A modular approach for item response theory modeling with the R package flirt.

The new R package flirt is introduced for flexible item response theory (IRT) modeling of psychological, educational, and behavior assessment data. flirt integrates a generalized linear and nonlinear mixed modeling framework with graphical model theory. The graphical model framework allows for efficient maximum likelihood estimation. The key feature of flirt is its modular approach to facilitate convenient and flexible model specifications. Researchers can construct customized IRT models by simply selecting various modeling modules, such as parametric forms, number of dimensions, item and person covariates, person groups, link functions, etc. In this paper, we describe major features of flirt and provide examples to illustrate how flirt works in practice.

Asymptotically Correct Person Fit z-Statistics For the Rasch Testlet Model.

A well-known person fit statistic in the item response theory (IRT) literature is the l z statistic (Drasgow et al. in Br J Math Stat Psychol 38(1):67-86, 1985). Snijders (Psychometrika 66(3):331-342, 2001) derived l z ∗ , which is the asymptotically correct version of l z when the ability parameter is estimated. However, both statistics and other extensions later developed concern either only the unidimensional IRT models or multidimensional models that require a joint estimate of latent traits across all the dimensions. Considering a marginalized maximum likelihood ability estimator, this paper proposes l zt and l zt ∗ , which are extensions of l z and l z ∗ , respectively, for the Rasch testlet model. The computation of l zt ∗ relies on several extensions of the Lord-Wingersky algorithm (1984) that are additional contributions of this paper. Simulation results show that l zt ∗ has close-to-nominal Type I error rates and satisfactory power for detecting aberrant responses. For unidimensional models, l zt and l zt ∗ reduce to l z and l z ∗ , respectively, and therefore allows for the evaluation of person fit with a wider range of IRT models. A real data application is presented to show the utility of the proposed statistics for a test with an underlying structure that consists of both the traditional unidimensional component and the Rasch testlet component.

A nationwide analysis of incidence and outcome of breast cancer in the country of Surinam, during 1994-2003.

In this study, we describe the incidence, treatment, and outcome of breast cancer (BC) during the period 1994-2003 in the South-American country of Surinam and compare these with those of BC in the Netherlands. Pathology reports and hospital charts from all BC cases diagnosed between 1994 and 2004 were retrieved from Surinam's single pathology laboratory and its five hospitals. Data on demographics, tumor characteristics, treatment, and follow-up were gathered. We compared our data to BC statistics of first generation immigrants from Surinam to the Netherlands. 421 patients were diagnosed with BC during the study period. The age-adjusted incidence rate was 26 per 100,000 compared to 65/100,000 in first generation Surinamese women in the Netherlands. The majority had a fairly advanced stage at presentation, with 60% of tumors larger than 2 cm, and 41.6% with lymph node involvement. Because of the absence of radiotherapy facilities, local treatment in most patients was radical mastectomy. Adjuvant hormonal therapy (51.6%) was administered more frequently than adjuvant chemotherapy (20.3%). A significant number of patients were lost to follow-up, resulting in a median follow-up duration of only 23 months. The 5-year overall survival was 79%. BC incidence in Surinam is low compared to that in the western world, but the advanced stage at diagnosis, the low utilization of systemic adjuvant therapy, and the inadequate follow-up may lead to poor outcomes. A number of steps are underway to improve the level of cancer care in Surinam.

Similarity in depressive symptom profile in a population-based study of migrants in the Netherlands.

