Browsing by Author "Zehnder, C."

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    Late Acute Humoral Rejection in Low-Risk Renal Transplant Recipients Induced With an Interleukin-2 Receptor Antagonist and Maintained With Standard Therapy: Preliminary Communication
    (ELSEVIER SCIENCE INC, 2011) Morales, J.; Contreras, L.; Zehnder, C.; Pinto, V.; Elberg, M.; Araneda, S.; Herzog, C.; Calabran, L.; Aguilo, J.; Ferrario, M.; Buckel, E.; Fierro, J. A.
    Low-risk renal transplant recipients treated with standard immunosuppressive therapy including interleukin-2 receptor (IL-2R) antagonist show a low incidence of early rejection episodes but few reports have examined the incidence and severity of late rejection processes. This study evaluated retrospectively cellular and antibody-mediated rejection (AMR) among 42 recipients selected because they showed low panel-reactive-antibodies, short cold ischemia time, no delayed graft function, and therapy including basiliximab (Simulect) induction. The mean observation time was 6.6 years. Sixty-seven percent of donors were deceased. Ten-year patient and death-censored graft survivals were 81% and 78%, respectively. Seven patients lost their kidneys due to nonimmunologic events. The seven recipients who experienced cellular rejection episodes during the first posttransplant year had them reversed with steroids. Five patients displayed late acute AMR causing functional deterioration in four cases including 1 graft loss. De novo sensitization occurred in 48% of recipients including patients without clinical rejection. In conclusion, long-term follow-up of kidney transplant recipients selected by a low immunologic risk showed a persistent risk of de novo sensitization evolving to acute AMR in 11% of cases. Although immunologic events were related to late immunosuppressive reduction, most graft losses were due to nonimmunologic factors.
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    On doing relevant and rigorous experiments: Review and recommendations.
    (2018) Lonati, S.; Quiroga, Bernardo F.; Zehnder, C.; Antonakis, J.
    Although experiments are the gold standard for establishing causality, several threats can undermine the internal validity of experimental findings. In this article, we first discuss these threats, which include the lack of consequential decisions and outcomes, deception, demand effects and unfair comparisons, as well as issues concerning statistical validity (e.g., minimum sample size per cell, estimating variance correctly). We expose each problem, show potential solutions, and bring to the fore issues of relevance of the findings (i.e., external and ecological validity). Thereafter, we take stock of the state-of-the-science regarding validity threats using a representative sample of 468 recent experiments from 258 articles published in top-tier journals. We compare research practices in three fields of study—management, social psychology, and economics, which regularly use experimental research—to operations management, which has more recently begun to use the experimental paradigm. Our results underscore the importance for journals and authors to follow what we identify to be best-practice methodological suggestions (i.e., the “ten commandments” of experimental research). We show that—on average—markers of methodological rigor and generalizability positively and significantly predict the citations received by published articles. Finally, given that experiments are infeasible in some settings, we conclude with a brief review of often overlooked quasi-experimental designs, which are useful for generating strong counterfactuals and hence allow making causal claims in the field.