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Biomedical subjects

J Talmon

Publications and source records attributed to J Talmon.

At least 19 recordsLinked to original sources
PubMed1999

The VATAM guidelines.

Evaluation and assessment of the impact of information and communication technology in medicine is gaining interest. Unfortunately, till now there were no agreed upon approaches. The objective of the VATAM project is to develop guidelines that will assist assessors to set-up and execute studies. This paper describes the background of the VATAM project and provides an account of the current state of the guidelines. It concludes with an indication of the developments that will take place in the short term to further elaborate the guidelines and some considerations for consolidation of VATAM's results.

Databases, Factual↗
PubMed1999

Inventory of validation approaches in selected health telematics projects.

This paper presents the results from an inventory of validation approaches and methodologies which have been used in selected health telematics projects. The inventory was performed in the VATAM Validation of Telematic Applications in Medicine project, HC1115HC. The purpose of the inventory was to analyse the methodologies and their application assumptions in order to identify possibilities for harmonization and consolidation. The inventory was performed using five validation dimensions: IT-development; quality; user; technology assessment and marketing. The inventory results show that possibilities exist to synthesise methodologies and to provide practical guidance and support for projects that are developing health telematics applications. All stakeholders in health telematics projects, i.e. users, health care decision-makers, developers, suppliers and IT-industries, can benefit from practical validation guidelines and support for validation when guidelines are represented in a usable, easy to access and informative way.

Humans↗
PubMed1999

Validating a decision support system for anti-epileptic drug treatment. Part I: initiating anti-epileptic drug treatment.

In this contribution the validation of a prototype decision support system that implements a model of expertise for initiating anti-epileptic drug treatment is described. Since domain experts were of the opinion that prescribing was a rather straightforward process we used only one expert neurologist for knowledge elicitation. To determine the correctness of the system we intended to compare the contents of the system's prescriptions with the majority decision of three neurologists. Because of a large variation in prescribing a majority decision could not be obtained in many cases. Even a Delphi procedure did not yield a majority decision in a large number of cases. Therefore a consensus meeting was organised to discuss cases where discrepancies remained. In the process the participating neurologists formulated prescription guidelines. These guidelines were used as a reference to determine the correctness of the prescriptions of both the system and of the neurologists. The acceptability of all prescriptions for each case was rated by the two neurologists who did not write a prescription for that case. From both comparisons it could be concluded that the system was at least as good in prescribing as individual neurologists.

Adolescent↗
PubMed1999

Validating a decision support system for anti-epileptic drug treatment. Part II: adjusting anti-epileptic drug treatment.

A model of expertise for monitoring antiepileptic drug treatment was implemented in a decision support system. We validated the advice of the system regarding treatment decisions at first follow-up with 265 paper cases based on patient records. The reference for comparison is based on the opinions of neurologists. We found considerable variation among the decisions of five neurologists. It could be shown that the system agreed with (groups of) neurologists at least as often as individual neurologists did. The correctness of the system was consistently higher than that of each of the neurologists, when the majority decision of the remaining neurologists constituted the standard.

Anticonvulsants↗
PubMed1999

Agreement and correctness in adjusting antiepileptic drug treatment: a need for rational drug treatment?

PURPOSE: To study interobserver variation in treatment decisions in a first follow-up contact after initiation of antiepileptic drug (AED) treatment. The results should aid us in the assessment of whether decision support can be of value in this situation. METHODS: Data from patient records were used to construct 270 different test cases containing information about the course of the disease after initiation of drug treatment. The cases were presented to five neurologists from different general hospitals who previously agreed about the diagnosis and the initial treatment for these cases. They were asked to write a prescription for each test case. RESULTS: All five neurologists agreed on a treatment decision in 21.9% of the 265 cases available for analysis. Each neurologist made a decision different from the decisions taken by all other neurologists in 14.0-19.6% of the cases. Kappa values for agreement among individual neurologists as well as for agreement between an individual and the group of his peers were low. In 82.6% of the cases, a majority of the neurologists agreed on a treatment decision. Comparing the decisions of individual neurologists with the majority decision reference (219 cases) showed a significant difference in correctness (range, 67.1-82.6%) among the neurologists. CONCLUSIONS: The fact that a majority decision could be reached in a considerable number of cases, as well as the variability in adjustment of an initiated drug treatment, leads us to the conclusion that decision support can contribute to a rational adjustment of drug treatment.