OBJECTIVE: Depression is a clinical syndrome developed in Western Europe and North-America. The expression of symptoms and the impact of symptoms on functioning may therefore be expected to vary across cultures and languages. Our first aim was to study differences in depressive symptom profile between indigenous and non-Western immigrant populations in the Netherlands. We hypothesized that differences in expression of depressive symptoms would be more likely in the domains of mood and cognitions, and less likely in the domains of psychomotor and vegetative symptoms. Our second aim was to study ethnic differences in the association of depressive symptoms and general functioning. METHOD: In a random community sample stratified for ethnicity in Amsterdam, the Netherlands, depressive symptoms were assessed by bilingual interviewers using the Composite International Diagnostic Interview (CIDI 2.1) and the Symptom Checklist-90-Revised (SCL-90-R). Impairments in functioning were measured by the World Health Organization Disability Assessment Schedule II (WHODAS II). Results were obtained from 812 subjects: N = 321 native Dutch, N = 213 Turkish-Dutch, N = 191 Moroccan-Dutch, N = 87 Surinamese-Dutch. Differences in depressive symptom expression were tested by differential item functioning. RESULTS: The prevalence of DSM-IV depressive disorder and the overall level of depressive symptoms were higher in the Turkish and Moroccan immigrant groups compared to native Dutch subjects. Ethnic differences in item functioning of depressive symptoms were rare, and equally unlikely in all four symptom domains. Depression was equally associated with functional impairment across ethnic groups. CONCLUSION: Although depressive symptoms were more common among migrants than in the indigenous population, both the depressive symptom profile and the associated functional impairments were comparable. These findings may help diminishing concerns about the validity of using existing diagnostic procedures among ethnic minority groups.

Raising awareness of carrier testing for hereditary haemoglobinopathies in high-risk ethnic groups in the Netherlands: a pilot study among the general public and primary care providers.

BACKGROUND: In the Netherlands no formal recommendations exist concerning preconceptional or antenatal testing for carriership of hereditary haemoglobinopathies. Those at highest risk may be unaware of the possibility of carrier screening. While universal newborn screening has recently been introduced, neither preconceptional nor antenatal carrier testing is routinely offered by health care services to the general public. A municipal health service and a foundation for public information on medical genetics undertook a pilot project with the aim of increasing knowledge and encouraging informed choice. Two groups were targeted: members of the public from ethnic groups at increased risk, and primary health care providers. This study examines the effectiveness of culturally specific 'infotainment' to inform high-risk ethnic groups about their increased risk for haemoglobinopathies. In addition, the study explores attitudes and intentions of primary care providers towards haemoglobinopathy carrier testing of their patients from high-risk ethnic groups. METHODS: Informational sessions tailored to the public or professionals were organised in Amsterdam, and evaluated for their effect. Psychological parameters were measured using structured questionnaires based on the Theory of Planned Behaviour. RESULTS: The pre-test/post-test questionnaire showed that members of the public gained understanding of inheritance and carriership of haemoglobinopathies from the "infotainment" session (p < 0.01). Perceived behavioural control, i.e. the feeling that they could actually get tested if they wanted to, increased in the targeted age group of 18-45 years (N = 41; p < 0.05). 191 surveys were collected from general practitioners or midwives. Their attitude towards the education programme for high-risk ethnic groups was positive, yet they did not show strong intention to effectuate carrier testing of their patients on the basis of ethnicity. The main factor which explained their (lack of) intention was social norm, i.e. their perception of negative peer opinion (41% variance explained). The majority of primary health care providers felt that policy change was unnecessary. CONCLUSION: The "infotainment" programme may have a positive effect on people from high-risk groups, but informed general practitioners and midwives were reluctant to facilitate their patients' getting tested. Additional initiatives are needed to motivate primary care providers to facilitate haemoglobinopathy carrier testing for their patients from high-risk backgrounds.

Depression in old age (75+), the PIKO study.

BACKGROUND: Old people (75+) are underrepresented in studies on the prevalence of and risk factors for depression while the number of elderly people suffering from this mood disorder may be considerably higher than previously assumed. The role--if any--of age and gender in 'Geriatric Depression' is still unclear. METHODS: In this community-based study, prevalence of depressive symptomatology and risk indicators were assessed in 2850 participants aged 75 years or more. A clinically relevant level of depressive symptoms was defined as a score of > or =16 on the Centre for Epidemiologic Studies Depression scale (CES-D). Demographic data and questions related to physical and psychological health were recorded. Simple and multiple logistic regression techniques were used to determine the risk indicators (Odds Ratios, OR, with 95% confidence intervals, CI) with apparent importance to this population. RESULTS: The prevalence of depressive symptoms was assessed to be 31.1%. This is considerably higher than what has been found in younger elderly samples. The bivariate age effect was OR 1.05 (95% CI=1.03 to 1.07). Controlling for confounding, the effect of gender and age on depressive symptoms disappeared. CONCLUSIONS: Depressive symptoms are highly prevalent in the elderly population and increase with age. This increase seems to be attributable to age-related changes in risk factors rather than to ageing itself. With regard to the risk factors found, attention should perhaps be paid to functional disability, loneliness and apprehensiveness for falling since these risk indicators are amenable for improvement.

