Prognosticating with the hospitalized-patient one-year mortality risk score using information abstracted from the medical record

Study Cohort

The study, which was approved by our local research ethics board, took place at the Ottawa Hospital, a 1000-bed teaching hospital that is the primary referral center in our region. We used the hospital admission registry to identify all people 18 years or older who were admitted to a nonpsychiatric service at our hospital between January 1, 2011 and December 31, 2011 (this time frame corresponds with the year used to derive the HOMR score). We excluded overnight patients in the same-day surgery or the bone-marrow transplant units (since they would not have been included in the original study) and those without a valid health card number (which was required to link to provincial data to identify outcomes). From this list, we randomly selected 5000 patients.

Primary Data Collection

For each patient, we retrieved all data required to calculate the HOMR score from the medical record (Table 1). Patient registration information in our electronic medical record was used to identify patient age, sex, admitting service, number of emergency department (ED) visits in the previous year, number of admissions in the previous year (the nursing triage note was reviewed for each admission to determine if it was by ambulance), and whether or not the patient had been discharged from hospital in the previous 30 days. The admitting service consult note was used to determine the admitting diagnosis and whether or not the patient was admitted directly to the intensive care unit. If they were present, the emergency nursing triage note, the ED record of treatment, the admission consult note, the pre-operative consult note, and consult notes were all used to determine the patient’s comorbidities, living status, and home oxygen status. Admission urgency was determined using information from the patient registration information and the ED nursing triage note. All data were abstracted from information that had been registered prior to when the patient was physically transferred to their hospital bed. This ensured that we used only data available at the start of the admission.

Patient functional status has been shown to be strongly associated with survival⁴ but HOMR only indirectly captures functional information (through the patient’s living status). We, therefore, collected more detailed functional information from the medical record by determining if the patient was dependent for any activities of daily living (ADL) from the emergency nursing triage note, the ED record of treatment, the admission consult note, and the pre-operative consultation. We also collected information that might indicate frailty, which we defined per Clegg et al.⁵ as “a state of increased vulnerability to poor resolution of homeostasis following a stress.” This information included: delirium or more than 1 fall recorded on the emergency nursing triage note, the ED record of treatment, or the admission consultation note; or whether a geriatric nursing specialist assessment occurred in the ED in the previous 6 months. Finally, we recorded possible indicators of limited social support (no fixed address [from patient registration and nursing triage note], primary contact is not a family member [from the emergency notes, consult, and patient registration], and no religion noted in system [from patient registration]). Patients for whom religion status was missing were classified as having “no religion.”

Analysis

These data were encrypted and linked anonymously to population-based databases to determine whether patients died within 1 year of admission to hospital. We calculated the chart-HOMR score using information from the chart review and determined its association with the outcome using bivariate logistic regression. We compared observed and expected risk of death within 1 year of admission to hospital for each chart-HOMR score value, with expected risks determined from the external validation study.³ We regressed observed death risks on expected death risks for chart-HOMR scores (clustered into 22 groups to ensure adequate numbers in each group); and we gauged overall deviations from expected risk and the relationship between the observed and expected death risk (based on the chart-HOMR score) using the line’s intercept and slope, respectively.⁶ Next, we replicated methods from our studies^2,3 to calculate the administrative-HOMR score in our study cohort using administrative databases. We compared these chart-HOMR and administrative-HOMR scores (and scores for each of its components). Finally, we determined which of the socio-functional factors were associated with 1-year death risk independent of the chart-HOMR score. We used the likelihood ratio test to determine whether these additional socio-functional factors significantly improved the model beyond the chart-HOMR score.⁷ This test subtracted the -2 logL value of the full model from that containing the chart-HOMR score alone, comparing its value to the χ² distribution (with degrees of freedom equivalent to the number of additional parameters in the nested model) to determine statistical significance. All analyses were completed using SAS v9.4 (SAS Institute Inc., Cary, North Carolina).