Ambulatory Care↗
PubMed1998

Benzene exposure in car mechanics and road tanker drivers.

The purpose of this study was to identify professional factors related to benzene exposure and to deduce suitable safety measures. Atmospheric benzene, urinary muconic acid (tt-MA) and leukocyte alkaline phosphatase activity (LAPA) were evaluated among 66 car mechanics, 34 road tanker drivers, and 28 nonexposed workers. Professional and medical questionnaires were filled in at the same time. Atmospheric benzene was significantly higher among road tanker drivers than among car mechanics. The arithmetic mean +/- SD, median, and geometric mean values were, respectively, 0.48 +/- 1.49, 0.14, and 0.06 mg/m3 among car mechanics and 1.88 +/- 4.18, 0.68, and 0.65 mg/m3 among road tanker drivers. In the latter case the increase was caused by transport of unleaded petrol and correlated with the volume of the tank. Among car mechanics, tobacco smoking, windy conditions, dismantling of petrol filters, and handling of petrol increased atmospheric benzene levels. Urinary muconic acid was increased significantly among car mechanics (148 +/- 137, 127, and 111 micrograms/g) and among road tanker drivers (309 +/- 420, 137, and 151 micrograms/g) as compared with the controls (49 +/- 46, 33, and 33 micrograms/g). Among road tanker drivers, alcohol intake and transportation of unleaded petrol increased the excretion of muconic acid, which was also directly related to the volume of the tank. Among car mechanics, professional factors (dismantling of petrol filters, handling of and washing of hands with petrol) and nonprofessional factors (tobacco smoking and damaged skin on the hands and forearms) increased muconic acid excretion. In the control group, tobacco smoking increased its excretion. LAPA was not significantly modified among exposed workers. There was a weak but significant linear correlation between LAPA and muconic acid. These results suggest that to reduce exposure to benzene in unleaded petrol, individual and collective safety measures should be imposed in both occupations.

Air Pollutants, Occupational↗
PubMed1998

Computer-aided test selection and result validation-opportunities and pitfalls.

Dynamic test scheduling is concerned with pre-analytical preprocessing of the individual samples within a clinical laboratory production by means of decision algorithms. The purpose of such scheduling is to provide maximal information with minimal data production (to avoid data pollution and/or to increase cost-efficiency). Our experience shows that there is a practical limit to the extent of exploitation of the principle of dynamic test scheduling, unless it is automated in one way or the other. This paper analyses some issues of concern related to the profession of clinical biochemistry, when implementing such dynamic test scheduling within a Laboratory Information System (and/or an advanced analytical workstation). The challenge is related to 1) generation of appropriately validated decision models, and 2) mastering consequences of analytical imprecision and bias.

Algorithms↗
PubMed1997

VATAM: developing consensus in validation of health telematics applications.

VATAM (Validation of Telematics Applications in Medicine) is an EU supported project in the Health care sector of the Telematics Application Programme. Its objective is to assist other health telematics projects by providing a platform for discussion on validation, eventually resulting in 'guidelines for validation of telematics applications in medicine'. The VATAM work can be subdivided into three phases: the inventory phase (1996) in which information is collected on validation approaches in the Telematics Application Programme, previous efforts and expertise. The dissemination phase (1997) will be used to extend and adapt the framework developed in the inventory phase, through cooperation with other projects The experiences phase (1998) in which the projects are actually applying validation, will be used by VATAM to validate the VATAM methodology. VATAM has finished the inventory phase successfully and is now working on the dissemination phase by--among others--establishing contacts with other projects, and providing information on the inventory through the World Wide Web (URL: http:(/)/www-vatam.unimaas.nl). This paper discusses the approach adopted and the proposed VATAM framework to structure the large variety of validation approaches.

