Ottawa clinical decision rule helps identify subarachnoid hemorrhage

A new clinical decision rule had a sensitivity and a specificity approaching 100% in ruling out subarachnoid hemorrhage among patients who presented to an emergency department with acute headache, in a validation study reported Sept. 25 in JAMA.

Using this new tool, which requires only that the clinician answer six simple questions regarding the patient’s presentation, has the potential to reduce the number of costly and sometimes invasive procedures that are currently relied on to distinguish subarachnoid hemorrhage (SAH) from other pathologies in such patients, said Dr. Jeffrey J. Perry of the department of emergency medicine at the University of Ottawa (Ont.) and the clinical epidemiology program at the Ottawa Hospital Research Institute and his associates.

At present it can be very difficult to determine which patients require further investigation among those who present to the emergency department with acute severe headache but who are neurologically intact. Yet this is exactly the presentation of half of all patients who have SAH. It is estimated that approximately 6% of patients with confirmed SAHs were misdiagnosed during an initial ED evaluation.

Standard practice with such patients is to perform an unenhanced head CT, and to proceed to a lumbar puncture if the results of the CT are negative. But lumbar puncture carries some risk and can itself produce a headache that muddies the diagnostic picture.

Dr. Perry and his colleagues first devised three clinical decision rules to assist clinicians in ruling out SAH, then assessed the three rules for their accuracy, reliability, and acceptability to clinicians in a validation cohort of consecutive patients aged 16 years and older who presented to an ED with a nontraumatic headache that reached maximal intensity within 1 hour.

There were 2,131 study subjects with a mean age of 44 years. Approximately 61% were women, and 26% arrived at the ED by ambulance.

All of these participants were treated by attending physicians certified in emergency medicine or by supervised residents at 10 university-affiliated urban, Canadian tertiary care teaching hospitals during a 4-year period. All were alert and oriented, with no neurologic deficits.

A total of 132 patients (6.2%) were found to have SAH.

After comparing the performances of the three candidate decision rules, the investigators refined the decision tool to combine the six factors that were most predictive of SAH: age of 40 years or older, neck pain or stiffness, witnessed loss of consciousness, onset of headache during exertion, "thunderclap headache" (defined as instantly peaking pain), and limited neck flexion (defined as the inability to touch chin to chest when upright or to raise the head 8 cm off the bed when supine).

The presence of any one of these six factors indicates that SAH is possible and further investigation is required using CT and perhaps lumbar puncture, Dr. Perry and his associates said.

This refined clinical decision rule, which they termed the Ottawa SAH rule, had an overall sensitivity of 99.2% and a specificity of 99.6% in identifying SAHs when the derivation cohort and the validation cohort were combined. Of 232 patients with SAH in the cohorts altogether, this rule identified 260, Dr. Perry and his associates reported (JAMA 2013;310:1248-55)

This level of sensitivity and specificity is expected to be deemed clinically acceptable by emergency physicians.

"Following this rule would decrease the investigation rate" – the rate of further assessment using CT and lumbar puncture – "to 74.0% from the current investigation rate of 84.1%," they added.

The Ottawa SAH rule must be evaluated further before it can be adopted into clinical practice. "An implementation study is the next step required to determine how the Ottawa SAH rule performs in clinical practice, assess the actual effects on patient care and patient outcomes, and conduct a formal health economic analysis," the researchers noted.

After that, the rule "may help to standardize which patients with acute headache require investigations, and may provide evidence for physicians to use in deciding which patients require imaging to decrease the relatively high rate of missed SAH."

This study was supported by the Canadian Institutes for Health Research, the University of Ottawa, and the Vancouver Coastal Health Research Institute. No financial conflicts of interest were reported.

A new clinical decision rule had a sensitivity and a specificity approaching 100% in ruling out subarachnoid hemorrhage among patients who presented to an emergency department with acute headache, in a validation study reported Sept. 25 in JAMA.

Using this new tool, which requires only that the clinician answer six simple questions regarding the patient’s presentation, has the potential to reduce the number of costly and sometimes invasive procedures that are currently relied on to distinguish subarachnoid hemorrhage (SAH) from other pathologies in such patients, said Dr. Jeffrey J. Perry of the department of emergency medicine at the University of Ottawa (Ont.) and the clinical epidemiology program at the Ottawa Hospital Research Institute and his associates.

At present it can be very difficult to determine which patients require further investigation among those who present to the emergency department with acute severe headache but who are neurologically intact. Yet this is exactly the presentation of half of all patients who have SAH. It is estimated that approximately 6% of patients with confirmed SAHs were misdiagnosed during an initial ED evaluation.

Standard practice with such patients is to perform an unenhanced head CT, and to proceed to a lumbar puncture if the results of the CT are negative. But lumbar puncture carries some risk and can itself produce a headache that muddies the diagnostic picture.

Dr. Perry and his colleagues first devised three clinical decision rules to assist clinicians in ruling out SAH, then assessed the three rules for their accuracy, reliability, and acceptability to clinicians in a validation cohort of consecutive patients aged 16 years and older who presented to an ED with a nontraumatic headache that reached maximal intensity within 1 hour.

There were 2,131 study subjects with a mean age of 44 years. Approximately 61% were women, and 26% arrived at the ED by ambulance.

All of these participants were treated by attending physicians certified in emergency medicine or by supervised residents at 10 university-affiliated urban, Canadian tertiary care teaching hospitals during a 4-year period. All were alert and oriented, with no neurologic deficits.

