Genetic analysis of rare disorders: Bayesian estimation of twin concordance rates

Twin concordance rates provide insight into the possibility of a genetic background for a disease. These concordance rates are usually estimated within a frequentistic framework. Here we take a Bayesian approach. For rare diseases, estimation methods based on asymptotic theory cannot be applied due to very low cell probabilities. Moreover, a Bayesian approach allows a straightforward incorporation of prior information on disease prevalence coming from non-twin studies that is often available. An MCMC estimation procedure is tested using simulation and contrasted with frequentistic analyses. The Bayesian method is able to include prior information on both concordance rates and prevalence rates at the same time and is illustrated using twin data on cleft lip and rheumatoid arthritis

Bayesian psychometric scaling

In educational and psychological studies, psychometric methods are involved in the measurement of constructs, and in constructing and validating measurement instruments. Assessment results are typically used to measure student proficiency levels and test characteristics. Recently, Bayesian item response models received considerable attention to analyze test data and to measure latent variables. Bayesian psychometric modeling allows to include prior information about the assessment in addition to information available in the observed response data. An introduction is given to Bayesian psychometric modeling, and it is shown that this approach is very flexible, provides direct estimates of student proficiencies, and depends less on asymptotic results. Various Bayesian item response models are discussed to provide insight in Bayesian psychometric scaling and the Bayesian way of making psychometric inferences. This is done according to a general multilevel modeling approach, where observations are nested in students and items, and students are nested in schools. Different examples are given to illustrate the influence of prior information, the effects of clustered response data following a PISA study, and Bayesian methods for scale construction

Effects of twin separation in primary school

We studied the short- and long-term effects of classroom separation in twins on behavior problems and academic performance. Short-term effects were studied at age 7 in twins separated at age 5 and long-term effects at age 12 in twins who had been separated or together most of the time at school. Behavior problems were rated by mothers (Child Behavior Checklist at ages 3, 7 and 12) and teachers (Teacher Report Form at ages 7 and 12). Academic achievement was measured at age 12 using a national academic achievement test (CITO). At age 7, twins from separated pairs had more internalizing and externalizing problems than non-separated twins, as rated by both mothers and teachers. Only for the maternal ratings of internalizing problems, however, could these effects be attributed to the separation itself and not to preexisting problems (at age 3) between separated and nonseparated twins. Long-term effects of separation were significant for maternal and teacher ratings of internalizing and externalizing problems, but these effects could be explained by preexisting differences between separated and nonseparated groups. There were no differences in academic achievement between the separated and nonseparated group. These results suggest that the decision to separate twins when they go to school is based in part on the existing behavioral problems of the twins and that, in the long run, separation does not affect problem behavior or academic achievement. The findings were the same for monozygotic and dizygotic twins

High mathematics and reading performance:How important are environmental influences?

Earlier findings of international comparisons on school achievement are often interpreted to mean that there is only a small percentage of excellent students in the Netherlands. Inspired by research in behaviour genetics, it was investigated whether Dutch high-scoring children are less sensitive to environmental influences than the non-high-scoring students. To test this, the reading and mathematics scores from high-scoring and non-high-scoring students participating in the Programme for International Student Achievement (PISA) 2012, the Trends in International Mathematics and Science Study (TIMSS) 2011 and the Progress in International Reading and Literacy Study (PIRLS) 2011 were analyzed. Contrary to our expectations, the results suggest that high-scoring children are as sensitive to school influences as are non-high-scoring students, but more sensitive to the influence of individual socioeconomic status

Genetic etiology of stability of attention problems in young adulthood

Variation in attention problems in children and adolescents from non-clinical samples is highly heritable. It is unknown how attention problems develop later in life and whether the heritability in the general adult population is the same as in children and adolescents. We assessed the heritability and stability of individual differences in attention problems in the general young adult population and explored to what extent the stability can be attributed to genetic or environmental factors. On one or more occasions, young adult twins (age range, 18-30 years, N = 4,245) from the Netherlands Twin Registry filled out the attention problems (AP) subscale of the Young Adult Self-Report [Achenbach, 1997]: in 1991, N = 1,755 (of which 842 complete pairs), in 1995, N = 2,428 (1156 complete pairs) and in 1997, N = 2,344 (958 pairs). There was only a slight decrease in the average level of attention problems during young adulthood. The heritability at each occasion was around 40%. The correlation of attention problems across a period of 6 years was 0.42, and 77% of this correlation could be ascribed to genetic influences. Thus, individual differences in attention problems in young adulthood are heritable, and stability in individual differences over time can largely be ascribed to genetic influences. Genetic correlations across time were high, suggesting that the genes that influence variability in attention problems in late adolescence are largely the same as those that influence variability in early adulthood. © 2005 Wiley-Liss, Inc

