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Background: With the recent increase use of observation care, it is important to understand the characteristics of patients that utilize this care and either have a prolonged observation care stay or require admission., Methods: We a conducted a retrospective cohort study utilizing 5% sample data from Medicare patients age ≥65 years that was nationally representative in the year 2013. We performed a generalized estimating equation (GEE) logistic regression analysis to evaluate the relationship between an unsuccessful observation stay (defined as either requiring an inpatient admission from observation or having a prolonged observation stay) compared to having successful observation care. Observation cut offs of "successful" vs. "unsuccessful" were based on the CMS 2 midnight rule., Results: Of 154,756 observation stays in 2013, 19 percent (n = 29,604) were admitted to the inpatient service and 34,275 (22.2%) had a prolonged observation stay. The two diagnoses most likely to have an unsuccessful observation stay were intestinal infections (OR 1.56, 95% CI 1.32⁻1.83) and pneumonia (OR 1.26, 95% CI 1.13⁻1.41)., Conclusion: We found patients placed in observation care with intestinal infections and pneumonia to have the highest odds of either being admitted from observation or having a prolonged observation stay.

Introduction: The emergency department (ED) is an inherently high-risk setting. Risk scores can help practitioners understand the risk of ED patients for developing poor outcomes after discharge. Our objective was to develop two risk scores that predict either general inpatient admission or death/intensive care unit (ICU) admission within seven days of ED discharge., Methods: We conducted a retrospective cohort study of patients age > 65 years using clinical data from a regional, integrated health system for years 2009-2010 to create risk scores to predict two outcomes, a general inpatient admission or death/ICU admission. We used logistic regression to predict the two outcomes based on age, body mass index, vital signs, Charlson comorbidity index (CCI), ED length of stay (LOS), and prior inpatient admission., Results: Of 104,025 ED visit discharges, 4,638 (4.5%) experienced a general inpatient admission and 531 (0.5%) death or ICU admission within seven days of discharge. Risk factors with the greatest point value for either outcome were high CCI score and a prolonged ED LOS. The C-statistic was 0.68 and 0.76 for the two models., Conclusion: Risk scores were successfully created for both outcomes from an integrated health system, inpatient admission or death/ICU admission. Patients who accrued the highest number of points and greatest risk present to the ED with a high number of comorbidities and require prolonged ED evaluations., Competing Interests: Conflicts of Interest: By the WestJEM article submission agreement, all authors are required to disclose all affiliations, funding sources and financial or management relationships that could be perceived as potential sources of bias. No author has professional or financial relationships with any companies that are relevant to this study. There are no conflicts of interest or sources of funding to declare.

Background: Over the past decade, a growing number of older Medicare beneficiaries visit the Emergency Department (ED) and have been placed in observation care. We investigated and compared the prevalence and factors associated with patients age ≥ 65 years with Medicare insurance who are placed in the hospital, observation care, or discharged following an ED visit., Methods: We conducted a retrospective cohort study using data from a nationally representative 5% sample of Medicare patients age ≥ 65 years during the year 2013. We performed multiple generalized estimating equation (GEE) logistic regression analyses to assess the relationship between placement in a hospital vs. discharge, observation care vs. discharge, and observation care vs. admission., Results: Of 537,455 Medicare beneficiaries age ≥ 65 years who visited an ED in 2013, 48.0% (N= 258,083) were discharged, 10.5% (N=56,184) placed in observation care, and 41.5% (N=223,188) were admitted to the inpatient service following the ED visit. The top 2 diagnoses associated with placement in the hospital vs. discharge were ischemic heart disease and renal disease. Patients with symptomatic diagnoses such as chest pain and dizziness were more likely to be placed in observation care following an ED visit as compared to admission to the hospital., Conclusion: Compared to prior studies, we found a greater number of older Medicare ED patients placed in observation care and a lower number admitted to the hospital. Most common diagnoses of placement in observation care were symptom-based as compared to being admitted to the hospital which were disease-based.

