Impact of the Arrival Mode of Emergency Department Patients
Author: Charu Malhotra
Masters thesis, The University of Texas School of Health Information Sciences at Houston..
Background: The purpose of this study was to compare outcome data for patients who arrive from community-based hospital to Emergency Department (ED) (“transfer”) with patients who directly arrive in the ED (“direct”). The outcome measures were length of hospital stay, total cost, drug cost, and mortality rate.
Methodology: Data from Memorial Hermann (MH) Emergency room (ER) over two years was used. The population of patients included for this study was “inpatient” (patients admitted in the hospital), greater than 18 years of age. Patients with length of stay less than one day were excluded from the study. Overall, 9290 patients were studied of which 8681 patients (93.4%) were “Direct admissions to the emergency Room” and 609 patients (6.6%) were “Transfer patients who were transferred from a different facility”. The outcomes for the two patient groups were compared using statistical measures such as t-test and ANOVA. The statistical package used for the analysis was SAS. Using Logistic Regression, factors such as APRDRG levels, financial payment methods, injury severity scores (ISS), infection rates (complications) based on ICD-9 code, sex of the patient, and age were controlled when comparing the two patient groups.
Data Sources and Types: Data from Memorial Hermann Emergency Room (ER) records and UB92 data in the administrative database was used to perform the analysis.
Analysis: Patient data for the two patient groups (direct and transfer) were compared using statistical measures such as t-Test and ANOVA. A Logistic Regression analysis was performed to control for other factors to study the effect of transfer mode on patient survival rate as well.
Results: The data revealed that mortality for the Transfer group was twice that of the Direct. However, on performing a Logistic Regression to control for other effects such as age, Injury Severity Scores (ISS) and APRDRG level, the outcome was not as definitive. ANOVA analysis revealed that the Length of Stay (LOS) is influenced primarily by ISS and not by the mode of arrival (Transfer or Direct). Further analysis of data using other variables available in the Memorial Herman database may be necessary to conclusively determine the effect of marginal variables such as mode of arrival and payment. Since the number of “direct” patients is much larger than “transfer”, the analysis could be repeated by randomly selecting about 8% of the patients in the “direct” group to make a more balanced comparison.
Key Words: Emergency Room, Direct Transport, Mortality, Injury Severity Score (ISS), Length of Stay (LOS), ANOVA, Logistic Regression.