 patients with GCS score of 15, 8 (0.4%) required neurosurgical
intervention and 97 (5.3%) had clinically important brain injury. The NOC
and the CCHR both had 100% sensitivity but the CCHR was more specific (76.3%
vs 12.1%, P<.001) for predicting need for neurosurgical
intervention. For clinically important brain injury, the CCHR and the NOC
had similar sensitivity (100% vs 100%; 95% confidence interval [CI], 96%-100%)
but the CCHR was more specific (50.6% vs 12.7%, P<.001),
and would result in lower CT rates (52.1% vs 88.0%, P<.001).
The κ values for physician interpretation of the rules, CCHR vs NOC,
were 0.85 vs 0.47. Physicians misinterpreted the rules as not requiring imaging
for 4.0% of patients according to CCHR and 5.5% according to NOC (P = .04). Among all 2707 patients with a GCS score of 13
to 15, the CCHR had sensitivities of 100% (95% CI, 91%-100%) for 41 patients
requiring neurosurgical intervention and 100% (95% CI, 98%-100%) for 231 patients
with clinically important brain injury.
Conclusion For patients with minor head injury and GCS score of 15, the CCHR and
the NOC have equivalent high sensitivities for need for neurosurgical intervention
and clinically important brain injury, but the CCHR has higher specificity
for important clinical outcomes than does the NOC, and its use may result
in reduced imaging rates.
Each year, physicians in Canadian and US emergency departments (EDs)
treat more than 8 million patients with head injury, representing approximately
6.7% of the 120 million total ED visits.1 Although
some of these patients have sustained moderate or severe head injury leading
to death or serious morbidity, the vast majority of patients are classified
as having minimal or minor head injury.2,3 Patients
with minimal head injury have not experienced loss of consciousness or other
neurological alteration. Minor head injury or concussion
is defined by a history of loss of consciousness, amnesia, or disorientation
in a patient who is conscious and talking, ie, has a Glasgow Coma Scale (GCS)
score of 13 to 15.2- 6 Although
after a period of observation most patients with minor head injury can be
discharged without sequelae, a small portion deteriorate and require neurosurgical
intervention for intracranial hematoma.7,8 The
key to managing these patients is early diagnosis of intracranial injuries
using computed tomography (CT) followed by early craniotomy.2,9,10
Current use of CT for minor head injury is increasing rapidly, is highly
variable, and is inefficient. Between 1992 and 2000, use of CT imaging for
all conditions in US EDs has increased from 2.4% to 5.3% of all visits, a
120% increase.1 In 10 large Canadian hospitals,
the use of CT has increased 165%, from 30% to 80%, specifically for patients
with minor head injury.11 We previously demonstrated
large variation among similar Canadian teaching hospitals in ordering of CT
for minor head injury.11 Our data show that
90% of CTs are negative for clinically important brain injury.12 Inefficient
use of CT adds significantly to health care costs and adds to the burden of
overcrowding in EDs.13- 15 Rural
centers without CT scanners must arrange for costly and time-consuming transfers
of patients to larger urban centers for a CT scan.
Substantial potential for improving the efficiency of minor head injury
management appears possible through the application of clinical decision rules.
A clinical decision rule is derived from original
research and is defined as a decision-making tool that incorporates 3 or more
variables from the history, examination, or simple tests.16- 21 Two
decision rules have been independently developed to allow more selective ordering
of CT scans, more rapid discharge of patients with minor head injury, and
significant health care savings. The New Orleans Criteria (NOC) include 7
items (Box 1) that were developed
for a study of 1429 patients with minor head injury and a GCS score of 15,22 and have been widely disseminated in the United States.23 Our group derived the Canadian CT Head Rule (CCHR)
in a study of 3121 patients with minor head injury and a GCS score of 13 to
rule is based on 5 high-risk and 2 medium-risk criteria (Box 2).
Computed tomography is required for patients with minor head injury
with any 1 of the following findings. The criteria apply only to patients
who also have a Glasgow Coma Scale score of 15.
Older than 60 years
Drug or alcohol intoxication
Persistent anterograde amnesia (deficits in short-term
Visible trauma above the clavicle
Computed tomography is only required for patients with minor head injury
with any 1 of the following findings: Patients with minor head injury who
present with a Glasgow Coma Scale score of 13 to 15 after witnessed loss of
consciousness, amnesia, or confusion.
