Recruiting patients to medical research: double blind randomised trial of "opt-in" versus "opt-out" strategies.
OBJECTIVE
To evaluate the effect of opt-in compared with opt-out recruitment strategies on response rate and selection bias.


METHODS
Double blind randomised controlled trial.


METHODS
Two general practices in England.


METHODS
510 patients with angina.


METHODS
Patients were randomly allocated to an opt-in (asked to actively signal willingness to participate in research) or opt-out (contacted repeatedly unless they signalled unwillingness to participate) approach for recruitment to an observational prognostic study of patients with angina.


METHODS
Recruitment rate and clinical characteristics of patients.


RESULTS
The recruitment rate, defined by clinic attendance, was 38% (96/252) in the opt-in arm and 50% (128/258) in the opt-out arm (P = 0.014). Once an appointment had been made, non-attendance at the clinic was similar (20% opt-in arm v 17% opt-out arm; P = 0.86). Patients in the opt-in arm had fewer risk factors (44% v 60%; P = 0.053), less treatment for angina (69% v 82%; P = 0.010), and less functional impairment (9% v 20%; P = 0.023) than patients in the opt-out arm.


CONCLUSIONS
The opt-in approach to participant recruitment, increasingly required by ethics committees, resulted in lower response rates and a biased sample. We propose that the opt-out approach should be the default recruitment strategy for studies with low risk to participants.
Junghans
Cornelia
C
Department of Epidemiology and Public Health, Royal Free and UCL Medical School, London WC1E 7HD. C.Junghans@ucl.ac.uk
Feder
Gene
G
Hemingway
Harry
H
Timmis
Adam
A
Jones
Melvyn
M
D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000175:diagnosis* / Q000523:psychology; D004311:Double-Blind Method; D028744:Ethics Committees, Research; D005260:Female; D006801:Humans; D007258:Informed Consent; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D018579:Patient Selection / Q000941:ethics; D026684:Personal Autonomy; D011379:Prognosis; D012107:Research Design; D015983:Selection Bias