Increasing the statistical power of animal experiments with historical control data.

Low statistical power reduces the reliability of animal research; yet, increasing sample sizes to increase statistical power is problematic for both ethical and practical reasons. We present an alternative solution using Bayesian priors based on historical control data, which capitalizes on the observation that control groups in general are expected to be similar to each other. In a simulation study, we show that including data from control groups of previous studies could halve the minimum sample size required to reach the canonical 80% power or increase power when using the same number of animals. We validated the approach on a dataset based on seven independent rodent studies on the cognitive effects of early-life adversity. We present an open-source tool, RePAIR, that can be widely used to apply this approach and increase statistical power, thereby improving the reliability of animal experiments.

Parental Age in Relation to Offspring's Neurodevelopment.

Objective: Advanced parenthood increases the risk of severe neurodevelopmental disorders like autism, Down syndrome and schizophrenia. Does advanced parenthood also negatively impact offspring's general neurodevelopment?Method: We analyzed child-, father-, mother- and teacher-rated attention-problems (N = 38,024), and standardized measures of intelligence (N = 10,273) and educational achievement (N = 17,522) of children from four Dutch population-based cohorts. The mean age over cohorts varied from 9.73-13.03. Most participants were of Dutch origin, ranging from 58.7%-96.7% over cohorts. We analyzed 50% of the data to generate hypotheses and the other 50% to evaluate support for these hypotheses. We aggregated the results over cohorts with Bayesian research synthesis.Results: We mostly found negative linear relations between parental age and attention-problems, meaning that offspring of younger parents tended to have more attention problems. Maternal age was positively and linearly related to offspring's IQ and educational achievement. Paternal age showed an attenuating positive relation with educational achievement and an inverted U-shape relation with IQ, with offspring of younger and older fathers at a disadvantage. Only the associations with maternal age remained after including SES. The inclusion of child gender in the model did not affect the relation between parental age and the study outcomes.Conclusions: Effects were small but significant, with better outcomes for children born to older parents. Older parents tended to be of higher SES. Indeed, the positive relation between parental age and offspring neurodevelopmental outcomes was partly confounded by SES.

Robust longitudinal multi-cohort results: The development of self-control during adolescence.

Longitudinal data from multiple cohorts may be analyzed by Bayesian research synthesis. Here, we illustrate this approach by investigating the development of self-control between age 13 and 19 and the role of sex therein in a multi-cohort, longitudinal design. Three Dutch cohorts supplied data: the Netherlands Twin Register (NTR; N = 21,079), Research on Adolescent Development and Relationships-Young (RADAR-Y; N = 497), and Tracking Adolescents' Individual Lives Survey (TRAILS; N = 2229). Self-control was assessed by one measure in NTR and RADAR-Y, and three measures in TRAILS. In each cohort, we evaluated evidence for competing informative hypotheses regarding the development of self-control. Subsequently, we aggregated this evidence over cohorts and measures to arrive at a robust conclusion that was supported by all cohorts and measures. We found robust evidence for the hypothesis that on average self-control increases during adolescence (i.e., maturation) and that individuals with lower initial self-control often experience a steeper increase in self-control (i.e., a pattern of recovery). From self-report, boys have higher initial self-control levels at age 13 than girls, whereas parents report higher self-control for girls.

Explained Variance and Intraclass Correlation in a Two-Level AR(1) Model.

The total variance of a first-order autoregressive AR(1) time series is well known in time series literature. However, despite the increased use and interest in two-level AR(1) models, an equation for the total variance of these models does not exist. This paper presents an approximation of this total variance. It will be used to compute the unexplained and explained variance at each level of the model, the proportion of explained variance, and the intraclass correlation (ICC). The use of these variances and the ICC will be illustrated using an example concerning structured diary data about the positive affect of 96 married women.

Testing the hypothesis of tissue selectivity: the intersection-union test and a Bayesian approach.

MOTIVATION: Finding genes that are preferentially expressed in a particular tissue or condition is a problem that cannot be solved by standard statistical testing procedures. A relatively unknown procedure that can be used is the intersection-union test (IUT). However, two disadvantages of the IUT are that it is conservative and it conveys only the information of the least differing target tissue-other tissue pair. RESULTS: We propose a Bayesian procedure that quantifies how much evidence there is in the overall expression profile for selective over-expression. In a small simulation study, it is shown that the proposed method outperforms the IUT when it comes to finding selectively expressed genes. An application to publicly available data consisting of 22 tissues shows that the Bayesian method indeed selects genes with functions that reflect the specific tissue functions. The proposed method can also be used to find genes that are underexpressed in a particular tissue. AVAILABILITY: Both MATLAB and R code that implement the IUT and the Bayesian procedure in an efficient way, can be downloaded at http://ppw.kuleuven.be/okp/software/BayesianIUT/.

