Another new series of blogs here in the ADC website, from Ian Sinha of the Respiratory Unit, Alder Hey Children’s Hospital, Liverpool, UK, takes a look at explaining the deeper depths of critical appraisal of randomised controlled trials from the perspective of the Cochrane collaboration’s approach to this issue.
Clinical trials – reading between the lines
Just because a research study is called a “double-blind randomized controlled trial” (RCT), this may not be an accurate description. Even if it is a double-blind RCT, this does not mean it is scientifically robust.
The validity of an RCT is impaired by bias, which is defined in The Cochrane Handbook for Systematic Reviews of Interventions (the instruction manual for conducting Cochrane reviews – available at http://handbook.cochrane.org ) as “ a systematic error, or deviation from the truth, in results or inferences”. I take this to mean, in essence, an aspect of design, conduct, or reporting of an RCT that gives one treatment arm an unfair advantage over another.
Much work has been conducted to identify aspects of RCTs which can lead to bias. These aspects (domains) are described in detail in the Cochrane Handbook, which recommends that for each one, a trial is judged, as high-risk, low-risk, or unclear-risk of bias. In this series of blogs, I aim to discuss the fundamentals of these domains, and highlight some ‘short-cuts’ that busy clinicians can use when appraising reports of RCTs.
– Ian Sinha