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This study will validate a rule for physicians to use to determine which headache patients seen in emergency require investigation for possible subarachnoid haemorrhage. A subarachnoid hemorrhage (SAH) is type of hemorrhagic stroke caused by a rupture of a brain aneurysm. One percent of emergency department visits for a headache have a SAH. Half of all patients who have a SAH die within six months and of those who survive, almost half have permanent neurological symptoms. Currently SAHs are diagnosed using CT (a type of X-Ray) scans and lumbar punctures (LP) (where a needle is put into the lower back to get spinal fluid). CT scans can miss up to 10% of SAHs. Lumbar punctures miss fewer SAHs, however it is a painful and invasive procedure. Currently there are no guidelines to help physicians decide which of these patients require investigations for this important disorder. Patients who have a delay in diagnosis fare much worse than those who receive prompt treatment. Given the need for a correct diagnosis and the cost and invasiveness of over investigating patients, a clinical decision rule is needed to determine which patients with a headache require prompt evaluation. This study is currently validating the proposed rules in 8 Canadian sites. We anticipating completing the study in April 2009.
Principal Investigator: Dr. Jeffrey Perry
Co-Investigators: Dr. Ian Stiell, Dr. Marco Sivilotti, Dr. Michael Bullard,
Dr. Corrine Hohl, Dr. Merril Pauls, Dr. George Wells, Doug Coyle, Dr. Andrew Worster, Dr. Howard Lesiuk
Funding Agency: Canadian Institutes of Health Research (CIHR)
Duration of Study: 4 years
For more information, please contact Jane Sutherland, Study Coordinator.
Background
Acute headache is a common emergency department (ED) problem accounting for 4.5% of all ED visits.
The most important emergent diagnosis in this patient population is non-traumatic
subarachnoid hemorrhage (SAH),
a type of hemorrhagic stroke which has a 50% mortality rate but only accounts for 1% of ED visits for headache.
Current strategies using computed tomography (CT) and/or lumbar puncture (LP) to investigate
patients with headache to rule out SAH are inefficient and lead to increased ED length of stay and
increased health care costs.
The ED use of CT has risen substantially in Canada leading to considerable inefficiency,
with over 95% of scans for "rule out SAH" being negative for SAH.
LP is recommended when CT is negative, as CT can miss 2-10% of SAHs.
LPs are invasive, painful procedures with potential patient complications (infection, post LP headache).
Additional costs occur when patients from rural/remote areas are transferred for investigation.
Despite the inefficiency of current investigations, up to 40% of patients with SAH are
initially misdiagnosed resulting in poorer outcomes.
This renewal application builds on previous a CIHR grant to derive a clinical decision rule
for acute headache to rule out SAH (phase I, CIHR (67107, 2004-2006).
In phase I, we prospectively enrolled 1808 patients from six tertiary care hospital EDs
with 115 positive SAH cases.
This represented 69% of all eligible patient visits during the study period.
From this cohort we derived several highly sensitive clinical decision rules to
direct investigations to rule out SAH.
We were able to derive several rules with retrospective sensitivity of 100% (95% CI 97-100%) for SAH,
while reducing investigation rates to 63% from the current rate of 84%.
The final clinical decision rule will allow physicians to be more selective in
ordering investigations with fewer missed SAH and fewer LP complications.
Objectives
The goal of phase II is to prospectively assess the accuracy of the
three best performing clinical decision rules derived in phase I in a
new set of alert neurologically intact ED patients with acute headache without altering patient care.
The specific objectives are to assess prospectively:
i) the accuracy or classification performance of each proposed clinical decision rule to rule out SAH;
ii) the reliability of each clinical decision rule;
iii) the clinical sensibility, i.e. physicians' accuracy, comfort and ease of use with applying each rule;
iv) the potential of the each rule to reduce investigations (i.e. cranial CT and lumbar puncture);
v) the potential for refinement of the rules (improve specificity);
vi) the potential savings with widespread implementation of the most efficient rule
in a preliminary economic evaluation.
Methods
This four year prospective cohort will be conducted in the EDs of 10 university affiliated Canadian hospitals.
Data management and analysis will be conducted at the clinical epidemiology unit of the
Ottawa Hospital Research Institute.
In this validation study, patients will be managed according to standard clinical practice and
not according to any of the proposed clinical decision rules.
The study will enrol consecutive alert patients over 15 years of age with acute non-traumatic headache.
Emergency physicians will assess and classify each patient for the need for investigation
according to each proposed rule to rule out SAH prior to CT or LP.
A subset of patients will be examined independently by two physicians.
The classification performance of each rule for predicting SAH will be assessed with
95% confidence intervals for sensitivity, specificity, negative predictive value,
positive predictive value and likelihood ratios, which will allow users to estimate
the probability of the outcomes in patients, given a negative status for the final "Canadian SAH Rule".
Reliability will be assessed by the kappa coefficient.
We will attempt to refine (i.e. improve specificity without loss of sensitivity) the rules
by recursive partitioning analysis techniques.
The preliminary economic analysis will determine the potential incremental cost savings
from a societal perspective that could be attributed to use of the rule.
The estimated sample size is 2700 patients (including 170 SAH cases).
Importance
This prospective validation study is an essential step in the development of an accurate, reliable, and
clinically sensible decision rule and must be undertaken before any rule can be recommended for actual patient care.
The final SAH Rule will permit physicians to standardize care of alert neurologically intact
non-traumatic acute headache patients and be much more selective in performing CT and LP.
The best rule will be subsequently implemented to lower health care costs,
decrease morbidity of unnecessary LPs and decrease the mortality of missed SAHs.
The impact of this rule should be similar to the Ottawa Ankle Rules that have been readily
adopted by physicians and have significantly reduced health care costs.
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