A retrospective study is performed a posteriori, using information on events that have taken place in the past. In most cases some or most of the data has already been gathered and stored in the registry. Unlike the prospective studies, a retrospective study usually does not need to follow patients into the future and often require less time to conduct than prospective studies. In a retrospective study, different patient populations can be compared for one or several outcomes.
Retrospective studies are important for several reasons:
Given the significant number of centres contributing to the EBMT registry, retrospective studies conducted with the data collected by the EBMT, can have an important impact on epidemiological surveillance, evaluation of the disease, and impact of the treatment on survival and disease progression.
In some instances, when clinical trials are not possible, it may be the case that only retrospective studies are available to compare different treatments.
Retrospective studies help define prognostic factors to be used so that the therapeutic strategy may vary depending on the predicted risks.
Those studies are extremely helpful to assess the feasibility of prospective studies and to help in their design.
Retrospective studies are relatively inexpensive and faster to conduct than others studies.
In case of a rare disease, the EBMT Registry allows patients to be pooled from many centres achieving, therefore, an evaluable study population.