@article {Adamis137, author = {D Adamis and F C Martin and A Treloar and A J D Macdonald}, title = {Capacity, consent, and selection bias in a study of delirium}, volume = {31}, number = {3}, pages = {137--143}, year = {2005}, doi = {10.1136/jme.2002.000919}, publisher = {Institute of Medical Ethics}, abstract = {Objectives: To investigate whether different methods of obtaining informed consent affected recruitment to a study of delirium in older, medically ill hospital inpatients. Design: Open randomised study. Setting: Acute medical service for older people in an inner city teaching hospital. Participants: Patients 70 years or older admitted to the unit within three days of hospital admission randomised into two groups. Intervention: Attempted recruitment of subjects to a study of the natural history of delirium. This was done by either (a) a formal test of capacity, followed by either a request for consent or an attempt at obtaining assent from a proxy, or (b) a combined informal capacity/consent process. Main outcome measures: Prevalence and severity of delirium, and, as case mix measures, length of hospital stay and destination on discharge. Results: Recruitment of subjects through establishing formal capacity and then informed consent was less successful (43.9\% v 74\% of those approached) and, compared with those recruited through the usual combined capacity/consent approach, yielded a sample with less cognitive impairment, lower severity of delirium, lower probability of case note diagnosis of delirium and lower rate of entering a care home. Conclusions: Methods of obtaining informed consent may significantly influence the case mix of subjects recruited to a study of delirium. Stringent testing of capacity may exclude patients with delirium from studies, thus rendering findings less generalisable. A different method is necessary to achieve an ethical balance between respecting autonomy through obtaining adequate informed consent and avoiding sample bias.}, issn = {0306-6800}, URL = {https://jme.bmj.com/content/31/3/137}, eprint = {https://jme.bmj.com/content/31/3/137.full.pdf}, journal = {Journal of Medical Ethics} }