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PubMed1999

Combined use of pulsed and color M-mode Doppler echocardiography for the estimation of pulmonary capillary wedge pressure: an empirical approach based on an analytical relation.

OBJECTIVES: We sought a noninvasive estimation of pulmonary capillary wedge pressure (Pw) by means of the information obtained from transmitral pulsed Doppler and color M-mode Doppler flow propagation velocity (FPV). BACKGROUND: Pulsed Doppler parameters have limited accuracy for the estimation of Pw because they are determined by left atrial pressure and other parameters such as ventricular relaxation. Recently, a good correlation has been found between the rate of ventricular relaxation (tau, tau) and FPV measured by color M-mode Doppler echocardiography. METHODS: We studied 20 patients who underwent invasive hemodynamic monitoring. By multilinear regression analysis, the relationships between Pw and Doppler parameters, FPV, and a noninvasive estimate (P(est)) based on the Weiss' equation (substituting tau for 1/FPV) were determined. A simplified index based on the results obtained was then tested in an additional group of 34 patients. RESULTS: By multiple regression analysis only isovolumic relaxation time (IVRT) (p = 0.0096) and P(est) (p = 0.0043) were related to Pw. A derived empirical index, 10(3)/([2 x IVRT] + FPV), was strongly correlated with Pw in the entire group according to the regression equation Pw = 4.5 x (10(3)/[[2 x IVRT] + FPV]) - 9 (r = 0.89, p < 0.0001, [standard error of the estimate] SEE = 3.3 mm Hg). The sensitivity and specificity for the prediction of Pw > 15 mm Hg were 90% and 100%, respectively. CONCLUSIONS: The combined use of FPV as a surrogate for tau and IVRT permits a close prediction of Pw.

Blood Flow Velocity↗
PubMed2005

An empiric approach to level of care determinations: the importance of executive measures.

BACKGROUND: The ability to predict the level of care received by elderly retirees was compared in a discriminant model and using a classification tree derived from cognitive and noncognitive variables. Methods. Participants were 193 residents (mean age, 79.1+/-5.1 years) of a single, 1,500-bed, continuing care retirement community. They were given a battery of cognitive measures that included tests of general cognition, memory, and executive control function. A multivariate discriminant model of level of care was compared with a classification tree. RESULTS: Residents in congregate high-rises (n=115) differed significantly from those in apartment settings (n=78) with respect to age, Executive Interview (EXIT 25), and the Executive Clock-Drawing Task (CLOX). Only age and executive control function measures (CLOX1, EXIT 25, and Trail Making Test Part B [Trails B]) contributed independently to a discriminant model of level of care (Wilke's lambda=0.92; F [df 4,170]=3.48; p <.01). Sixty-three percent of participants were correctly classified. A classification tree derived from the same variable set was more accurate (75% correctly classified). Age, CLOX1, and EXIT 25 made the most important contributions to the model. The EXIT 25 and CLOX1 thresholds empirically derived from this model coincide with the fifth percentiles for these instruments in a young adult sample. CONCLUSIONS: Executive control function appears to be most responsible for the effect of cognition on level of care. Young adult norms may be most relevant when the effects of cognitive impairment on functional status are assessed.

Activities of Daily Living↗
PubMed2002

Determination of melting temperature for variant detection using dHPLC: a comparison between an empirical approach and DNA melting prediction software.

