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Indirect comparison meta-analysis of aspirin therapy after coronary surgery

BMJ 2003; 327 doi: (Published 04 December 2003) Cite this as: BMJ 2003;327:1309
  1. Eric Lim, specialist registrar in cardiothoracic surgery (eric.lim2{at},
  2. Ziad Ali, senior house officer in cardiothoracic surgery1,
  3. Ayyaz Ali, clinical fellow in cardiothoracic surgery1,
  4. Tom Routledge, specialist registrar in cardiothoracic surgery1,
  5. Lyn Edmonds, clinical library manager2,
  6. Douglas G Altman, professor of statistics in medicine3,
  7. Stephen Large, consultant cardiothoracic surgeon1
  1. 1Department of Cardiothoracic Surgery, Papworth Hospital, Cambridge CB3 8RE
  2. 2Clinical Library Service, Papworth Hospital
  3. 3Cancer Research UK/NHS Centre for Statistics in Medicine, Institute for Health Services, Oxford OX3 7LF
  1. Correspondence to: E Lim, Department of Cardiothoracic Surgery, Royal Brompton Hospital, London SW3 6NP
  • Accepted 30 September 2003


Objectives To evaluate the efficacy of low and medium dose aspirin therapy after coronary surgery by using an indirect comparison meta-analysis.

Data sources Systematic literature search of Medline, Embase, Cochrane controlled trials register, and trial register sites on the internet.

Study selection Outcome was evaluated by angiography and reported as graft occlusion and rate of events in patients. Trials that did not include aspirin as the sole therapy or did not have a placebo control arm were excluded. Articles were assessed for eligibility and quality and grouped according to dosage. The estimated difference in effect of low and medium dose aspirin on graft occlusion was obtained by combining the estimated log relative risks of low dose with placebo and medium dose with placebo.

Results For graft occlusion, the medium dose trials yielded a relative risk reduction of 45% compared with 26% for the low dose trials. The greater effect in the medium dose trials is summarised by a relative risk ratio of 0.74 (95% confidence interval 0.52 to 1.06; P = 0.10) for graft occlusion and 0.81 (0.57 to 1.16; P = 0.25) for events in patients.

Conclusions Medium dose aspirin may more successfully reduce graft occlusion than low dose regimens within the first year after coronary surgery.


  • Contributors EL had the original idea for the study, designed the study, abstracted data, drafted the manuscript, and is guarantor. ZA and AA carried out the data abstraction, designed the study, and assisted in drafting the manuscript. TR carried out data abstraction and assisted in drafting the manuscript. LE performed the literature search and assisted in drafting the manuscript. DGA performed the statistical analysis, designed the study, and drafted the manuscript. SL assisted in drafting the manuscript

  • Funding None

  • Competing interests None declared

  • Ethical approval Not required.

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