Stig Kjær Andersen

An algebra of Bayesian belief universes for knowledge based systems

Causal probabilistic networks (CPNs) have proved to be a useful knowledge representation tool for modeling domains where causal relations-in a broad sense-are a natural way of relating domain concepts and where uncertainty is inherited in these relations. The domain is modeled in a CPN by use of a directed graph where the nodes represent concepts in the domain and the arcs represent causal relations. Furthermore, the quantitative relation between a node and its immediate causes is expressed as conditional probabilities. During the last few years, several schemes based on probability theory for incorporating and propagating new information throughout a CPN has emerged. As long as the domain can be modeled by use of a singly connected CPN (i. e., no more than one path between any pair of nodes), the schemes operate directly in the CPN and perform conceptually simple operations in this structure. When it comes to more complicated structures such as multiply connected CPNs (i. e., more than one path is allowed between pairs of nodes), the schemes operate in derived structures where the embedded domain knowledge no longer is as explicit and transparent as in the CPN. Furthermore, the simplicity in the operations is lost also. This report outlines a scheme-the algebra of Bayesian belief universes-for absorbing and propagating evidence in multiply connected CPNs. The scheme provides a secondary structure, a junction tree, and a simple set of algebraic operations between objects in this structure, Collect Evidence and Distribute Evidence. These are the basic tools for making inference in a CPN domain model and yield a calculus as simple as in the case of singly connected CPNs.

Biologic Variation is Important for Interpretation of Thyroid Function Tests

Large variations exist in thyrotropin (TSH) and thyroid hormones in serum. The components of variation include preanalytical, analytical, and biologic variation. This is divided into between- and within-individual variation. The latter consists of circadian and seasonal differences although there are indicators of a genetically determined starting point. The ratio of within- to between-individual variation describes the reliability of population-based reference ranges. This ratio is low for serum TSH, thyroxine (T(4)) and triiodothyronine (T(3)) indicating that laboratory reference ranges are relatively insensitive to aberrations from normality in the individual. Solutions are considered but reducing the analytical variation below the calculated analytical goals of 7%, 5% and 12% for serum T(3), T(4), and TSH does not improve diagnostic performance. Neither does determination of the individual set-point and reference range. In practice this means that population-based reference ranges are necessary but that it is important to recognize their limitations for use in individuals. Serum TSH responds with amplification to minor alterations in T(4) and T(3). A consistently abnormal TSH probably indicates that T(4) and T(3) are not normal for the individual even when inside the laboratory reference range. This underlines the importance of TSH in diagnosis and monitoring of thyroid dysfunctions. Also, it implies that subclinical thyroid disease may be defined in purely biochemical terms. Under critical circumstances such as pregnancy where normal thyroid function is of importance for fetal brain development, subclinical thyroid disease should be treated. Even TSH within the reference range may be associated with slightly abnormal thyroid function of the individual. The clinical importance of such small abnormalities in thyroid function in small children and pregnant women for brain development remains to be elucidated.

A munin network for the median nerve-a case study on loops

Causal probabilistic networks have proved to be a useful knowledge representation tool for domains having a natural description in terms of causal relations involving uncertainty between domain concepts. This article describes a network modeling diseases affecting the median nerve. The qualitative structure of the model and the quantitative pathophysiological

Global conditioning for probabilistic inference in belief networks

In this paper we propose a new approach to probabilistic inference on belief networks, global conditioning, which is a simple generalization of Pearls (1986b) method of loop-cutset conditioning. We show that global conditioning, as well as loop-cutset conditioning, can be thought of as a special case of the method of Lauritzen and Spiegelhalter (1988) as refined by Jensen et al (1990a; 1990b). Nonetheless, this approach provides new opportunities for parallel processing and, in the case of sequential processing, a tradeoff of time for memory. We also show how a hybrid method (Suermondt and others 1990) combining loop-cutset conditioning with Jensens method can be viewed within our framework. By exploring the relationships between these methods, we develop a unifying framework in which the advantages of each approach can be combined successfully.

Modelling and implementing electronic health records in Denmark

The Danish Health IT strategy [1] points out that integration between electronic health records (EHR) systems has a high priority. A prerequisite for real integration and semantic interoperability is agreement of the data content and the information models. The National Board of Health is working on a common model for EHR, but it is not yet fully developed. At the same time several development and implementation projects are taking place at a regional level. These EHRs are built on information models from different vendors and are based on different integration platforms. The Danish EHR observatory, which has been monitoring the development of EHRs in Denmark since 1998, have analysed the challenges of using different information models and integration platforms. This paper also reports new tendencies in modelling and integration platforms globally and how this is reflected in the National development.

Thiocyanate in food and iodine in milk: from domestic animal feeding to improved understanding of cretinism.

