Research Relationship between hospital volume and early outcomes in acute ischemic stroke patients treated with recombinant tissue plasminogen activator Tomoki Wada1*, Hideo Yasunaga2, Ryota Inokuchi1, Hiromasa Horiguchi3, Kiyohide Fushimi4, Takehiro Matsubara1, Susumu Nakajima1, and Naoki Yahagi1 Background There is controversy whether the annual number of acute ischemic stroke patients receiving stroke thrombolysis per hospital (hospital volume) is associated with outcomes in these patients. Aims The study aims to assess the relationship between hospital volume and early outcomes in acute ischemic stroke patients treated with recombinant tissue plasminogen activator. Methods Patients with acute ischemic stroke treated with recombinant tissue plasminogen activator from July 1, 2010 to March 31, 2012 were identified in the Japanese Diagnosis Procedure Combination database. Hospital volume was categorized into three levels (low, medium, and high volume) to obtain approximately equal numbers of patients in each group. Primary outcomes were seven-day mortality and functional independence (modified Rankin Scale score of 0 to 2) at discharge. Univariate analyses and multivariate logistic regression analyses fitted with generalized estimating equations were performed. Results We identified 7476 eligible patients, including 2339 (31·3%) treated in low-volume hospitals (1–7 patients annually), 2670 (35·7%) in medium-volume hospitals (8–16 patients annually), and 2467 (33·0%) in high-volume hospitals (17–48 patients annually). Seven-day mortality and functional independence at discharge were comparable among the three hospital volume groups (P = 0·17 for seven-day mortality; P = 0·22 for functional independence at discharge). The comparability between groups persisted after multivariate adjustment.
Conclusion Hospital volume was not significantly associated with seven-day mortality or functional independence at discharge in acute ischemic stroke patients treated with recombinant tissue plasminogen activator in Japan. Key words: hospital volume, ischemic stroke, population-based study, recombinant tissue plasminogen activator, stroke facilities, thrombolysis
Correspondence: Tomoki Wada*, Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. E-mail: [email protected] 1 Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Tokyo, Japan 2 Department of Health Economics and Epidemiology Research, The University of Tokyo, Tokyo, Japan 3 Department of Clinical Data Management and Research, Clinical Research Center, National Hospital Organization Headquarters, Tokyo, Japan 4 Department of Health Care Informatics, Tokyo Medical and Dental University, Tokyo, Japan
Aims
Received: 16 January 2014; Accepted: 2 April 2014; Published online 18 July 2014 Conflict of interest: None declared. Funding: This study was funded by a Grant-in-Aid for Research on Policy Planning and Evaluation from the Ministry of Health, Labour and Welfare, Japan (No. H22-Policy-031); a Grant-in-Aid for Scientific Research B (No. 22390131) from the Ministry of Education, Culture, Sports, Science and Technology; and a grant from the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST program) from the Council for Science and Teckhnology Policy, Japan (No. 0301002001001). DOI: 10.1111/ijs.12311 © 2014 World Stroke Organization
Introduction Stroke is one of the leading causes of death and disability worldwide (1,2). Intravenous recombinant tissue plasminogen activator (rtPA) was demonstrated as an effective treatment for patients with acute ischemic stroke when given within 4·5 h after onset (3–5), and thrombolysis with rtPA has become widely used around the world (6–9). The relationship between hospital volume and outcomes according to various types of medical and surgical procedures has been investigated (10). Most studies concluded that higher hospital volume was associated with better outcomes. However, the relationship between the annual number of acute ischemic stroke patients treated with rtPA per hospital and outcomes is controversial (11,12). Considering that the overall burden of ischemic stroke is substantial, and thrombolysis with rtPA is provided in various facilities, an evaluation of the volume–outcome relationship is highly important.
In the present study, hospital volume was defined as the annual number of acute ischemic stroke patients treated with rtPA in an individual hospital. The goal of our study was to determine whether hospital volume had an impact on the seven-day mortality and functional independence of patients at discharge.