High Risk for Neurosurgical Intervention
1. Glasgow Coma Scale score lower than 15 at 2 hours
2. Suspected open or depressed skull fracture
3. Any sign of basal skull fracture†
4. Two or more episodes of vomiting
5. 65 years or older
Medium Risk for Brain Injury Detection
by Computed Tomographic Imaging
6. Amnesia before impact of 30 or more minutes
7. Dangerous mechanism‡
*The rule is not applicable if the patient did not experience a trauma,
has a Glasgow Coma Scale score lower than 13, is younger than 16 years, is
taking warfarin or has a bleeding disorder, or has an obvious open skull fracture.
†Signs of of basal skull fracture include hemotympanum, racoon
eyes, cerebrospinal fluid, otorrhea or rhinorrhea, Battle’s sign.
‡Dangerous mechanism is a pedestrian struck by a motor vehicle,
an occupant ejected from a motor vehicle, or a fall from an elevation of 3
or more feet or 5 stairs.
Decision tools may not perform as well in a validation setting as they
did in the initial derivation phase.26 Therefore,
the goal of this study was to prospectively compare the accuracy, reliability,
and potential impact of the CCHR and the NOC in minor head injury patients.
Such a validation study is an essential step prior to the implementation of
a decision rule for patient care.
We conducted this prospective cohort study in 9 Canadian tertiary care
teaching hospital EDs. We considered for enrollment consecutive adults who
had sustained acute minor head injury. Eligibility was based on the patient’s
having all of the following: (1) blunt trauma to the head resulting in witnessed
loss of consciousness, definite amnesia, or witnessed disorientation; (2)
initial ED GCS score of 13 or greater as determined by the treating physician,
and (3) injury within the previous 24 hours. Patients were ineligible if they
were younger than 16 years; had minimal head injury, ie, no loss of consciousness,
amnesia, or disorientation; had no clear history of trauma as the primary
event; had an obvious penetrating skull injury or obvious depressed skull
fracture; had focal neurological deficit; had unstable vital signs associated
with major trauma; had a seizure prior to assessment in the ED; had a bleeding
disorder or used oral anticoagulants; had returned for reassessment of the
same injury; or were pregnant. The hospital research ethics boards approved
the protocol without the need for informed consent. Patients who were followed
up through a telephone interview by the study nurse had an opportunity to
give verbal consent at that time.
All patient assessments were performed by emergency medicine attending
or resident physicians, who were trained by means of a 1-hour lecture session
given by the principal investigator. Although some physicians had participated
in the CCHR derivation study, none had previously used either decision rule
in clinical practice. After assessment and prior to CT, physicians recorded
their findings and rule interpretations on standardized data collection forms.
The CCHR and NOC rules were printed one on top of the other in large boxes
on the data collection form.27 When feasible,
some patients were independently assessed by a second emergency physician
to judge interobserver agreement.
The primary outcome was “need for neurosurgical intervention”
and the secondary outcome was “clinically important brain injury”
on CT. Need for neurosurgical intervention was defined as either death within
7 days secondary to head injury or the need for any of the following procedures
within 7 days: craniotomy, elevation of skull fracture, intracranial pressure
monitoring, or intubation for head injury (demonstrated on CT).
