Delirium prevalence, diagnostic uncertainty and outcomes in ORCHARD-EPR: validation against prospective reference cohorts

Abstract Background Delirium is underdiagnosed in older inpatients. We determined clinically ascertained delirium prevalence, characteristics and outcomes after implementation of mandatory cognitive/delirium screening via the electronic patient record (EPR) compared to previously acquired prospective cohorts. Methods Acute general medicine patients aged ≥70 years in two separate cohorts were included (i) the Oxford Cognitive Comorbidity, Frailty and Ageing Research Database (ORCHARD-EPR, 2017–2019) and (ii) prospective cohorts (2010–2018). The ORCHARD-EPR cognitive screen included the Confusion Assessment Method, and 10-point Abbreviated Mental Test (AMT) with delirium diagnosis = certain/uncertain/no. In the prospective cohorts, delirium was diagnosed by Diagnostic and Statistical Manual of Mental Disorders, 4th Edition criteria. Odds ratios for in-hospital mortality were adjusted for age, sex, comorbidity and illness severity. Results Among 18 614 ORCHARD-EPR patients (mean/SD age = 82.9/7.4 years, dementia = 20%), certain delirium (delirium = yes or ICD-10 delirium code) was present in 3077/18 614 (17%,95%CI 16%–17%) of whom 1199/3077 (39%) had dementia, and uncertain delirium (delirium = uncertain and no ICD-10 code) in 2007 (11%,10%–11%) of whom 773/2007 (39%) had dementia. In the prospective cohorts (n = 731, mean/SD age = 82.7/7.1 years, dementia = 21%), 277 (38%, 34%–42%, both P 0.001) had delirium of whom 97 (35%) had dementia. Frailty, AMT 8, infection and hyponatraemia (Standardised Mean Difference-SMD all 0.1) but not comorbid dementia (SMD = 0.009) were more common in certain vs uncertain delirium. Excess mortality was similar in certain and uncertain delirium and the prospective cohorts. Discussion Delirium diagnostic uncertainty was frequent particularly in the absence of key delirium risk factors and delirium prevalence, even combining both certain and uncertain cases, was lower than in the prospective cohorts. Nevertheless, co-occurrence with dementia and outcomes were similar indicating validity of screening and research potential of ORCHARD-EPR.