Toward disentangling sources of individual differences in appraisal and anger.

A theoretical framework is presented to explain individual differences in situation-specific emotional experience in terms of three different sources of variance: (a) individual differences in how one appraises one's circumstances, (b) individual differences in how appraisals are related to the experience of emotion, and (c) individual differences independent from situation and appraisal. The relative contribution and nature of these sources was examined empirically for the experience of anger based on data from two directed imagery studies (total N=1,192). Consistent results across the two studies demonstrated that variability in anger experience primarily stems from variability in how a situation is appraised and to a smaller extent from individual differences in the relations between the appraisals and anger and individual differences independent of appraisal. The findings further identified frustration as the central appraisal involved in anger. Implications for emotion theories and anger management programs are discussed.

Anxiety symptoms and cognitive performance in later life: results from the longitudinal aging study Amsterdam.

OBJECTIVES: This study investigates whether, and if so how, anxiety symptoms are related to cognitive decline in elderly persons and whether anxiety symptoms precede cognitive decline. METHOD: Data were obtained from the Longitudinal Aging Study Amsterdam. Anxiety symptoms were measured with the Hospital Anxiety and Depression Scale. General cognitive functioning was measured with the Mini-Mental State Examination, episodic memory with the Auditory Verbal Learning Test, fluid intelligence with the Raven's Coloured Progressive Matrices and information processing speed with the coding task. Multilevel analyses were performed to investigate the relationship between anxiety symptoms and cognitive decline over 9 years, taking into account confounding variables. RESULTS: Although not consistent across all dimensions of cognitive functioning, a curvilinear effect of anxiety on cognitive performance was found. Furthermore, we found that previous measurement of anxiety symptoms were not predictive of cognitive decline at a later time-point. CONCLUSION: This study suggests that the effect of anxiety on cognition depends on the severity of the present anxiety symptoms with mild anxiety associated with better cognition, whereas more severe anxiety is associated with worse cognition. The effect of anxiety symptoms on cognitive functioning seems to be a temporary effect, anxiety is not predictive of cognitive decline.

CFA Models with a General Factor and Multiple Sets of Secondary Factors.

We propose a class of confirmatory factor analysis models that include multiple sets of secondary or specific factors and a general factor. The general factor accounts for the common variance among manifest variables, whereas multiple sets of secondary factors account for the remaining source-specific dependency among subsets of manifest variables. A special case of the model is further proposed which constrains the specific factor loadings to be proportional to the general factor loadings. This proportional model substantially reduces the number of model parameters while preserving the essential structure of the general model. Furthermore, the proportional model allows for the interpretation of latent variables as the expected values of the observed manifest variables, decomposition of the variances, and the inclusion of interactions, similar to generalizability theory. We provide two applications to illustrate the utility of the proposed class of models.

EGFR and K-ras mutation analysis in non-small cell lung cancer: comparison of paraffin embedded versus frozen specimens.

