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PubMed1976

Hospital prognosis of myocardial infarction with respect to risk factors.

Out of 9922 patients with ischaemic heart disease [IHD] hospitalized during a decade, clinico-pathological data of 796 patients with acute myocardial infarction [MI] were analyzed in detail. With the aid of a logico-probabilistic model, the author made an attempt to quantify the individual risks of the hospital prognosis of MI and to obtain the so-called cumulative risk of MI. The prognostic relevances of the characters investigated were tested by Bayes' theorem. By reducing the matrix "character-disease", the original number of 201 characters was reduced to 34, which were divided into five classes, as follows: a] anamnestic data about the occurrence of risk factors, b] data on coronary pains, c] objective clinical, electrocardiographic, or roentgenological findings, d] duration of the praehospitalization phase, e] patient's sex and age. The cumulative risk [sum of partial risks] amounted to 60% and less in MI with a favourable hospital prognosis [that is, at lethality lesser than 5%]; to 61%--100% with a medium fair hospital prognosis [at lethality from 6% to 30%], and to more than 101% with a poor hospital prognosis [at lethality of 41% and higher]. A comparative test of the prognostic index, performed in a different referral area, showed a relatively good practical usability of the criteria described.

Acute Disease↗
PubMed1999

How specific should immunological memory be?

Protection against infection hinges on a close interplay between the innate immune system and the adaptive immune system. Depending on the type and context of a pathogen, the innate system instructs the adaptive immune system to induce an appropriate immune response. Here, we hypothesize that the adaptive immune system stores these instructions by changing from a naive to an appropriate memory phenotype. In a secondary immune reaction, memory lymphocytes adhere to their instructed phenotype. Because cross-reactions with unrelated Ags can be detrimental, such a qualitative form of memory requires a sufficient degree of specificity of the adaptive immune system. For example, lymphocytes instructed to clear a particular pathogen may cause autoimmunity when cross-reacting with ignored self molecules. Alternatively, memory cells may induce an immune response of the wrong mode when cross-reacting with subsequent pathogens. To maximize the likelihood of responding to a wide variety of pathogens, it is also required that the immune system be sufficiently cross-reactive. By means of a probabilistic model, we show that these conflicting requirements are met optimally by a highly specific memory lymphocyte repertoire. This explains why the lymphocyte system that was built on a preserved functional innate immune system has such a high degree of specificity. Our analysis suggests that 1) memory lymphocytes should be more specific than naive lymphocytes and 2) species with small lymphocyte repertoires should be more vulnerable to both infection and autoimmune diseases.

Animals↗
PubMed1999

Tyrosinase inactivation in organic solvents.

The inactivation of the catecholase activity of mushroom tyrosinase was investigated under nonaqueous conditions. The enzyme was immobilized on glass beads, and assays were conducted in chloroform, toluene, amyl acetate, isopropyl ether, and butanol. The reaction components were pre-equilibrated for 2 weeks with a saturated salt solution at a water activity of 0.90. The initial reaction velocity varied between 1.3 x 10(3) mol product/((mol enzyme)(min)) in toluene and 8.7 x 10(3) mol product/((mol enzyme)(min)) in amyl acetate. The turnover number varied between 8.1 x 10(3) mol product/mol enzyme in toluene and 7.2 x 10(4) mol product/mol enzyme in amyl acetate. In each solvent, the tyrosinase reaction inactivation parameters were represented by a probabilistic model. Changes in the probability of inactivation were followed throughout the course of the reaction using a second model which relates the reaction velocity to the amount of product formed. These models reveal that the inactivation rate of tyrosinase decreases as the reaction progresses, and that the inactivation kinetics are independent of the quinone concentration in toluene, chloroform, butanol, and amyl acetate. Significant effects of quinone concentration were, however, observed in isopropyl ether. The likelihood of inactivation of the enzyme was found to be greatest toward the beginning of the reaction. In the latter phase of the reaction, inactivation probability was less and tended to remain constant until the completion of the reaction.