Clinically important brain injury was defined as any acute brain finding
revealed on CT and that would normally require admission to hospital and neurosurgical
follow-up. This definition was standardized based on the results of a formal
survey of 129 academic neurosurgeons, neuroradiologists, and emergency physicians
at 8 study sites and has been used by our group previously.12,28 All
brain injuries were considered clinically important unless the patient was
neurologically intact and had 1 of the following lesions on CT (1) solitary
contusion of less than 5 mm in diameter, (2) localized subarachnoid blood
less than 1 mm thick, (3) smear subdural hematoma less than 4 mm thick, or
(4) closed depressed skull fracture not through the inner table. After the
clinical examination, patients underwent standard CT of the head according
to the judgment of the treating physician. The CT scans were interpreted by
qualified staff neuroradiologists who were blinded to the information on the
data collection sheet. We have previously demonstrated the reliability of
these CT interpretations.12
We could not demand routine CT for all patients with minor head injury
because current practice at the study hospitals was that only 70% of eligible
patients currently undergo CT imaging. Consequently, all enrolled patients
who did not have imaging underwent a structured 14-day proxy outcome measure
administered by a registered nurse over the telephone. According to this tool,
patients were classified as having no clinically important brain injury if
they met all of the following explicit criteria at 14 days: headache absent
or mild, no complaints of memory or concentration problems, no seizure or
focal motor findings, and returned to normal daily activities. The assessment
of these criteria was made by a registered nurse who was unaware of the patient’s
status for the individual clinical predictor variables. Patients who did not
fulfill these criteria were recalled for clinical assessment and CT. Patients
could only be classified as having “brain injury” based on their
CT findings. We have previously validated the proxy outcome measure in a study
of 172 patients.29 Patients who could not be
reached were excluded from the final analysis. We searched for the names of
these latter patients in the ED records of the study hospitals during the
ensuing 30 days to ensure that no adverse outcomes were missed.
The 2 rules were assessed for their classification performance (ie,
sensitivity and specificity) for need for neurosurgical intervention and for
clinically important brain injury. The CCHR and the NOC were compared in the
cohort of patients who presented with a GCS score of 15. In addition, the
CCHR was assessed for all patients in the study, ie, those with presenting
GCS scores of 13 to 15. The “criterion interpretation” of the
rules, ie, positive or negative for the outcome measures, was made by an adjudication
committee that reviewed patient records and physician data form responses.
Interobserver agreement for each variable and for interpretation of the 2
rules was measured with the weighted κ coefficient. We evaluated accuracy
of the interpretations of the rule by the treating physician vs the criterion
interpretation by the investigators. We also descriptively presented data
regarding the physicians’ theoretical comfort and perceived ease of
use of the rules. Finally, we estimated the potential referral fractions for
CT based on the percentage of patients who would require CT according to the
2 rules. The referral fraction is an important measure of the usefulness of
a decision rule and reflects the potential impact on practice.
All P values were 2-tailed. Ninety-five percent
confidence intervals (CIs) were calculated for estimates, where appropriate.
Proportions were compared between the CCHR and NOC with unadjusted χ2 analysis. We estimated that a sample size of 2500 patients with minor
head injury and 1800 patients with a GCS score of 15 would be required to
provide a sufficient number of head injury cases to allow a 95% CI of 97%
to 100% around a sensitivity of 99%. All analyses were conducted using various
statistical software programs including SAS, version 8.2 for Unix (SAS Institute
Inc, Cary, NC) and P<.05 was considered statistically
From June 2000 to December 2002, 4248 eligible patients were seen in
the study hospitals. Of these, 2707 patients had data forms completed by the
physicians and had complete outcome assessments (80.2% had CT; 19.8% had the
proxy outcome assessment tool). In addition 1330 eligible patients did not
have data forms completed by the physicians, and another 211 patients had
data forms but no outcome assessments, ie, no CT and could not be reached
for the proxy outcome. A total of 307 different physicians participated.
Table 1 compares the characteristics
of the entire patient group and the subgroup with a GCS score of 15. In these
2 cohorts, 1.5% and 0.4%, respectively, required neurosurgical intervention
and 8.5% and 5.3% of cases, respectively, had clinically important brain injury
(Table 2). All patients with clinically
important brain injury were identified in the ED without the need for the
proxy outcome assessment tool. Among the 97 patients with clinically unimportant
injury, none required neurosurgical intervention.
Among the eligible patients not enrolled, demographic and clinical characteristics
were very similar to those of the enrolled patients (data not shown). In addition,
the 211 patients who had no outcome assessment were similar to the enrolled
patients other than having undergone no imaging (data not shown). In 13 cases,
patients with acute brain injury were discharged from the ED without the physician
identifying the lesion on CT; however, only 2 of these patients had clinically
important brain injury. These patients were subsequently identified by routine
radiological review 1 or 2 days after the initial ED visit. No patients experienced
an adverse outcome and neither of the 2 missed clinically important brain
injury cases required hospitalization.27
Table 3 compares the performance
of various clinical predictors between patients with and without clinically
important brain injury, showing both univariate association and interobserver
agreement. Three of the 7 NOC criteria and 7 of 7 CCHR criteria showed statistically
significant association. Other variables associated with brain injury included
an initial GCS score of 13, any decrease in GCS score after arrival in the
ED, and an object recall test score of less than 3 out of 3. The κ values
for interobserver agreement of these variables ranged from 0.18 to 1.0.