Computer Communication Networks↗
PubMed1995

Framework for quality assessment of knowledge.

One of the key issues in the development (and subsequent application) of medical knowledge-be it in terms of a KBS or otherwise-is the assessment of its quality. We present a framework for how to manage and make measurable the quality of the semantic as well as pragmatic aspects of the knowledge embedded in classification models during the development of such models.

Artificial Intelligence↗
PubMed1994

A methodology for evaluation of knowledge-based systems in medicine.

Evaluation is critical to the development and successful integration of knowledge-based systems into their application environment. This is of particular importance in the medical domain--not only for reasons of safety and correctness, but also to reinforce the users' confidence in these systems. In this paper we describe an iterative, four-phased development evaluation cycle covering the following areas: (i) early prototype development, (ii) validity of the system, (iii) functionality of the system, and (iv) impact of the system.

Artificial Intelligence↗
PubMed1994

Information technology factors in transferability of knowledge based systems in medicine.

The history of knowledge based systems in medicine has been that they are generally very localised, serving a special need in a single setting. Very few have proven to be capable of transfer to a distant environment. With the advent of tele-medical services and the associated transfer of data and knowledge in such services, the ability of medical KBS to transfer will be crucial to the success of tele-medical services. Differences in knowledge acquisition methods, knowledge representation techniques and in the epidemiological composition of training databases may influence viable transfer of knowledge based systems. Through experiments we demonstrate how rule-based systems may impose inflexible demands on data, how different knowledge acquisition techniques acquire different aspects of knowledge, though trained on a common training database, and how different knowledge acquisition techniques show varying degrees of robustness to slight changes in training databases.

Algorithms↗
PubMed1994

Development of ECG criteria to diagnose the number of narrowed coronary arteries in rest angina using new self-learning techniques.

Recently, an evaluation of the value of the resulting electrocardiogram recorded during chest pain for identifying high-risk patients with three-vessel or left main stem coronary artery disease has resulted in the definition of one characteristic pattern: ST-segment depression in leads I, II, and V4-V6 and elevation in lead aVR. This study evaluated the generation of such criteria using two self-learning techniques: neural networks and induction algorithms. In 113 patients, five variables, including the amount of ST elevation, the number of leads with abnormal ST-segments, and this above-mentioned characteristic sign, were correlated with the number of narrowed vessels. All patients were randomly subdivided into a training (n = 63) and test set (n = 50), stratified for both this characteristic sign and for the vessel involved. Using the learning set, the neural network and the induction algorithm were trained separately to identify (1) pure left main stem disease and (2) three-vessel disease and left main stem disease. The neural network was trained for 1,000 runs. The induction algorithm was trained, allowing all variables to be used in any order. The experiments were repeated after adding weight factors to promote the recognition of the more severe cases. Subsequently, the ST elevation in all 12 leads was added to the training and test sets, once with and once without the polarity of the ST deviation. Altogether, 18 different combinations were evaluated. Basically, the neural network and the induction algorithm approach misclassified the same cases in corresponding test combinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1992

Lupus anticoagulant antibodies inhibit collagen-induced adhesion and aggregation of human platelets in vitro.