Bayesian Analysis of Heterogeneous Residual Variance in Canine Behaviour

Non-additive effects like for instance genotype-environment interactions and genetically structured heterogeneity of residual variance are notoriously dependent on scale: many statistical non-additive phenomena disappear after a careful choice of transformation of the phenotypic values. Particularly for behavioural measures, scale is a delicate matter. We present a novel Bayesian approach that assesses heterogeneity in environmental variance as a function of genetic effects, where the scale is defined by a psychometric model based on item-response theory. This makes analysis results independent of what items are in a particular test version. We apply the method to fearful behaviour in dogs and compare results with the more usual sum score approac

Inclusivity in online platforms: Recruitment strategies for improving participation of diverse sociodemographic groups

Governments are increasingly implementing smart and digital approaches to promoting citizen participation. However, whether online participation platforms are tools that improve inclusivity in citizen participation remains underexplored. To address this gap, this article focuses on the role of recruitment messages and their effect on participation in an online participation platform by gender and age. A field experiment with a neighborhood census sample (N = 6,066) shows that online participation dips for younger and older citizens and is equal among women and men. For the age groups between 60 and 75, differences in the control and intervention recruitment messages significantly impacted participation. These findings can help public managers tailor recruitment strategies to facilitate inclusive participation and represent a first step toward learning what types of messages are effective for whom.Algorithms and the Foundations of Software technolog

Transverse Fluctuations in an Ising Spin-Glass:Fe0.4Mg0.6Cl2

ac-susceptibility and neutron-diffraction experiments show that Fe0.4Mg0.6Cl2 is a three-dimensional Ising spin-glass with a transition temperature Tsg = 3.4 K. Inelastic-scattering experiments show a sharp spin-wave peak at the zone center for all temperature T~<2Tsg. This is the first direct observation of long-wavelength excitation in a spin-glass system. We suggest that it is due to the precession of spin clusters around the easy axis

Acute and delayed mild coagulopathy are related to outcome in patients with isolated traumatic brain injury

INTRODUCTION: The relationship between isolated traumatic brain injury (TBI) associated coagulopathy and patient prognosis frequently lacks information regarding the time course of coagulation disorders throughout the post-traumatic period. This study was conducted to assess the prevalence and time course of post-traumatic coagulopathy in patients with isolated TBI and the relationship of these hemostatic disorders with outcome. METHODS: The local Human Subjects Committee approved the study. We retrospectively studied the medical records of computed tomography (CT)-confirmed isolated TBI patients with an extracranial abbreviated injury scale (AIS) <3 who were primarily referred to a Level 1 trauma centre in Amsterdam (n = 107). Hemostatic parameters including activated partial thromboplastin time (aPTT), prothrombin time (PT), platelet count, hemoglobin, hematocrit, glucose, pH and lactate levels were recorded throughout a 72-hour period as part of a routine standardized follow-up of TBI. Coagulopathy was defined as a aPPT >40 seconds and/or a PTT in International Normalized Ratio (INR) >1.2 and/or a platelet count <120*10(9)/l. RESULTS: Patients were mostly male, aged 48 ± 20 years with a median injury severity score of 25 (range 20 to 25). Early coagulopathy as diagnosed in the emergency department (ED) occurred in 24% of all patients. The occurrence of TBI-related coagulopathy increased to 54% in the first 24 hours post-trauma. In addition to an increased age and disturbed pupillary reflex, both coagulopathy upon ED arrival and during the first 24 hours post-trauma provided an independent prognostic factor for unfavorable outcome (odds ratio (OR) 3.75 (95% CI 1.07 to 12.51; P = 0.04) and OR 11.61 (2.79 to 48.34); P = 0.003). CONCLUSIONS: Our study confirms a high prevalence of early and delayed coagulopathy in patients with isolated TBI, which is strongly associated with an unfavorable outcome. These data support close monitoring of hemostasis after TBI and indicate that correction of coagulation disturbances might need to be considered