We have previously studied the economic cost utilization

Transcription

1 Length of Stay and Total Hospital Charges of Clipping Versus Coiling for Ruptured and Unruptured Adult Cerebral Aneurysms in the Nationwide Inpatient Sample Database 2002 to 2006 Brian L. Hoh, MD; Yueh-Yun Chi, PhD; Matthew F. Lawson, MD; J. Mocco, MD, MS; Fred G. Barker II, MD Background and Purpose We have previously reported the difference in length of stay and hospital charges for patients with cerebral aneurysms treated with either clipping or coiling at our institution. We now report an analysis of the same comparison at a national level conducted using the Nationwide Inpatient Sample database. Methods We obtained the Nationwide Inpatient Sample from the Healthcare Cost and Utilization Project, Agency for Healthcare Quality and Research. The Nationwide Inpatient Sample is the largest all-payer inpatient care database in the US and represents 20% of all inpatient admissions to US nonfederal hospitals. Hospitalizations for clipping or coiling of ruptured and unruptured cerebral aneurysms from 2002 to 2006 were identified by cross-matching International Classification of Diseases-9 codes for diagnoses of subarachnoid hemorrhage (430) or unruptured cerebral aneurysm (437.3) with procedure codes for clipping (39.51) or coiling (39.79, 39.72, or 39.52) of cerebral aneurysms. Length of hospital stay and total hospital charges for clipping and coiling were compared using linear mixed models adjusted for the following patient and hospital-specific factors: gender, age, race/ethnicity, admission source and type, median income level in patient s postal code of residence, payer for care, comorbidities, and hospital cerebral aneurysm case volume, bed size, teaching status, rural/urban location, and geographic region. Results There were 9635 hospitalizations for ruptured aneurysm treatments (6019 clipping, 3616 coiling) and 9399 hospitalizations for unruptured aneurysm treatments (4700 clipping, 4699 coiling). For ruptured aneurysm patients, after adjusting for the effects of patient-specific and hospital-specific factors, clipping compared to coiling was associated with significantly longer length of stay (P) and significantly higher total hospital charges (P). For unruptured aneurysm patients, clipping compared to coiling was associated with significantly longer length of stay (P) and significantly higher total hospital charges (P). After adjusting for the effects of hospital-level and patient-level characteristics, clipping as compared to coiling was associated with an average of 1.2-times more days in hospitalization for ruptured patients and was associated with an average of 1.8-times more days in hospitalization for unruptured patients. On average, clipping resulted in $ more in total charge for ruptured patients and resulted in $ more in total charge for unruptured patients after considering all relevant hospital and patient characteristics. Conclusions The results of this nationwide analysis differed from the findings of our single institution study. Clipping compared to coiling was associated with significantly longer lengths of stay and significantly higher total hospital charges for both ruptured and unruptured aneurysm patients. (Stroke. 2010;41: ) Key Words: aneurysm clipping coiling hospital charges length of hospitalization We have previously studied the economic cost utilization of clipping vs coiling cerebral aneurysms at our own institution. 1 We found in 565 cerebral aneurysm patients treated either surgically (306 patients) or endovascularly (259 patients) that open surgical clipping was associated with similar lengths of stay and lower total hospital charges in ruptured aneurysm patients compared to endovascular treatment and longer lengths of stay and lower total hospital charges in unruptured aneurysm patients. Our previous study reflected the findings at a single institution. We now report an analysis of the same question conducted at the national level using the Nationwide Inpatient Sample (NIS) database. Critical analyses of medical cost utilization are necessary in the current health care economic Received September 29, 2009; final revision received October 16, 2009; accepted October 29, From Department of Neurological Surgery (B.L.H., M.F.L., J.D.M.), Department of Epidemiology and Health Policy Research (Y.-Y.C.), University of Florida, Gainesville, Fla; Neurosurgical Service (F.G.B.), Massachusetts General Hospital, Boston, Mass. Correspondence to Brian L. Hoh, MD, Department of Neurological Surgery, University of Florida, P.O. Box , Gainesville, FL brian.hoh@neurosurgery.ufl.edu 2010 American Heart Association, Inc. Stroke is available at DOI: /STROKEAHA

