randomised controlled trials critical appraisal Archives

Randomised Controlled Trials are quantitative experimental studies in which individuals are allocated to receive one of multiple clinical interventions or a control at random. Interventions that individuals may be subjected to in Randomised Controlled Trials include treatment (or placebo), prevention strategies, screening programs, diagnostic tests, different settings, or educational models.

RCTs are excellent at providing answers to questions seeking the effectiveness of different interventions.

Hierarchy of evidence

Characteristics of Randomised Controlled Trials

include one (or more) treatment arm and a control arm
participants are allocated at random to one of the groups
both the participants and the researchers remain unaware of which intervention was allocated to the groups
each group is treated identically (except the intervention being investigated)
participants are analysed within their assigned group, irrespective of the allocated intervention
analysis aims to estimate the size of the difference in predefined outcomes between the groups

What Makes RCTs Superior To Other Research Methods?

In RCTs, which are experimental studies, exposure is controlled by the researcher. On the other hand, in cohort and case control studies, which are observational studies, the researcher follows the outcomes related to exposures over which they had no control.

Whilst other study designs can point out associations between an intervention and an outcome, they are not able to exclude the effect of an extraneous factor linked to both.

Randomised Controlled Trials ~ Parallel Design vs Crossover Design

There are 2 types of RCTs:

Parallel Design: in this type of RCT, each group of participants is exposed to one of the interventions only; intervention assigned to each group is determined at random
Crossover Design: in this type of RCT, each participant is subjected to all the interventions within the study in successive periods; first intervention allocated is determined at random

Blinding – Single vs Double

In the ideal RCT, both the participants and the clinicians are left unaware of which participants are receiving which intervention. This is what we refer to as blinding. Blinding reduces the risk of ascertainment bias (when some members of the target population are more likely to be included in the sample than others) and observation bias (when a researcher’s expectations, opinions, or prejudices influence what they perceive or record in a study). An RCT without any type of blinding is referred to as an open trial.

Retrieved from http://regulatoryworld.blogspot.com/2014/08/clinical-trials-at-glance-part-1_31.html on 18th February 2023

Ethical Considerations

Prior to the start of a Randomised Controlled Trial, there needs to be genuine doubt on whether one intervention is superior to another, as well as a balance between any potential risks to the participants and potential benefits to future patients.

Thus, one needs to keep in mind that it is unethical to expose participants to a presumably inferior or potentially harmful intervention. It is also unethical to deprive patients from an intervention which is presumed to be beneficial.

RCTs Limitations

recruitment difficulties
blinding difficulties
costly and time consuming
requires large sample size to detect small intervention effects
not ideal for screening or interventions with rare outcomes or outcomes emerging after long intervals
randomisation may not be possible due to patient preferences or clinicians’ decisions

Critically Appraising Randomised Controlled Trials

critical appraisal of randomised controlled trials depend on reporting accuracy
results tend to emphasise statistical significance instead of clinical importance
small sample size leads to insufficient ability in detecting significant differences
poor randomisation reporting
poor blinding
no follow up

CASP TOOL for RCT

CASP Tool for critically appraising Randomised Controlled Trials can be found here.

To view blogpost featuring Cochrane videos on all types of studies please click here.

Did you find the above nursing information useful? Follow us on Facebook and fill in your email address below to receive new blogposts in your inbox as soon as they’re published 🙂

What are the key concepts of critical appraisal? This blogpost features a very good series of critical appraisal training videos published by Cochrane Mental Health on Youtube (full credits can be found at the bottom of this blogpost).

Hierarchy of Evidence

Critical Appraisal Introduction

In this first video, the key concepts of critical appraisal are introduced, and the learning objectives for the series are clearly defined.

Systematic Reviews and Meta Analysis

In this second video, we are introduced to the fundamentals of systematic reviews and the ways in which we can apply the critical appraisal concepts of validity, trustworthiness of results, and value and relevance using the CASP checklist. The full text version of the study by Hay et al (2019) mentioned in this video can be found here.

Randomised Controlled Trials

In this third video, we are introduced to the fundamentals of randomised controlled trials and the ways in which we can apply the critical appraisal concepts of validity, trustworthiness of results, and value and relevance using the CASP checklist. The full text version of the study by Sugg et al (2018) mentioned in this video can be found here.

Cohort Studies Critical Appraisal

In this fourth video, we are introduced to the fundamentals of cohort studies and the ways in which we can apply the critical appraisal concepts of validity, trustworthiness of results, and value and relevance using the CASP checklist. The full text version of the study by Gerhard et al (2015) can be found here.

Case Control Studies

In this fifth video, we are introduced to the fundamentals of case control studies and the ways in which we can apply the critical appraisal concepts of validity, trustworthiness of results, and value and relevance using the CASP checklist. The full text version of the study by Drucker et al (2018) can be found here.

Cross Sectional Studies

In this sixth video, we are introduced to the fundamentals of cross-sectional control studies and the ways in which we can apply the critical appraisal concepts of validity, trustworthiness of results, and value and relevance. The full text version of the study by Boden et al (2010) can be found here.

Diagnostic Studies Critical Appraisal

In this seventh and last video, we are introduced to the fundamentals of diagnostic studies and the ways in which we can apply the critical appraisal concepts of validity, trustworthiness of results, and value and relevance using the CASP checklist. The full text version of the study by Hollis et al (2018) can be found here.

Reference

The above embedded videos are part of a project which was developed to enhance research use and development across two NHS Trusts.

The project founding partners were:

Cochrane Common Mental Disorders
Northumberland, Tyne and Wear NHS Foundation Trust (NTW), UK
Tees, Esk and Wear Valleys NHS Foundation Trust (TEWV), UK

Delivery of the project was supported by the Centre for Reviews and Dissemination at the University of York.

Funding Acknowledgement: The production of the critical appraisal modules was jointly funded by:

Economic and Social Research Council (ESRC), UK – as part of the University of York ESRC Impact Acceleration Account (ES/M500574/1)
Northumberland, Tyne and Wear NHS Foundation Trust (NTW), UK
Tees, Esk and Wear Valleys NHS Foundation Trust (TEWV), UK
University of York, UK

Cochrane Review Group Funding Acknowledgement: The National Institute for Health Research (NIHR) is the largest single funder of the Cochrane Common Mental Disorders Group.

Disclaimer: the views and opinions expressed herein are those of the module authors and do not necessarily reflect those of the ESRC, NIHR, the National Health Service (NHS), the Department of Health and Social Care or the University of York.