Bayesian specification analysis and estimation of simultaneous equation models using Monte Carlo methods

Bayesian procedures for specification analysis or diagnostic checking of modeling assumptions for structural equations of econometric models are developed and applied using Monte Carlo numerical methods. Checks on the validity of identifying restrictions, exogeneity assumptions and other specifying assumptions are performed using posterior distributions for discrepancy vectors and functions representing departures from specifying assumptions. Several mappings or functions of reduced form coefficients are defined and their posterior distributions are computed. A restricted reduced form approach is used to compute posterior distributions for structural parameters. These procedures are applied in analyses of two econometric models

Explaining Adaptive Radial-Based Direction Sampling

In this short paper we summarize the computational steps of Adaptive Radial-Based Direction Sampling (ARDS), which can be used for Bayesian analysis of ill behaved target densities. We consider one simulation experiment in order to illustrate the good performance of ARDS relative to the independence chain MH algorithm and importance sampling

Adaptive polar sampling, a class of flexibel and robust Monte Carlo integration methods

Adaptive Polar Sampling (APS) algorithms are proposed for Bayesian analysis of models with nonelliptical, possibly, multimodal posterior distributions. A location-scale transformation and a transformation to polar coordinates are used. After the transformation to polar coordinates, a Metropolis-Hastings method or, alternatively, an importance sampling method is applied to sample directions and, conditionally on these, distances are generated by inverting the cumulative distribution function. A sequential procedure is applied to update the initial location and scaling matrix in order to sample directions in an efficient way. Tested on a set of canonical mixture models that feature multimodality, strong correlation, and skewness, the APS algorithms compare favourably with the standard Metropolis-Hastings and importance samplers in terms of flexibility and robustness. APS is applied to several econometric and statistical examples. The empirical results for a regression model with scale contamination, an ARMA-GARCH-Student t model with near cancellation of roots and heavy tails, a mixture model for economic growth, and a nonlinear threshold model for industrial production growth confirm the practical flexibility and robustness of APS

Hospitalisations at the end of life: using a sentinel surveillance network to study hospital use and associated patient, disease and healthcare factors

<p>Abstract</p> <p>Background</p> <p>Hospital deaths following several hospital admissions or long hospital stays may be indicative of a low quality of dying. Although place of death has been extensively investigated at population level, hospital use in the last months of life and its determinants have been studied less often, especially in Europe and with a general end-of-life patient population. In this study we aim to describe hospital use in the last three months of life in Belgium and identify associated patient, disease and healthcare factors.</p> <p>Methods</p> <p>We conducted a retrospective registration study (13 weeks in 2004) with the Belgian Sentinel Network of General Practitioners, an epidemiological surveillance system representative of all GPs in Belgium, covering 1.75% of the total Belgian patient population. All registered non-sudden or expected deaths of patients (aged one year or older) at the GPs' practices were included. Bivariate and regression analyses were performed.</p> <p>Results</p> <p>The response rate was 87%. The GPs registered 319 deaths that met inclusion criteria. Sixty percent had been hospitalised at least once in the last three months of life, for a median of 19 days. The percentage of patients hospitalised increased exponentially in the last weeks before death; one fifth was admitted in the final week of life. Seventy-two percent of patients hospitalised at least once in the final three months died in hospital. A palliative treatment goal, death from cardiovascular diseases, the expression of a wish to die in an elderly home and palliative care delivery by the GP were associated with lower hospitalisation odds.</p> <p>Conclusion</p> <p>Hospital care plays a large role in the end of patients' lives in Belgium, especially in the final weeks of life. The result is a high rate of hospital deaths, showing the institutionalised nature of dying. Patients' clinical conditions, the expression of preferences and also healthcare characteristics such as being treated as a palliative care patient, seem to be associated with hospital transfers. It is recommended that hospitalisation decisions are only made after careful consideration. Short admissions in the final days of life should be prevented in order to make dying at home more feasible.</p

Nationwide monitoring of end-of-life care via the Sentinel Network of General Practitioners in Belgium: the research protocol of the SENTI-MELC study