2 338 Stroke February 2010 environment. In 2008, national health care spending in the US was $2.4 trillion, and by 2018 it is projected to be $4.4 trillion and to comprise just more than one-fifth of the Gross Domestic Product. 2 The way in which health care dollars are being spent is being critically examined and is a key element in comparative effectiveness research. Materials and Methods We obtained the NIS database from the Agency for Healthcare Quality and Research s Healthcare Cost and Utilization Project (Rockville, Md). The NIS is the largest all-payer hospital inpatient database in the US and contains data approximating a 20% stratified sample of US hospitals. For each sampled hospital, all inpatient admissions for the year are contained in the NIS, so annual case volumes for hospitals can be calculated. The NIS includes data for 8 million hospital admissions each year, which is approximately one-fifth of all inpatient admissions to US nonfederal hospitals. For more information regarding the NIS database, please see Hospitalizations for clipping or coiling of ruptured and unruptured cerebral aneurysms from 2002 to 2006 were collected from the NIS by cross-matching International Classification of Diseases (ICD)-9 codes for diagnoses of subarachnoid hemorrhage (430) or unruptured cerebral aneurysm (437.3) with procedure codes for clipping (39.51) or coiling (39.79, 39.72, or 39.52) of cerebral aneurysm. The ICD-9 codes used for aneurysm clipping and coiling (39.79, 39.72, or 39.52) have previously been validated 3 and used in published studies. 4 8 In addition, the ICD-9 procedure codes were used for identifying temporary tracheostomy (31.1), permanent tracheostomy (31.2 or 31.29), and ventriculostomy (02.2). Ruptured aneurysm (430) and unruptured aneurysm (437.3) adult patients (age older than 18 years) were studied separately because of the highly disparate nature of these 2 distinct conditions. Clipping vs coiling of cerebral aneurysms were compared for 2 primary end points, length of hospital stay and total hospital charges, both of which are coded in the NIS database. The analysis was adjusted for the following patient-specific factors that are coded in the NIS database: gender, age, race, admission source (emergency room, transfer from another hospital, transfer from long-term care, routine), admission type (emergency, urgent, elective, trauma center), the use of permanent tracheostomy, median income level in patient s postal code ( $36 000, $ $44 999, $45 000), payer (Medicare, Medicaid, private insurance, self-pay, no charge, other), and comorbidities (alcohol abuse, anemia, congestive heart failure, chronic pulmonary disease, coagulopathy, depression, diabetes with or without chronic complications, drug abuse, hypertension, liver disease, fluid and electrolyte disorders, metastatic cancer, other neurological disorders, obesity, peripheral vascular disorders, pulmonary circulation disorders, renal failure, solid tumor without metastasis, peptic ulcer disease excluding bleeding, valvular disease). The models also accounted for hospital-level factors: hospital region (Northeast, Midwest, South, West), hospital location (rural, urban), teaching status, bed size (small, medium, large), and hospital annual case volume of cerebral aneurysm treatments. Patients with both clipping (39.51) and coiling (39.79, 39.72, or 39.52) procedure codes were excluded in the analysis. Hospital annual case volume of cerebral aneurysm treatments was determined by the ranking of total aneurysm treatments (ie, clipping and coiling, ruptured and unruptured) across all sampled hospitals. For each year from 2002 to 2006, each individual hospital s case volume of cerebral aneurysm treatments was defined as high if the number of total aneurysm treatments equaled or exceeded the third quartile of aneurysm treatments across all sampled hospitals and was defined as low if otherwise. To simultaneously account for hospital-level and patient-level variation in length of stay and total charges, linear mixed models were used to compare and make inferences about the differences between charges for clipping and coiling procedures. In hierarchical models such as the ones we used, it is possible to detect separate effects at the individual hospital level (ie, that certain hospitals provide expensive or