Define retrospective clinical trial

The existence of this publicly-available record is vital to address the well-documented problems of publication bias and reporting bias.

Distortion of the medical literature in this way is a very real problem for everyone. It affects the evidence base on which doctors make clinical decisions when they see their patients. In an ideal world, all clinical trials that are carried out would be registered before the first patient is enrolled. Unfortunately, we do not live in an ideal world and, for many reasons, not all researchers publish their findings or register their studies before they start.

This is a problem because people who give up their time to take part in research expose themselves to the inherent risks of clinical research. They do this in the belief that the findings will be published and will benefit others. Receiving a manuscript reporting a trial that was not registered before the study started presents a difficult dilemma for the editor.

What should they do? Reject the manuscript? Consider it for publication? There are ethical arguments both ways. It may also remove the incentive for researchers to register prospectively through the knowledge that they will still be able to publish their results. On the other hand, there is an ethical responsibly to publish research that human participants have taken part in.

Even if it was clear who was exposed to tire manufacturing chemicals based on employee records, it would also be important to take into account or adjust for other differences that could have influenced mortality, i. If smokers were older than non-smokers, then the unequal age distribution would exaggerate the strength of association between smoking and lung cancer. For example, it might be important to know whether the subjects smoked, or drank, or what kind of diet they ate.

However, it is unlikely that a retrospective cohort study would have accurate information on these many other risk factors. The video below provides a brief explanation of the distinction between retrospective and prospective cohort studies. Intervention studies clinical trials are experimental research studies that compare the effectiveness of medical treatments, management strategies, prevention strategies, and other medical or public health interventions.

Their design is very similar to that of a prospective cohort study. However, in cohort studies exposure status is determined by genetics, self-selection, or life circumstances, and the investigators just observe differences in outcome between those who have a given exposure and those who do not.

In clinical trials exposure status the treatment type is assigned by the investigators. Ideally, assignment of subjects to one of the comparison groups should be done randomly in order to produce equal distributions of potentially confounding factors. Sometimes a group receiving a new treatment is compared to an untreated group, or a group receiving a placebo or a sham treatment. Sometimes, a new treatment is compared to an untreated group or to a group receiving an established treatment. For more on this topic see the module on Intervention Studies.

In summary, the characteristic that distinguishes a clinical trial from a cohort study is that the investigator assigns the exposure status in a clinical trial, while subjects' genetics, behaviors, and life circumstances determine their exposures in a cohort study. Key Concept: Common features of both prospective and retrospective cohort studies. All Rights Reserved.

Date last modified: July 19, See the full definition for retrospective in the English Language Learners Dictionary. Thesaurus: All synonyms and antonyms for retrospective. Nglish: Translation of retrospective for Spanish Speakers.

Britannica English: Translation of retrospective for Arabic Speakers. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free! Log in Sign Up. Save Word. Definition of retrospective Entry 1 of 2.

Definition of retrospective Entry 2 of 2. Other Words from retrospective Did you know? Other Words from retrospective Adjective retrospectively adverb. Did you know? Examples of retrospective in a Sentence Adjective They issued a retrospective report. Noun The museum is featuring a retrospective of Picasso's early works. First Known Use of retrospective Adjective , in the meaning defined at sense 1a 1 Noun , in the meaning defined above.

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