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BMJ. 1996 May 11; 312(7040): 1215–1218.
PMCID: PMC2350940

Why we need observational studies to evaluate the effectiveness of health care.


The view is widely held that experimental methods (randomised controlled trials) are the "gold standard" for evaluation and that observational methods (cohort and case control studies) have little or no value. This ignores the limitations of randomised trials, which may prove unnecessary, inappropriate, impossible, or inadequate. Many of the problems of conducting randomised trials could often, in theory, be overcome, but the practical implications for researchers and funding bodies mean that this is often not possible. The false conflict between those who advocate randomised trials in all situations and those who believe observational data provide sufficient evidence needs to be replaced with mutual recognition of the complementary roles of the two approaches. Researchers should be united in their quest for scientific rigour in evaluation, regardless of the method used.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Stauffer RN. Ten-year follow-up study of total hip replacement. J Bone Joint Surg Am. 1982 Sep;64(7):983–990. [PubMed]
  • Black N. The relationship between evaluative research and audit. J Public Health Med. 1992 Dec;14(4):361–366. [PubMed]
  • Brewin CR, Bradley C. Patient preferences and randomised clinical trials. BMJ. 1989 Jul 29;299(6694):313–315. [PMC free article] [PubMed]
  • Lilford RJ, Jackson J. Equipoise and the ethics of randomization. J R Soc Med. 1995 Oct;88(10):552–559. [PMC free article] [PubMed]
  • Schulz KF. Subverting randomization in controlled trials. JAMA. 1995 Nov 8;274(18):1456–1458. [PubMed]
  • Fowler FJ, Jr, Wennberg JE, Timothy RP, Barry MJ, Mulley AG, Jr, Hanley D. Symptom status and quality of life following prostatectomy. JAMA. 1988 May 27;259(20):3018–3022. [PubMed]
  • Dixon J, Glennerster H. What do we known about fundholding in general practice? BMJ. 1995 Sep 16;311(7007):727–730. [PMC free article] [PubMed]
  • Chalmers I. Minimizing harm and maximizing benefit during innovation in health care: controlled or uncontrolled experimentation? Birth. 1986 Sep;13(3):155–164. [PubMed]
  • Black N, Johnston A. Volume and outcome in hospital care: evidence, explanations and implications. Health Serv Manage Res. 1990 Jul;3(2):108–114. [PubMed]
  • Maw R, Bawden R. Spontaneous resolution of severe chronic glue ear in children and the effect of adenoidectomy, tonsillectomy, and insertion of ventilation tubes (grommets). BMJ. 1993 Mar 20;306(6880):756–760. [PMC free article] [PubMed]
  • Hlatky MA, Califf RM, Harrell FE, Jr, Lee KL, Mark DB, Pryor DB. Comparison of predictions based on observational data with the results of randomized controlled clinical trials of coronary artery bypass surgery. J Am Coll Cardiol. 1988 Feb;11(2):237–245. [PubMed]
  • Ward LC, Fielding JW, Dunn JA, Kelly KA. The selection of cases for randomised trials: a registry survey of concurrent trial and non-trial patients. The British Stomach Cancer Group. Br J Cancer. 1992 Nov;66(5):943–950. [PMC free article] [PubMed]
  • Stiller CA. Centralised treatment, entry to trials and survival. Br J Cancer. 1994 Aug;70(2):352–362. [PMC free article] [PubMed]
  • Schwartz D, Lellouch J. Explanatory and pragmatic attitudes in therapeutical trials. J Chronic Dis. 1967 Aug;20(8):637–648. [PubMed]
  • Moher D, Jadad AR, Nichol G, Penman M, Tugwell P, Walsh S. Assessing the quality of randomized controlled trials: an annotated bibliography of scales and checklists. Control Clin Trials. 1995 Feb;16(1):62–73. [PubMed]
  • Korn EL, Baumrind S. Randomised clinical trials with clinician-preferred treatment. Lancet. 1991 Jan 19;337(8734):149–152. [PubMed]
  • Zelen M. A new design for randomized clinical trials. N Engl J Med. 1979 May 31;300(22):1242–1245. [PubMed]

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