inexpensive care across all patients treated) and at the level of specific procedures across different hospitals. The models allowed a hierarchical analysis by assuming a common hospital-specific intercept after adjusting for patient-specific characteristics. The common intercepts varied across hospitals to model systematic hospital-level variation that might, in some cases, be sufficiently large to overwhelm the charge or length of stay differences between procedures. Furthermore, the intercepts were assumed to be functions of the 5 hospital-level factors: hospital region, hospital location, teaching status, bed size, and hospital volume of cerebral aneurysm treatments. A type I error rate of 0.05 was used to determine statistical significance; for significant factors that have 2 levels, Scheffe correction was applied for pair-wise step-down comparisons. Because in-hospital deaths can artificially shorten the mean length of hospitalization, we also conducted the length of hospitalization analysis after excluding all patients who died before hospital discharge. In comparing total hospital charges across the 5 years from 2002 to 2006, we assumed a 3% annual inflation rate for each year and used the adjusted charges in the linear mixed models to evaluate differences between procedures. To meet the distributional requirements of a linear mixed model, we used the logarithm of length of hospital stay and the square root of total inflation-adjusted charges as targeted outcomes in analyses. For patients who stayed in the hospital for 1 day, a 1-day stay was assumed. Results Comparison of Clipping vs Coiling A search in the NIS sample database years 2002 to 2006 for cross-matches of the ICD-9 diagnosis codes for subarachnoid hemorrhage (430) or unruptured cerebral aneurysm (437.3) with procedure codes for clipping (39.51) or coiling (39.79, 39.72, or 39.52) of cerebral aneurysms yielded 9347 hospitalizations for ruptured aneurysms (5783 clipping, 3564 coiling) and 9174 hospitalizations for unruptured aneurysms (4513 clipping, 4661 coiling). The patient demographic and hospital characteristics of the ruptured and unruptured aneurysm hospitalizations are shown in Table 1. Descriptive statistics for the length of hospital stay and total hospital charges for ruptured and unruptured aneurysm hospitalizations are shown in Table 2. We note that the average length of hospitalization was higher for clipping than for coiling regardless of whether the hospitalization was for treatment of a ruptured or an unruptured aneurysm. The crude average of total hospital charges was higher with coiling than with clipping for patients with ruptured aneurysm, but it was higher with clipping than with coiling for patients with unruptured aneurysm. These comparisons are unadjusted, however, for hospital-specific and patient-specific factors, and they may not be inferential given the potential substructures of clipping and coiling populations, which can be introduced by hospital and patient characteristics. To make valid inferences about the association between treatment procedures and targeted outcomes (length of hospital stay and total hospital charges), we used linear mixed models to account for both hospital-level and patient-level variation. Ruptured aneurysm patients and unruptured aneurysm patients were studied separately. After removing missing data, 4979 ruptured aneurysm hospitalizations (from 314 hospitals) and 5107 unruptured aneurysm hospitalizations (from 274 hospitals) were analyzed for modeling the length of stay, and 4966 ruptured aneurysm hospitalizations (from 314 hospitals) and 5103 unruptured aneurysm hospitaliza-

3 Hoh et al Economics of Aneurysm Clipping vs Coiling 339 Table 1. Patient Demographics and Hospital Characteristics for 9347 Ruptured Aneurysm and 9174 Unruptured Aneurysm Hospitalizations Clipping (N 5783) Ruptured Coiling (N 3564) Clipping (N 4513) Unruptured Coiling (N 4661) N of in-hospital death 778 (14%) 562 (16%) 130 (3%) 103 (2%) Admission source ED 3140 (55%) 1432 (40%) 672 (15%) 423 (9%) Another hospital 1420 (25%) 1273 (36%) 303 (7%) 297 (6%) Another facility 230 (4%) 112 (3%) 64 (1%) 69 (2%) Court/law enforcement Routine/other 950 (16%) 734 (21%) 3444 (77%) 3858 (83%) Admission type Emergency 3375 (66%) 1821 (58%) 724 (18%) 612 (14%) Urgent 1348 (26%) 1033 (32%) 562 (14%) 795 (19%) Elective 378 (7%) 282 (9%) 2786 (68%) 2858 (67%) Trauma center 26 (1%) 22 (1%) Age, mean SD Female 3960 (69%) 2419 (68%) 3369 (75%) 3490 (75%) White 2454 (61%) 1579 (69%) 2225 (73%) 2458 (79%) Permanent tracheostomy 112 (2%) 55 (2%) Median income level $ (29%) 827 (24%) 1073 (24%) 1098 (24%) $ $44, (25%) 940 (27%) 1153 (26%) 1152 (25%) $ (46%) 1675 (49%) 2178 (50%) 2303 (51%) Payer Medicare 1157 (20%) 912 (25%) 988 (22%) 1426 (30%) Medicaid 777 (13%) 424 (12%) 563 (12%) 409 (9%) Private insurance 2914 (51%) 1723 (49%) 2566 (57%) 2494 (54%) Self-pay 623 (11%) 328 (9%) 203 (4%) 144 (3%) No charge 52 (1%) 34 (1%) 24 (1%) 34 (1%) Other 249 (4%) 132 (4%) 165 (4%) 145 (3%) Hospital region Northeast 1001 (17%) 604 (17%) 768 (17%) 789 (17%) Midwest 1125 (20%) 750 (21%) 898 (20%) 1270 (27%) South 2509 (43%) 1497 (42%) 2022 (45%) 1834 (39%) West 1148 (20%) 713 (20%) 825 (18%) 768 (17%) Teaching status: Yes 4657 (81%) 3126 (88%) 3835 (85%) 4187 (90%) Hospital location: Urban 5657 (98%) 3533 (99%) 4392 (97%) 4625 (99%) Bed size Small 199 (3%) 81 (2%) 251 (6%) 124 (3%) Medium 957 (17%) 447 (13%) 652 (14%) 489 (10%) Large 4627 (80%) 3036 (85%) 3610 (80%) 4048 (87%) Aneurysm volume Low 1914 (33%) 413 (12%) 1047 (23%) 482 (10%) High 3869 (67%) 3151 (88%) 3466 (77%) 4179 (90%) ED indicate emergency department. tions (from 274 hospitals) were analyzed for modeling the total charges. The missing data were largely attributable to missing racial and admission type information. For patients with fully observed data and therefore being considered in the advanced modeling, the median length of stay was 9 days and the median total charge was $ In contrast, for patients with missing data and therefore being excluded in the modeling, the median length of stay was 9 days and the median total charge was $ For ruptured aneurysm patients, after adjusting for patientspecific and hospital-specific factors, clipping compared to coiling was associated with significantly longer lengths of hospitalization (P) and significantly higher total hospital charges (P ). The same conclusion was drawn for the unruptured aneurysm hospitalizations. For unruptured aneurysm patients, after adjusting for patientspecific and hospital-specific factors, clipping compared to coiling was associated with significantly longer length of stay (P) and significantly higher total hospital charges (P). After adjusting for the effects of hospital-level and patientlevel characteristics, clipping as compared to coiling was associated with an average of 1.2-times more days in hospitalization for ruptured patients and was associated with an average of 1.8-times more days in hospitalization for unruptured patients. On average, clipping resulted in $ more in total charge for ruptured patients and resulted in $ more in total charge for unruptured patients after considering all relevant hospital and patient characteristics. Ruptured Aneurysm Patients For ruptured aneurysm patients, using linear mixed models, factors significantly associated with length of hospitalization are depicted in Table 3. Factors significantly associated with length of hospitalization after excluding in-hospital deaths are shown in Supplemental Table I, available online at Factors significantly associated with total hospital charges are shown in Table 4. Unruptured Aneurysm Patients For unruptured aneurysm patients, using linear mixed models, factors significantly associated with length of hospitalization are listed in Table 5. Factors significantly associated with length of hospitalization after excluding in-hospital deaths are shown in Supplemental Table II, available online at Factors significantly associated with total hospital charges are shown in Table 6. Discussion The analysis of economic cost utilization of medical procedures is increasingly important in the current health care environment and is critical to comparative effectiveness research. There have been relatively few studies comparing the economic costs of clipping vs coiling of intracranial aneurysms. 1,9 13 These have been reviewed and summarized previously. 1 A recent study calculated US cost estimates for disability, hospitalization, retreatment, and rebleeding, and included these in the total costs for patients treated with clipping vs coiling in the International Subarachnoid Aneurysm Trial (it should be noted that the majority of the patients were not treated in the US); it was found that although coiling was associated with better outcomes, it was also associated with higher total costs than clipping. 14 We previously reported our analysis of the effects of clipping vs coiling of ruptured and unruptured aneurysms on length of hospitalization and hospital costs at our own single institution. 1 Of 565 cerebral aneurysm patients, 306 patients