BACKGROUND: Mutational analysis of the Epidermal Growth Factor Receptor (EGFR) and K-ras genes to select non-small cell lung cancer (NSCLC) patients for treatment with novel EGFR tyrosine kinase inhibitors is an appealing possibility currently under investigation. Although frozen tumor tissue would probably be the optimal source for analysis, the most common source of tumor material is fixed and paraffin embedded (FPE) archival specimens. Here, we evaluate how different procedures of tissue sample processing and preservation may affect the outcome of EGFR and K-ras mutation analysis. Furthermore, we compare the sensitivity of the analysis using genomic DNA (gDNA) versus RNA. METHODS: We used PCR amplification and direct sequencing to analyze EGFR and K-ras genes in paired FPE and frozen tumor samples corresponding to 47 NSCLC patients. In frozen samples, the analysis was carried out using both gDNA and RNA extracted in parallel. RESULTS: Whereas 100% of frozen samples were successfully amplified, the rate of successful PCR amplification in FPE samples was approximately 50%. We detected three previously described EGFR point mutations in 2 samples. In ten other samples, a K-ras mutation was observed. These mutations were detected in DNA extracted from frozen samples as well as in DNA obtained from FPE tissue. In addition, 10 nucleotide changes, were detected in FPE samples that were not detected in the frozen specimens. Upon re-analysis, these nucleotide changes could not be confirmed and were most likely the result of paraffin embedding and fixation procedures. All mutations found in gDNA were also detected in the corresponding RNA and, in two cases, the presence of the mutant allele was easier to identify by using RNA. CONCLUSIONS: Our results indicate that RNA extracted from frozen tissue is the preferred source for EGFR and K-ras mutation testing. When analyzing FPE samples, reducing the size of the amplified fragments would increase PCR success rate, and care should be taken to control for false-positive results.

Quality of life of adult retinoblastoma survivors in the Netherlands.

BACKGROUND: To assess the quality of life (QoL) and predictors thereof in Dutch adult hereditary and non-hereditary retinoblastoma (RB) survivors. METHODS: In this population-based cross-sectional study, a generic QoL questionnaire (SF-36) and a disease-specific interview were administered to 87 adult RB survivors aged 18 to 35 years. Their QoL data were compared with those of a Dutch healthy reference group. Among the RB hereditary/non-hereditary survivors, the QoL was compared and predictors for QoL were identified by linear multiple regression analyses. RESULTS: As a group, RB survivors scored significantly lower than the reference group on the SF-36 subscale 'mental health' (t = -27, df = 86, p < 0.01). Hereditary RB survivors scored lower on the subscale 'general health' (t = 2.6, df = 85, p < 0.01) than non-hereditary RB survivors. Having experienced bullying, as a child was a predictor for the SF-36 subscales: 'physical functioning' (p < 0.05), 'role functioning physical' (p < 0.01), 'role functioning emotional' (p < 0.05) and 'social functioning' (p < 0.01). Having experienced bullying (p < 0.01), but also subjective experience of impairment related to RB (p < 0.05), was predictors for 'general health'. Subjective experience of impairment was a predictor for 'vitality' (p < 0.01) and 'bodily pain' (p < 0.01). CONCLUSION: In this exploratory study, it appears that the group of adult RB survivors experience a relatively good overall but slightly decreased QoL compared with the reference group. However, they report more problems with regard to their mental health (anxiety, feelings of depression, and loss of control). Hereditary RB survivors differ significantly from non-hereditary RB survivors only in 'general health'. Bullying in childhood and subjective experience of impairment are the main predictors of a worse QoL. In order to prevent worsening of QoL, or perhaps to improve it, clinicians should make an inventory of these issues at an early stage. We recommend further research to assess the specific psychological factors that may lead to mental health problems in this population.

Drive for thinness, affect regulation and physical activity in eating disorders: a daily life study.

Using Ecological Momentary Assessment, the within patient associations between drive for thinness, emotional states, momentary urge to be physically active and physical activity were studied in 32 inpatients with an eating disorder. Participants received an electronic device and had to indicate at nine random times a day during 1 week their momentary drive for thinness, positive and negative emotional states and their urge to be physically active and physical activity. Multilevel analyses indicated that patients with higher mean levels for urge to be physically active were characterized by lower body mass index (BMI) and chronically negative affect whereas patients with higher mean levels for physical activity were characterized by lower BMI and higher dispositions for drive for thinness. In addition, within patient relations between drive for thinness and urge to be physically active were moderated by BMI and chronically negative affect whereas within patient relations between drive for thinness and physical activity were moderated by BMI. Finally, also positive emotional states were significantly associated with physical activity within patients. By using a daily process design, characteristics of physical activity were revealed that have not been identified with assessment methods that have a lower time resolution.