The accuracy of the 2 rules is compared in Table 4 for the 1822 patients with a GCS score of 15. The sensitivities
for need for neurosurgical intervention were 100% (95% CI, 63%-100%) for the
CCHR and the NOC and their respective specificities were 76.3% (95% CI, 74%-78%)
vs 12.1% (95% CI, 11%-14%; P<.001). The CCHR and
NOC were both 100% (95% CI, 96%-100%) sensitive for clinically important brain
injury and their respective specificities were 50.6% (95% CI, 48%-53%) and
12.7% (95% CI, 11%-14%; P<.001). For all 145 cases
of brain injury, including the 48 cases of clinically unimportant injury,
the sensitivities were 93.1% for CCHR and 98.6% for NOC and the specificities
were 51.4% for CCHR and 12.9% for NOC.
Table 5 summarizes the classification
performance of the CCHR for all 2707 minor head injury patients in the cohort,
ie, those with a GCS score of 13 to 15. For 41 cases of neurosurgical intervention,
using only the 5 high-risk criteria, CCHR had a sensitivity of 100% (95% CI,
91%-100%) and a specificity of 65.6% (95% CI, 64%-67%). For clinically important
brain injury using the 7 high- and medium-risk criteria, the sensitivity was
100% (95% CI, 98%-100%) and the specificity was 41.1% (95% CI, 39%-43%).
The weighted κ value for physician interpretation of the overall
rules in 49 cases was 0.85 (95% CI, 0.58-0.92) for the CCHR and 0.47 (95%
CI, −0.13 to 1.0) for the NOC. A value greater than 0.6 is generally
considered to reflect reasonable agreement.
Clinical acceptability was assessed in 2 ways. Using a 5-point scale,
physicians indicated that they would have been uncomfortable or very uncomfortable
in applying the CCHR for 9.5% (95% CI, 8%-11%) of cases compared with 11.7%
(95% CI, 10%-13%) for NOC (P=.03). Physicians misinterpreted
the rules as not requiring imaging on the data forms, in contrast to subsequent
investigator interpretation that imaging was indicated, for 4.0% (95% CI,
3%-5%) of cases according to CCHR and 5.5% (95% CI, 5%-7%) according to NOC
Potential impact on CT ordering was evaluated by estimating the proportion
of patients who would require CT imaging according to the rules. Among patients
with a GCS score of 15, the rate was 52.1% (95% CI, 50%-54%) for the CCHR
and 88.0% (95% CI, 86%-89%) for the NOC (P<.001).
For the entire cohort of 2707 patients, the CT imaging rate according to CCHR
would have been 62.4% (95% CI, 61%-64%); the actual CT rate for these cases
was 80.2% at the 9 study sites. The potential impact on ED crowding was assessed
by measuring the mean ED length of stay among the 1884 patients (GCS 13-15)
whose CT scan showed no injury. Patients who did not undergo CT (n = 447)
spent approximately 2.5 fewer hours in the ED (180.8 vs 323.9 minutes; P<.01) than patients who had undergone CT imaging (n = 1437).
In this large prospective comparison of clinical decision rules for
the use of CT in minor head injury, both the CCHR and the NOC were highly
sensitive for 2 important outcome measures, need for neurosurgical intervention
and clinically important brain injury for patients with a GCS score of 15.
On the other hand, the specificity of the CCHR was higher than that of the
NOC and application of the CCHR would result in lower use of CT imaging. In
addition, the reliability of physician interpretation of the CCHR was higher,
reflecting better interobserver agreement. Clinician acceptance of both rules
appeared to be similarly high. The NOC were only developed for use in patients
with GCS score of 15. As measured in the larger cohort of patients with a
GCS score of 13 to 15, the CCHR had 100% sensitivity for identifying clinically
important brain injury and patients requiring neurosurgical intervention.
