RCTs – a note on terminology

RCT is variously used to stand for one of two things:

  • Randomised Controlled Trial
  • Randomised Clinical Trial

For the most part, when I’m talking about an RCT, it’s understood as a Randomised Clinical Trial, though I use them interchangeably because I can get away with it – but not everyone can.

What is the difference? A randomised clinical trial is a randomised controlled trial conducted in a clinical setting (i.e. in hospitals and surgeries) by medical practitioners, looking at the effects of medical treatments and interventions upon patient outcomes. They are also interventionist trials – that is, the triallists intervene to specify which treatments particular patients receive. They intervene to give some patients a control treatment, and others an experimental treatment, according to the trial protocol.

These are not features necessary to RCTs. Obviously not all RCTs are conducted in clinical settings, by medical professionals or looking at the effects of medical treatments upon patient outcomes – we can, for instance, do an RCT on the effects of a fertilizer on crop

-growth, or an educational intervention on standardised test scores. But even medical RCTs don’t have to be clinical trials. We could perform RCTs which relate to medicine but which are trials on the performance of doctors or other healthcare professionals (the famous trial into the effectiveness of nurse-practitioners, or the EBM group’s trial of doctors’ knowledge of relevant literature according to age and whether they had EBM training). Other medical RCTs may be at the patho-physiological level – we can perform an RCT on whether a chemical prevents the growth of bacteria in a petry dish (and often do),

but this is not a clinical trial. Nor is it the sort of thing that EBM advocates want to put at the top of their hierarchies of evidence! So when we talk about RCTs as the gold standard of evidence in medicine, we’re talking specifically about randomised clinical trials, and excluding at least some randomised controlled trials.