Primary care patients with mental health problems: outcome of a randomised clinical trial.

BACKGROUND: The prevalence of patients with mental health problems in general practice is high, and at least one-third of these problems last for 6 months or longer. Patients with these problems take up more time during a consultation and attend more frequently. AIM: This study investigated the effectiveness of problem-solving treatment for primary care patients with mental health problems. The hypothesis was that patients receiving problem-solving treatment from a nurse would have fewer symptoms after 3 months, or a lower attendance rate, compared with patients receiving the usual care from the GP. DESIGN OF THE STUDY: Randomised clinical trial. SETTING: Twelve general practices in Amsterdam and 12 nurses from a mental healthcare institution. METHOD: A sample of patients aged >or=18 years were screened for mental health problems with the general health questionnaire (GHQ-12) in the waiting room of the general practices, and were randomised. Patients receiving the problem-solving treatment were required to complete four to six treatment sessions, while patients in the control group were treated as usual by the GP. RESULTS: No significant difference was found between the groups in terms of improved psychopathology or a decrease in attendance rate. Post-hoc analyses showed a sub-group of patients with more severe pathology who may benefit from problem-solving treatment. CONCLUSION: The main results show that problem-solving treatment provided by a nurse adds little to the usual care from the GP for frequent attenders with mental health problems. Post-hoc analyses show that there may be a sub-group of more severely depressed patients who could benefit from problem-solving treatment.

A Variational Maximization-Maximization Algorithm for Generalized Linear Mixed Models with Crossed Random Effects.

We present a variational maximization-maximization algorithm for approximate maximum likelihood estimation of generalized linear mixed models with crossed random effects (e.g., item response models with random items, random raters, or random occasion-specific effects). The method is based on a factorized variational approximation of the latent variable distribution given observed variables, which creates a lower bound of the log marginal likelihood. The lower bound is maximized with respect to the factorized distributions as well as model parameters. With the proposed algorithm, a high-dimensional intractable integration is translated into a two-dimensional integration problem. We incorporate an adaptive Gauss-Hermite quadrature method in conjunction with the variational method in order to increase computational efficiency. Numerical studies show that under the small sample size conditions that are considered the proposed algorithm outperforms the Laplace approximation.

Statistical inference in generalized linear mixed models: a review.

We present a review of statistical inference in generalized linear mixed models (GLMMs). GLMMs are an extension of generalized linear models and are suitable for the analysis of non-normal data with a clustered structure. A GLMM contains parameters common to all clusters (fixed regression effects and variance components) and cluster-specific parameters. The latter parameters are assumed to be randomly drawn from a population distribution. The parameters of this population distribution (the variance components) have to be estimated together with the fixed effects. We focus on the case in which the cluster-specific parameters are normally distributed. The cluster-specific effects are integrated out of the likelihood so that the fixed effects and variance components can be estimated. Unfortunately, the integral over the cluster-specific effects is intractable for most GLMMs with a normal mixing distribution. Within a classical statistical framework, we distinguish between two broad classes of methods to handle this intractable integral: methods that rely on a numerical approximation to the integral and methods that use an analytical approximation to the integrand. Finally, we present an overview of available methods for testing hypotheses about the parameters of GLMMs.

Mixed model estimation methods for the Rasch model.

Mixed models take the dependency between observations based on the same person into account by introducing one or more random effects. After introducing the mixed model framework, it is explained, by taking the Rasch model as a generic example, how item response models can be conceptualized as generalized linear and nonlinear mixed models. Common estimation methods for generalized linear and nonlinear models are discussed. In a simulation study, the performance of four estimation methods is assessed for the Rasch model under different conditions regarding the number of items and persons, and the degree of interindividual differences. The estimation methods included in the study are: an approximation of the integral over the random effect by means of Gaussian quadrature; direct maximization with a sixth-order Laplace approximation to the integrand; a linearized approximation of the nonlinear model employing PQL2; and finally a Bayesian MCMC method. It is concluded that the estimation methods perform almost equally well, except for a slightly worse recovery of the variance parameter for PQL2 and MCMC.