This prospective validation study was designed and conducted according
to strict methodological standards,16- 18,30,31 similar
to our previous approach of comparing 2 decision rules for cervical spine
radiography.19,32 The outcome
measures of clinically important brain injury and need for neurosurgical intervention
were carefully defined and are clearly of clinical importance. Patients were
selected for the study according to explicit and transportable inclusion criteria
rather than on the subjective decision of physicians to order CT imaging.
A large number of patients with a wide spectrum of injury severity were enrolled.
We did, however, exclude children as we believe that pediatric cases require
unique criteria and should be investigated in a large separate study. Also
evaluated were other important measures besides accuracy, including interobserver
agreement, acceptability, and potential impact on practice.
This study has potential limitations although most apply equally to
the evaluation of both rules. While not all eligible cases were enrolled,
no selection bias could be detected and the characteristics of enrolled and
nonenrolled patients were similar. Patient enrollment required ED physicians
to assess patients and voluntarily complete data forms in the midst of their
busy clinical responsibilities. In many instances, this was not feasible.
Some patients could not be reached for follow-up but we believe it is highly
unlikely that any experienced important missed injury because such patients
were completely intact neurologically and were considered to be very low risk
by the physicians. In addition, none of these patients returned to the treating
hospital or any other regional neurosurgical center within 30 days after their
initial ED visit with minor head injury. Although some patients were transferred
from other hospitals, only a few of those patients had undergone CT imaging
prior to arrival and the treating physicians did not know the status of the
patient’s brain injury prior to their assessment.
Some may be concerned about the use of clinically important brain injury
as one of the outcome measures although it was applied equally to both rules.
There has been very good acceptance of this definition by Canadian academic
neurosurgeons, neuroradiologists, and emergency physicians who see this as
a pragmatic and safe outcome measure.28 Practice
in most Canadian centers is to neither admit nor have a neurosurgeon follow
up the patients with clinically unimportant lesions on CT. Furthermore, the
primary outcome, need for neurosurgical intervention, was tightly defined
and is clearly of clinical importance. Finally, a secondary analysis found
similar performance of both rules for all brain injuries, regardless of clinical
Not all study patients underwent CT imaging because the Canadian clinicians
in the study occasionally do not order imaging when they consider patients
to be low risk. Cases were classified as having no clinically important injury
only if they satisfied all criteria on the 14-day proxy outcome tool, which
has been validated and which was used equally for both rules.29
One potential concern is whether Canadian physicians, who are more familiar
with the CCHR, could have unconsciously biased the response to favor the CCHR.
We believe this is unlikely. The NOC were accurately and prominently presented
on the data forms and physicians were well informed of these criteria. In
addition, our data demonstrated that few errors were made by the physicians
in interpreting the NOC.
Several factors might account for our findings of lower specificity
for the NOC compared with the CCHR. First, NOC was originally derived in a
sample of 520 patients and then validated in a sample of 909 patients, with
a total of only 6 patients who required neurosurgical intervention. Our study
found NOC to have a specificity of 12.1% for brain injury even though this
rule was designed only for use in patients with a GCS score of 15. We also
found low specificity for the NOC when we conducted a retrospective review
performed on our phase 1 database of 3121 patients. Second, we believe that
a number of the NOC criteria lack accuracy or reliability when used to evaluate
patients with minor head injury. The data presented in this study show that
only 3 of 7 NOC criteria have a significant association with clinically important
brain injury. Only 2 of the NOC criteria displayed κ values exceeding
0.60. In contrast, all 7 of the CCHR variables showed a statistical association
with clinically important brain injury and 5 of 7 displayed κ values
The true test of a clinical decision rule is whether clinical behavior
is affected.33- 36 Toward
this end, we are now conducting a randomized multicenter implementation trial
that compares strategies using and not using the CCHR as a guide for the use
of CT imaging. Only through such real-life implementation studies can the
potential impact of these decision tools be determined.37- 39
In summary, this study confirmed the high sensitivity of both the CCHR
and NOC rules for imaging in patients with minor head injury with a GCS score
of 15. The CCHR had higher specificity and reliability and would have greater
potential impact on CT ordering rates than the NOC. In addition, the CCHR
performed equally well in a larger and more severely injured cohort of patients
presenting with GCS scores ranging from 13 to 15. These data suggest that
the CCHR has the potential to improve efficiency in the use of CT imaging
for patients with minor head injury.