Detection of DNA sequence variants by the use of denaturing high-performance liquid chromatography (dHPLC) is a relatively new method (Underhill et al., 1997) and has distinct advantages over other methods such as single-strand conformation polymorphism (SSCP), direct sequencing, and DNA chip hybridization. The dHPLC-based single-nucleotide polymorphism (SNP) screening relies on different DNA thermodynamic properties between perfectly matched base pairs in homoduplex molecules and single base-pair mismatches in heteroduplex DNAs. Separation of the two forms of duplex DNAs by dHPLC is based on ionic forces between the negatively charged DNA and the hydrophobic stationary phase, which consists of C(18) chains on PSDVB (polystyrene-divinylbenzene) beads coated with a positively charged ion-pairing agent (TEAA, triethylammonium acetate). Removal of the DNA from the TEAA-coated beads is dependent upon a mobile organic phase, in the form of a linear acetonitrile gradient. The major factor that influences the success of dHPLC to detect sequence variation is the thermal stability of the duplex DNA, which is determined by the melting temperature (TM(50)), where 50% of the DNA strand is single stranded and 50% is double stranded. The TM(50) predicts the best probability of detecting a single base-pair change based on the altered thermodynamics it imparts to the DNA duplex. Generally, there are two ways to determine this melting temperature, either empirically or with the aid of predictive DNA melting analysis software. Such programs include the DNAMelt program located on the Stanford University DNA Sequencing and Technology Center website, MeltCalc (Schutz and von Ahsen 1999), and WAVEMAKER, the proprietary melting analysis software provided with the Transgenomic WAVE dHPLC system. The goal of the current study was to determine whether currently available predictive DNA melting programs could be used to increase efficiency and throughput of SNP detection. A wide range of amplicons, differing in both size and GC composition, were selected for analysis to simulate the broad spectrum of PCR products that may be encountered during a large-scale dHPLC screening project.

Chromatography, High Pressure Liquid↗
PubMed2005

Isofemale lines in Drosophila: an empirical approach to quantitative trait analysis in natural populations.

Founding isofemale lines from wild collected females is a basic tool for investigating the genetic architecture of Drosophila natural populations. The method permits the analysis of quantitative traits under laboratory conditions, with a much broader scope than the mere evidence of a significant genetic heterogeneity among lines. Genetic variability is generally demonstrated by a significant coefficient of intraclass correlation, but several experimental precautions are needed and explained here. The relationship between classical (additive) heritability and intraclass correlation is not straightforward, presumably because the genetic bottlenecks due to the initiation of the lines unravel a significant, nonadditive genetic variance due to dominance and epistatic effects. It is thus suggested to consider intraclass correlation as a specific genetic parameter that enables comparisons between different traits, different populations or different environments. The use of isofemale lines is, however, not restricted to the calculation of an intraclass correlation. It can be used to estimate genetic correlations among traits or environments. The method is also convenient for the analysis of phenotypic plasticity in relation to an environmental gradient. A precise description of the response curves (the reaction norms) is possible, distinguishing trait parameters and plasticity parameters. A fairly general conclusion is that, for a given trait, mean value and plasticity are genetically independent. It is also possible to analyze traits, which, like sexual dimorphism, must be measured on different individuals, and even to demonstrate their genetic variability. In many cases, further empirical and theoretical analyses are possible and needed. It is argued that, in the future, isofemale lines will have an increasing significance among the various techniques appropriate to the analysis of quantitative evolutionary genetics in a diversity of species.

Animals↗
PubMed1975

A theoretical and empirical approach to the study of development.

Developmental psychology, in spite of its dynamic growth, has not, thus far, generated a general theory of human development. Present developmental theories are either cognitive or ontogenetic, or both. All are descriptive. Their powers of explanation are limited. None of them include emotional development. It is argued that a theory of development in order to claim generality must (a) include emotional development, and (b) offer means of explaining, rather than only describing, developmental transformations. A nonontogenetic theory of development, called theory of positive disintegration, appears to fulfill these conditions. It is built on Jacksonian principles of evolution of levels of functioning. The central concept of the theory is that of multilevelness of developmental phenomena. Development is seen to be a function of the level of behavioral organization. The theory defines five levels. Each level constitutes a distinct structure. The dynamic elements of the structure of each level are identified. Positive disintegration is the name for the process by which the structure of a higher level replaces the structure of a lower one. The theory explains different developmental patterns by introducing the concept of developmental potential (DP). Although DP is a purely logical notion, it is given observable dimensions designated as dimensions of mental functioning. There are five of these and they correspond to psychomotor, sensual, imaginational, intellectual, and emotional modes of functioning. The first half of the monograph is devoted to the conceptual structure of the theory. The second half to empirical tests of the theory. Three such tests were made on data generated from an atomistic analysis of autobiographies. The first test consisted of the comparison of developmental cross-sections obtained from different sources of data (subjects) with the overall pattern of five levels of development. The different cross-sections overlap with each other and with different segments of the total theoretical pattern. Superimposed on each other they reconstitute the total pattern. The second test consisted of a comparison between computed and clinically derived values for DP for each subject in the study. The third test was a comparison of DP values obtained from early and late parts of an autobiography. An empirical equation for DP was used in the second and the third test. Parameters represented in the equation appear sufficient to account for individual differences in patterns and levels of development.