<p>Abstract</p> <p>Background</p> <p>End-of-life care has become an issue of great clinical and public health concern. From analyses of official death certificates, we have societal knowledge on how many people die, at what age, where and from what causes. However, we know little about how people are dying. There is a lack of population-based and nationwide data that evaluate and monitor the circumstances of death and the care received in the final months of life. The present study was designed to describe the places of end-of-life care and care transitions, the caregivers involved in patient care and the actual treatments and care provided to dying patients in Belgium. The patient, residence and healthcare characteristics associated with these aspects of end-of-life care provision will also be studied. In this report, the protocol of the study is outlined.</p> <p>Methods/Design</p> <p>We designed a nationwide mortality follow-back study with data collection in 2005 and 2006, via the nationwide Belgian Sentinel Network of General Practitioners (GPs) i.e. an existing epidemiological surveillance system representative of all GPs in Belgium, covering 1.75% of the total Belgian population. All GPs were asked to report weekly, on a standardized registration form, every patient (>1 year) in their practice who had died, and to identify patients who had died "non-suddenly." The last three months of these patients' lives were surveyed retrospectively. Several quality control measures were used to ensure data of high scientific quality.</p> <p>Discussion</p> <p>In 2005 and 2006, respectively 1385 and 1305 deaths were identified of which 66% and 63% died non-suddenly. The first results are expected in 2007. Via this study, we will build a descriptive epidemiological database on end-of-life care provision in Belgium, which might serve as baseline measurement to monitor end-of-life care over time. The study will inform medical practice as well as healthcare authorities in setting up an end-of-life care policy. We publish the protocol here to inform others, in particular countries with analogue GP surveillance networks, on the possibilities of performing end-of-life care research. A preliminary analysis of the possible strengths, weaknesses and opportunities of our research is outlined.</p

Study protocol of KLIMOP: a cohort study on the wellbeing of older cancer patients in Belgium and the Netherlands

<p>Abstract</p> <p>Background</p> <p>Cancer is mainly a disease of older patients. In older cancer patients, additional endpoints such as quality of survival and daily functioning might be considered equally relevant as overall or disease free survival. However, these factors have been understudied using prospective designs focussing on older cancer patients. Therefore, this study will focus on the impact of cancer, ageing, and their interaction on the long-term wellbeing of older cancer patients.</p> <p>Methods/Design</p> <p>This study is an observational cohort study. We aim to recruit 720 cancer patients above 70 years with a new diagnosis of breast, prostate, lung or gastrointestinal cancer and two control groups: one control group of 720 patients above 70 years without a previous diagnosis of cancer and one control group of 720 cancer patients between 50 - 69 years newly diagnosed with breast, prostate, lung or gastrointestinal cancer. Data collection will take place at inclusion, after six months, after one year and every subsequent year until death or end of the study. Data will be collected through personal interviews (consisting of socio-demographic information, general health information, a comprehensive geriatric assessment, quality of life, health locus of control and a loneliness scale), a handgrip test, assessment of medical records, two buccal swabs and a blood sample from cancer patients (at baseline). As an annex study, caregivers of the participants will be recruited as well. Data collection for caregivers will consist of a self-administered questionnaire examining depression, coping, and burden.</p> <p>Discussion</p> <p>This extensive data collection will increase insight on how wellbeing of older cancer patients is affected by cancer (diagnosis and treatment), ageing, and their interaction. Results may provide new insights, which might contribute to the improvement of care for older cancer patients.</p

Inventory of current EU paediatric vision and hearing screening programmes

Background: We examined the diversity in paediatric vision and hearing screening programmes in Europe. Methods: Themes relevant for comparison of screening programmes were derived from literature and used to compile three questionnaires on vision, hearing and public-health screening. Tests used, professions involved, age and frequency of testing seem to influence sensitivity, specificity and costs most. Questionnaires were sent to ophthalmologists, orthoptists, otolaryngologists and audiologists involved in paediatric screening in all EU fullmember, candidate and associate states. Answers were cross-checked. Results: Thirty-nine countries participated; 35 have a vision screening programme, 33 a nation-wide neonatal hearing screening programme. Visual acuity (VA) is measured in 35 countries, in 71% more than once. First measurement of VA varies from three to seven years of age, but is usually before the age of five. At age three and four picture charts, including Lea Hyvarinen are used most, in children over four Tumbling-E and Snellen. As first hearing screening test otoacoustic emission (OAE) is used most in healthy neonates, and auditory brainstem response (ABR) in premature newborns. The majority of hearing testing programmes are staged; children are referred after one to four abnormal tests. Vision screening is performed mostly by paediatricians, ophthalmologists or nurses. Funding is mostly by health insurance or state. Coverage was reported as >95% in half of countries, but reporting was often not first-hand. Conclusion: Largest differences were found in VA charts used (12), professions involved in vision screening (10), number of hearing screening tests before referral (1-4) and funding sources (8)