4 340 Stroke February 2010 Table 2. Length of Hospitalization and Total Hospital Charges After 3% Inflation Adjustments for Clipping vs Coiling in Ruptured and Unruptured Aneurysm Patients Ruptured Unruptured Clipping Coiling Clipping Coiling Length of stay, days Minimum/maximum 1/247 1/134 1/182 1/149 Mean SD Length of stay excluding in-hospital deaths Minimum/maximum 1/247 1/134 1/182 1/149 Mean SD Hospital charges, $ Minimum/maximum 67.7/ / / / Mean SD were treated with clipping and 259 patients were treated with coiling. In the unruptured aneurysm patients (367 patients), clipping compared to coiling was associated with longer hospital stay but lower hospital costs. In the ruptured aneurysm patients (198 patients), clipping compared to coiling was associated with similar length of hospital stay and lower hospital costs. Our single center findings in the ruptured aneurysm patients differed from previous studies in which clipping compared to coiling was associated with longer hospital stay 9,11,13 (1 study corroborated our finding that clipping and coiling had similar lengths of hospital stay 12 ) and higher 9 or similar hospital costs One additional study analyzed unruptured aneurysm patients and found Table 3. Patient-Specific and Hospital-Specific Factors Significantly Associated With Length of Hospitalization in Ruptured Aneurysm Patients Factor Associated With Longer Stay P Treatment Clipping coiling Permanent tracheostomy With permanent tracheostomy Hospital volume Higher volume Hospital region Northeast Midwest Admission source Transfer from another hospital ED Admission type Emergency urgent elective Payer Medicaid Age Older Diabetes mellitus Diabetes mellitus with chronic complications Absence of hypertension Neurologic disorders Peripheral vascular disorders Renal failure results similar to the unruptured aneurysm patients in our single center study, ie, clipping was associated with longer length of hospitalization but lower hospital costs. 10 The difference between the findings of our previous single center study and some of the other previous studies in the literature, all of which were conducted outside the US, raised the question of whether our single center findings could be generalized to other US centers. We therefore performed an analysis of the same question at the national level using the NIS database. Our findings at the national level using the NIS demonstrate that in ruptured aneurysm patients, clipping compared to coiling was associated with significantly longer length of stay (P) and significantly higher total hospital charges (P). The crude average total hospital charges for ruptured aneurysm patients appear to be lower with clipping if not the same as with coiling, as seen in Table 2; Table 4. Patient-Specific and Hospital-Specific Factors Significantly Associated With Total Hospital Charges in Ruptured Aneurysm Patients Factor Associated With Higher Charges P Treatment Clipping coiling Permanent tracheostomy With permanent tracheostomy Hospital volume Higher volume Admission type Emergency, urgent, trauma center elective Payer Medicaid Age Older Gender Male Diabetes mellitus Diabetes mellitus with chronic complications Neurological disorders Peripheral vascular disorders

5 Hoh et al Economics of Aneurysm Clipping vs Coiling 341 Table 5. Patient-Specific and Hospital-Specific Factors Significantly Associated With Length of Hospitalization in Unruptured Aneurysm Patients Factor Associated With Longer Stay P Treatment Clipping coiling Permanent tracheostomy With permanent tracheostomy Admission source Transfer from another hospital ED, routine/birth/other Admission type Emergency, urgent, trauma center elective Race Not white Age Older Anemia Diabetes mellitus with chronic complications Drug abuse Absence of hypertension Neurological disorders Peripheral vascular disorders Renal failure however, when linear mixed models are performed to adjust for patient-specific and hospital-specific factors, the total hospital charges are significantly lower with coiling than clipping. For unruptured aneurysm patients, clipping compared to coiling was associated with significantly longer length of stay (P) and significantly higher total hospital charges (P). A number of other factors were associated with Table 6. Patient-Specific and Hospital-Specific Factors Significantly Associated With Total Hospital Charges in Unruptured Aneurysm Patients Factor Associated With Higher