On the explaining-away phenomenon in multivariate latent variable models.

Many probabilistic models for psychological and educational measurements contain latent variables. Well-known examples are factor analysis, item response theory, and latent class model families. We discuss what is referred to as the 'explaining-away' phenomenon in the context of such latent variable models. This phenomenon can occur when multiple latent variables are related to the same observed variable, and can elicit seemingly counterintuitive conditional dependencies between latent variables given observed variables. We illustrate the implications of explaining away for a number of well-known latent variable models by using both theoretical and real data examples.

A nonlinear mixed model framework for item response theory.

Mixed models take the dependency between observations based on the same cluster into account by introducing 1 or more random effects. Common item response theory (IRT) models introduce latent person variables to model the dependence between responses of the same participant. Assuming a distribution for the latent variables, these IRT models are formally equivalent with nonlinear mixed models. It is shown how a variety of IRT models can be formulated as particular instances of nonlinear mixed models. The unifying framework offers the advantage that relations between different IRT models become explicit and that it is rather straightforward to see how existing IRT models can be adapted and extended. The approach is illustrated with a self-report study on anger.

Recent developments in maximum likelihood estimation of MTMM models for categorical data.

Maximum likelihood (ML) estimation of categorical multitrait-multimethod (MTMM) data is challenging because the likelihood involves high-dimensional integrals over the crossed method and trait factors, with no known closed-form solution. The purpose of the study is to introduce three newly developed ML methods that are eligible for estimating MTMM models with categorical responses: Variational maximization-maximization (e.g., Rijmen and Jeon, 2013), alternating imputation posterior (e.g., Cho and Rabe-Hesketh, 2011), and Monte Carlo local likelihood (e.g., Jeon et al., under revision). Each method is briefly described and its applicability for MTMM models with categorical data are discussed.

Effectiveness of case management among older adults with early symptoms of dementia and their primary informal caregivers: a randomized clinical trial.

BACKGROUND: It is believed that timely recognition and diagnosis of dementia is a pre-condition for improving care for both older adults with dementia and their informal caregivers. However, diagnosing dementia often occurs late in the disease. This means that a significant number of patients with early symptoms of dementia and their informal caregivers may lack appropriate care. OBJECTIVES: To compare the effects of case management and usual care among community-dwelling older adults with early symptoms of dementia and their primary informal caregivers. DESIGN: Randomized controlled trial with measurements at baseline and after 6 and 12 months. SETTING: Primary care in West-Friesland, the Netherlands. PARTICIPANTS: 99 pairs of community-dwelling older adults with dementia symptoms (defined as abnormal screening for symptoms of dementia) and their primary informal caregivers. INTERVENTION: 12 months of case management by district nurses for both older adults and informal caregivers versus usual care. PRIMARY OUTCOME: informal caregiver's sense of competence. SECONDARY OUTCOMES: caregiver's quality of life, depressive symptoms, and burden, and patient's quality of life. Process measurements: intervention fidelity and caregiver's satisfaction with the quality of case management. RESULTS: Linear mixed model analyses showed no statistically significant and clinically relevant differences over time between the two groups. The process evaluation revealed that intervention fidelity could have been better. Meanwhile, informal caregivers were satisfied with the quality of case management. CONCLUSION: This study shows no benefits of case management for older adults with dementia symptoms and their primary informal caregivers. One possible explanation is that case management, which has been recommended among diagnosed dementia patients, may not be beneficial if offered too early. However, on the other hand, it is possible that: (1) case management will be effective in this group if more fully implemented and adapted or aimed at informal caregivers who experience more severe distress and problems; (2) case management is beneficial but that it is not seen in the timeframe studied; (3) case management might have undetected small benefits. This has to be established. Trial registration ISCRTN83135728.