Agaricales↗
PubMed2000

A trial to determine the risk of decompression sickness after a 40 feet of sea water for 200 minute no-stop air dive.

BACKGROUND: The USN93 probabilistic model of decompression sickness (DCS) predicts a DCS risk of 3.9% after a 40 ft of seawater (fsw) for 200 min no-stop air dive, although little data is available to evaluate the accuracy of this prediction. Based on an analysis of Navy Safety Center data from diving on U.S. Navy standard air decompression tables, the observed incidence of DCS for this type of dive is 0.11%. Knowing the true incidence of the dive is important for deciding whether or not to adopt proposed probability based decompression procedures for U.S. Navy diving. HYPOTHESIS: The risk of DCS after a 40 fsw for 200 min no-stop air dive is 3.9%. METHODS: We conducted a closed sequential trial to determine the DCS incidence on this dive. RESULTS: Of 30 military divers who completed 91 dives, there were 2 cases of DCS (2.2%, 95% CI: 0.27 7.7%). The study was terminated early after the second DCS case because of the presence of neurological symptoms and signs. CONCLUSIONS: This study demonstrates that the incidence of DCS in a laboratory setting is higher than observed in fleet diving. Use of the 40 fsw for 200 min schedule in a decompression computer is likely to result in DCS incidence 2.5- to 70-fold greater than that observed in U.S. Navy diving using table-based procedures.

Adult↗
PubMed2001

Integrated pest management and allocation of control efforts for vector-borne diseases.

Applications of various control methods were evaluated to determine how to integrate methods so as to minimize the number of human cases of vector-borne diseases. These diseases can be controlled by lowering the number of vector-human contacts (e.g., by pesticide applications or use of repellents), or by lowering the proportion of vectors infected with pathogens (e.g., by lowering or vaccinating reservoir host populations). Control methods should be combined in such a way as to most efficiently lower the probability of human encounter with an infected vector. Simulations using a simple probabilistic model of pathogen transmission suggest that the most efficient way to integrate different control methods is to combine methods that have the same effect (e.g., combine treatments that lower the vector population; or combine treatments that lower pathogen prevalence in vectors). Combining techniques that have different effects (e.g., a technique that lowers vector populations with a technique that lowers pathogen prevalence in vectors) will be less efficient than combining two techniques that both lower vector populations or combining two techniques that both lower pathogen prevalence, costs being the same. Costs of alternative control methods generally differ, so the efficiency of various combinations at lowering human contact with infected vectors should be estimated at available funding levels. Data should be collected from initial trials to improve the effects of subsequent interventions on the number of human cases.

Animals↗
PubMed2001

Purposeful assessment techniques (PAT) applied to an OSCE-based measurement of competencies in a pediatric dentistry curriculum.

Careful measurements of knowledge, attitude, and psychomotor and communication skills are necessary components of testing in a competency-based approach to education in dentistry. In an effort to address these requirements, Baylor College of Dentistry (BCD), Dallas, Texas, has applied Purposeful Assessment Techniques (PAT) to the Objective Structured Clinical Examination (OSCE) currently in use. PAT are those techniques that allow one to work toward development of linear measurement scales that are "person-free" and "item-free." Person-free measurement means that useful data are produced regardless of the group being measured and item-free measurement means that it does not matter which mix of items is completed over the course of an assessment. The Rasch probabilistic model and a guiding definition of Objective Measurement were used in an effort to implement PAT for the BCD OSCE. A Rasch analysis of a BCD-administered OSCE produced an item map that demonstrated the range of difficulty of items by student performance. This item map can be used to determine which items can be repeated on subsequent tests to allow for linear measurement of students' progression through the curriculum. The movement toward PAT described in this paper demonstrates how careful and evolving measurement in dental education can be of great benefit to faculty, staff, students, and the public.

Clinical Competence↗
PubMedDate not supplied

[Financial requirements for health services demands for diabetes and hypertension in Mexico: 2001-2003].

