Optimal designs for health risk assessments using fractional polynomial models.

Fractional polynomials (FP) have been shown to be more flexible than polynomial models for fitting data from an univariate regression model with a continuous outcome but design issues for FP models have lagged. We focus on FPs with a single variable and construct D-optimal designs for estimating model parameters and I-optimal designs for prediction over a user-specified region of the design space. Some analytic results are given, along with a discussion on model uncertainty. In addition, we provide an applet to facilitate users find tailor made optimal designs for their problems. As applications, we construct optimal designs for three studies that used FPs to model risk assessments of (a) testosterone levels from magnesium accumulation in certain areas of the brains in songbirds, (b) rats subject to exposure of different chemicals, and (c) hormetic effects due to small toxic exposure. In each case, we elaborate the benefits of having an optimal design in terms of cost and quality of the statistical inference.

Predicting the Impact of Diffuse Alveolar Damage through Open Lung Biopsy in Acute Respiratory Distress Syndrome-The PREDATOR Study.

The aim of this retrospective and international study is to identify those clinical variables associated with diffuse alveolar damage (DAD), and to explore the impact of DAD on hospital mortality risk. Inclusion criteria were: adult patients with acute respiratory distress syndrome (ARDS) undergoing open lung biopsy (OLB) during their intensive care unit (ICU) management. The main end-points were: DAD and hospital mortality. In the training (n = 193) and validation cohorts (n = 65), the respiratory rate (odd ratio (OR) 0.956; confidence interval (CI) 95% 0.918; 0.995) and coronary ischemia (OR 5.974; CI95% 1.668; 21.399) on the day of ARDS had an average area under the receiver operating characteristic curve (AUROC) of 0.660 (CI95% 0.585; 0.736) and 0.562 (0.417; 0.706), respectively. PEEP (OR 1.131; CI95% 1.051; 1.218) and coronary ischemia (OR 6.820; CI95% 1.856; 25.061) on the day of OLB had an average AUROC of 0.696 (CI95% 0.621; 0.769) and 0.534 (CI95% 0.391; 0.678), respectively, to predict DAD. DAD (OR 2.296; CI95% 1.228; 4.294), diabetes mellitus requiring insulin (OR 0.081; CI95% 0.009; 0.710) and the respiratory rate (OR 1.045; CI95% 1.001; 1.091) on the day of ARDS had an average AUROC of 0.659 (CI95% 0.583; 0.737) and 0.513 (CI95% 0.361; 0.664) to predict hospital mortality and DAD (OR 2.081; CI95% 1.053; 4.114), diabetes mellitus requiring insulin (OR 0.093; CI95% 0.009; 0.956), PaCO2 (OR 1.051; CI95% 1.019; 1.084), and platelets count (OR 0.999; CI95% 0.999; 0.999) the day of OLB had an average AUROC of 0.778 (CI95% 0.710; 0.843) and 0.634 (CI95%0.481; 0.787) to predict hospital mortalty in the training and validation cohorts, respectively. In conclusion, DAD could not to be predicted clinically and was significantly associated with hospital mortality.

Prevalence of orthorexia nervosa in university students and its relationship with psychopathological aspects of eating behaviour disorders.

INTRODUCTION: Orthorexia nervosa (ON) is characterized by an obsession with healthy eating, which may lead to severe physical, psychological and social disorders. It is particularly important to research this problem in populations that do not receive clinical care in order to improve early detection and treatment. OBJECTIVE: The aim of this study was to research the prevalence of ON in a population of Spanish university students and to analyze the possible associations between ON and psychological traits and behaviors that are common to ED. METHOD: A cross-sectional study with 454 students from the University of Castilla La Mancha, Spain. In total, 295 women and 159 men participated, aged between 18 and 41 years. The ORTO-11-ES questionnaire and the Eating Disorder Inventory (EDI-2) were used for this study. The chi squared test was used to compare the homogeneity among the different groups. RESULTS: The scores on the ORTO-11-ES suggested that 17% of students were at risk of ON. The scores on the EDI-2 for the group at risk of ON were significant, compared to the remaining individuals, regarding their drive for thinness (17.1% vs 2.1%), bulimia (2.6% vs 0%), body dissatisfaction (26.3% vs. 12.4%), perfectionism (14.5% vs 4.8%), interoceptive awareness (13.2% vs 1.3%), asceticism (15.8% vs 3.7%) and impulsiveness (9.2% vs 1.9%). DISCUSSION AND CONCLUSION: These findings suggest that many of the psychological and behavioral aspects of ED are shared by people who are at risk of ON. Future research should use longitudinal data, examining the temporal relationship among these variables or other underlying variables that may contribute to the concurrence of ED and ON.

Adaptation and validation of the Spanish version of the ORTO-15 questionnaire for the diagnosis of orthorexia nervosa.

The aim of this study was the validation and analysis of the psychometric properties of a Spanish translation of the ORTO-15 questionnaire; an instrument designed to assess orthorexia nervosa behavior. Four hundred and fifty-four Spanish university students (65% women) aged between 18 and 51 years (M = 21.48 ± 0.31) completed the Spanish version of ORTO-15 and the Eating Disorders Inventory-2 (EDI-2). The Principal Component Analysis suggested a three-factor structure for the abbreviated 11-item version of the instrument. The internal consistency of the measurement was adequate (Cronbach's alpha = 0.80). The proposed test demonstrated a good predictive capacity at a threshold value of <25 (efficiency 84%, sensitivity 75% and specificity 84%). Our results support the psychometric properties of the proposed Spanish shortened-version of the ORTO-15 as being a reliable tool for assessing orthorexia nervosa. Its use is expected to greatly contribute to a better understanding of the impact of this disorder in Spain.

A web-based tool for designing experimental studies to detect hormesis and estimate the threshold dose.

Hormesis has been widely observed and debated in a variety of context in biomedicine and toxicological sciences. Detecting its presence can be an important problem with wide ranging implications. However, there is little work on constructing an efficient experiment to detect its existence or estimate the threshold dose. We use optimal design theory to develop a variety of locally optimal designs to detect hormesis, estimate the threshold dose and the zero-equivalent point (ZEP) for commonly used models in toxicology and risk assessment. To facilitate use of more efficient designs to detect hormesis, estimate threshold dose and estimate the ZEP in practice, we implement computer algorithms and create a user-friendly web site to help the biomedical researcher generate different types of optimal designs. The online tool facilitates the user to evaluate robustness properties of a selected design to various model assumptions and compare designs before implementation.