title: [Clinical relevance of retrospective observations].
abstract: Many retrospective observational studies have been published in the recent literature. In the current issue of this journal two papers deal with retrospective analysis of observations after different surgical interventions: one concerns surgery for hilar cholangiocarcinoma, the other surgery for oesophageal carcinoma. Studies of this design are hard to interpret due to a number of methodological issues: (a) cohort effects: both the patient population and diagnostic procedures may have changed over time; (b) the learning curve of the healthcare provider, in this case the surgeon; and (c) confounding by indication: the data studied is biased by medical decision-making. However, the results of these studies inform healthcare providers and patients about survival and complication rates, among other things. Although they are not properly designed according to basic evidence-based medicine guidelines, these studies still provide us with clinically relevant information about current experience of medical interventions.
authors.affiliation: UMC St Radboud, Nijmegen, Afd. Maag-, Darm- en Leverziekten, the Netherlands. m.g.h.vanoijen-3@umcutrecht.nl
authors.forename: Martijn G H
authors.initials: MG
authors.lastname: van Oijen
mesh_terms: D015982:Bias; D003627:Data Interpretation, Statistical; D019317:Evidence-Based Medicine; D006801:Humans; D015588:Observer Variation; D012189:Retrospective Studies