Randomized trials versus observational studies in adolescent pregnancy prevention

Guyatt, Gordon H.; DiCenso, Alba; Farewell, Vern; Willan, Andrew; Griffith, Lauren

« Previous Next »Journal of Clinical Epidemiology
Volume 53, Issue 2 , Pages 167-174, February 2000

Randomized trials versus observational studies in adolescent pregnancy prevention

Gordon H. Guyatt
- Department of Clinical Epidemiology & Biostatistics, Room 2C12, McMaster University Faculty of Health Sciences, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5,
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada L8N 3Z5,
- Corresponding author. Tel.: (905) 525-9140, ext. 22900; Fax: (905) 577-0017.(Gordon H. Guyatt)
Alba DiCenso
- Department of Clinical Epidemiology & Biostatistics, Room 2C12, McMaster University Faculty of Health Sciences, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5,
- School of Nursing, McMaster University, Hamilton, Ontario, Canada L8N 3Z5,
Vern Farewell
- Department of Statistical Science, University College, London, UK
Andrew Willan
- Department of Clinical Epidemiology & Biostatistics, Room 2C12, McMaster University Faculty of Health Sciences, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5,
Lauren Griffith
- Department of Clinical Epidemiology & Biostatistics, Room 2C12, McMaster University Faculty of Health Sciences, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5,

Received 1 May 1999; received in revised form 24 June 1999; accepted 26 July 1999.

Abstract

The objective of this study is to compare the results of randomized trials and observational studies of interventions to prevent adolescent pregnancy. We identified published and unpublished reports through computerized searches of CATLINE, CINAHL, CONFERENCE PAPERS INDEX, DISSERTATION ABSTRACTS ONLINE, EMBASE, ERIC, MEDLINE, NTIS, POPLINE, PsycINFO, and SOCIOLOGICAL ABSTRACTS; manual searches of eight relevant journals; reference lists from primary articles; and contact with content experts. We included randomized trials and observational studies that evaluated the impact of primary prevention interventions including sex education classes, school-based clinics, free-standing clinics, physician/nurse practitioner practice-based service, improved access, and community-based programs on four outcomes: sexual intercourse, birth control use, responsible sexual behavior, or pregnancy in adolescents. One investigator abstracted the data and a second conducted a detailed review of the abstraction. We identified 13 randomized trials and 17 observational studies. We generated estimates of the impact of the interventions separately for males and females for all four outcomes for both observational studies and randomized trials. For six of the eight outcomes the summary odds ratios for the observational studies showed a significant intervention benefit (P < 0.05) while the randomized trials did not show a benefit for any outcome in either females or males. The difference between the results of the observational studies and randomized trials was statistically significant in two of the eight outcomes (P < 0.05 for initiation of intercourse and pregnancy in females). Observational studies yield systematically greater estimates of treatment effects than randomized trials of adolescent pregnancy prevention interventions. Public policy or individual patient treatment decisions should be based on observational studies only when randomized trials are unavailable and only with careful consideration of possible biases.

Keywords: Randomized trials, Observational studies, Adolescent pregnancy, Prevention strategies