Corresponding Author: Ian G. Stiell, MD,
MSc, FRCPC, Clinical Epidemiology Unit, F657, Ottawa Health Research Institute,
1053 Carling Ave, Ottawa, Ontario, Canada K1Y 4E9.
Author Contributions: Dr Stiell had full access
to all of the data in the study and takes responsibility for the integrity
of the data and the accuracy of the data analysis.
Study concept and design: Stiell, Schull, Brison,
Cass, Eisenhauer, Dreyer, Reardon, Greenberg, Lesiuk, MacPhail, Wells.
Acquisition of data: Stiell, Clement, Rowe,
Schull, Brison, Cass, Eisenhauer, McKnight, Bandiera, Holroyd, Lee, Dreyer,
Analysis and interpretation of data: Stiell,
Worthington, Lesiuk, Wells.
Drafting of the manuscript: Stiell, Clement,
Rowe, Schull, Eisenhauer, Reardon.
Critical revision of the manuscript for important
intellectual content: Rowe, Brison, Cass, Eisenhauer, McKnight, Bandiera,
Holroyd, Lee, Dreyer, Worthington, Reardon, Greenberg, Lesiuk, MacPhail, Wells.
Statistical analysis: Stiell, Wells.
Obtained funding: Stiell, Clement.
Administrative, technical, or material support:
Clement, Schull, Brison, Cass, Eisenhauer, Bandiera, Lee, Dreyer, Worthington,
Reardon, Lesiuk, MacPhail.
Study supervision: Stiell, Clement, Rowe, Brison,
Eisenhauer, McKnight, Holroyd, Greenberg.
Financial Disclosures: None reported.
Funding/Support: This study was funded by peer-reviewed
grants MT-13700 from the Canadian Institutes of Health Research and 11996N
from the Ontario Ministry of Health Emergency Health Services Committee. Dr
Stiell holds a Distinguished Investigator Award, Dr Schull holds a New Investigator
Award, and Dr Rowe holds a Canada Research Chair, all from the Canadian Institutes
of Health Research.
Role of the Sponsor: The Canadian Institutes
of Health Research had no role in the design and conduct of the study; the
collection, management, analysis, and interpretation of data; or the preparation,
review, or approval of the manuscript.
Participating Hospitals:Alberta: University of Alberta Hospital, Edmonton; British Columbia: Royal Columbian Hospital, New Westminster, and Vancouver
General Hospital, Vancouver; and Ontario: Kingston
General Hospital, Kingston; Ottawa Hospital–Civic Campus and Ottawa
Hospital–General Campus, Ottawa; Sunnybrook and Women's College Health
Sciences Centre, Toronto; London Health Sciences Centre–Victoria Campus,
London; and St Michael’s Hospital, Toronto.
Acknowledgment: We thank the following for
their much appreciated efforts: study nurses Erica Battram, RN, Kim Bradbury,
RN, Pamela Sheehan, RN, and Taryn MacKenzie, RN, from The Ottawa Hospitals;
Kathy Bowes, RN, from Kingston General Hospital; Karen Code, RN, and Ann Zerdin,
RN, from Sunnybrook and Women’s College; Virginia Blak-Genoway, RN,
from St Michael’s Hospital; Evelyn Gilkinson, RN, and Sharon Mason from
London Health Sciences Centre; Percy MacKerricher, RN, from the Royal Columbian
Hospital; Jan Buchanan, RN, from Vancouver General Hospital; Jackie Miller,
RN, Lloyd Tapper, RN, and Terry Shewchuk, RN, from University of Alberta Hospital;
data management MyLinh Tran and Emily Moen; manuscript preparation Irene Harris,
all of whom received salary support; all the nurses and clerks at the study
sites who assisted with case identification and data collection. We are particularly
grateful to the many staff physicians and residents who patiently completed
thousands of data collection forms and without whose voluntary assistance
this study would not have been possible.