A preliminary study of the diagnostic accuracy of the Gerontological Personality disorders Scale (GPS).

BACKGROUND: There is still a lack of diagnostic instruments that are specifically developed to diagnose personality disorders in the elderly. OBJECTIVE: To develop a reliable and valid screening instrument to assess personality disorders in older adults. METHOD: The draft version of the screening instrument (52 items) consists of two sections: one for patients and one for informants. The diagnostic accuracy of the instrument has been assessed in the Netherlands in 159 elderly patients in an ambulatory department of geriatric psychiatry and 96 informants. RESULTS: In the patient section, sixteen items had a reasonable score for both sensitivity and specificity (approximately 70%). The internal consistency was moderate for habitual behavior (HAB; 7 items) and good for biographical information (BIO; 9 items). The test and retest reliability was moderate for HAB and excellent for BIO. The informant section, on the other hand, had a low score for sensitivity (45%) and a good score for specificity (78%). CONCLUSION: A specific instrument has been developed to diagnose personality disorders in older adults. However, further research is necessary to improve the diagnostic accuracy of the Gerontological Personality disorders Scale (GPS).

Examining the psychometric characteristics of the Dutch childhood health assessment questionnaire: room for improvement?

The aim of this study was to examine the psychometric characteristics of the childhood health assessment questionnaire-disability index (CHAQ-DI). Seventy-six patients with juvenile idiopathic arthritis (JIA), age range 4.8-15.8 years, completed a CHAQ questionnaire one or more times. In total, 321 CHAQ questionnaires were available for analysis. Factor analysis and correlation were used to analyse the data. The analysis indicated that 12 items could be removed from the original 30 items of the CHAQ-DI. Also the addition of "aids and assistance" to the overall scoring method of the CHAQ-DI did not contribute to the overall measuring concept of the CHAQ-DI. The psychometric characteristics of the CHAQ-DI could be improved by removing 12 items from the original 30 items. Moreover, a simple scoring method, without the addition of aids and assistance to the total CHAQ-DI improves sensitivity to change of the CHAQ-DI.

[Construction of a scale to signal personality disorders in the elderly]. / Constructie van een schaal voor signalering van persoonlijkheidsstoornissen bij ouderen.

Till now, no specific diagnostic instruments to detect personality disorders in the elderly are available. The aim of our study was to contribute to the construction of a reliable en valid instrument for the detection of personality disorders in older adults. Therefore, a draft version of the instrument was constructed both for the patient and the informant. Both the patient and the informant version of the instrument included 52 items with the same content. These items concerned Habitual behaviour (HAB), Biographical information (BIO) and Observation of actual behaviour (OBS). 159 clients of 60 years and older of a Dutch ambulatory mental health care organisation were assessed with the screening instrument. In 96 of the 159 outpatients one or more informants were included. The results indicate that the internal consistency of seven HAB items, nine BIO items and five OBS items was moderate to good with regard to both the patient and informant instrument. Test-retest reliability of the 21 items of the patient instrument was moderate with regard to HAB, excellent with regard to BIO and moderate with regard to OBS. Interrater reliability of OBS was also moderate. The criterion validity (criterion: DSM-IV TR Axis II classification) of HAB, BIO and OBS based on the 21 items of the patient instrument was fair and with regard to the same 21 items of the informant instrument insufficient. In conclusion, sixteen out of 52 potential items of the patient's draft version of the screening instrument can be used to detect a possible personality disorder. These sixteen items from the HAB and BIO scale are named the Gerontological Personality disorder Scale (GPS). Medical doctors, psychologists and nurses working in ambulatory mental health organisation can use the GPS as a resource during the diagnostic process. Whether the GPS can be used beyond mental health organisations, for example by general practitioners is a subject for future studies.

Confirmatory Latent Class Analysis: Model Selection Using Bayes Factors and (Pseudo) Likelihood Ratio Statistics.

Inequality constraints among class specific probabilities can be used to assign a specific meaning to the classes in a latent class model. Different models arise if different sets of constraints are used. In this paper, model selection using Bayes factors, and, (pseudo) likelihood ratio statistics evaluated using posterior predictive p-values, will be discussed. It will be illustrated that these Bayesian selection criteria do not suffer from the same flaw as maximum likelihood based selection criteria. Using a small simulation study it will be shown that, in the context of the simulation study, Bayes factors and the pseudo likelihood ratio statistic have the best proporties. The article will be concluded with an example.