This paper presents the results of a prospective study aimed at identifying financial requirements to provide and finance healthcare services during the period 2001-2003, for high blood pressure and diabetes, the two main chronic diseases demanding healthcare services in Mexico. The study population was drawn from Mexico's three main healthcare institutions: The Ministry of Health (SSA); the Mexican Institute of Social Security (IMSS); and the Institute for Social Security and Services for State Workers (ISSSTE). The costing method was based on instrumentation and consensus techniques per average case management. Six Box-Jenkins probabilistic models were constructed to estimate the epidemiologic change for the period 2001-2003. Study findings suggest that if risk factors and healthcare provision models remain unchanged, the financial consequences would have a greater impact on the Ministry of Health, followed by IMSS and ISSSTE. Financial requirements for both diseases will account for nearly 2% of the total budget allocated to the uninsured, and 3.5% for the insured population. Indirect costs showed a similar trend in the three institutions, representing nearly 23% above total direct costs.

Ambulatory Care↗
PubMedDate not supplied

[Analysis of probabilistic characteristics of brain biopotentials in healthy humans using electronic computer technology].

Results are given of determination by means of a Minsk-22 electronic computer of the probabilistic characteristics and correlation coefficients for some parameters of the background EEG (frontal-occipital records) in a group of healthy subjects. The parameters studied (the number and amplitude of alpha- and other waves) are subject to the normal law of distribution of random values. A probabilistic model of background EEG has been plotted. Correlations between the factors of the statistic model of background EEG have been studied. The results presented in the paper may prove useful in studying the EEG characteristics and the functional state of the brain.

Brain↗
PubMed1991

Probabilistic analysis of fertility and fecundity: an application to Tombia in Rivers State of Nigeria.

"This paper discusses fertility and fecundity from a probablistic point of view, using Tombia [Nigeria] as a case study. The fertility distribution in Tombia, fertility beyond a given time, infertility rate, measures of central tendencies and dispersion of the fertility distribution in Tombia, prediction of age at menopause in Tombia and projection of fertility beyond a given time are discussed. The emphasis is on the discussion and interpretation of the results obtained in the probabilistic models developed therein."

Africa↗
PubMed2002

Diving methods and decompression sickness incidence of Miskito Indian underwater harvesters.

Diving conditions, dive profiles, and symptoms of decompression sickness (DCS) in a group of Miskito Indian underwater seafood harvesters are described. Dive profiles for 5 divers were recorded with dive computers, and DCS symptoms were assessed by neurological examination and interview. Divers averaged 10 dives a day over a 7-day period with a mean depth of 67 +/- 7 FSW (306 +/- 123 kPa) and average in-water time of 20.6 +/- 6.3 minutes. Limb pain was reported on 10 occasions during 35 man-days of diving. Symptoms were typically managed with analgesic medication rather than recompression. Indices of the decompression stress were estimated from the recorded profiles using a probabilistic model. We conclude that the dives were outside the limits of standard air decompression tables and that DCS symptoms were common. The high frequency of limb pain suggests the potential for dysbaric bone necrosis for these divers.

Adult↗
PubMed2003

Analysis of bacterial RM-systems through genome-scale analysis and related taxonomy issues.

Recognition sites for type II restriction and modification enzymes in genomes of several bacteria are recognized as semi-palindromic motifs and are avoided at a significant degree. The key idea of contrast word analysis with respect to RMS recognition sites, is that under-represented words are likely to be selected against. Starting from over- or underrepresented words corresponding to RMS recognition sites in specific clades, the specificity of unknown R-M systems can be highlighted. Among the known restriction enzymes, that are described in the REBASE database of restriction and modification systems, many of their recognition sites are still uncharacterized. Eventually, this motivates studies aimed at assessing horizontal transferring events of RMS in micro-organisms through the analysis of word usage biases in well-determined genomic regions. A probabilistic model is built on a first-order Markovian chain. Statistics on the k-neighborhood of a word is carried out to assess the biological significance of a genomic motif. Efficient word counting procedures have been implemented and statistics are used for the assessment of the significance of individual words in large sequences. On the basis of the set of most avoided words, and in accordance to the IUPAC coding standards, suggestions are made regarding potential recognition sequences. In certain cases, a comparison of avoided palindromic words in taxonomically related bacteria shows a pattern of relatedness of their R-M systems. For strengthening this analysis, the primary protein structure of all type II R-M systems known in REBASE have been blasted against the nr-GENBANK database. The combination of these analyses has revealed some interesting examples of possible horizontal transfer events of R-M systems.