Charges P Treatment Clipping coiling Permanent tracheostomy With permanent tracheostomy Admission source Transfer from another hospital ED, transfer from another facility routine/other Admission type Trauma center Race Not white Income $ Payer Self-pay Age Older Drug abuse Neurologic disorders length of hospitalization and total hospital charges (Tables 5 and 6, and Supplemental Table II), highlighting the complex nature of this disease, treatment modalities, and the complexities involved in analysis of economic cost utilization. Clipping as compared to coiling, after the adjustment for all-related factors, was associated with an average of 1.2- times more days in hospitalization for ruptured patients and was associated with an average of 1.8-times more days in hospitalization for unruptured patients. On average, clipping resulted in $ more in total charge for ruptured patients and resulted in $ more in total charge for unruptured patients after considering all relevant hospital and patient characteristics. It is interesting that higher hospital volume of ruptured admissions was associated with longer length of stay and higher total charges. This may reflect that more complex patients are transferred to higher-volume centers, or that higher-volume centers are less efficient. There was no association with volume of unruptured admissions with length of stay and total charges, however, which argues against the explanation that higher-volume centers are less efficient. There are several limitations to our analysis. This current analysis only studied the index hospitalization. Patients treated with coiling probably have a higher incidence of aneurysm recurrence than clipped patients, thus necessitating follow-up imaging, whether invasive or noninvasive, and potentially further aneurysm treatment procedures. The present analysis does not include the charges associated with subsequent imaging, aneurysm treatments, and hospitalizations. Additionally, this analysis does not account for charges associated with rehabilitation stay or long-term nursing care, for which significant costs are incurred. Data on length of stay and total charges at rehabilitation hospitals or long-term nursing care facilities are not included in the NIS but are certainly sources of significant costs to the health care system. More study is warranted. Another limitation of our study is the lack of a single ICD-9 code specific for coiling of cerebral aneurysm during some of the study period. The ICD-9 codes we used were (other endovascular repair [of aneurysm] of other vessels [coil embolization or occlusion]), (endovascular repair or occlusion of head and neck vessels [coil embolization of occlusion]), and (other repair of aneurysm). These codes have previously been validated 3 and used in previous published studies. 4 8 The inaccuracies of coding for surgical and endovascular treatment of cerebral aneurysms have recently been reported in a study that compared the state of Maryland administrative database (the Maryland Health Service Cost Review Commission administrative database) with a single-institution departmental clinical database. This study found that the state of Maryland database (ie, the data reported by coders at a single Maryland hospital) had a low sensitivity and positive predictive value for coding endovascular treatment for aneurysms at that hospital. 15 Our study may differ from the Maryland study because our study utilizes a different database and, perhaps more significantly, a different time span. The Maryland study spanned a 17-year period beginning in 1991, whereas our study is limited to a more recent era

6 342 Stroke February 2010 ( ). This may be an important distinction, because the ICD-9 procedure codes and were not introduced for endovascular cerebral aneurysm treatment until October It is reassuring that our findings are consistent with other studies. 9,11 13 Three studies obtained their data from the International Subarachnoid Aneurysm Trial, 9,11,13 and 1 obtained data from a departmental database. 