Recognising delirium in frail hospital inpatients
Kathy Whittamore is a clinical researcher working as part of the Medical Crises in Older People programme at the University of Nottingham. She recently completed her MPhil looking at ways of recognising dementia in acute hospital inpatients. Before becoming a clinical researcher, I worked for some time as a health care assistant on a psychiatric assessment unit. Despite working at the ‘coal face’ of a mental health ward, I was never told what delirium was, its risk factors, its causes and – perhaps most importantly – how to recognise it. Since 2008, the Medical Crises in Older People (MCOP) research programme at the University of Nottingham has led a workstream devoted to better understanding the mental health problems of older patients on acute medical wards. When I began working as a researcher on the project I was educated in how to identify both delirium and dementia, but the more I learned the more I realised how many other healthcare professionals where not aware of what delirium was or how to recognise it. Delirium can be difficult to identify in older patients because it presents in a variety of different ways and can be difficult to distinguish from more long-term cognitive impairments such as dementia. As I worked on the programme, I became focussed on this issue of helping staff to identify delirium and decided to base my MPhil around this. There are several diagnostic and severity scales which are available to help spot delirium but not all of them have been properly evaluated. There is no recognised “best test” for delirium. One of the better-developed tools I identified was the Delirium Rating Scale-Revised-98 (DRS-R-98), however there was limited data on its validity in the populations of older people that I was working with. I decided to try to understand how and whether it might be used as an aid to recognition in these cohorts. As part of the MCOP programme, the Better Mental Health cohort study was untaken, recruiting 250 patients, aged 70 or older, from 12 wards of Nottingham University Hospitals who had been admitted as an emergency and screened positive for mental health problems. Along with a battery of psychometric and health status measures, the DRS-R-98 was used to identify delirium. A sub-sample of the participants were also assessed by a clinician, including 49 psychiatric and 53 geriatric medical evaluations, where delirium was diagnosed using DSM IV criteria. One hundred and seven (43%) of the participants had DRS-diagnosed delirium, representing 27% (95% CI 24-31%) of all acutely admitted patients over 70. One hundred and six (43%) of participants (or 27% of all admissions) had a prior diagnosis of dementia, of whom 72 (68%) had DRS-diagnosed delirium. By using the clinical assessments as a ‘gold standard’ twenty (22%) had clinician-diagnosed delirium and 36 (39%) had DRS-diagnosed delirium. The sensitivity of the DRS-R-98 was 0.75 (95% CI 0.56-0.93), and the specificity 0.71 (95% CI 0.66-0.76). ROC analysis was conducted and the area under the curve was 0.76 (95% CI 0.63 – 0.88), indicating moderate discriminating ability. The sensitivity and specificity of the DRS-R-98 were moderate – illustrating that delirium could be missed or misdiagnosed if the DRS-R-98 wass used alone to detect delirium in older patients on general hospital wards. Therefore, in clinical practice, the DRS-R-98 could augment, but not replace, clinical assessment. However, it is sufficiently valid to be used in epidemiological studies, where non-differential misclassification causes a loss of statistical power but does not change the direction of association.