Methods Study design and setting This retrospective cohort study used data from the Diagnosis Procedure Combination (DPC) database, which is a nationwide Japanese administrative claims and discharge abstract database. The total number of recorded patients was approximately 7 million in 2011, which represented approximately 50% of all acute care inpatient hospitalizations in Japan. In total, 1075 hospitals, including all 82 university teaching hospitals, participated in the database as of March 2012. The database contains a unique hospital identifier, and patient demographics, diagnoses, drugs used, surgical and medical procedures performed, and hospital discharge status. It also includes detailed clinical data for specific diseases, such as the date of stroke onset, modified Rankin Scale Vol 10, January 2015, 73–78
73
Research (mRS) scores, and Japan Coma Scale (JCS) scores on admission for patients with stroke. Recorded diagnoses include a primary diagnosis on admission, preexisting comorbidities, and complications occurring after admission. These are separately recorded with the International Classification of Diseases and Related Health Problems, Tenth revision (ICD-10) codes and text data in the Japanese language. Drugs and procedures are recoded with the dates of use or implementation. Physicians in charge are responsible for recording the diagnoses in the DPC database. Our study was approved by the Institutional Review Boards and the Ethics Committee of The University of Tokyo. Selection of participants Patient inclusion criteria were as follows: admission to hospital with a primary diagnosis of ischemic stroke from July 1, 2010 to March 31, 2012; admission to hospital on the day of stroke onset or the following day; and treatment with rtPA on the day of stroke onset or the following day. We included patients who were admitted to hospital and received rtPA on the day following stroke onset in the case of patients who suffered a stroke shortly before midnight and were admitted to hospital and received rtPA soon after midnight. The ICD-10 code I63.x was used to determine the diagnosis of ischemic stroke. During the study period, intravenous rtPA administration was approved in Japan at a dose of 0.6 mg/kg only for patients within three-hours after stroke onset, based on the Japan Alteplase Clinical Trial (13). Data collection and processing We collected the following data: patient age and gender; preexisting comorbidities including atrial fibrillation (I48), heart failure (I50.x), and chronic renal failure (N18.x or N19); JCS scores on admission; emergency magnetic resonance imaging (MRI) performed on the same day or one-day before rtPA administration; routes of rtPA administration (intravenous or intra-arterial); admission to stroke care units (SCUs); hospital volume; hospital type (university or community hospitals); length of hospital stay; and discharge status. The JCS is a scale widely used in Japan to measure impaired consciousness (14,15). A JCS score of 0 indicates alert consciousness. Single-digit scores (1–3) indicate patients who are awake without any stimuli. Double-digit scores (10, 20, 30) indicate patients who can be aroused by some stimuli. Triple-digit scores (100, 200, 300) indicate coma. JCS and Glasgow Coma Scale assessments are well correlated (16). Hospital volume was defined as the annual number of acute ischemic stroke patients treated with rtPA in an individual hospital. Hospital volume was categorized into three levels (low, medium, and high volume) to obtain approximately equal numbers of patients in each group. Outcomes Primary outcomes were seven-day mortality and functional independence at discharge. We chose seven-day mortality with reference to the understanding that provision of acute stroke care and prevention of complications were generally achieved within the first seven-days (17). Neurological status with an mRS score of 0 to 2 was defined as functional independence. Attending
74
Vol 10, January 2015, 73–78
T. Wada et al. physicians evaluated their patients’ mRS scores at discharge. A secondary outcome was the occurrence of intracranial hemorrhage (ICH) after admission. ICH was identified by the ICD-10 codes I60.x, I61.x, I62.x. We also used ICD-10 code I638 with the text data ‘hemorrhagic infarction’ to identify ICH. Statistical analysis Continuous data were described by medians and interquartile ranges. Categorical data, including age (
Conclusion Hospital volume was not significantly associated with seven-day mortality or functional independence at discharge in acute ischemic stroke patients treated with recombinant tissue plasminogen activator in Japan. Key words: hospital volume, ischemic stroke, population-based study, recombinant tissue plasminogen activator, stroke facilities, thrombolysis
Correspondence: Tomoki Wada*, Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. E-mail: [email protected] 1 Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Tokyo, Japan 2 Department of Health Economics and Epidemiology Research, The University of Tokyo, Tokyo, Japan 3 Department of Clinical Data Management and Research, Clinical Research Center, National Hospital Organization Headquarters, Tokyo, Japan 4 Department of Health Care Informatics, Tokyo Medical and Dental University, Tokyo, Japan
Aims
Received: 16 January 2014; Accepted: 2 April 2014; Published online 18 July 2014 Conflict of interest: None declared. Funding: This study was funded by a Grant-in-Aid for Research on Policy Planning and Evaluation from the Ministry of Health, Labour and Welfare, Japan (No. H22-Policy-031); a Grant-in-Aid for Scientific Research B (No. 22390131) from the Ministry of Education, Culture, Sports, Science and Technology; and a grant from the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST program) from the Council for Science and Teckhnology Policy, Japan (No. 0301002001001). DOI: 10.1111/ijs.12311 © 2014 World Stroke Organization
Introduction Stroke is one of the leading causes of death and disability worldwide (1,2). Intravenous recombinant tissue plasminogen activator (rtPA) was demonstrated as an effective treatment for patients with acute ischemic stroke when given within 4·5 h after onset (3–5), and thrombolysis with rtPA has become widely used around the world (6–9). The relationship between hospital volume and outcomes according to various types of medical and surgical procedures has been investigated (10). Most studies concluded that higher hospital volume was associated with better outcomes. However, the relationship between the annual number of acute ischemic stroke patients treated with rtPA per hospital and outcomes is controversial (11,12). Considering that the overall burden of ischemic stroke is substantial, and thrombolysis with rtPA is provided in various facilities, an evaluation of the volume–outcome relationship is highly important.
