How to analyse a clinical trial

Reviewed and revised 26 August 2015


  • clinicians must be able to critically appraise clinical trials to determine their internal validity
  • trials should adhere to the CONSORT statement (CONsolidated Standards of Reporting Trials)
  • appraisal involves sequential pertinent information assessment



  • should include blinding, randomisation and primary end point analysed


  • clear, transparent with accurate record of conduct and findings.
  • objective
  • trial design
  • methods: participants, interventions, primary endpoints, randomization, blinding
  • results: number randomized in each group, number analysed, result for each group and precision, adverse events or side effects.
  • conclusion: general interpretation
  • registration
  • funding


  • scientific background and rationale for study
  • discuss any current data and reason for equipoise
  • present specific objectives or hypotheses


  • describe trial design: parallel, multi-arm parallel, crossover, cluster
  • type of randomisation
  • allocation ratio
  • eligibility criteria with reasons
  • setting and location where data collected
  • intervention with sufficient detail to allow replication (how and when administered)
  • outcomes: primary and secondary (how and when assessed)
  • changes to trial outcomes after commencement with reasons
  • sample size calculation
  • interim analyses and stopping triggers
  • randomization: technique, type, allocation concealment mechanism, implemenation
  • blinding
  • similarity of intervention
  • statistical methods for outcome assessment
  • additional analyses (sub-group and adjusted analyses)

Flow diagram and reasons (CONSORT diagram)

  • assessed for eligibility
  • underwent randomization
  • losses and exclusion
  • assessed for primary outcome


  • recruitment and follow up
  • reasons for stopping trial early
  • base line data
  • numbers analysed
  • outcomes: primary and secondary with confidence intervals
  • absolute and relative effect sizes
  • pre-specified and subgroup analyses
  • harms in each group
  • intention to treat


  • limitations
  • bias
  • imprecision
  • generalisability (external validity)
  • interpretation of results
  • balance of benefits and harms
  • consideration and comparison of other relevant evidence

Other information

  • registration number
  • name of trial registry
  • full trial protocol
  • funding and other support

References and Links


Journal articles

  • Ospina-Tascón GA, Büchele GL, Vincent JL. Multicenter, randomized, controlled trials evaluating mortality in intensive care: doomed to fail? Crit Care Med. 2008 Apr;36(4):1311-22. PMID: 18379260.

FOAM and web resources

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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