Behavior↗
PubMed2005

Suitability of the health and social care resources for persons requiring long-term care in Spain: an empirical approach.

The objective of this paper is to examine the suitability of specific facilities for dependent persons for meeting users' needs. A total of 1265 users of social and health facilities for dependent persons were interviewed in a study carried out in a typical southern European region with a Mediterranean welfare system: the Valencia Autonomous Region in Spain. Data were obtained on users' socio-demographic profile, health, functional dependence, cognition, social support and housing suitability. Based on these data and the institutional definitions of the specific facilities for dependent persons, the suitability index was drawn up for each facility and suitability was evaluated using discriminant analysis. The results give a high suitability index for most of the facilities (between 0.661 for Units for Home Hospitalisation and 1.000 for Units for Psychiatric Hospitalisation). But a significant percentage of patients (17% in Hospitals for Chronically Ill and Long-stay Patients) could be cared for in different facilities to the ones they actually use.

Aged↗
PubMed2006

Plugging space into predator-prey models: an empirical approach.

Extrapolating ecological processes from small-scale experimental systems to scales of natural populations usually entails a considerable increase in spatial heterogeneity, which may affect process rates and, ultimately, population dynamics. We demonstrate how information on the heterogeneity of natural populations can be taken into account when scaling up laboratory-derived process functions, using the technique of moment approximation. We apply moment approximation to a benthic crustacean predator-prey system, where a laboratory-derived functional response is made spatial by including correction terms for the variance in prey density and the covariance between prey and predator densities observed in the field. We also show how moment approximation may be used to incorporate spatial information into a dynamic model of the system. While the nonspatial model predicts stable dynamics, its spatial equivalent also produces bounded fluctuations, in agreement with observed dynamics. A detailed analysis shows that predator-prey covariance, but not prey variance, destabilizes the dynamics. We conclude that second-order moment approximation may provide a useful technique for including spatial information in population models. The main advantage of the method is its conceptual value: by providing explicit estimates of variance and covariance effects, it offers the possibility of understanding how heterogeneity affects ecological processes.

Amphipoda↗
PubMed2003

Do children with myelomeningocele and hydrocephalus display nonverbal learning disabilities? An empirical approach to classification.

As a group, children with myelomeningocele (MM) and early-onset hydrocephalus demonstrate many of the features of the syndrome of nonverbal learning disabilities (NLD). However, the frequency with which individual children display a pattern of neuropsychological functioning consistent with the NLD syndrome is unknown. We addressed this question by comparing the prevalence of NLD in 32 children with MM and shunted hydrocephalus to that in a group of 27 healthy siblings. Participants, who were between 8 and 15 years of age, completed a neuropsychological test battery that included 11 measures of possible assets and 17 measures of possible deficits that define the NLD syndrome. As a group, children with MM and shunted hydrocephalus displayed many of the specific assets and deficits. However, they also displayed significantly more variability in their patterns of assets and deficits than siblings, reflecting the substantial individual differences that characterize children with MM. About 50% of the children with myelomeningocele displayed a pattern of assets and deficits consistent with the NLD syndrome. Classification as NLD was weakly related to cumulative medical risk, as well as to left-handedness. The findings suggest a need for caution in making generalizations regarding the applicability of the NLD model to children with MM and early-onset hydrocephalus.

Adolescent↗
PubMed2004

Obesity and unhealthy life-years in adult Finns: an empirical approach.

