What is a Retrospective Study?

Tricia Christensen
Tricia Christensen

Retrospective study can be defined in several different ways. It is often seen as a “looking backward in time,” to determine causal factors, but how study data or participants get selected can vary greatly. For instance, a chart audit could be a form of retrospective study, in which all people chosen were those that had some disease or other factor in common. Alternately, a study could look at the deaths of a number of people and try to retrospectively determine cause. In either case, this can’t be a double blind or well-selected study because the study wasn’t designed before the events occurred.

A chart retrospective study reviews medical records after the patient has been treated.
A chart retrospective study reviews medical records after the patient has been treated.

Chart audit is a good example of a retrospective study because it attempts to gather information about events that occurred and determine if a pattern of problems in medical treatment emerge. These audits don’t necessarily involve any interaction with patients, but they might or they might involve interviews with medical workers. Such studies could try to find the cause of continued infections, high incidence of disease, low patient satisfaction rate, or many other things, and they do so by analyzing what medical charts reveal and by searching for more data.

In some cases, it’s very easy for a chart audit to provide conclusive information on things. For example, if a doctor at a hospital is failing to write down medicine allergies, and there is a sudden upsurge in anaphylactic responses in patients, it can be pretty clear where the problem lies. Sometimes the matter isn’t as simple, like the sudden increase in percentage points of hospital deaths. It may not always be possible to conclude from data in the past whether these are at all related, and the answers may be more hypothesis than true conclusions due to inadequate information. Mysteries may stay mysteries because the experiment was designed after the fact.

With many other forms of the retrospective study, this is one of the downfalls. Since the event has already occurred, it has created its own group of participants in a less than scientific way. It’s impossible to rigorously apply the same study participant tests to make certain there aren’t huge variables in participants that will mar or blur any data results. This doesn’t mean the retrospective study is not worthwhile, but it may mean conclusions drawn from it are less scientific or more subject to scrutiny.

On the other hand, some studies must always be retrospective. For instance, those trying to determine the cause of heart defects would identify only those people with them and draw from that group to evaluate cause. This is also called a case-control study, and sometimes researchers would develop a second group of study participants who did not have heart defects and ask the same types of questions or perform the same tests on both groups. This would allow for comparison of the data, which if found identical, would clearly not indicate a particular causal faction.

Case-control is still a look-back or a retrospective study because participants are those with a specific outcome that has already occurred. In a way, this is actually a greater control than randomly surveying people who might have heart defects. The case-control study might show any features in common amount those with heart defects and conclusions could thus be drawn about its cause, if the right factors are evaluated or the right questions asked.

Tricia Christensen
Tricia Christensen

Tricia has a Literature degree from Sonoma State University and has been a frequent wiseGEEK contributor for many years. She is especially passionate about reading and writing, although her other interests include medicine, art, film, history, politics, ethics, and religion. Tricia lives in Northern California and is currently working on her first novel.

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