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At least 109 records · Page 6Linked to original sources
PubMed1993

The infectious risks of transfusions in the United States: a decision-analytic approach.

INTRODUCTION: The development of AIDS as a result of HIV transmission and of cirrhosis as a result of chronic non-A, non-B hepatitis are the greatest infectious risks associated with transfusion in the United States. The goal of this study is to provide explicit quantitative guidelines to determine when the risk of death from all causes associated with transfusion exceeds the risk associated with anemia. METHODS: This study uses a decision-analytic model. RESULTS: On the basis of reported transfusion complication rates and an independent worst-case calculation of the risk of AIDS and non-A, non-B hepatitis, transfusion with red blood cells should be recommended as long as each unit received reduces the patient's risk of dying from anemia by at least 1/1100. DISCUSSION: Because of the relative safety of the blood supply as a result of universal screening and donor deferral, the overestimation in practice of fatal infectious complications, and the possible underestimation of the risk of anemia, undertransfusion has the potential to be as serious a problem in the United States as is overtransfusion. Although caution should be exercised not to undertransfuse when a patient has an appreciable risk of anemia-associated death, we must be wary not to overtransfuse for temporary relief of morbidity.

Acquired Immunodeficiency Syndrome↗
PubMed1996

The empirical identification of insomnia subtypes: a cluster analytic approach.

Over the past 15 years, there has been considerable debate concerning the extent to which insomnia patients can be classified into diagnostic subtypes. Despite this debate, relatively little research has been conducted to empirically determine whether naturally occurring insomnia subtypes might be identified within populations of sleep clinic patients. In the current study we used a hierarchical cluster analysis to empirically identify subtypes among a mixed group of normal sleepers and the insomnia outpatients who presented to our sleep center over the past decade. Using factor-analytically derived composite variables that summarized data obtained from sleep history questionnaires and polysomnographic monitoring, this clustering procedure resulted in the identification of 14 subgroups that varied between four and 34 patients/subjects in size. Subsequently, subgroup mean scores for the composite variables used in the clustering procedure were used to construct profiles for each of the 14 clusters. A multivariate profile analysis, employed to elucidate subgroup differences, showed that these cluster profiles differed in terms of their configural shapes, average elevations, and degrees of interscale differences. Furthermore, both DSM-III-R (American Psychiatric Association) and International Classification of Sleep Disorders (ICSD) insomnia diagnoses, assigned independent of cluster findings, suggested that these subtypes differed significantly in regard to their diagnostic compositions. Nevertheless, a far-from-perfect concordance was observed between such clinically assigned diagnoses and cluster group membership. In fact, many of the empirically identified groups were composed of various DSM-III-R and/or ICSD diagnostic subtypes. These results provided only partial support for current DSM and ICSD insomnia categories. However, our results support the existence of multiple, clinically discrete insomnia subtypes and provide information that may be useful in future revisions of current insomnia nosologies.

Adult↗
PubMed1999

Analytic approach to the critical density in cellular automata for traffic flow.

The jamming transition in the stochastic traffic cellular automaton of Nagel and Schreckenberg [J. Phys. I 2, 2221 (1992)] is examined. We argue that most features of the transition found in the deterministic limit do not persist in the presence of noise, and suggest instead to define the transition to take place at that critical density rho(c) at which a large initial jam just fails to dissolve. We show that rho(c)=v(J)/(v(J)+v(F)), where v(F) is the velocity of noninteracting vehicles and v(J) is the speed of the dissolution wave moving into the jam. An approximate analytic calculation of v(J) in the framework of a simple renormalization scheme is presented, which explicitly displays the effect of the interaction between vehicles during the acceleration stage of the Nagel-Schreckenberg rules with maximum velocity v(max)>1. The analytic prediction is compared to numerical simulations. We find a remarkable correspondence between the analytic expression for v(J) and a phase diagram obtained numerically by Lübeck et al.

Journal Article↗
PubMed1988

The process of gas exchange in systemic circulation in a hyperbaric environment: an analytical approach.

A mathematical model is proposed to deal with the simultaneous transport of oxygen (O2) and carbon dioxide (CO2) in systemic capillaries and the surrounding tissue in a hyperbaric environment. The transport in the capillary region depends on molecular diffusion (radial as well as axial), the convective effect of the blood, and the saturation of haemoglobin with O2 and CO2. The corresponding equation in the tissue region describes the transport of the species due to radial and axial diffusion in the tissue and consumption of O2 in the metabolic process. The production of CO2 inside the tissue is incorporated through the respiratory quotient. The saturation of blood with O2 and CO2 have been approximated by linear functions to simulate the conditions of the hyperbaric environment. The resulting system of governing equations with the physiologically relevant boundary conditions is solved analytically. The concentration of O2 is shown to decrease from the core of the capillary to the tissue periphery, whereas the concentration of CO2 increases. It is shown that very little of the CO2 is transported radially. The location of the vulnerable point from the point of view of CO2 accumulation is found to be the corner (x = R2, z = L) situated at the periphery of the tissue near the venous end of the capillary. The accumulation of O2 and CO2 in the tissue is discussed in terms of various dimensionless parameters. It is found that the accumulation of CO2 increases whereas that of O2 decreases in the hyperbaric environment. Finally, it is surmised that one of the major causes of discomfort among divers could be excessive accumulation of CO2 in the tissue.

