Education And Debate

Systematic reviews and lifelong diseases

BMJ 2002; 325 doi: (Published 17 August 2002) Cite this as: BMJ 2002;325:381
  1. Heather E Elphick, lecturera,
  2. Anton Tan, specialist registrar in paediatricsb,
  3. Deborah Ashby, professor of medical statisticsc,
  4. Rosalind L Smyth, Brough professor of paediatric medicine (
  1. aUniversity of Liverpool Institute of Child Health, Alder Hey Children's Hospital, Liverpool L12 2AP
  2. bRespiratory Unit, Alder Hey Children's Hospital
  3. cWolfson Institute of Preventive Medicine, Barts and The London, Queen Mary's School of Medicine and Dentistry, University of London EC1M 6B9
  1. Correspondence to: R L Smyth
  • Accepted 20 February 2002

Systematic reviews of randomised controlled trials provide an evidence base for treatment but too often fail to give adequate information on long term outcomes. Elphick and colleagues discuss the limitations of the systematic review of randomised controlled trials for patients with chronic or lifelong diseases and suggest that long term observational studies have a place in the evaluation of the benefits and risks of treatment

Synthesis of evidence from systematic reviews of randomised controlled trials is considered thegold standard when evaluating the effectiveness of treatments, yet systematic reviews do not always place as much emphasis on information about adverse effects or safety issues. 1 2 In people with chronic, or lifelong,diseases long term outcomes are particularly important but are much less likely to be evaluated inrandomised controlled trials. We discuss the results of a recent systematic review of randomised controlled trials of antibiotic therapy in cystic fibrosis, which provided preliminary information about antibiotic resistance but not about other adverse effects. Although the review suggested that this finding should be investigated by a further clinical trial, we discuss why this may be neither the most feasible nor the most efficient study design with which to evaluate long term outcomes in lifelong diseases.

Summary points

A systematic review suggested that there was an increase in antibiotic resistance in patients treated with one compared with two antibiotics

Systematic reviews of randomised controlled trials are often unable to provide adequate information about long term outcomes, which are important for people with chronic diseases

A tension exists in randomised controlled trials between evaluating short term outcomes, which may indicate a need to change practice, and continuing the trial for sufficient time to evaluate long term outcomes

Databases specialising in a particular disease can play a part in capturing information on patients prospectively, provided the clinical questions are …

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