BACKGROUND: Obesity is more strongly related to morbidity and disability than to mortality. Obese individuals are thus expected to have more unhealthy life-years than normal-weight persons. The objective of the present study was to quantify the number of excess unhealthy life-years in obese individuals. METHODS: A representative cohort of 19 518 Finnish men and women aged 20 to 92 years was followed for 15 years. Participation rate was 83%. Obesity was defined as a body mass index of 30.0 or higher. The number of unhealthy life-years due to premature work disability, hospitalization for coronary heart disease, and need for long-term medication was calculated per category of body mass index. RESULTS: During the follow-up of 15 years, obese men who never smoked aged 20 to 64 years had, on average, 0.63 more years of work disability, 0.36 more years of coronary heart disease, and 1.68 more years of longterm medication use, than normal-weight counterparts. Obese women had, respectively, 0.52, 0.46, and 1.49 more years from these conditions than normal weight women. The excess risks of morbidity and disability due to obesity were highest in the youngest age groups and exceeded those of mortality in all age groups. Obese men and women 65 years and older who never smoked had, respectively, 1.71 and 1.41 excess unhealthy life-years (not statistically significant) due to premature need for long-term medication compared with normal-weight subjects, but no excess unhealthy life-years due to coronary heart disease. CONCLUSIONS: Obesity has a lifetime impact on disability and morbidity. A further increase in obesity will lead to an increase in unhealthy life-years and in direct and indirect health care costs.

Adult↗
PubMed1990

An empirical approach to classification and treatment planning for psychiatric inpatients.

Treatment efforts for psychiatric patients traditionally are organized according to diagnosis, length of stay, age, and level of management difficulty. The current study, prompted by an attempt to reorganize services for 178 patients at a regional psychiatric hospital, examined the incidence of 72 problems exhibited either in the community prior to admission or within the institution. Factor and cluster analyses were used to identify clinically important subgroups of patients. Implications of the results for institutional organization also are discussed.

Activities of Daily Living↗
PubMed1994

Assessment of predictive models for binary outcomes: an empirical approach using operative death from cardiac surgery.

Predictive models in medical research have gained popularity among physicians as an important tool in medical decision making. Eight methodological strategies for creating predictive models are compared in a large, complex data base consisting of preoperative risk and operative outcome data on 12,712 patients undergoing coronary artery bypass grafting and entered into the Department of Veterans Affairs Cardiac Surgery Risk Assessment Program between April 1987 and March 1990. The models under consideration were developed to predict operative death (any death within 30 days following the surgical procedure or later if the result of a perioperative complication). The two strategies with the best predictive power among the eight examined were stepwise logistic regression alone and data reduction by cluster analysis combined with clinical judgement followed by a logistic regression model. The additive model based on unadjusted relative risks, the model based on Bayes' Theorem, and the logistic model using all candidate variables were good alternatives. Whether or not we imputed values did not have a significant impact on the predictive power of the models.

Aged↗
PubMed1980

Bringing the models together: an empirical approach to combining variables used to explain health actions.

Considerable confusion has existed among researchers with regard to the selection of a particular model of health behavior for study, and many investigators have long felt that the actual number of truly distinct concepts relevant to explaining health-related actions is considerably lower than the large number of variables currently employed. This paper explores selected approaches and models which have been advanced to explain health actions, in terms of structural similarities and differences identified by a panel of judges who are the relevant experts in this field. Judges were asked to partition a set of 109 variables, representing 14 different models, into 12-14 groups on the basis of similarity. The structural similarities among the variable groups were evaluated using Smallest Space Analysis. Six interpretable factors emerged from the analyses: (1) accessibility to health care, (2) evaluation of health care, (3) perception of symptoms and threat of disease, (4) social network characteristics, (5) knowledge about disease, and (6) demographic characteristics. The results of the study provide a first step in developing a unified framework for explaining health actions.

Attitude to Health↗
PubMed1998

Patient education and diabetes research: a failure! Going beyond the empirical approaches.

A literature review of 37 papers cited by MEDLINE between 1986 and April 1996 under the terms "diabetes", "patient education" and "randomized" was carried out. The articles were analysed on the basis of a check list (Educational Procedure Check List), which contains 27 items grouped into 8 areas: study objectives, educational objectives, population, educational strategy, content, evaluation, outcome, final results. The results of our study show that authors do not describe the educational interventions that they have used; thus, we suggest that editors request randomized trial studies containing information on identification of patients' needs, elaboration of learning objectives, and planning and running of the program and the evaluation system used.

Diabetes Mellitus↗