Objective: Vital signs are critical markers of illness severity in the emergency department (ED). Providers need to understand the abnormal vital signs in older adults that are problematic. We hypothesized that in patients age > 65 years discharged from the ED, there are abnormal vital signs that are associated with an admission to an inpatient bed within 7 days of discharge., Methods: We conducted a retrospective cohort study using data from a regional integrated health system of members age > 65 years during the years 2009 to 2010. We used univariate contingency tables to assess the relationship between hospital admission within 7 days of discharge and vital sign (including systolic blood pressure [sBP], heart rate [HR], body temperature, and pulse oximetry [SpO 2 ] values measured closest to discharge) using standard thresholds for abnormal and thresholds derived from the study data., Results: Of 104,025 ED discharges, 4,638 (4.5%) were followed by inpatient admission within 7 days. Vital signs had a greater odds of admission beyond a single cutoff. The vital signs with at least twice the odds of admission were sBP < 97 mm Hg (odds ratio [OR] = 2.02, 95% CI = 1.57-2.60), HR > 101 beats/min (OR = 2.00 95% CI = 1.75-2.29), body temperature > 37.3°C (OR = 2.14, 95% CI = 1.90-2.41), and pulse oximetry < 92 SpO 2 (OR = 2.04, 95% CI = 1.55-2.68). Patients with two vital sign abnormalities per the analysis had the highest odds of admission. A majority of patients discharged with abnormal vital signs per the analysis were not admitted within 7 days of ED discharge., Conclusion: While we found a majority of patients discharged with abnormal vital signs as defined by the analysis, not to be admitted after discharge, we identified vital signs associated with at least twice the odds of admission., (© 2017 by the Society for Academic Emergency Medicine.)

Study Objective: The emergency department (ED) is an inherently high-risk setting. Our objective is to identify the factors associated with the combined poor outcome of either death or an ICU admission shortly after ED discharge in older adults., Methods: We conducted chart review of 600 ED visit records among adults older than 65 years that resulted in discharge from any of 13 hospitals within an integrated health system in 2009 to 2010. We randomly chose 300 patients who experienced the combined outcome within 7 days of discharge and matched case patients to controls who did not experience the outcome. Two emergency physicians blinded to the outcome reviewed the records and identified whether a number of characteristics were present. Predictors of the outcome were identified with conditional logistic regression., Results: Of 1,442,594 ED visits to Kaiser Permanente Southern California in 2009 to 2010, 300 unique cases and 300 unique control records were randomly abstracted. Characteristics associated with the combined poor outcome included cognitive impairment (adjusted odds ratio [AOR] 2.10; 95% confidence interval [CI] 1.19 to 3.56), disposition plan change (AOR 2.71; 95% CI 1.50 to 4.89), systolic blood pressure less than 120 mm Hg (AOR 1.48; 95% CI 1.00 to 2.20), and pulse rate greater than 90 beats/min (AOR 1.66; 95% CI 1.02 to 2.71)., Conclusion: We found that older patients discharged from the ED with a change in disposition from "admit" to "discharge," cognitive impairment, systolic blood pressure less than 120 mm Hg, and pulse rate greater than 90 beats/min were at increased risk of death or ICU admission shortly after discharge. Increased awareness of these high-risk characteristics may improve ED disposition decisionmaking., (Copyright © 2016 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.)

Study Objective: We assess whether a panel of emergency department (ED) crowding measures, including 2 reported by the Centers for Medicare & Medicaid Services (CMS), is associated with inpatient admission and death within 7 days of ED discharge., Methods: We conducted a retrospective cohort study of ED discharges, using data from an integrated health system for 2008 to 2010. We assessed patient transit-level (n=3) and ED system-level (n=6) measures of crowding, using multivariable logistic regression models. The outcome measures were inpatient admission or death within 7 days of ED discharge. We defined a clinically important association by assessing the relative risk ratio and 95% confidence interval (CI) difference and also compared risks at the 99th percentile and median value of each measure., Results: The study cohort contained a total of 625,096 visits to 12 EDs. There were 16,957 (2.7%) admissions and 328 (0.05%) deaths within 7 days. Only 2 measures, both of which were patient transit measures, were associated with the outcome. Compared with a median evaluation time of 2.2 hours, the evaluation time of 10.8 hours (99th percentile) was associated with a relative risk of 3.9 (95% CI 3.7 to 4.1) of an admission. Compared with a median ED length of stay (a CMS measure) of 2.8 hours, the 99th percentile ED length of stay of 11.6 hours was associated with a relative risk of 3.5 (95% CI 3.3 to 3.7) of admission. No system measure of ED crowding was associated with outcomes., Conclusion: Our findings suggest that ED length of stay is a proxy for unmeasured differences in case mix and challenge the validity of the CMS metric as a safety measure for discharged patients., (Copyright © 2015 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.)