A total of 132 patients (6.2%) were found to have SAH.

After comparing the performances of the three candidate decision rules, the investigators refined the decision tool to combine the six factors that were most predictive of SAH: age of 40 years or older, neck pain or stiffness, witnessed loss of consciousness, onset of headache during exertion, "thunderclap headache" (defined as instantly peaking pain), and limited neck flexion (defined as the inability to touch chin to chest when upright or to raise the head 8 cm off the bed when supine).

The presence of any one of these six factors indicates that SAH is possible and further investigation is required using CT and perhaps lumbar puncture, Dr. Perry and his associates said.

This refined clinical decision rule, which they termed the Ottawa SAH rule, had an overall sensitivity of 99.2% and a specificity of 99.6% in identifying SAHs when the derivation cohort and the validation cohort were combined. Of 232 patients with SAH in the cohorts altogether, this rule identified 260, Dr. Perry and his associates reported (JAMA 2013;310:1248-55)

This level of sensitivity and specificity is expected to be deemed clinically acceptable by emergency physicians.

"Following this rule would decrease the investigation rate" – the rate of further assessment using CT and lumbar puncture – "to 74.0% from the current investigation rate of 84.1%," they added.

The Ottawa SAH rule must be evaluated further before it can be adopted into clinical practice. "An implementation study is the next step required to determine how the Ottawa SAH rule performs in clinical practice, assess the actual effects on patient care and patient outcomes, and conduct a formal health economic analysis," the researchers noted.

After that, the rule "may help to standardize which patients with acute headache require investigations, and may provide evidence for physicians to use in deciding which patients require imaging to decrease the relatively high rate of missed SAH."

This study was supported by the Canadian Institutes for Health Research, the University of Ottawa, and the Vancouver Coastal Health Research Institute. No financial conflicts of interest were reported.

A new clinical decision rule had a sensitivity and a specificity approaching 100% in ruling out subarachnoid hemorrhage among patients who presented to an emergency department with acute headache, in a validation study reported Sept. 25 in JAMA.

Using this new tool, which requires only that the clinician answer six simple questions regarding the patient’s presentation, has the potential to reduce the number of costly and sometimes invasive procedures that are currently relied on to distinguish subarachnoid hemorrhage (SAH) from other pathologies in such patients, said Dr. Jeffrey J. Perry of the department of emergency medicine at the University of Ottawa (Ont.) and the clinical epidemiology program at the Ottawa Hospital Research Institute and his associates.

At present it can be very difficult to determine which patients require further investigation among those who present to the emergency department with acute severe headache but who are neurologically intact. Yet this is exactly the presentation of half of all patients who have SAH. It is estimated that approximately 6% of patients with confirmed SAHs were misdiagnosed during an initial ED evaluation.

Standard practice with such patients is to perform an unenhanced head CT, and to proceed to a lumbar puncture if the results of the CT are negative. But lumbar puncture carries some risk and can itself produce a headache that muddies the diagnostic picture.

Dr. Perry and his colleagues first devised three clinical decision rules to assist clinicians in ruling out SAH, then assessed the three rules for their accuracy, reliability, and acceptability to clinicians in a validation cohort of consecutive patients aged 16 years and older who presented to an ED with a nontraumatic headache that reached maximal intensity within 1 hour.

There were 2,131 study subjects with a mean age of 44 years. Approximately 61% were women, and 26% arrived at the ED by ambulance.

All of these participants were treated by attending physicians certified in emergency medicine or by supervised residents at 10 university-affiliated urban, Canadian tertiary care teaching hospitals during a 4-year period. All were alert and oriented, with no neurologic deficits.

A total of 132 patients (6.2%) were found to have SAH.

After comparing the performances of the three candidate decision rules, the investigators refined the decision tool to combine the six factors that were most predictive of SAH: age of 40 years or older, neck pain or stiffness, witnessed loss of consciousness, onset of headache during exertion, "thunderclap headache" (defined as instantly peaking pain), and limited neck flexion (defined as the inability to touch chin to chest when upright or to raise the head 8 cm off the bed when supine).

The presence of any one of these six factors indicates that SAH is possible and further investigation is required using CT and perhaps lumbar puncture, Dr. Perry and his associates said.

This refined clinical decision rule, which they termed the Ottawa SAH rule, had an overall sensitivity of 99.2% and a specificity of 99.6% in identifying SAHs when the derivation cohort and the validation cohort were combined. Of 232 patients with SAH in the cohorts altogether, this rule identified 260, Dr. Perry and his associates reported (JAMA 2013;310:1248-55)

This level of sensitivity and specificity is expected to be deemed clinically acceptable by emergency physicians.

"Following this rule would decrease the investigation rate" – the rate of further assessment using CT and lumbar puncture – "to 74.0% from the current investigation rate of 84.1%," they added.

The Ottawa SAH rule must be evaluated further before it can be adopted into clinical practice. "An implementation study is the next step required to determine how the Ottawa SAH rule performs in clinical practice, assess the actual effects on patient care and patient outcomes, and conduct a formal health economic analysis," the researchers noted.

After that, the rule "may help to standardize which patients with acute headache require investigations, and may provide evidence for physicians to use in deciding which patients require imaging to decrease the relatively high rate of missed SAH."

This study was supported by the Canadian Institutes for Health Research, the University of Ottawa, and the Vancouver Coastal Health Research Institute. No financial conflicts of interest were reported.