https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377048/
Background
Run-in periods are occasionally used in randomized clinical trials to exclude patients after inclusion, but before randomization. In theory, run-in periods increase the probability of detecting a potential treatment effect, at the cost of possibly affecting external and internal validity. Adequate reporting of exclusions during the run-in period is a prerequisite for judging the risk of compromised validity. Our study aims were to assess the proportion of randomized clinical trials with run-in periods, to characterize such trials and the types of run-in periods and to assess their reporting.
• What is a run-in period?
 ◦ A run-in period is a time period after inclusion, but before randomization, used to exclude certain patients. Other pre-randomization periods exist, for example, extended screening periods and washout periods. These different pre-randomization periods may overlap in purpose, design and terminology
• What types of run-in periods exist and which patients are excluded?
 ◦ During the run-in period, all patients receive the same intervention, for example, active treatment, placebo treatment or no intervention. Patients are excluded due to, for example, noncompliance to treatment or data collection, non-response to treatment or response to placebo
• What are the reasons for using a run-in period?
 ◦ By excluding certain patients, for example, noncompliers or placebo responders, run-in period may increase a study’s power, that is, chance of detecting a potential treatment effect
• What other terms are used for a run-in period?
 ◦ Similar terms used are lead-in periods, single-blind placebo periods and enrichment periods
• What potential problem does run-in period cause?
 ◦ The use of a run-in period may affect external validity, by exclusion of patients from the clinical study population, as well as internal validity, by the risk of unblinding or exaggeration of the intention-to-treat effect estimate
• What is needed to assess the possible impact of a run-in period on trial results?
 ◦ We propose that the study reader would want to study the number of excluded patients, reasons for exclusion and their baseline characteristics. These aspects should, therefore, be reported in the trial publications




protocol del estudio predimed ii - Predimed-Pluswww.predimedplus.com › 2016/07
PDF https://www.predimedplus.com/wp-content/uploads/2016/07/Prot...
1. En enero de 2014, el Comité Directivo (Steering Committee), siguiendo el consejo
del DSMB (Data Safety and Monitoring Board), decidió enmendar el Protocolo y
eliminar el criterio de pérdida de peso de 1,5 kg propuesto durante el **período de
rodaje inicial (run-in)**. Dicho cambio solo afectó a los primeros 70 participantes que
fueron elegibles y aleatorizados en 2 centros de vanguardia.
7.2. El período de rodaje (run-in) o evaluación previa a la aleatorización dura 4
semanas. Comprende una visita inicial de selección, una llamada telefónica de
refuerzo a las 2 semanas y otra visita de evaluación al final.




https://www.tremedica.org/wp-content/uploads/n27_tradyterm-s...
Sin.: run-in period [primera acepción].
Notas: Usualmente es un período previo a la inclusión o enrollment de un sujeto en el ensayo clínico, incluido en el
período inicial (baseline period), en el que los candidatos reciben un tratamiento equivalente a alguno de los que se
evaluará en el ensayo (el placebo o un fármaco) para determinar su tolerancia o aceptación del tratamiento, obtener
información sobre el cumplimiento terapéutico, determinar el valor de ciertas variables, familiarizarse con las técnicas
de medición, finalizar los tratamientos precedentes, etc. Los candidatos que presenten reacciones adversas al tratamiento o que no hayan cumplido las pautas prescritas no participarán en el ensayo (Nahler, 1994; Meinert, 1996).