Materials and Methods
All adult medical patients discharged from the SIU-School of Medicine (SIU-SOM) Hospitalist service from Memorial Medical Center from January 1, 2015 to January 1, 2017 were studied retrospectively to determine if vital sign instability at the time of discharge were significant predictors of any cause (avoidable and unavoidable) hospital readmission within 30 days. Exclusion criteria were transfer to another acute care hospital, leaving the hospital against medical advice, or death. The any cause readmission within 30 days of hospital discharge endpoint was selected because it is the measure used by the Medicare Hospital Readmission Reduction Program.
Vital sign instability was defined as: temperature ≥37.8 °C, heart rate ≥100 beats per minute, respiratory rate >24 breaths per minute, systolic blood pressure ≤90 mmHg, or oxygen saturation <90 % (Nguyen et al, 2016).
Memorial Medical Center is a 507 bed not-for-profit university-affiliated tertiary care center located in Springfield, Illinois, USA. The SIU-SOM Hospitalist service is the general internal medicine residency teaching service staffed by board certified or board eligible hospitalist faculty. Patients for the hospitalist service are primarily admitted via the hospital emergency department or transferred from other regional hospitals with acute medical issues. Elective hospital admissions are extremely rare for this service.
Data on age, gender, diagnosis related group (DRG), International Classification of Disease (ICD) diagnosis codes, emergency department visits in the last 6 months, length of stay, hospital readmission within 30 days, vital signs, and the other variables in the HOSPITAL score (Table 1) and LACE index (Table 2) were extracted from the electronic health record in a de-identified manner for analysis. Missing laboratory data (hemoglobin and sodium from the day of discharge) were coded to be in the normal range.
The study hospital does not have a distinct oncology admitting service. To address the increased risk of readmission in oncology patients found in other studies using the HOSPITAL score, this study classified patients with oncology related diagnosis ICD codes to have been discharged from an oncology service. This reflects local practice patterns where hospitalists often admit patients to the general medicine service for oncologists. Because data is only available from the study hospital, readmissions at other hospitals will not be detected.