Sample size calculation for recurrent events data in one‐arm studies

In some exceptional circumstances, as in very rare diseases, nonrandomized one‐arm trials are the sole source of evidence to demonstrate efficacy and safety of a new treatment. The design of such studies needs a sound methodological approach in order to provide reliable information, and the determination of the appropriate sample size still represents a critical step of this planning process. As, to our knowledge, no method exists for sample size calculation in one‐arm trials with a recurrent event endpoint, we propose here a closed sample size formula. It is derived assuming a mixed Poisson process, and it is based on the asymptotic distribution of the one‐sample robust nonparametric test recently developed for the analysis of recurrent events data. The validity of this formula in managing a situation with heterogeneity of event rates, both in time and between patients, and time‐varying treatment effect was demonstrated with exhaustive simulation studies. Moreover, although the method requires the specification of a process for events generation, it seems to be robust under erroneous definition of this process, provided that the number of events at the end of the study is similar to the one assumed in the planning phase. The motivating clinical context is represented by a nonrandomized one‐arm study on gene therapy in a very rare immunodeficiency in children (ADA‐SCID), where a major endpoint is the recurrence of severe infections. Copyright © 2012 John Wiley & Sons, Ltd.     

Parental Competence in Italy: A Comparison Between Italian and Immigrant Parents

The migration experience could influence parental competence perception in immigrant parents. Within this framework the current work focuses on immigrant parenthood and whether a family’s migratory path could lead parents to feel less competent in their parental roles. The aim of the present study is to analyze perceptions of parental competence and family routines among immigrant and Italian parents during the middle childhood stages. The results showed that immigrant parents perceive themselves as more competent than Italians. Immigrants also attribute more importance to the dimension of relational and regulatory routines in daily family life than do Italian parents. Professionals can use these findings to better understand how best to enhance practices and strategies appropriate to the complexity of these intercultural contexts.     

Improving the causal treatment effect estimation with propensity scores by the bootstrap

AStA Advances in Statistical Analysis - When observational studies are used to establish the causal effects of treatments, the estimated effect is affected by treatment selection bias. The inverse...