Objectives: To identify predictors of hospital inpatient admission of older Medicare beneficiaries after discharge from the emergency department (ED)., Design: Retrospective cohort study., Setting: Nonfederal California hospitals (n = 284)., Participants: Visits of Medicare beneficiaries aged 65 and older discharged from California EDs in 2007 (n = 505,315)., Measurements: Using the California Office of Statewide Health Planning and Development files, predictors of hospital inpatient admission within 7 days of ED discharge in older adults (≥65) with Medicare were evaluated., Results: Hospital inpatient admissions within 7 days of ED discharge occurred in 23,340 (4.6%) visits and were associated with older age (70-74: adjusted odds ratio (AOR) = 1.12, 95% confidence interval (CI) = 1.07-1.17; 75-79: AOR = 1.18, 95% CI = 1.13-1.23; ≥80: AOR = 1.4, 95% CI = 1.35-1.46), skilled nursing facility use (AOR = 1.82, 95% CI = 1.72-1.94), leaving the ED against medical advice (AOR = 1.82, 95% CI = 1.67-1.98), and the following diagnoses with the highest odds of admission: end-stage renal disease (AOR = 3.83, 95% CI = 2.42-6.08), chronic renal disease (AOR = 3.19, 95% CI = 2.26-4.49), and congestive heart failure (AOR = 3.01, 95% CI = 2.59-3.50)., Conclusion: Five percent of older Medicare beneficiaries have a hospital inpatient admission after discharge from the ED. Chronic conditions such as renal disease and heart failure were associated with the greatest odds of admission., Competing Interests: The authors have no conflicts of interest in association with this study., (© 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society.)

Background: Emergency department (ED) crowding has been identified as a major threat to public health., Objectives: We assessed patient transit times and ED system crowding measures based on their associations with outcomes., Research Design: Retrospective cohort study., Subjects: We accessed electronic health record data on 136,740 adults with a visit to any of 13 health system EDs from January 2008 to December 2010., Measures: Patient transit times (waiting, evaluation and treatment, boarding) and ED system crowding [nonindex patient length-of-stay (LOS) and boarding, bed occupancy] were determined. Outcomes included individual inpatient mortality and admission LOS. Covariates included demographic characteristics, past comorbidities, severity of illness, arrival time, and admission diagnoses., Results: No patient transit time or ED system crowding measure predicted increased mortality after control for patient characteristics. Index patient boarding time and lower bed occupancy were associated with admission LOS (based on nonoverlapping 95% CI vs. the median value). As boarding time increased from none to 14 hours, admission LOS increased an additional 6 hours. As mean occupancy decreased below the median (80% occupancy), admission LOS decreased as much as 9 hours., Conclusions: Measures indicating crowded ED conditions were not predictive of mortality after case-mix adjustment. The first half-day of boarding added to admission LOS rather than substituted for it. Our findings support the use of boarding time as a measure of ED crowding based on robust prediction of admission LOS. Interpretation of measures based on other patient ED transit times may be limited to the timeliness of care.

Objectives: Early death after emergency department (ED) discharge may signal opportunities to improve care. Prior studies are limited by incomplete mortality ascertainment and lack of clinically important information in administrative data. The goal in this hypothesis-generating study was to identify patient and process of care themes that may provide possible explanations for early postdischarge mortality., Methods: This was a qualitative analysis of medical records of adult patients who visited the ED of any of six hospitals in an integrated health system (Kaiser Permanente Southern California [KPSC]) and died within 7 days of discharge in 2007 and 2008. Nonmembers, visits to non-health plan hospitals, patients receiving or referred to hospice care, and patients with do not attempt resuscitation or do not intubate orders (DNAR/DNI) were excluded. Under the guidance of two qualitative research scientists, a team of three emergency physicians used grounded theory techniques to identify patient clinical presentations and processes of care that serve as potential explanations for poor outcome after discharge., Results: The source population consisted of a total of 290,092 members with 446,120 discharges from six KPSC EDs in 2007 and 2008. A total of 203 deaths occurred within 7 days of ED discharge (0.05%). Sixty-one randomly chosen cases were reviewed. Patient-level themes that emerged included an unexplained persistent acute change in mental status, recent fall, abnormal vital signs, ill-appearing presentation, malfunctioning indwelling device, and presenting symptoms remaining at discharge. Process-of-care factors included a discrepancy in history of present illness, incomplete physical examination, and change of discharge plan by a third party, such as a consulting or admitting physician., Conclusions: In this hypothesis-generating study, qualitative research techniques were used to identify clinical and process-of-care factors in patients who died within days after discharge from an ED. These potential predictors will be formally tested in a future quantitative study., (© 2013 by the Society for Academic Emergency Medicine.)

