Intended for healthcare professionals


Evidence based purchasing: understanding results of clinical trials and systematic reviews

BMJ 1995; 311 doi: (Published 21 October 1995) Cite this as: BMJ 1995;311:1056
  1. T Fahey, senior registrar in public health medicinea,
  2. S Griffiths, director of public health medicine,a,
  3. T J Peters, senior lecturer in medical statisticsb
  1. aDepartment of Public Health Medicine and Health Policy, Oxfordshire Health, Oxford OX3 9DZ
  2. bDepartment of Social Medicine, University of Bristol, Bristol BS8 2PR
  1. Correspondence to: Dr T Fahey, Department of Social Medicine, University of Bristol, Bristol BS8 2PR.
  • Accepted 25 July 1995


Objective: To assess whether the way in which the results of a randomised controlled trial and a systematic review are presented influences health policy decisions.

Design: A postal questionnaire to all members of a health authority within one regional health authority.

Setting: Anglia and Oxford regional health authorities.

Subjects: 182 executive and non-executive members of 13 health authorities, family health services authorities, or health commissions.

Main outcome measures: The average score from all health authority members in terms of their willingness to fund a mammography programme or cardiac rehabilitation programme according to four different ways of presenting the same results of research evidence—namely, as a relative risk reduction, absolute risk reduction, proportion of event free patients, or as the number of patients needed to be treated to prevent an adverse event.

Results: The willingness to fund either programme was significantly influenced by the way in which data were presented. Results of both programmes when expressed as relative risk reductions produced significantly higher scores when compared with other methods (P<0.05). The difference was more extreme for mammography, for which the outcome condition is rarer.

Conclusions: The method of reporting trial results has a considerable influence on the health policy decisions made by health authority members.


  • Source of funding None.

  • Conflict of interest None.

  • Accepted 25 July 1995
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