Derivation and validation of a clinical prediction rule for delirium in patients admitted to a medical ward: an observational study

Abstract

ObjectivesTo develop and validate a simple clinical prediction rule, based on variables easily measurable at admission, to identify patients at high risk of developing delirium during their hospital stay on an internal medicine ward.DesignProspective study of two cohorts of patients admitted between 1 May and 30 June 2008 (derivation cohort), and between 1 May and 30 June 2009 (validation cohort).SettingA tertiary hospital in Donostia-Gipuzkoa (Spain).ParticipantsIn total 397 patients participated in the study. The mean age and incidence of delirium were 75.9 years and 13%, respectively, in the derivation cohort, and 75.8 years and 25% in the validation cohort.Main outcome measuresThe predictive variables analysed and finally included in the rule were: being aged 85 years old or older, being dependent in five or more activities of daily living, and taking two or more psychotropic drugs (antipsychotics, benzodiazepines, antidepressants, anticonvulsant and/or antidementia drugs). The variable of interest was delirium as defined by the short Confusion Assessment Method, which assesses four characteristics: acute onset and fluctuating course, inattention, disorganised thinking and altered level of consciousness.ResultsWe developed a rule in which the individual risk of delirium is obtained by adding one point for each criterion met (age≥85, high level of dependence, and being on psychotropic medication). The result is considered positive if the score is ≥1. The rule accuracy was: sensitivity=93.4% (95% CI 85.5% to 97.2%), specificity=60.6% (95% CI 54.1% to 66.8%), positive predictive value=44.4% (95% CI 36.9% to 52.1%) and negative predictive value=96.5% (95% CI: 92% to 98.5%). The area under the receiver operator characteristic (ROC) curve was 0.85 for the validation cohort.ConclusionsThe presence or absence of any of the three predictive factors (age≥85, high level of dependence and psychotropic medication) allowed us to classify patients on internal medicine wards according to the risk of developing delirium. The simplicity of the variables in our clinical prediction rule means that the data collection required is feasible in busy medicine units.

Predicting delirium: a review of risk-stratification models

“…Martinez et al [27] included all adults, and age N 85 emerged as a model element; Kobayashi et al [19] included all adults, and their model included age stratifications at 50 and 75; Douglas et al [28] included adults as young as 50, and age N80 emerged as a significant factor.…”

Risk Factors for Delirium in Older Medical Inpatients in Tanzania

“…Functional dependency has been measured in a number of ways, including through assessment of dependency using the Katz Activities of Daily Living (ADL) questionnaire [26,28,29]. However, by reporting functioning by difficulties with ADL, (dressing, feeding, etc.)…”

A Pharmacist–Physician Intervention Model Using a Computerized Alert System to Reduce High-Risk Medication Use in Elderly Inpatients

“…The cutoff of four or more medications was chosen by the expert panel to identify patients highly likely to present a pharmacotherapeutic problem requiring an intervention. A lower threshold of two or more psychoactive agents has been associated with delirium [26,27]. The use of more than three psychotropic agents has been related to a higher risk of ADEs [28].…”