12 Nevertheless, the inaccuracies of coding are a limitation of any study that uses a large administrative clinical database such as the NIS. If the sensitivity for coding endovascular procedures were low in the NIS during the study period and uncoded procedures were systematically much more expensive than coded procedures, then our results could have been biased. However, it might be expected that especially expensive hospital admissions would be coded with special care for accuracy, because administrative databases originate in data that hospitals use to bill payers for care. A final limitation of this study is the retrospective nonrandomized nature of the data. Patients were not randomized to clipping vs coiling; therefore, there is significant potential for selection bias and other uncontrolled factors that could significantly influence length of hospitalization and total hospital charges. We attempted to address this by performing a linear mixed-model multivariate analysis that adjusted for several patient-specific and hospital-specific factors. Summary The results of this nationwide analysis differed from the findings of our single-institution study. Clipping compared to coiling was associated with significantly longer lengths of stay and significantly higher total hospital charges for both ruptured and unruptured aneurysm patients in the US from 2002 to Acknowledgments The Nationwide Inpatient Sample Database was obtained from the Agency for Healthcare Quality and Research s Healthcare Cost and Utilization Project (Rockville, MD). Disclosures Hoh is a consultant for Micrus Endovascular, San Jose, CA, Codman Neurovascular, Raynham, MA, and Actelion, Basel, Switzerland. Mocco is a consultant for Actelion, Basel, Switzerland, and Codman Neurovascular, Raynham, MA. References 1. Hoh BL, Chi YY, Dermott MA, Lipori PJ, Lewis SB. The effect of coiling versus clipping of ruptured and unruptured cerebral aneurysms on length of stay, hospital cost, hospital reimbursement, and surgeon reimbursement at the University of Florida. Neurosurgery. 2009;64: Office of the Actuary in the Centers for Medicare and Medicaid Services. NHE projections Forecast summary and selected tables Available at: proj2008.pdf. 3. Hoh BL, Rabinov JD, Pryor JC, Carter BS, Barker FG II. In-hospital morbidity and mortality after endovascular treatment of unruptured intracranial aneurysms in the United States, : Effect of hospital and physician volume. AJNR Am J Neuroradiol. 2003;24: Barker FG II, Amin-Hanjani S, Butler WE, Hoh BL, Rabinov JD, Pryor JC, Ogilvy CS, Carter BS. Age-dependent differences in short-term outcome after surgical or endovascular treatment of unruptured intracranial aneurysms in the United States, Neurosurgery. 2004; 54: Cowan JA Jr, Ziewacz J, Dimick JB, Upchurch GR Jr, Thompson BG. Use of endovascular coil embolization and surgical clip occlusion for cerebral artery aneurysms. J Neurosurg. 2007;107: Shea AM, Reed SD, Curtis LH, Alexander MJ, Villani JJ, Schulman KA. Characteristics of nontraumatic subarachnoid hemorrhage in the United States in Neurosurgery. 2007;61: Andaluz N, Zuccarello M. Recent trends in the treatment of cerebral aneurysms: Analysis of a nationwide inpatient database. J Neurosurg. 2008;108: Crowley RW, Yeoh HK, Stukenborg GJ, Ionescu AA, Kassell NF, Dumont AS. Influence of weekend versus weekday hospital admission on mortality following subarachnoid hemorrhage. Clinical article. J Neurosurg. 2009;111: Bairstow P, Dodgson A, Linto J, Khangure M. Comparison of cost and outcome of endovascular and neurosurgical procedures in the treatment of ruptured intracranial aneurysms. Australas Radiol. 2002;46: Halkes PH, Wermer MJ, Rinkel GJ, Buskens E. Direct costs of surgical clipping and endovascular coiling of unruptured intracranial aneurysms. Cerebrovasc Dis. 2006;22: Wolstenholme J, Rivero-Arias O, Gray A, Molyneux AJ, Kerr RS, Yarnold JA, Sneade M. International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group. Treatment pathways, resource use, and costs of endovascular coiling versus surgical clipping after ASAH. Stroke. 2008;39: Niskanen M, Koivisto T, Ronkainen A, Rinne J, Ruokonen E. Resource use after subarachnoid hemorrhage: Comparison between endovascular and surgical treatment. Neurosurgery. 2004;54: Javadpour M, Jain H, Wallace MC, Willinsky RA, ter Brugge KG, Tymianski M. Analysis of cost related to clinical and angiographic outcomes of aneurysm patients enrolled in the international subarachnoid aneurysm trial in a north american setting. Neurosurgery. 2005;56: Maud A, Lakshminarayan K, Suri MF, Vazquez G, Lanzino G, Qureshi AI. Cost-effectiveness analysis of endovascular versus neurosurgical treatment for ruptured intracranial aneurysms in the United States. J Neurosurg. 2009;110: Woodworth GF, Baird CJ, Garces-Ambrossi G, Tonascia J, Tamargo RJ. Inaccuracy of the administrative database: Comparative analysis of two databases for the diagnosis and treatment of intracranial aneurysms. Neurosurgery. 2009;65: