9. How to Critically Appraise a Randomized Controlled Trial

  1. Hywel C. Williams DSc, FRCP2,
  2. Michael Bigby MD3,
  3. Andrew Herxheimer MB, FRCP4,
  4. Luigi Naldi MD5,
  5. Berthold Rzany MD, ScM6,
  6. Robert P. Dellavalle MD, PhD, MSPH7,
  7. Yuping Ran8 and
  8. Masutaka Furue9
  1. Hywel C. Williams

Published Online: 6 JUN 2014

DOI: 10.1002/9781118357606.ch9

Evidence-Based Dermatology, 3

Evidence-Based Dermatology, 3

How to Cite

Williams, H. C. (2014) How to Critically Appraise a Randomized Controlled Trial, in Evidence-Based Dermatology, 3 (eds H. C. Williams, M. Bigby, A. Herxheimer, L. Naldi, B. Rzany, R. P. Dellavalle, Y. Ran and M. Furue), John Wiley & Sons, Ltd, Oxford, UK. doi: 10.1002/9781118357606.ch9

Editor Information

  1. 2

    Centre of Evidence Based Dermatology, University of Nottingham, Nottingham, UK

  2. 3

    Department of Dermatology, Harvard Medical School, and Beth Israel Deaconess Medical Center, Boston, MA, USA

  3. 4

    UK Cochrane Centre, Oxford, UK

  4. 5

    Centro Studi Gruppo Italiano Studi Epidemiologici in Dermatologia, Department of Dermatology, Ospedali Riuniti, Bergamo, Italy

  5. 6

    RZANY & HUND, Privatpraxis für Dermatologie und Ästhetische Medizin, Berlin, Germany

  6. 7

    Department of Dermatology, University of Colorado Denver, Aurora, USA

  7. 8

    Department of Dermatovenereology, West China Hospital, Sichuan University, Chengdu, P. R. China

  8. 9

    Department of Dermatology, Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka, Japan

Author Information

  1. Centre of Evidence-Based Dermatology, University of Nottingham, Nottingham, UK

Publication History

  1. Published Online: 6 JUN 2014
  2. Published Print: 1 AUG 2014

ISBN Information

Print ISBN: 9781118357675

Online ISBN: 9781118357606



  • blinding;
  • dermatology;
  • intention-to-treat (ITT) analysis;
  • randomized controlled trial (RCT)


This chapter provides guidance on the evaluation of randomized controlled trial (RCT) of complex interventions. Trials are often divided into those that are explanatory and measure efficacy or pragmatic and measure effectiveness, whereas in reality they lie on a pragmatic– explanatory continuum. Four main factors are associated with altering the estimation of the risk estimate, usually by inflating the claimed benefit. These are discussed in the chapter. The chapter assess the four components of randomization generation/concealment, blinding, accounting for all those randomized with an intention-to-treat (ITT) analysis, and comparing a trial protocol with what was eventually published in order to assess selective reporting outcome bias, other topic-specific items may need to be assessed in order to make sense of the value of a particular RCT. It provides a clear description of how the disease was defined. Misinterpreting trials with negative results is a common error in dermatology clinical trials.