Transport of iodine in the mammary gland into breast milk plays a central role in various fields of prevention of thyroid diseases. First, a sufficient content of iodine in the mothers milk is necessary for normal brain development in the breastfed child. This is attained by expression during lactation in the mammary gland of the sodium iodide symporter (NIS), also responsible for iodine transport in the thyroid. Milk iodine content varies with the iodine intake of the mother, and urinary iodine excretion in groups of mothers seems to be a valuable indicator of the iodine status of their breastfed children. Second, iodine in dairy products provides a considerable part of iodine intake in many populations. Thiocyanate from rapeseed feeding of cows decreases milk iodine content, probably by competitive inhibition of NIS in the mammary gland. Alterations in feeding of dairy cows may alter the iodine content of consumer milk, and this may influence the risk of thyroid diseases in the population. Thiocyanate inhibition of iodine transport into milk may also be operative in humans with a high thiocyanate intake. This could further impair iodine status in breastfed children in low-iodine intake areas of the world. It can be speculated that a low-iodine content of mothers milk because of inhibition of NIS in the mammary gland may be one factor of importance for development of myxedematous cretinism.

Screening for overt thyroid disease in early pregnancy may be preferable to searching for small aberrations in thyroid function tests

Thyroid hormones are important regulators of foetal development, and in recent years, there has been much focus on the screening and treatment of pregnant women for even small aberrations in thyroid function tests. We searched PubMed for publications on thyroid function and pregnancy outcomes including child cognition, and included references from the retrieved articles. Both small aberrations in thyroid function tests in early pregnancy and an increase in risk of pregnancy complications may be caused by a functional change in the uteroplacental unit. Thus, the association found in several studies between small thyroid test abnormalities and pregnancy complications may be due to confounding, and thyroid hormone therapy will have no effect. On the other hand, screening of thyroid function in early pregnancy may identify 200–300 women with undiagnosed overt hypothyroidism per 100 000 pregnancies, which is at least five times more than the number of hypothyroid newborns identified by screening. A number of studies indicate that untreated overt thyroid disease in pregnancy may lead to complications. The potential benefit of screening and early therapy is supported by evidence, indicating that even severe maternal hypothyroidism does not lead to neurocognitive deficiencies in the child, if the condition is detected and treated during the first half of pregnancy. Screening and therapy for overt thyroid dysfunction in early pregnancy may be indicated, rather than focusing on identifying and treating small aberrations in thyroid function tests.

Under surveillance, yet looked after: telehomecare as viewed by patients and their spouse/partners

Introduction: In this research project, a group of heart patients were transferred from traditional hospital settings to home hospitalisation across sectors. The project involved patients with heart failure and arrhythmia. Aim: The aim was to understand the experiences and attitudes of patients and their spouses/partners with regard to the application of telehomecare technology as an option within home hospitalisation. Methods: A phenomenological hermeneutic approach was used to collect and interpret the findings and data. A triangulation of data collection techniques was applied using participation observation and qualitative interviews with patients and spouse/partner. Data were analysed from the perspective of the sociology of everyday life. Findings: The impact of home hospitalisation on patients is described according to several themes: security, freedom, increased awareness of own symptoms, being ‘looked after’ but annoyed with their spouse/partner. The patients experience a seamless cross-sector patient care process. The impact on the spouse/partner includes elements of increased responsibility, nervous tension, and invasion of privacy. Conclusion: Patients believe that home hospitalisation speeds up the process of returning to everyday life, both physically and mentally. It is important to be aware of certain anxieties experienced by the patients spouse/partner about home hospitalisation, and these anxieties may also affect the patient.

Development, implementation and diffusion of EHR systems in Denmark

The Danish EHR-Observatory has monitored Danish EHR projects for several years with respect to a number of parameters such as diffusion, diffusion rate, barriers and limitations, and experience gained. The results of the 2002 monitoring reveal that investment in IT is relatively low and the diffusion rate is below the estimated level. The EHR projects gain a lot of valuable experience, but the coordination of evaluation results should be improved.

Clustering clinical models from local electronic health records based on semantic similarity

BACKGROUND Clinical models in electronic health records are typically expressed as templates which support the multiple clinical workflows in which the system is used. The templates are often designed using local rather than standard information models and terminology, which hinders semantic interoperability. Semantic challenges can be solved by harmonizing and standardizing clinical models. However, methods supporting harmonization based on existing clinical models are lacking. One approach is to explore semantic similarity estimation as a basis of an analytical framework. Therefore, the aim of this study is to develop and apply methods for intrinsic similarity-estimation based analysis that can compare and give an overview of multiple clinical models. METHOD For a similarity estimate to be intrinsic it should be based on an established ontology, for which SNOMED CT was chosen. In this study, Lin similarity estimates and Sokal and Sneath similarity estimates were used together with two aggregation techniques (average and best-match-average respectively) resulting in a total of four methods. The similarity estimations are used to hierarchically cluster templates. The test material consists of templates from Danish and Swedish EHR systems. The test material was used to evaluate how the four different methods perform. RESULT AND DISCUSSION The best-match-average aggregation technique performed better in terms of clustering similar templates than the average aggregation technique. No difference could be seen in terms of the choice of similarity estimate in this study, but the finding may be different for other datasets. The dendrograms resulting from the hierarchical clustering gave an overview of the templates and a basis of further analysis. CONCLUSION Hierarchical clustering of templates based on SNOMED CT and semantic similarity estimation with best-match-average aggregation technique can be used for comparison and summarization of multiple templates. Consequently, it can provide a valuable tool for harmonization and standardization of clinical models.