Intended for healthcare professionals

Education And Debate

How to read a paper: Papers that report drug trials

BMJ 1997; 315 doi: (Published 23 August 1997) Cite this as: BMJ 1997;315:480
  1. Trisha Greenhalgh, senior lecturer (
  1. a Unit for Evidence-Based Practice and Policy, Department of Primary Care and Population Sciences, University College London Medical School/Royal Free Hospital School of Medicine, Whittington Hospital, London N19 5NF

    “Evidence” and marketing

    If you prescribe drugs, the pharmaceutical industry is interested in you and is investing a staggering sum of money trying to influence you. The most effective way of changing the prescribing habits of a clinician is through personal representatives (known in Britain as “drug reps” and in North America as “detailers”), who travel round with a briefcase full of “evidence” in support of their wares.1

    Pharmaceutical “reps” do not tell nearly as many lies as they used to (drug marketing has become an altogether more sophisticated science), but they have been known to cultivate a shocking ignorance of basic epidemiology and clinical trial design when it suits them.2 It often helps their case, for example, to present the results of uncontrolled trials and express them in terms of before and after differences in a particular outcome measure.3 The recent correspondence in the Lancet and BMJ on placebo effects should remind you why uncontrolled before and after studies are the stuff of teenage magazines, not hard science.4 5 6 7 8 9 10 11 12

    Making decisions about treatment

    Sackett and colleagues have argued that before giving a drug to a patient the doctor should:

    Summary points

    Pharmaceutical “reps” are now much more informative than they used to be, but they may show ignorance of basic epidemiology and clinical trial design

    The value of a drug should be expressed in terms of safety, tolerability, efficacy, and price

    The efficacy of a drug should ideally be measured in terms of clinical end points that are relevant to patients; if surrogate end points are used they should be valid

    Promotional literature of low scientific validity (such as uncontrolled before and after trials) should not be allowed to influence practice

    • identify, for this patient, the ultimate objective of treatment (cure, prevention of recurrence, limitation of functional …

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