In the present study, hospital volume was defined as the annual number of acute ischemic stroke patients treated with rtPA in an individual hospital. The goal of our study was to determine whether hospital volume had an impact on the seven-day mortality and functional independence of patients at discharge.
Methods Study design and setting This retrospective cohort study used data from the Diagnosis Procedure Combination (DPC) database, which is a nationwide Japanese administrative claims and discharge abstract database. The total number of recorded patients was approximately 7 million in 2011, which represented approximately 50% of all acute care inpatient hospitalizations in Japan. In total, 1075 hospitals, including all 82 university teaching hospitals, participated in the database as of March 2012. The database contains a unique hospital identifier, and patient demographics, diagnoses, drugs used, surgical and medical procedures performed, and hospital discharge status. It also includes detailed clinical data for specific diseases, such as the date of stroke onset, modified Rankin Scale Vol 10, January 2015, 73–78
73
Research (mRS) scores, and Japan Coma Scale (JCS) scores on admission for patients with stroke. Recorded diagnoses include a primary diagnosis on admission, preexisting comorbidities, and complications occurring after admission. These are separately recorded with the International Classification of Diseases and Related Health Problems, Tenth revision (ICD-10) codes and text data in the Japanese language. Drugs and procedures are recoded with the dates of use or implementation. Physicians in charge are responsible for recording the diagnoses in the DPC database. Our study was approved by the Institutional Review Boards and the Ethics Committee of The University of Tokyo. Selection of participants Patient inclusion criteria were as follows: admission to hospital with a primary diagnosis of ischemic stroke from July 1, 2010 to March 31, 2012; admission to hospital on the day of stroke onset or the following day; and treatment with rtPA on the day of stroke onset or the following day. We included patients who were admitted to hospital and received rtPA on the day following stroke onset in the case of patients who suffered a stroke shortly before midnight and were admitted to hospital and received rtPA soon after midnight. The ICD-10 code I63.x was used to determine the diagnosis of ischemic stroke. During the study period, intravenous rtPA administration was approved in Japan at a dose of 0.6 mg/kg only for patients within three-hours after stroke onset, based on the Japan Alteplase Clinical Trial (13). Data collection and processing We collected the following data: patient age and gender; preexisting comorbidities including atrial fibrillation (I48), heart failure (I50.x), and chronic renal failure (N18.x or N19); JCS scores on admission; emergency magnetic resonance imaging (MRI) performed on the same day or one-day before rtPA administration; routes of rtPA administration (intravenous or intra-arterial); admission to stroke care units (SCUs); hospital volume; hospital type (university or community hospitals); length of hospital stay; and discharge status. The JCS is a scale widely used in Japan to measure impaired consciousness (14,15). A JCS score of 0 indicates alert consciousness. Single-digit scores (1–3) indicate patients who are awake without any stimuli. Double-digit scores (10, 20, 30) indicate patients who can be aroused by some stimuli. Triple-digit scores (100, 200, 300) indicate coma. JCS and Glasgow Coma Scale assessments are well correlated (16). Hospital volume was defined as the annual number of acute ischemic stroke patients treated with rtPA in an individual hospital. Hospital volume was categorized into three levels (low, medium, and high volume) to obtain approximately equal numbers of patients in each group. Outcomes Primary outcomes were seven-day mortality and functional independence at discharge. We chose seven-day mortality with reference to the understanding that provision of acute stroke care and prevention of complications were generally achieved within the first seven-days (17). Neurological status with an mRS score of 0 to 2 was defined as functional independence. Attending
74
Vol 10, January 2015, 73–78
T. Wada et al. physicians evaluated their patients’ mRS scores at discharge. A secondary outcome was the occurrence of intracranial hemorrhage (ICH) after admission. ICH was identified by the ICD-10 codes I60.x, I61.x, I62.x. We also used ICD-10 code I638 with the text data ‘hemorrhagic infarction’ to identify ICH. Statistical analysis Continuous data were described by medians and interquartile ranges. Categorical data, including age (