The multidimensionality of self-report schizotypy in a psychiatric population: an analysis using multidimensional Rasch models.

There is increasing empirical evidence from factor analytical studies that schizotypy is composed of three dimensions. All studies into the multidimensionality of schizotypy used common factor analysis of scales, either exploratory or confirmatory. We argue that for research into the multidimensionality of schizotypy with dichotomous item responses on questionnaires (as with the Schizotypal Personality Questionnaire [SPQ], Raine 1991) much can be learned using generalized multidimensional Rasch models (GMRMs). GMRMs require a priori postulated models of schizotypy, which can be tested in confirmatory analyses. We hypothesized four competing models of schizotypy, based on the literature and clinical impressions-two two-dimensional models and two three-dimensional models. We also hypothesized that items differ in the degree they are indicative of a particular dimension of schizotypy. The sample was 418 psychiatric inpatients and outpatients, with moderate levels of psychopathology, who filled in the SPQ. Both three-dimensional models yielded a much better fit to the data than both two-dimensional models. Our revised three-dimensional model, a revision of that by Raine et al. (1994) and Gruzelier (1996), yielded the best fit. It consisted of positive schizotypy, disorganization, and negative schizotypy. The results strongly suggest that schizotypy, as measured with the SPQ, is a three-dimensional construct.

Cultural differences in functional status measurement: analyses of person fit according to the Rasch model.

For many reasons it is preferable to use established health related outcome instruments. The validity of an instrument, however, can be affected when used in another culture or language other than what it was originally developed. In this paper, the outcome on functional status measurement using a preliminary version of the Dutch translated 'Pediatric Evaluation of Disability Inventory' (PEDI) was studied involving a sample of 20 non-disabled Dutch children and American peers, to see if a cross-cultural validation procedure is needed before using the instrument in the Netherlands. The Rasch model was used to analyse the Dutch data. Score profiles were not found to be compatible with the score profiles of American children. In particular, ten items were scored differently with strong indications that these were based on inter-cultural differences. Based on our study, it is argued that cross-cultural validation of the PEDI is necessary before using the instrument in the Netherlands.

Intraindividual variability in infant behavior.

Longitudinal observational data of infant crying, fretting/fussing, and smiling and the time spent in physical contact with the mother were used in a study on behavioral variability. The infants were followed weekly for a 15-month period. Evidence was found of an important intraindividual variability in the studied behaviors, specifically between the ages of 0 and 5 months, 5 and 10 months, but not between 10 and 15 months. Results are discussed and analyzed in the light of earlier literature. The possible functions and the factors underlying variability in development as well as its methodological implications are discussed.

Psychometric analysis of an advance directive.

OBJECTIVES: Reliability and validity are as necessary for predrafted advance directive forms as they are for all clinical assessment instruments. Performance of predrafted advance directive forms with both lay persons and clinicians is relevant. Evidence relating to test- retest reliability, content validity, and criterion-related validity of one form, the Medical Directive, has been documented for outpatients. The authors investigated construct validity and external validity among outpatients, physicians, and the general public. METHODS: Four hundred ninety-five outpatients, 513 physicians, and 102 members of the general public were surveyed with the Medical Directive. Preference for 11 specific treatments in four to six illness scenarios were recorded. Mokken modeling of responses was used to produce a psychometric scale of receptiveness-to-treatment and desirability of treatments. The Kuder Richardson-20 statistic, Friedman's procedure for analysis of variance, and the Kruskall-Wallis test were used, respectively, to measure inter-item reliability, the relation with scenarios, and the relation between physicians' general goals for care and their scaled preferences. RESULTS: All model diagnostic tests indicated a close-fitting scale for all three respondent groups. Kuder Richardson-20 for outpatients (.98), physicians (.97), and the public (.93) demonstrated high inter-item reliability. Treatment desirabilities were related to invasiveness. Receptiveness-to-treatment was related to prognoses and disabilities of described illness scenarios among each group and to physicians' goals for care. CONCLUSIONS: The Medical Directive has construct validity in relations among specific treatment preferences and between treatment preferences, illness scenarios, and goals for care. External validity is supported by study of separate outpatient, physician, and general public populations. The treatment items constitute a highly reliable scale that can be used in further empirical research regarding life-sustaining treatment.