Blood Circulation↗
PubMed2001

Comparative effects of short-term psychodynamic psychotherapy and cognitive-behavioral therapy in depression: a meta-analytic approach.

UNLABELLED: This article reviews the efficacy of short-term psychodynamic psychotherapy (STPP) in depression compared to cognitive-behavioral therapy (CBT) or behavioral therapy (BT). In this review, only studies in which at least 13 therapy sessions were performed have been included, and a sufficient number of patients per group were treated (N > or = 20). With regard to outcome criteria, the results were reviewed for improvements in depressive symptoms, general psychiatric symptoms, and social functioning. Six studies met the inclusion criteria. RESULTS: In 58 of the 60 comparisons (97%) performed in the six studies and their follow-ups, no significant difference could be detected between STPP and CBT/BT concerning the effects in depressive symptoms, general psychiatric symptomatology, and social functioning. Furthermore, STPP and CBT/BT did not differ significantly with regard to the patients that were judged as remitted or improved. According to a meta-analytic procedure described by R. Rosenthal (1991) the studies do not differ significantly with regard to the patients that were judged as remitted or improved after treatment with STPP or CBT/BT. The mean difference between STPP and CBT/BT concerning the number of patients that were judged as remitted or improved corresponds to a small effect size (post-assessment: phi = 0.08, follow-up assessment: phi = 0.12). Thus, STPP and CBT/BT seem to be equally effective methods in the treatment of depression. However, because of the small number of studies which met the inclusion criteria, this result can only be preliminary. Furthermore, it applies only to the specific forms of STPP that were examined in the selected studies and cannot be generalized to other forms of STPP. Further studies are needed to examine the effects of specific forms of STPP in both controlled and naturalistic settings. Furthermore, there are findings indicating that 16-20 sessions of both STPP and CBT/BT are insufficient for most patients to achieve lasting remission. Future studies should address the effects of longer treatments of depression.

Adult↗
PubMed1995

Decision making in nosocomial pneumonia. An analytic approach to the interpretation of quantitative bronchoscopic cultures.

Quantitative cultures of specimens obtained at fiberoptic bronchoscopy have been used to diagnose nosocomial pneumonia in research settings, but their clinical role remains controversial. We reviewed the literature comparing these culture techniques with other accepted methods to diagnose pneumonia in mechanically ventilated patients and extracted data to describe the receiver operator characteristics (ROC) of quantitative cultures of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) samples. Analysis of ROCs reveals that these tests have a discriminating power comparable or superior to that of many widely accepted routinely used tests. Current data do not suggest that either culture technique offers an advantage over the other. Since benefits of antibiotic therapy of pneumonia and risks of treatment of noninfected critically ill patients are not well quantified, universally applicable recommendations for appropriate values to define an abnormal test result cannot logically be made. Multiple decision analytic tools show that values lower than those previously recommended are more appropriate in patients suspected of having pneumonia unless the risk of antibiotic therapy is judged to be extreme. On the basis of these findings, we suggest guidelines for clinicians' interpretation of PSB and BAL quantitative culture results.

Bacteria↗
PubMed1987

Electric and magnetic fields of the brain computed by way of a discrete systems analytical approach: theory and validation.

It is shown how the stationary volume conduction phenomena in the brain, namely the electric and magnetic fields can be described in discrete terms. The volume conductor is sampled in space by introducing a sampling distance corresponding to the uncertainty in the measurements. In this way, a three-dimensional lattice is needed with equidistantly spaced nodes. The electric and magnetic properties of such a lattice are assumed to be equivalent to that of brain and other tissues. The electric and magnetic potential fields are calculated for each node as the output of a linear feedback system which has the impressed currents as the input. By way of the feedback loop the reflection phenomena at the boundaries between media of different conductivity can be taken into account. This discrete formalism has been implemented in a software system. To demonstrate the validity and accuracy of this system a number of analytically tractable problem in volume conduction has been evaluated.

Animals↗
PubMedDate not supplied

An analytical approach to quantify uniformity artifacts for circular and noncircular detector motion in single photon emission computed tomography imaging.

