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Endgames Statistical Question

Open label crossover trials

BMJ 2013; 346 doi: (Published 28 June 2013) Cite this as: BMJ 2013;346:f4186
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}

Researchers compared transdermal fentanyl with sustained release oral morphine in the treatment of chronic non-cancer pain. A randomised, open label, crossover trial design was used. Transdermal fentanyl was administered using patches. Participants were 256 patients (aged 26­82 years) with chronic non­cancer pain who had been previously treated with opioids. The treatment period for both transdermal fentanyl and oral morphine lasted four weeks.1

The outcome measures included patients’ preference for treatment (transdermal fentanyl or sustained release oral morphine), pain control, quality of life, and safety assessments. The researchers reported that transdermal fentanyl was preferred to sustained release oral morphine by patients with chronic non­cancer pain previously treated with opioids. The main reason for preference was superior pain relief, which was achieved with less constipation and an enhanced quality of life.

Which of the following statements, if any, are true?

  • a) The crossover trial is referred to as a “within subject” study design

  • b) Confounding was minimised in the comparison of treatments

  • c) It was essential that …

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