Estimating the population impact of preventive interventions from randomized trials.
Growing concern about the limited generalizability of trials of preventive interventions has led to several proposals concerning the design, reporting, and interpretation of such trials. This paper presents an epidemiologic framework that highlights three key determinants of population impact of many prevention programs: the proportion of the population at risk who would be candidates for a generic intervention in routine use, the proportion of those candidates who are actually intervened on through a specific program, and the reduction in incidence produced by that program among recipients. It then describes how the design of a prevention trial relates to estimating these quantities. Implications of the framework include the following: (1) reach is an attribute of a program, whereas external validity is an attribute of a trial, and the two should not be conflated; (2) specification of a defined target population at risk is essential in the long run and merits greater emphasis in the planning and interpretation of prevention trials; (3) with due attention to sampling frame and sampling method, the process of subject recruitment for a trial can yield key information about quantities that are important for assessing its potential population impact; and (4) exclusions during subject recruitment can be conceptually separated into intervention-driven, program-driven, and trial-design-driven exclusions, which have quite different implications for trial interpretation and for estimating population impact of the intervention studied.
Harborview Injury Prevention and Research Center, University of Washington, Seattle, WA, USA. koepsell@u.washington.edu
Thomas D
TD
Koepsell
Douglas F
DF
Zatzick
Frederick P
FP
Rivara
D003627:Data Interpretation, Statistical; D015340:Epidemiologic Research Design; D006801:Humans; D008962:Models, Theoretical; D011315:Preventive Medicine; D016032:Randomized Controlled Trials as Topic
Milbank Q. 2008 Dec;86(4):581-600
19120981
Am J Prev Med. 2006 Jan;30(1):67-73
16414426
Arch Intern Med. 2008 Jan 28;168(2):133-5
18227357
Am J Public Health. 2008 Aug;98(8):1359-66
18556609
Stat Methods Med Res. 2001 Jun;10(3):195-216
11446148
Lancet. 2002 Nov 16;360(9345):1531-9
12443589
Prev Med. 1986 Sep;15(5):451-74
3534875
Drug Alcohol Depend. 2008 Nov 1;98(1-2):123-8
18579319
Stat Med. 1999 Jun 30;18(12):1467-74
10398285
BMJ. 2008 Nov 11;337:a2390
19001484
Stat Med. 2007 Jan 15;26(1):20-36
17072897
JAMA. 2003 Sep 24;290(12):1624-32
14506122
Annu Rev Public Health. 2007;28:413-33
17150029
Am J Public Health. 2003 Aug;93(8):1261-7
12893608
Lancet. 2005 Jan 1-7;365(9453):82-93
15639683
J Natl Cancer Inst. 1985 Mar;74(3):543-51
3883037
C R Biol. 2007 Apr;330(4):281-98
17502285
JAMA. 2007 Mar 21;297(11):1233-40
17374817
Annu Rev Public Health. 2000;21:121-45
10884949
Eval Health Prof. 2006 Mar;29(1):126-53
16510882
Am J Public Health. 2006 Dec;96(12):2254-9
16809591
N Engl J Med. 2002 Oct 3;347(14):1087-93
12362011
Int J Epidemiol. 1985 Mar;14(1):32-8
3872850
Am J Public Health. 1999 Sep;89(9):1322-7
10474547
N Engl J Med. 1989 Jul 20;321(3):129-35
2664509
Psychiatry. 2009 Winter;72(4):346-59
20070133
J Trauma Stress. 2007 Aug;20(4):401-12
17721951
J Pharmacol Pharmacother. 2010 Jul;1(2):100-7
21350618