Treatment of Ruptured and Unruptured Cerebral Aneurysms
Treatment of Ruptured and Unruptured Cerebral Aneurysms
Data were obtained from the NIS, a component of the Healthcare Cost and Utilization Project (HCUP) sponsored by the Agency for Healthcare Research and Quality and the US Department of Health and Human Services and the largest all-payer inpatient care database in the USA. It contains data on eight million discharges from more than 1000 hospitals each year, which approximates to a 20% stratified sample of all US community hospitals. The NIS and other administrative databases have been extensively used to analyze trends of practice in various medical fields in the USA, such as cardiology, psychiatry, gastrointestinal surgery and spinal surgery. Here we conducted a retrospective cohort study on data extracted from the NIS to describe trends in treating cerebral aneurysms in the USA.
Approval for the project was obtained from the Partners/Brigham and Women's Hospital Institutional Review Board. Annual NIS data files from 1998 to 2007 were obtained from the HCUP Central Distributor (Rockville, Maryland, USA). The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes were used to define diagnostic as well as treatment groups. Ruptured aneurysms were defined by code 430.0 (SAH) or 431.0 (intracerebral hemorrhage) and unruptured aneurysms by code 437.3 (cerebral artery aneurysm, not ruptured). Patients with both a ruptured and unruptured aneurysm in one hospitalization were included in the ruptured group. The ICD-9-CM procedure code 39.51 has long been established for microsurgical clipping and was used to categorize those treated by open surgery. For endovascular therapies, dedicated procedure codes 39.72 (endovascular repair or occlusion of head and neck vessels) and 39.79 (other endovascular procedures on head and neck vessels) were defined in 2001. Before that time, 39.52 (other repair of aneurysm) was used to identify endovascular treatment for a cerebral aneurysm. As the code 39.52 might also include open surgical treatments such as wrapping, in our analyses, patients with code 39.52 were also required to carry a code of 88.41 (angiography of cerebral arteries) and not any procedure codes indicating open craniotomy in the same hospitalization to be categorized as having endovascular coiling. These methods were similar to those described in other investigations of neurosurgical patients. Only patients with an aneurysm who underwent treatment were included; those who carried diagnostic codes for cerebral aneurysms but not procedure codes for either surgical clipping or endovascular coiling were excluded from analyses. Data from the year 1998, when the NIS sampling and weighting strategy was redesigned to improve national representativeness, up to the year 2007, the latest database publicly available, were included in the analyses. This period therefore included the 5 years before as well as after publication of the ISAT results.
Differences in demographic and hospital characteristics by diagnostic and treatment groups were examined using χ and t tests for binary and continuous variables, respectively. Multivariable logistic regression was used to calculate the ORs and 95% CIs for the likelihood of using endovascular treatment as well as in-hospital mortality for both SAH and unruptured aneurysm groups after adjusting for age, sex, race (white, black and other), household income quartile, comorbidity score, geographic region, hospital size and hospital teaching status. Medical comorbidity stratification was performed using the Charlson comorbidity index adapted for use on ICD-9-CM codes.
Multivariable linear regression was used to examine the association of the above-mentioned variables with postoperative length of stay and total charge for the hospitalization. The NIS categorizes hospital bed size as small, medium and large, based on the hospital's region, location and teaching status, so that approximately one-third of the hospital in a given region, location and teaching status combination would fall into each category. The NIS database provides information only on the total charge for the inpatient hospitalization, which represents the sum of all charges during the hospitalization except for professional fees. Logarithmic transformation was used for length of stay and total charges when performing the analyses because of the significant positive skew of the data. Statistical significance was defined as a type I error <0.05. Statistical analyses were performed using the unweighted data with SAS version 9.2 (SAS Institute Inc, Cary, North Carolina, USA).
Methods
Data were obtained from the NIS, a component of the Healthcare Cost and Utilization Project (HCUP) sponsored by the Agency for Healthcare Research and Quality and the US Department of Health and Human Services and the largest all-payer inpatient care database in the USA. It contains data on eight million discharges from more than 1000 hospitals each year, which approximates to a 20% stratified sample of all US community hospitals. The NIS and other administrative databases have been extensively used to analyze trends of practice in various medical fields in the USA, such as cardiology, psychiatry, gastrointestinal surgery and spinal surgery. Here we conducted a retrospective cohort study on data extracted from the NIS to describe trends in treating cerebral aneurysms in the USA.
Approval for the project was obtained from the Partners/Brigham and Women's Hospital Institutional Review Board. Annual NIS data files from 1998 to 2007 were obtained from the HCUP Central Distributor (Rockville, Maryland, USA). The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes were used to define diagnostic as well as treatment groups. Ruptured aneurysms were defined by code 430.0 (SAH) or 431.0 (intracerebral hemorrhage) and unruptured aneurysms by code 437.3 (cerebral artery aneurysm, not ruptured). Patients with both a ruptured and unruptured aneurysm in one hospitalization were included in the ruptured group. The ICD-9-CM procedure code 39.51 has long been established for microsurgical clipping and was used to categorize those treated by open surgery. For endovascular therapies, dedicated procedure codes 39.72 (endovascular repair or occlusion of head and neck vessels) and 39.79 (other endovascular procedures on head and neck vessels) were defined in 2001. Before that time, 39.52 (other repair of aneurysm) was used to identify endovascular treatment for a cerebral aneurysm. As the code 39.52 might also include open surgical treatments such as wrapping, in our analyses, patients with code 39.52 were also required to carry a code of 88.41 (angiography of cerebral arteries) and not any procedure codes indicating open craniotomy in the same hospitalization to be categorized as having endovascular coiling. These methods were similar to those described in other investigations of neurosurgical patients. Only patients with an aneurysm who underwent treatment were included; those who carried diagnostic codes for cerebral aneurysms but not procedure codes for either surgical clipping or endovascular coiling were excluded from analyses. Data from the year 1998, when the NIS sampling and weighting strategy was redesigned to improve national representativeness, up to the year 2007, the latest database publicly available, were included in the analyses. This period therefore included the 5 years before as well as after publication of the ISAT results.
Differences in demographic and hospital characteristics by diagnostic and treatment groups were examined using χ and t tests for binary and continuous variables, respectively. Multivariable logistic regression was used to calculate the ORs and 95% CIs for the likelihood of using endovascular treatment as well as in-hospital mortality for both SAH and unruptured aneurysm groups after adjusting for age, sex, race (white, black and other), household income quartile, comorbidity score, geographic region, hospital size and hospital teaching status. Medical comorbidity stratification was performed using the Charlson comorbidity index adapted for use on ICD-9-CM codes.
Multivariable linear regression was used to examine the association of the above-mentioned variables with postoperative length of stay and total charge for the hospitalization. The NIS categorizes hospital bed size as small, medium and large, based on the hospital's region, location and teaching status, so that approximately one-third of the hospital in a given region, location and teaching status combination would fall into each category. The NIS database provides information only on the total charge for the inpatient hospitalization, which represents the sum of all charges during the hospitalization except for professional fees. Logarithmic transformation was used for length of stay and total charges when performing the analyses because of the significant positive skew of the data. Statistical significance was defined as a type I error <0.05. Statistical analyses were performed using the unweighted data with SAS version 9.2 (SAS Institute Inc, Cary, North Carolina, USA).
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