Amino Acid Sequence↗
PubMed2003

Fundamental space radiobiology.

The unique feature of the space radiation environment is the dominance of high-energy charged particles (HZE or high LET radiation) emitted by the Sun and galactic sources, or trapped in the Van Allen radiation belts. These charged particles present a significant hazard to space flight crews, and accelerator-based experiments are underway to quantify the health risks due to unavoidable radiation exposure. There are three principal properties of charged particles that distinguish them from conventional radiation, i.e. gamma rays and x-rays. First, they have a defined range in matter rather than an exponential absorption profile. Second, they undergo nuclear reactions to produce secondary particles. Third, and most important, they deposit their energy along well-defined linear paths or tracks rather than diffuse fields. The structured energy deposition pattern interacts on multiple scales with the biological structures of DNA, cells and tissues to produce correlated patterns of damage that evade repair systems. Traditional concepts of dose and its associated normalization parameter, RBE (relative biological effectiveness), break down under experimental scrutiny, and probabilistic models of risk based on the number of particle traversals per cell may be more appropriate. Unique patterns of DNA damage, gene expression, mobilization of repair proteins, activation of cytokines and remodeling of cellular microenvironment are observed following exposure to high LET radiation. At low levels of exposure the communication of bioactive substances from irradiated to unirradiated "bystander" cells can amplify the damage and cause a significant deviation from linearity in dose vs. response relations. Under some circumstances, there is even a multigenerational delay in the expression of radiation-induced genetic damage (genomic instability) which is not strictly dose dependent. These issues and the experimental evidence derived from ground based experiments at particle accelerators are presented along with speculation about how modified inertial conditions might perturb homeostatic responses to radiation to further complicate risk assessment for space flight.

Animals↗
PubMed1992

Expert systems in histopathology. V. DS theory, certainty factors and possibility theory.

Uncertainty management for the evaluation of evidence based on linguistic and conceptual data is taking advantage of developments in the Dempster-Shafer (DS) theory of evidence, possibility theory and fuzzy logic. The DS theory offers the capability to assess the uncertainty of different subsets of assertions in a domain and the way in which uncertainty is affected by accumulating evidence. The DS theory goes beyond probability theory in its ability to represent ignorance about certain aspects of a situation. However, the theory is very sensitive to the numerical assessments provided by users and can lead to intuitively unexpected and even undesirable results. Certainty factors are widely used in various expert systems. Their definition and updating may follow either a probabilistic model or fuzzy set theoretic concept.

Data Interpretation, Statistical↗
PubMed2004

[Monitoring and risk assessment of campylobacter infections].

The aim of a national study of a "Quantitative Risk Assessment of Campylobacter infections and broiler chicken" at the Federal Institute for Risk Assessment is to estimate the chicken meat associated risk of Campylobacteriosis in Germany by using probabilistic models. Furthermore, process parameters (modelling parameters) with the most vital impact on the risk of Campylobacteriosis due to chicken meat have to be elaborated to give recommendations for risk management options in the whole food chain. The outcome of Joint FAO/WHO Expert Consultations on Risk Assessment of Microbiological Hazards in Foods (JEMRA) with respect to Campylobacter spp. in broiler chickens are the baseline for the national approach. In addition, national studies from Canada, Denmark and The Netherlands have to be considered. Typical regional data with respect to the disease, to risk factors in Germany and to the qualitative and quantitative occurrence of Campylobacter in broiler chickens along the "farm-to-fork" continuum have to be collected and validated for elaboration of the four elements of a risk assessment. Data on the prevalence of the agent at different stages of the food chain given in available surveillance systems in Germany are limited with respect to their suitability as incoming parameters for the models. A monitoring programme, as required in the Directive 2003/99/EC on the monitoring of zoonoses and zoonotic agents, as well as coordinated programmes for the official food control authorities, could improve the data baseline for risk assessment studies for instance. To collect all necessary information on the quantitative load of Camylobacter in broiler chickens will go beyond the scope of any existing or future monitoring systems. Results can only be achieved by detailed studies. Beside this, regional data on production and processing of broiler chicken, consumption data and information on the behaviour of consumers in households when preparing broiler chicken products are relevant for assessing the final risk to the consumers. For some questions, especially with respect to the dose-response-relation, internationally used models have to be applied. The national study is embedded in a national epidemiological network of "Foodborne Infections in Germany" which is coordinated by the Robert-Koch-Institute and supported by the Federal Ministry of Education and Research (BMBF).

Animal Husbandry↗
PubMed2005

Marfan syndrome--a diagnostic challenge caused by phenotypic and genetic heterogeneity.

OBJECTIVES: Marfan syndrome (MFS) is an autosomal dominant inherited connective tissue disorder caused by mutations in the fibrillin-1 (FBN1) gene with variable clinical manifestations in the cardiovascular, musculoskeletal and ocular systems. METHODS: Data of moleculor genetic analysis and a catalogue of clinical manifestations including aortic elastic parameters were mined in order to (i) assess aortic abnormality before and during medical treatment, and to (ii) identify novel correlations between the genotype and phenotype of the disease using hierarchical cluster analysis and logistic regression analysis. A score measure describing the similarity between a patient's clinical symptoms and a characteristic phenotype class was introduced. RESULTS: A probabilistic model for monitoring the loss of aortic elasticity was built on merely aortic parameters of 34 patients with classic MFS and 43 control subjects showing a sensitivity of 82% and a specificity of 96%. The clinical phenotypes of 100 individuals with classical or suspected MFS were clustered yielding four different phenotypic expressions. The highest correlation was found between FBN1 missense mutations, which manifested as ectopia lentis, skeletal major and skin minor criteria, and two out of four clustered phenotypes. The probability of the presence of a missense mutation in both phenotype classes is approximately 70%. CONCLUSIONS: Monitoring of aortic elastic properties during medical treatment may serve as additional criterion to indicate elective surgical interventions. Genotype-phenotype correlation may contribute to anticipate the clinical consequences of specific FBN1 mutations more comprehensively and may be helpful to identify MFS patients at risk at on early stage of disease.

Adolescent↗
PubMed2003

Haplotype motifs: an algorithmic approach to locating evolutionarily conserved patterns in haploid sequences.

The promise of plentiful data on common human genetic variations has given hope that we will be able to uncover genetic factors behind common diseases that have proven difficult to locate by prior methods. Much recent interest in this problem has focused on using haplotypes (contiguous regions of correlated genetic variations), instead of the isolated variations, in order to reduce the size of the statistical analysis problem. In order to most effectively use such variation data, we will need a better understanding of haplotype structure, including both the general principles underlying haplotype structure in the human population and the specific structures found in particular genetic regions or sub-populations. This paper presents a probabilistic model for analyzing haplotype structure in a population using conserved motifs found in statistically significant sub-populations. It describes the model and computational methods for deriving the predicted motif set and haplotype structure for a population. It further presents results on simulated data, in order to validate the method, and on two real datasets from the literature, in order to illustrate its practical application.

Algorithms↗
PubMed1991

Probabilistic diagnosis using a reformulation of the INTERNIST-1/QMR knowledge base. II. Evaluation of diagnostic performance.

We have developed a probabilistic reformulation of the Quick Medical Reference (QMR) system. In Part I of this two-part series, we described a two-level, multiply connected belief-network representation of the QMR knowledge base and a simulation algorithm to perform probabilistic inference on the reformulated knowledge base. In Part II of this series, we report on an evaluation of the probabilistic QMR, in which we compare the performance of QMR to that of our probabilistic system on cases abstracted from continuing medical education materials from Scientific American Medicine. In addition, we analyze empirically several components of the probabilistic model and simulation algorithm.

Algorithms↗