Levels of Evidence Dr Chetan Khatri Steering Committee, STARSurg

Evidence Based Medicine An approach to medical practice intended to optimize decision-making by emphasizing the use of evidence from well designed and conducted research Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Evidence Based Medicine Patient Values & Expectations Best External Evidence Individual clinical expertise EBM Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Levels of Evidence Easy but least likely Difficult but most likely Tricky one Trickiest! Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Personal Communications Letters and personal viewpoints Usually by experts in their field Can include consensus statements by a group of experts Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Observational Studies Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Case Series / Case Reports Detailed report of the presentation, signs and symptoms and subsequent management of a patient Now only done for rare conditions / unusual presentations Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Case Control Typically retrospective Study of exposure in a case group with a disease and a control group without the disease Proportion of exposed in each group = odds ratio Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Case Control AdvantagesDisadvantages Quick and cheapInefficient for examining rare exposures Good for diseases with long latent periods Cannot calculate incidence Good for rare diseases Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Cohort Study Prospective study Compares development of disease in exposed and non-exposed groups Incidence of disease in each group = relative risk Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Cohort Study AdvantagesDisadvantages Good for evaluation of rare exposures Inefficient for evaluation of rare diseases Can examine multiple effects of single exposure Expensive and time consuming Loss to follow up affects results Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Cohort Study Exposure to factor Smokers Exposure to factor Smokers No exposure to factor Non-smokers No exposure to factor Non-smokers Disease Lung cancer Disease Lung cancer No disease Disease Lung cancer Disease Lung cancer No disease Population cohort Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Interventional studies Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Eligibility assessment Excluded Randomisation Intervention X Intervention Y Analysis Lost to follow up / discontinuted Randomised Controlled Trials

RCT – How to randomise? Often done by a computer Ensures groups are similar, and avoids allocation bias and confounding When? Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

RCT – Blinding Non-blind Single-blind Double-blind Triple-bind Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Adaptive Trials Trials whereby patient responses to exposures are evaluated throughout the study, and the trial is modified accordingly – Modifications may include: dose, eligibility criteria, sample size, or treatment setting Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

A priori Process of defining study methods before a study is conducted Usually designed according to a PICOS model, with defined statistical tests and outcomes to be described In multicentre studies, it reduced performance between collaborators. Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Systematic Reviews and Meta- Analysis Review – A simple review of key papers and viewpoint Systematic review – uses a defined search strategy and assesses study qaulity Meta-analysis – Combine data from primary studies and analyse Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England

Questions? Protocol Launch Meeting and Research Skills Course September 16 th 2015, RCS England