Page 196 - Prevention and Treatment of Incisional Hernia- New Techniques and Materials

Chapter 9
centre of the primary investigator. On the other hand including patients from several centres will create a larger group of eligible patients and thus a higher likelihood of achieving the sample size in a shorter time period. For some less common conditions, a multi-centre approach is prerequisite to enrol a large enough cohort of patients. It is essential that the authors report variations in expertise related to the surgical technique under investigation.
Inclusion criteria, exclusion criteria and eligibility
To minimize selection bias all consecutive eligible patients during the study period should be considered for inclusion. The reasons for non-inclusion in the trial and the number of these should be monitored and reported. To know which patients are eligible a clear and detailed description of inclusion and exclusion criteria should be given. If reporting a subset of hernia patients, for example only those undergoing laparoscopic surgery, then clear reasons for why the subgroup were selected for that particular intervention, and how many patients over the same study period had an alternative intervention.
Dropouts and lost to follow-up
Inevitably subjects will become lost to follow-up and will not be available for measurement of the primary endpoint. Some patients will not receive the allocated treatment according to the randomization because of errors, a preoperative surgical decision, an intraoperative change in therapy or because the patient withdraws consent to participate. Nevertheless a description of the entire Intention To Treat (ITT) population has to be provided and every patient accounted for, preferably in a ow diagram. This will make it clear to the reader which patients are included in the study analysis. The baseline data of the study population with the distribution of the predictor variables and possible confounding variables should be provided for the ITT population in the rst table of the manuscript. This table will allow evaluation of the concordance between di erent groups in comparative studies. The variables should be listed with their frequency or mean value, their range and their standard deviation. For analysis of the primary and secondary endpoints of the study the decision about the use of the ITT or PP population, is based on the type of statistical hypothesis (superiority versus equivalence).
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