The effect of circulating lupus anticoagulant on platelet interaction with collagen and other proteins was tested, with the aim of understanding the role of membrane phospholipids in platelet function. Plasma samples from 26 systemic lupus erythematosus (SLE) patients, containing circulating lupus anticoagulant (LAC), were examined for their effect on adhesion and aggregation of normal human platelets. We find that SLE plasma, but not normal plasma, inhibits platelet adhesion to collagen in a concentration-dependent manner. At a plasma concentration of 1% the inhibition was 73 +/- 9% (mean +/- SD). In sharp contrast, there was no effect on platelet adhesion to fibronectin. Purified IgG from the same plasma samples also had an inhibitory effect. At 15 micrograms/ml (comparable in IgG concentration to 0.1% plasma) it inhibited adhesion to collagen by 33 +/- 11%. Inhibition could be abolished by preincubation of the LAC-containing plasma with cardiolipin (CL), phosphatidylinositol (PI), and, to a lesser extent, phosphatidylserine (PS) but not with phosphatidylcholine (PC) or phosphatidylethanolamine (PE). Inhibition could also be abolished by preincubation of the LAC-containing plasma with a 10-fold excess of washed normal platelets. The effect of 1% LAC plasma on platelet aggregation was as striking, showing 79 +/- 26% inhibition of collagen-induced aggregation, and it could also be abolished by preincubation of the LAC plasma with cardiolipin. In contrast, the effect of LAC plasma on thrombin-induced aggregation was rather modest. Our results indicate that antiphospholipid antibodies interfere with platelet adhesion and stimulation by collagen in vitro and point to an important role of external plasma membrane phospholipids, particularly PI, in collagen-induced platelet activation.

Adult↗
PubMed1987

Hydrocortisone inhibits antigen-induced rise in intracellular free calcium concentration and abolishes leukotriene C4 production in leukemic basophils.

Antigenic stimulation of rat basophilic leukemia cells (RBL-3H3) elevates intracellular free Ca2+ concentration ([Ca2+]i) and induces production of leukotriene C4 (LTC4). This model was used to examine the role of Ca2+ in LTC4 formation, and inhibition by hydrocortisone (HC). HC, at a physiological concentration (2 x 10(-7) M), selectively prevented the stimulatory effect of the antigen on LTC4 production whereas the response to calcium ionophore (A23187) remained unimpaired. The inhibition by HC was time-dependent: half maximal response was reached at 2 hour and maximal response at 3 hours. Addition of arachidonic acid (3 micrograms/ml) did not overcome the inhibitory action of HC. An elevated [Ca2+]i is known to be essential for the activation of both 5-lipoxygenase and phospholipase A2. The stimulatory effect of the antigen on LTC4 production was abolished when the cells were incubated in Ca2+-deficient medium. Likewise, calcium ionophore stimulation shows dependence on extracellular Ca2+. Half maximal stimulation by the antigen and calcium ionophore was observed at external Ca2+ concentration of 150 microM and 40 microM respectively. Treatment with HC largely prevented the antigen-induced rise in [Ca2+]i, measured by Quin 2. In addition, HC reduced by 70% the accumulation of 45Ca2+ induced by the antigen. Collectively, these results demonstrate for the first time that HC reduces antigen-induced elevation of [Ca2+]i, and this may be associated with the inhibitory action of HC on LTC4 formation. This property could be partly responsible for the antiallergic and antiinflammatory activities of HC.

Animals↗
PubMed1983

Structural analysis of insulin determinants seen by T cells directed by H-2 genes.

The magnitude of the immune response of lymphocytes to defined antigenic determinants of ungulate insulins is controlled by the products of H-2 genes. Based on the crystallographically solved structure of porcine insulin, the close homology of all the ungulate insulins, and the amino acid substitutions, we built models of the different insulins. We analyzed the likely conformations of the antigenic determinants, and proposed structural specificities accounting for the immunologic phenomena observed.

Animals↗
PubMed1979

Immune response genes have a variable influence on the selection of antigenic foreign and self determinants of insulin.

We studied the proliferative response of mouse T lymphocytes to determinants on ungulate insulins. The immunopotency of defined determinants on the molecule was found to be regulated by three factors: the immune response genes of the immunized mouse, the mode of presentation of insulin on cells or in adjuvant, and the intramolecular cooperativity between different determinants on the insulin molecule. Autosensitization against self determinants was observed under specific conditions. These findings emphasize the variable expression of immune response genes.

Animals↗