Study Objective: Hospitalizations that occur shortly after emergency department (ED) discharge may reveal opportunities to improve ED or follow-up care. There currently is limited, population-level information about such events. We identify hospital- and visit-level predictors of bounce-back admissions, defined as 7-day unscheduled hospital admissions after ED discharge., Methods: Using the California Office of Statewide Health Planning and Development files, we conducted a retrospective cohort analysis of adult (aged >18 years) ED visits resulting in discharge in 2007. Candidate predictors included index hospital structural characteristics such as ownership, teaching affiliation, trauma status, and index ED size, along with index visit patient characteristics of demographic information, day of service, against medical advice or eloped disposition, insurance, and ED primary discharge diagnosis. We fit a multivariable, hierarchic logistic regression to account for clustering of ED visits by hospitals., Results: The study cohort contained a total of 5,035,833 visits to 288 facilities in 2007. Bounce-back admission within 7 days occurred in 130,526 (2.6%) visits and was associated with Medicaid (odds ratio [OR] 1.42; 95% confidence interval [CI] 1.40 to 1.45) or Medicare insurance (OR 1.53; 95% CI 1.50 to 1.55) and a disposition of leaving against medical advice or before the evaluation was complete (OR 1.90; 95% CI 1.89 to 2.0). The 3 most common age-adjusted index ED discharge diagnoses associated with a bounce-back admission were chronic renal disease, not end stage (OR 3.3; 95% CI 2.8 to 3.8), end-stage renal disease (OR 2.9; 95% CI 2.4 to 3.6), and congestive heart failure (OR 2.5; 95% CI 2.3 to 2.6). Hospital characteristics associated with a higher bounce-back admission rate were for-profit status (OR 1.2; 95% CI 1.1 to 1.3) and teaching affiliation (OR 1.2; 95% CI 1.0 to 1.3)., Conclusion: We found 2.6% of discharged patients from California EDs to have a bounce-back admission within 7 days. We identified vulnerable populations, such as the very old and the use of Medicaid insurance, and chronic or end-stage renal disease as being especially at risk. Our findings suggest that quality improvement efforts focus on high-risk individuals and that the disposition plan of patients consider vulnerable populations., (Copyright © 2013 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.)

Background: Syncope remains challenging for Emergency Department (ED) physicians due to difficulties in assessing the risk of future adverse outcomes. The aim of this meta-analysis is to establish the incidence and etiology of adverse outcomes as well as the predictors, in patients presenting with syncope to the ED., Methods: A systematic electronic literature review was performed looking for eligible studies published between 1990 and 2010. Studies reporting multivariate predictors of adverse outcomes in patients presenting with syncope to the ED were included and pooled, when appropriate, using a random-effect method. Adverse events were defined as 'incidence of death, or of hospitalization and interventional procedures because of arrhythmias, ischemic heart disease or valvular heart disease'., Results: 11 studies were included. Pooled analysis showed 42% (CI 95%; 32-52) of patients were admitted to hospital. Risk of death was 4.4% (CI 95%; 3.1-5.1) and 1.1% (CI 95%; 0.7-1.5) had a cardiovascular etiology. One third of patients were discharged without a diagnosis, while the most frequent diagnosis was 'situational, orthostatic or vasavagal syncope' in 29% (CI 95%; 12-47). 10.4% (CI 95%; 7.8-16) was diagnosed with heart disease, the most frequent type being bradyarrhythmia, 4.8% (CI 95%; 2.2-6.4) and tachyarrhythmia 2.6% (CI 95%; 1.1-3.1). Palpitations preceding syncope, exertional syncope, a history consistent of heart failure or ischemic heart disease, and evidence of bleeding were the most powerful predictors of an adverse outcome., Conclusion: Syncope carries a high risk of death, mainly related to cardiovascular disease. This large study which has established the most powerful predictors of adverse outcomes, may enable care and resources to be better focused at high risk patients., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Background. It is unclear whether history and physical examination findings can predict abnormalities on head computed tomography (CT) believed to indicate increased risk of lumbar-puncture- (LP-) induced brain herniation. The objectives of this study were to (1) identify head CT findings felt to be associated with increased risk of brain herniation and (2) to assess the ability of history and physical examination to predict those findings. Methods. Using a modified Delphi survey technique, an expert panel defined CT abnormalities felt to predict increased risk of LP-induced brain herniation. Presence of such findings on CT was compared with history and physical examination (H&P) variables in 47 patients. Results. No H&P variable predicted "high-risk" CT; combining H&P variables to improve sensitivity led to extremely low specificity and still failed to identify all patients with high-risk CT. Conclusions. "High-risk" CT is not uncommon in patients with clinical characteristics known to predict an absence of actual risk from LP, and thus it may not be clinically relevant. "Overdiagnosis" will be increasingly problematic as technological advances identify increasingly subtle deviations from "normal."

