Early mortality in patients with acute myelogenous leukemia treated in teaching versus non‐teaching hospitals: A large database analysis
Authors: Adam Levin, Ariel Kleman, Lisa Rein, Sergey Tarima, Laura C. Michaelis, Karen Sue Carlson, Mehdi Hamadani, Timothy S. Fenske, Parameswaran Hari, Ehab Atallah, Binod Dhakal
Journal: American Journal of Hematology (2017)

There is an increasing amount of evidence that suggests factors such as treatment center volume and teaching status influence patient outcomes in various malignant conditions such as breast,1 colorectal,2 esophageal,3 and head and neck cancers.4 Specifically, treatment at a teaching or academic hospital has been shown to improve patient mortality rates for these solid tumor malignancies. We sought to investigate the impact of teaching hospital status on mortality in patients with acute myelogenous leukemia (AML). We analyzed the relationship between hospital teaching status and clinical outcomes among adult patients with a primary discharge diagnosis of AML using the National Inpatient Sample (NIS) from 2008 to 2013. The NIS is part of the Healthcare Cost and Utilization Project (HCUP) that is sponsored by the Agency for Healthcare Research and Quality.5 Each year of the NIS includes over seven million inpatient stays from U.S. hospitals and represents more than 95% of the U.S. population. The de-identified data includes a primary diagnosis, the principle problem for which the patient was admitted, as well as secondary diagnosis codes, demographic information, and hospital characteristics. Patient characteristics (age, race, sex, insurance status, and Charlson comorbidity index) and clinical outcomes (in-hospital mortality, 7-day in-hospital mortality, common complications, and length of stay) were compared across hospital teaching status using ANOVA for continuous variables and logistic regression for categorical variables. Multiple logistic regressions were used to compare binary outcomes by hospital teaching status adjusting for patient characteristics. All data analyses accounted for complex NIS survey design (survey weights, strata, clusters, and domains of interest where applicable). AML was identified using the International Classification of Diseases, 9th revision (ICD-9) diagnosis code of 205 as the primary diagnosis.6 Secondary diagnoses were identified using the following ICD-9 codes: 453.40 for deep vein thrombosis (DVT), 415.1 for pulmonary embolism (PE), 578.9 for gastrointestinal hemorrhage, 459.0 for unspecified hemorrhage, 431 for intracranial hemorrhage (ICH), 410 for acute myocardial infarction (AMI), 427.9 for cardiac dysrhythmia, 434.91 for stroke, and 286.6 for disseminated intravascular coagulation (DIC). To be classified as a teaching hospital, the discharge hospital must meet one of the following criteria: have an AMA-approved residency program, have membership in the Council of Teaching Hospitals, or a ratio of full-time equivalent interns and residents to beds of .25 or higher.5 Between 2008 and 2013, there were 27 542 inpatient admissions with a primary diagnosis of AML. Non-teaching hospitals accounted for 8322 admissions and teaching hospitals accounted for 19 220 admissions. On unadjusted analyses, patients at non-teaching hospitals were older (mean age 67.1 years vs. 58.1 years, P < .0001) and had a higher Charlson comorbidity index (CCI) (mean 3.05 vs. 2.78, P < .0001). Patients treated at teaching hospitals had higher rates of DIC (5.01% vs. 3.18%, P < .0001), ICH (1.09% vs. 0.74%, P = .0120), and PE (1.03% vs. 0.72%, P = .0185). The rate of gastrointestinal bleeding was higher at the non-teaching hospitals (2.34% vs. 1.85%, P = .0264). Rates of overall bleeding, AMI, and cardiac arrhythmia were similar between both groups (Table 1). The 7-day in-hospital mortality was significantly higher in non-teaching hospitals, 9.92% vs. 5.63% (P < .0001), as well as the overall in-hospital mortality (15.7% non-teaching vs. 14.3% teaching, P = .0087). On multiple logistic regression analysis, teaching hospitals had statistically significant lower odds of early (7-day) mortality compared to non-teaching hospitals (OR 0.733, 95% CI 0.657–0.817; P < .001). Age (OR 1.036, 95% CI 1.031–1.041; P < .001) and CCI (OR 1.540, 95% CI 1.361–1.742; P < .001) were positively associated with odds of early mortality. Female gender had improved early mortality odds (OR 0.873, 95% CI 0.793–0.960; P = .005) while race was not found to have an impact on early mortality. On the contrary, with respect to overall in-hospital mortality, teaching hospitals were found to have increased odds of in-hospital mortality (OR 1.103, CI 1.013–1.201, P = .025). To our knowledge, this the largest study that has examined early hospital mortality in AML. The overall in-hospital mortality rate was 14.7%. Multiple logistic regression for 7-day in-hospital mortality demonstrated decreased odds of mortality at teaching hospitals, supporting this as an independent risk factor. Interestingly, teaching hospitals had a small but significant increased odds of overall in-hospital mortality. One likely hypothesis is that the patient population in the teaching hospitals is sicker and includes patients transferred from the non-teaching hospitals that require a higher level of care. Patients presenting with AML at community hospitals may be more likely to be transferred to tertiary care centers if they present with more severe manifestations, require leukopheresis, have a tentative diagnosis of acute promyelocytic leukemia, or are young and fit enough for cytotoxic induction. While patients at non-teaching hospitals were older and had higher CCI, patients treated at teaching hospitals had higher rates of serious complications including DIC, ICH, and PE, which again suggests an increased proportion of sicker patients. The improved early mortality in teaching hospitals may be due to a variety of factors including earlier recognition and evaluation of acute leukemia and its complications, better adherence to guidelines for supportive care such as prophylactic antimicrobials and transfusion support, dedicated oncology wards with experienced staff, and access to clinical trials. Our study is limited by its retrospective and observational design. The database used lacks important information regarding factors such as cytogenetics and treatment used that would impact early mortality in AML and thus cannot be analyzed as independent risk factors. Teaching hospitals are often tertiary care referral centers that have close associations with universities. Along with this comes increased resources and access to highly specialized providers and medical staff. It is difficult to determine whether the improved mortality at teaching hospitals is a result of higher volume or more specialized care and resources. Further investigation is needed to elucidate specific treatment center factors that improve patient outcomes so that these benefits can be implemented across all hospital systems. Nothing to report.