Capacity, consent, and selection bias in a study of delirium.
OBJECTIVE
To investigate whether different methods of obtaining informed consent affected recruitment to a study of delirium in older, medically ill hospital inpatients.


METHODS
Open randomised study.


METHODS
Acute medical service for older people in an inner city teaching hospital.


METHODS
Patients 70 years or older admitted to the unit within three days of hospital admission randomised into two groups.


METHODS
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.


METHODS
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 generalizable. A different method is necessary to achieve an ethical balance between respecting autonomy through obtaining adequate informed consent and avoiding sample bias.
Adamis
D
D
Academic Unit, Ladywell House, 330 Lewisham High Street, London SE13 6JZ, UK. dimaadamis@yahoo.com
Martin
F C
FC
Treloar
A
A
Macdonald
A J D
AJ
D000368:Aged; D003693:Delirium / Q000523:psychology / Q000628:therapy*; D005260:Female; D006801:Humans; D007258:Informed Consent; D008297:Male; D016743:Mental Competency; D018579:Patient Selection; D012107:Research Design; D015983:Selection Bias
Ann Intern Med. 1990 Dec 15;113(12):941-8
2240918
Arch Intern Med. 1990 Aug;150(8):1717-21
2383166
J Am Geriatr Soc. 1992 Jun;40(6):601-6
1587979
Ann Intern Med. 1993 Sep 15;119(6):474-81
8357112
Psychol Med. 1994 Feb;24(1):145-53
8208879
J Am Geriatr Soc. 1994 Aug;42(8):809-15
8046190
Am J Med. 1994 Sep;97(3):278-88
8092177
J Gen Intern Med. 1998 Apr;13(4):234-42
9565386
J Geriatr Psychiatry Neurol. 1998 Fall;11(3):118-25; discussion 157-8
9894730
N Engl J Med. 1999 Mar 4;340(9):669-76
10053175
N Engl J Med. 1999 May 6;340(18):1430-4
10228198
Dement Geriatr Cogn Disord. 1999 Sep-Oct;10(5):339-41
10473935
Gen Hosp Psychiatry. 1995 Mar;17(2):75-9
7789787
JAMA. 1996 Mar 20;275(11):852-7
8596223
J Am Geriatr Soc. 1996 Aug;44(8):1001-2
8708287
J Am Geriatr Soc. 1997 Feb;45(2):174-8
9033515
Arch Gen Psychiatry. 1997 Feb;54(2):117-20
9040278
Int J Geriatr Psychiatry. 1997 Jun;12(6):609-13
9215940
Int J Geriatr Psychiatry. 1997 Jun;12(6):614-8
9215941
J Med Ethics. 1997 Oct;23(5):271-6
9358345
BMJ. 1997 Oct 25;315(7115):1059
9366735
Am J Med. 1997 Nov;103(5):410-8
9375710
J Gen Intern Med. 1998 Mar;13(3):204-12
9541379
J Am Geriatr Soc. 2001 May;49(5):516-22
11380742
Hosp Med. 2001 Jun;62(6):351-4
11436442
Gerontologist. 1970 Spring;10(1):20-30
5420677
J Psychiatr Res. 1975 Nov;12(3):189-98
1202204
Crit Care Med. 1985 Oct;13(10):818-29
3928249
J Am Geriatr Soc. 1988 Dec;36(12):1099-104
3192888
Psychol Med. 1989 Nov;19(4):1015-22
2594878
Arch Intern Med. 1992 Feb;152(2):334-40
1739363