University of Zurich

About: University of Zurich is a education organization based out in Zurich, Switzerland. It is known for research contribution in the topics: Population & Medicine. The organization has 50842 authors who have published 124042 publications receiving 5304521 citations. The organization is also known as: UZH & Uni Zurich.

The Balanced Accuracy and Its Posterior Distribution

Abstract: Evaluating the performance of a classification algorithm critically requires a measure of the degree to which unseen examples have been identified with their correct class labels. In practice, generalizability is frequently estimated by averaging the accuracies obtained on individual cross-validation folds. This procedure, however, is problematic in two ways. First, it does not allow for the derivation of meaningful confidence intervals. Second, it leads to an optimistic estimate when a biased classifier is tested on an imbalanced dataset. We show that both problems can be overcome by replacing the conventional point estimate of accuracy by an estimate of the posterior distribution of the balanced accuracy.

Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials

Abstract: Objective To test the efficacy of supplemental vitamin D and active forms of vitamin D with or without calcium in preventing falls among older individuals. Data sources We searched Medline, the Cochrane central register of controlled trials, BIOSIS, and Embase up to August 2008 for relevant articles. Further studies were identified by consulting clinical experts, bibliographies, and abstracts. We contacted authors for additional data when necessary. Review methods Only double blind randomised controlled trials of older individuals (mean age 65 years or older) receiving a defined oral dose of supplemental vitamin D (vitamin D 3 (cholecalciferol) or vitamin D 2 (ergocalciferol)) or an active form of vitamin D (1α-hydroxyvitamin D 3 (1α-hydroxycalciferol) or 1,25-dihydroxyvitamin D 3 (1,25-dihydroxycholecalciferol)) and with sufficiently specified fall assessment were considered for inclusion. Results Eight randomised controlled trials (n=2426) of supplemental vitamin D met our inclusion criteria. Heterogeneity among trials was observed for dose of vitamin D (700-1000 IU/day v 200-600 IU/day; P=0.02) and achieved 25-hydroxyvitamin D 3 concentration (25(OH)D concentration: v ≥60 nmol/l; P=0.005). High dose supplemental vitamin D reduced fall risk by 19% (pooled relative risk (RR) 0.81, 95% CI 0.71 to 0.92; n=1921 from seven trials), whereas achieved serum 25(OH)D concentrations of 60 nmol/l or more resulted in a 23% fall reduction (pooled RR 0.77, 95% CI 0.65 to 0.90). Falls were not notably reduced by low dose supplemental vitamin D (pooled RR 1.10, 95% CI 0.89 to 1.35; n=505 from two trials) or by achieved serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l (pooled RR 1.35, 95% CI 0.98 to 1.84). Two randomised controlled trials (n=624) of active forms of vitamin D met our inclusion criteria. Active forms of vitamin D reduced fall risk by 22% (pooled RR 0.78, 95% CI 0.64 to 0.94). Conclusions Supplemental vitamin D in a dose of 700-1000 IU a day reduced the risk of falling among older individuals by 19% and to a similar degree as active forms of vitamin D. Doses of supplemental vitamin D of less than 700 IU or serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l may not reduce the risk of falling among older individuals.

A Kingdom-Level Phylogeny of Eukaryotes Based on Combined Protein Data

Abstract: Current understanding of the higher order systematics of eukaryotes relies largely on analyses of the small ribosomal subunit RNA (SSU rRNA). Independent testing of these results is still limited. We have combined the sequences of four of the most broadly taxonomically sampled proteins available to create a roughly parallel data set to that of SSU rRNA. The resulting phylogenetic tree shows a number of striking differences from SSU rRNA phylogeny, including strong support for most major groups and several major supergroups.