Objectives: The risk of short-term mortality after an emergency department (ED) visit for syncope is poorly understood, resulting in prognostic uncertainty and frequent hospital admission. The authors determined patterns and risk factors for short-term mortality after a diagnosis of syncope or near syncope to aid in medical decision-making., Methods: A retrospective cohort study was performed of adult members of Kaiser Permanente Southern California seen at 11 EDs from 2002 to 2006 with a primary discharge diagnosis of syncope or near syncope (International Classification of Diseases, Ninth Revision [ICD-9] 780.2). The outcome was 30-day mortality. Proportional hazards time-to-event regression models were used to identify risk factors., Results: There were 22,189 participants with 23,951 ED visits, resulting in 307 deaths by 30 days. A relatively lower risk of death was reached within 2 weeks for ages 18 to 59 years, but not until 3 months or more for ages 60 and older. Preexisting comorbidities associated with increased mortality included heart failure (hazard ratio [HR] = 14.3 in ages 18 to 59 years, HR = 3.09 in ages 60 to 79 years, HR = 2.34 in ages 80 years plus; all p < 0.001), diabetes (HR = 1.49, p = 0.002), seizure (HR = 1.65, p = 0.016), and dementia (HR = 1.41, p = 0.034). If the index visit followed one or more visits for syncope in the previous 30 days, it was associated with increased mortality (HR = 1.86, p = 0.024). Absolute risk of death at 30 days was under 0.2% in those under 60 years without heart failure and more than 2.5% across all ages in those with heart failure., Conclusions: The low risk of death after an ED visit for syncope or near syncope in patients younger than 60 years old without heart failure may be helpful when deciding who to admit for inpatient evaluation. The presence of one or more comorbidities that predict death and a prior visit for syncope should be considered in clinical decisions and risk stratification tools for patients with syncope. Close clinical follow-up seems advisable in patients 60 years and older due to a prolonged risk of death., (© 2012 by the Society for Academic Emergency Medicine.)

Study Objective: The emergency department (ED) is an inherently high-risk setting. Early death after an ED evaluation is a rare and devastating outcome; understanding it can potentially help improve patient care and outcomes. Using administrative data from an integrated health system, we describe characteristics and predictors of patients who experienced 7-day death after ED discharge., Methods: Administrative data from 12 hospitals were used to identify death after discharge in adults aged 18 year or older within 7 days of ED presentation from January 1, 2007, to December 31, 2008. Patients who were nonmembers of the health system, in hospice care, or treated at out-of-network EDs were excluded. Predictors of 7-day postdischarge death were identified with multivariable logistic regression., Results: The study cohort contained a total of 475,829 members, with 728,312 discharges from Kaiser Permanente Southern California EDs in 2007 and 2008. Death within 7 days of discharge occurred in 357 cases (0.05%). Increasing age, male sex, and number of preexisting comorbidities were associated with increased risk of death. The top 3 primary discharge diagnoses predictive of 7-day death after discharge included noninfectious lung disease (odds ratio [OR] 7.1; 95% confidence interval [CI] 2.9 to 17.4), renal disease (OR 5.6; 95% CI 2.2 to 14.2), and ischemic heart disease (OR 3.8; 95% CI 1.0 to 13.6)., Conclusion: Our study suggests that 50 in 100,000 patients in the United States die within 7 days of discharge from an ED. To our knowledge, our study is the first to identify potentially "high-risk" discharge diagnoses in patients who experience a short-term death after discharge., (Copyright © 2011 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.)

