A single-centre study with an intervention group and a retrospective control group was carried out in a tertiary hospital where the internal medicine department staff treats patients in 4 independent hospitalization wards. The intervention was carried out for 9 months: June 2017 to February 2018.
The study included elderly patients (≥ 65 years) who were polymedicated (5 or more chronic disease medications) and who had been admitted to one of the four internal medicine hospitalization wards during the study period. Patients with programmed admissions and patients who were discharged to nursing homes or long-term hospitals were excluded.
Patients admitted to one of the internal medicine hospitalization wards from June 2017 to February 2018 who met the inclusion criteria and signed the informed consent (IC) form were consecutively included. A clinical pharmacist who was integrated into the regular medical team carried out interventions on the patient’s treatment at different times during the healthcare process.
Patients admitted to the same hospitalization ward over the same months of 2014 who met the inclusion criteria were included in the control group. As the patients were recruited retrospectively, an IC form was not required.
The patients included in the study were divided into three groups according to HOSPITAL score: low risk of potentially avoidable readmission (0–4 points), intermediate risk (5–6 points), and high risk (≥ 7 points). The HOSPITAL score was calculated from seven parameters: haemoglobin (Hb) level < 12 g/dL in the last laboratory test prior to discharge (1 point), discharge from the oncology service (2 points), sodium < 135 mEq/L in the last laboratory test prior to discharge (1 point), procedures carried out during hospitalization according to the International Classification of Diseases (ICD-9) (1 point), urgent/emergent admission (1 point), number of hospitalizations during the previous year (0–1: 0 points, 2–5: 2 points, > 5: 5 points), and length of stay > 5 days (2 points) .
The following variables were collected from both patient groups through their electronic medical records: demographics (sex and age); degree of dependence (independent or low dependence, moderate dependence, and severe or total dependence); comorbidities (cognitive impairment, heart failure, stroke, chronic pulmonary disease, chronic liver disease, chronic kidney disease (CKD), and diabetes); diagnosis on admission and readmission classified according to the following categories: heart disease, respiratory disease, kidney disease, gastrointestinal disease, neurological disease, liver or biliary disease, endocrine system (diabetes or electrolyte abnormalities), infection, neoplasia (solid or haematological), and other; number of chronic medications; and number of medications from the HAMC list prescribed at discharge. From the HAMC list, the following groups of medications were considered: antiplatelets, oral anticoagulants, nonsteroidal anti-inflammatory drugs (NSAIDs), central nervous system depressants (benzodiazepines and opioids), antiarrhythmic agents (β-adrenergic blockers, digoxin, and amiodarone), insulin, oral hypoglycaemic agents, and diuretics (loop diuretics) . In addition, based on a consensus between internal medicine and pharmacy departments, the following drugs and therapeutic groups were included: diltiazem and verapamil (antiarrhythmic agents), thiazides (diuretics), and renin-angiotensin system inhibitors (angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs)).
At admission: Interview with the patient and/or main caregiver and medication reconciliation.
During hospitalization: Pharmacotherapeutic follow-up (validation of the prescriptions).
On discharge: Interview with the patient and/or main caregiver, including an educational intervention regarding postdischarge treatment (written treatment plan and written information about HAMC): information on changed dose, medication initiations or discontinuations and the detection and management of possible adverse events associated with the different HAMC.
At home (phone call follow-up): A phone call at 7 and 21 days after discharge, with completion of a questionnaire to measure the degree of knowledge of patients and/or their main caregivers regarding HAMC.
The questionnaire used to measure the patient’s knowledge of HAMC was a validated questionnaire of 11 questions. This questionnaire assesses knowledge in four dimensions: therapeutic objective (therapeutic indication and effectiveness), process of use (dosage, regimen, administration, and duration of treatment), safety (adverse reactions, precautions, contraindications, and interactions), and storage . The answers to the questions were categorized by the interviewing pharmacist as “is aware” or “is not aware” according to the information provided by the patient or caregiver.
Readmission was defined as all-cause 30-day hospital readmission. The readmission rate was determined in the whole patient population and in the 3 different categories of potentially avoidable readmission risk defined by the HOSPITAL score.
To analyse the cost of the intervention, the absolute risk reduction (ARR) of the readmission rate from the control to the intervention group and the number needed to treat (NNT) were calculated. The costs considered to do the analysis were a median cost per admission in patients older than 65 years of €4,392.45  and a median annual clinical pharmacist salary of €45,749.58 . The patient population who could be recipients of the intervention over 1 year was estimated to be 400.
The cost analysis was performed for all patients and for the patients in the 3 different categories of potentially avoidable readmission risk defined by the HOSPITAL score.
A descriptive analysis of baseline characteristics was performed on the patients in the control and intervention groups. Categorical and quantitative variables were tested by the χ2 test or Fisher's exact test, and continuous variables were assessed using the nonparametric Mann–Whitney-Wilcoxon U tests, as stipulated by the Shapiro–Wilk normality test. Categorical variables are presented as number and percentage, and continuous variables are presented as median and interquartile range (IQR).
A binary logistic regression was performed to analyse the effect of the intervention on readmission. In the multivariate analysis, all variables with statistically significant differences (p < 0.05) between the control and intervention groups were included. The results are expressed as odds ratio (OR) with 95% confidence interval (95% CI).
Statistical analysis was carried out using Stata® 16 statistical software (StataCorp. 2019. Stata Statistical Software: Release 16. College Station, TX: StataCorp LLC). A significance level of 5% was used in this study.