Clinical Study Types - for Librarians

PubMed: Randomized Controlled Trial [Publication Type]
A work that reports on a clinical trial that involves at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table.  Year introduced: 2008(1991)

Example in an elementary school classroom:  If we wanted to assess if sugar makes kids have extra energey, we could split the class in two, and gave each child a candy bar.  Half of the kids would get a candy bar that had a lot of sugar, and half would get a candy bar with sugar substitute.  The bars would be identical.  What makes this a randomized trial is that we wouldn't be the ones making the decision about who gets which bar.  In order to ensure an even distribution between boys/ girls, etc  we would use some process that randomizes the distribution. 

To help ensure a fair evaluation, it would be good if the kids didn't know which type of candy they got, AND the people administering the trial  also didn't know who got which type of candy bar.  That process is called blinding (or masking).  Whoever gave out the candy bars would know who got which, but the kids wouldn't, and the people running the trial wouldn't.  Ideally, even once the data is collected (on how much energy each kid has) and analyzed, the analysts wouldn't know the distribution either.  This makes sure that the data is clear of any pre-conceived notions, and lets the intervention results speak for themselves.

This is where you can find RCTs in the MeSH tree:

PubMed splits RCTs into two areas:  As Topic and Publication Type.  Which to use?  If you're doing a systematic review, use [publication type]. 

Basically, "Publication Type"  means it's an article about the results of a trial.  "As Topic" means it's about the general topic of trials: maybe how to recruit patients, or how to conduct a specific aspect of a trial.

Examples of articles that were tagged with each MeSH term:

• Publication Type: (these are probably the types of articles you want)
  • Randomized Trial of Three Anticonvulsant Medications for Status Epilepticus.
  • Randomized controlled trial of the immediate and long-term effect of massage on adult postburn scar
• As Topic: (you probably don't want these articles returned in your search results)
  • Strategies to improve recruitment to randomised trials.
  • Randomized, Controlled Trials in Health Insurance Systems.

There are a large number of hedges, or pre-built search filters, designed to help researchers locate clinical trials in the literature.  See the tab to the left for a listing of these.