Syncope is a common reason for emergency department (ED) visits, and patients are often admitted to exclude syncope of cardiovascular origin. Population-based data on patterns and predictors of cardiac outcomes may improve decision-making. Our objective was to identify patterns and predictors of short-term cardiac outcomes in ED patients with syncope. Administrative data from an integrated health system of 11 Southern California EDs were used to identify cardiac outcomes after ED presentation for syncope from January 1, 2002, to December 31, 2005. Syncope and cause of death were identified by codes from the International Classification of Disease, Ninth Revision. Cardiac outcomes included cardiac death and hospitalization or procedure consistent with ischemic heart disease, valvular disease, or arrhythmia. Predictors of cardiac outcomes were identified through multivariate logistic regression. There were 35,330 adult subjects who accounted for 39,943 ED visits for syncope. Risk of cardiac outcome sharply decreased following the 7 days after syncope. A 7-day cardiac outcome occurred in 893 cases (3%). Positive predictors of 7-day cardiac outcomes included age > or =60 years, male gender, congestive heart failure, ischemic heart disease, cardiac arrhythmia, and valvular heart disease. Negative predictors included dementia, pacemaker, coronary revascularization, and cerebrovascular disease. There was an age-dependent relation between 7-day cardiac outcomes and arrhythmia and valvular disease, with younger patients (<60 years of age) having greater risk of an event compared to their same-age counterparts. In conclusion, ED decision-making should focus on risk of cardiac event in the first 7 days after syncope and special attention should be given to younger patients with cardiac co-morbidities.

Study Objective: We identify predictors of 30-day serious events after syncope in older adults., Methods: We reviewed the medical records of older adults (age > or =60 years) who presented with syncope or near syncope to one of 3 emergency departments (EDs) between 2002 and 2005. Our primary outcome was occurrence of a predefined serious event within 30 days after ED evaluation. We used multivariable logistic regression to identify predictors of 30-day serious events., Results: Of 3,727 potentially eligible patients, 2,871 (77%) met all eligibility criteria. We excluded an additional 287 patients who received a diagnosis of a serious clinical condition while in the ED. In the final study cohort (n=2,584), we identified 173 (7%) patients who experienced a 30-day serious event. High-risk predictors included age greater than 90 years, male sex, history of an arrhythmia, triage systolic blood pressure greater than 160 mm Hg, abnormal ECG result, and abnormal troponin I level. A low-risk predictor was a complaint of near syncope rather than syncope. A risk score, generated by summing high-risk predictors and subtracting the low-risk predictor, can stratify patients into low- (event rate 2.5%; 95% confidence interval [CI] 1.4% to 3.6%), intermediate- (event rate 6.3%; 95% CI 5.1% to 7.5%), and high-risk (event rate 20%; 95% CI 15% to 25%) groups., Conclusion: We identified predictors of 30-day serious events after syncope in adults aged 60 years and greater. A simple score was able to stratify these patients into distinct risk groups and, if externally validated, might have the potential to aid ED decisionmaking.

Study Objective: Emergency physicians use noncontrast cranial computed tomographic (CT) imaging of headache patients to identify subarachnoid hemorrhage caused by aneurysms or arteriovenous malformations. Given sufficiently high sensitivity, CT imaging could be used as a definitive diagnostic study in these patients. The purpose of this study is to determine the sensitivity of noncontrast cranial CT in detecting all spontaneous subarachnoid hemorrhages and those caused by aneurysm or arteriovenous malformation., Methods: This was a retrospective review performed at an urban tertiary academic emergency department (ED). Using a combination of noncontrast cranial CT radiology coding, lumbar puncture results, International Classification of Diseases, Ninth Revision discharge diagnosis, and medical record review, we identified all patients who presented to a tertiary care academic ED from August 1, 2001, to December 31, 2004, with spontaneous subarachnoid hemorrhage. We determined whether patients were diagnosed by cranial CT or lumbar puncture, the presence of headache and level of consciousness at ED presentation, and whether or not they had an aneurysm or arteriovenous malformation., Results: We identified 149 patients who were diagnosed with spontaneous subarachnoid hemorrhage during the study period. Noncontrast cranial CT scan diagnosed 139 patients, and 10 were diagnosed with lumbar puncture. This yielded an overall CT scan sensitivity of 93% (95% confidence interval [CI] 88% to 97%). Of the 149 with subarachnoid hemorrhage, 117 (79%) had aneurysm or arteriovenous malformation; cranial CT scan demonstrated subarachnoid hemorrhage in 110 of the 117, for a sensitivity of 94% (95% CI 88% to 98%). For the 67 patients presenting with headache and normal mental status who had a subarachnoid hemorrhage and vascular lesions (either aneurysm or arteriovenous malformation), the sensitivity of cranial CT scan was 91% (95% CI 82% to 97%)., Conclusion: Noncontrast CT imaging exhibits inadequate sensitivity to serve as a sole diagnostic modality in detecting spontaneous subarachnoid hemorrhage caused by aneurysm or arteriovenous malformation.