Medical Research Terminology – What the Heck is an RCT, a Meta-analysis, a Systematic Review?
I have been reading an alarming book by Ben Goldacre, a British physician and journalist who writes a sometimes column for The Guardian called Bad Science, and has a website and a book with the same name. He also has two Ted Talk videos that provide a lot of information very fast, unlike his books.
Goldacre’s latest book is called Bad Pharma, about the deliberately biased and manipulated research on new drugs, misleading physicians and patients about the safety and usefulness of these products. The main strategies for doing this are exaggerating the positive results of studies and making sure that negative studies (those that don’t show a benefit to the product) never see the light of publication. Pharmaceutical companies have a clear motive for tweaking research results to favor their applications to regulatory agencies and to get their products to your local pharmacy and prescribed by your care provider. That motive is billions of dollars (or pounds, or euros) that are raked in on an annual basis for all the drugs that are sold. Some of these are lifesaving, and some may kill people. Dr. Goldacre’s new book runs to over 400 not-so-easy-to-read pages, but the slog is worth it if you want to understand how pharmaceutical research works. If you don’t care to read the book, you should at least understand some of the basic terminology that is used in these studies – you are reading brief summaries in the daily newspaper and in online publications – and remember that these sources spin the stories to appeal to the most readers. (Stories that report that a new drug doesn’t work as well as the established ones aren’t going to make the headlines, unless that drug is killing people.) If you don’t understand the lingo, you can’t possibly make a decision about whether the study is a real contribution to your understanding of the topic you are interested in or is just rubbish. Below are a few of the common terms that you should know to help you evaluate what you read. For terms not listed, you can always find a definition (or several – you might want to compare websites to see which has the clearest and best) by using a search engine. If you are really interested in learning this stuff, go to the Cochrane Collaboration Open Learning Material for Reviewers. If you just want a more complete list of definitions, go to the Cochrane Collaboration Glossary. However, a basic primer will get you started. Entries are alphabetical and sources are cited.
Adverse effects: In medicine, an undesired harmful effect resulting from a medication or other intervention such as surgery (Wikipedia)
Clinical trials: prospective biomedical or behavioral research studies on human subjects that are designed to answer specific questions about biomedical or behavioral interventions (novel vaccines, drugs, treatments, devices or new ways of using known interventions), generating safety and efficacy data (Wikipedia).
Control group: a group of subjects closely resembling the treatment group in many demographic variables but not receiving the active medication or factor under study and thereby serving as a comparison group when treatment results are evaluated (Dictionary.com).
Intervention: The process of intervening on people, groups, entities or objects in an experimental study. In controlled trials, the word is sometimes used to describe the regimens in all comparison groups, including placebo and no-treatment arms (Glossary, The Cochrane Collaboration)
Meta-analysis: the use of statistical methods to combine results of individual studies. This allows (the researcher) to make the best use of all the information we have gathered in our systematic review by increasing the power of the analysis. Meta-analysis is a two stage-process involving (a) computing summary statistics for each trial, (b) averaging the summary statistics (Cochrane Library).
Observational study: A study in which the investigators do not seek to intervene, and simply observe the course of events (Glossary, The Cochrane Collaboration).
Outcome: A component of a participant’s clinical and functional status after an intervention has been applied, that is used to assess the effectiveness of an intervention (Glossary, The Cochrane Collaboration).
Participant: An individual who is studied in a trial, often but not necessarily a patient (Glossary, The Cochrane Collaboration).
Placebo: a substance having no pharmacological effect but administered as a control in testing experimentally or clinically the efficacy of a biologically active preparation (Dictionary.com).
Prospective study: In evaluations of the effects of healthcare interventions, a study in which people are identified according to current risk status or exposure, and followed forwards through time to observe outcome. Randomised controlled trials are always prospective studies (Glossary, The Cochrane Collaboration).
Randomized controlled trial (RCT): Randomised controlled trials are the most rigorous way of determining whether a cause-effect relation exists between treatment and outcome and for assessing the cost effectiveness of a treatment. They have several important features:
Random allocation to intervention groups
Patients and trialists (researchers) should remain unaware of which treatment was given until the study is completed-although such double blind studies are not always feasible or appropriate
All intervention groups are treated identically except for the experimental treatment
Patients are normally analysed within the group to which they were allocated, irrespective of whether they experienced the intended intervention (intention to treat analysis)
The analysis is focused on estimating the size of the difference in predefined outcomes between intervention groups (British Medical Journal, BMJ 1998;316:201)
Retrospective study: A study in which the outcomes have occurred to the participants before the study commenced. Case-control studies are usually retrospective, cohort studies sometimes are, randomised controlled trials never are (Glossary, The Cochrane Collaboration).
Systematic review: A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making (The Cochrane Library).