Uniformity artifacts in rotating gamma camera tomography will result if there are errors in the correction factors which are routinely calculated from a static uniformity flood image. The accuracy of the correction factors is a function of the statistics in the collected flood image. Since the factors are applied to each projection view, an error in a correction factor will propagate as a projection error at the same pixel location for each view. For circular detector motion, the error in each projection is reconstructed as a ring whose maximum amplitude varies approximately inversely proportional to the square root of the distance of the projection error from the center of rotation. For noncircular detector motion the artifacts are not rings but are more complicated geometric curves. Simulations show that statistical fluctuations in the reconstructed image will mask the uniformity artifacts provided the correction flood satisfies minimum count requirements. An analytical expression is derived for the percent root-mean-square (% rms) error in the reconstruction and is compared with the percent relative amplitude error (% RAE) of the reconstructed artifacts in order to obtain expressions for uniformity flood counting statistics. For an elliptical source distribution with total counts equal to CT, the uniformity statistics required to reconstruct elliptical disks is inversely proportional to the square root of the area: U greater than or equal to KCT/area 1/2. The constant K depends on the filter function and type of detector motion.

Biophysical Phenomena↗
PubMed2001

An analytical approach to the measurement of equilibrium binding constants: application to EGF binding to EGF receptors in intact cells measured by flow cytometry.

In ligand binding studies, ligand depletion often limits the accuracy of the results obtained. This problem is approached by employing the simple observation that as the concentration of receptor in the assay is reduced, ligand depletion is also reduced. Measuring apparent K(D)'s of a ligand at multiple concentrations of receptor with extrapolation to infinitely low receptor concentration takes ligand depletion into account and, depending on the binding model employed, yields a K(D) within the defined limits of accuracy. We apply this analysis to the binding of epidermal growth factor (EGF) to the EGF receptor expressed in intact 32D cells, using a homogeneous fluorescein-labeled preparation of EGF and measuring binding by flow cytometry. Binding isotherms were carried out at varying cell densities with each isotherm fit to the generally applied model with two independent binding sites. Examination of the variation in the K(D)'s versus cell density yields a high-affinity site that accounts for 18% of the sites and a lower affinity site that accounts for the remainder. However, further examination of these data suggests that while consistent with each individual isotherm, the simple model of two independent binding sites that is generally applied to EGF binding to the EGF receptor is inconsistent with the changes in the apparent K(D)'s seen across varying cell densities.

Animals↗
PubMed1993

Classification of suicidal and nonsuicidal outpatients: a cluster-analytic approach.

The revised Beck Depression Inventory (BDI), Hopelessness Scale (BHS), Anxiety Inventory (BAI), and Scale for Suicide Ideation (SSI) were administered to 1,172 outpatients diagnosed with mixed psychiatric disorders. The SSI then was used to classify the patients into 127 (10.8%) suicide ideators and 1,045 (89.2%) nonideators. Both agglomerative-hierarchical and nonhierarchical cluster analyses then were employed to identify three types of nonideators, who represented anxious depressed, hopeless depressed, and below-average overall symptomatology, and four types of ideators, who reflected hopeless, anxious depressed, severely suicidal, and below-average overall symptomatology. Implications of these classification systems for describing psychopathology were discussed.

Adult↗
PubMed1999

The role of vitamin D in corticosteroid-induced osteoporosis: a meta-analytic approach.

OBJECTIVE: To determine if vitamin D is more effective than no therapy or calcium alone in the management of corticosteroid-induced osteoporosis, and to determine how vitamin D compares with other osteoporosis therapies, e.g., bisphosphonates, calcitonin, or fluoride, for this condition. METHODS: We evaluated all formulations of vitamin D, including its active metabolites and analogs. A systematic search for published and unpublished studies was conducted using MEDLINE (1966-December 1997), bibliographic references, abstracts from proceedings of recent national meetings, and contact with pharmaceutical companies and content experts. We included all randomized controlled trials lasting at least 6 months (and reporting extractable results), of patients receiving oral corticosteroids, that compared vitamin D with either 1) no therapy or calcium alone, or 2) bisphosphonates, calcitonin, or fluoride. The primary outcome measure of interest was change in lumbar spine bone mineral density. RESULTS: We found a moderate beneficial effect of vitamin D plus calcium versus no therapy or calcium alone (9 trials) (effect size 0.60; 95% confidence interval [95% CI] 0.34, 0.85; P < 0.0001). In comparisons of vitamin D with other osteoporosis therapies, bisphosphonates were more effective than vitamin D (6 trials) (effect size 0.57; 95% CI 0.09, 1.05). Calcitonin was similar in efficacy to vitamin D (4 trials) (effect size 0.03; 95% CI -0.39, 0.45). Fluoride was more effective than vitamin D, but there were only 2 trials. CONCLUSION: Vitamin D plus calcium is superior to no therapy or calcium alone in the management of corticosteroid-induced osteoporosis. Vitamin D is less effective than some osteoporosis therapies. Therefore, treatment with vitamin D plus calcium, as a minimum, should be recommended to patients receiving long-term corticosteroids.

Adrenal Cortex Hormones↗
PubMed1995

Analytical approaches relating genetic evolutionary pathways to prognostic factors.

Human solid tumors accumulate multiple genetic abnormalities as they progress to advanced stages. Multiparameter flow cytometry measurements of individual cells within each tumor may be useful in describing the genetic pathways taken by individual tumors during the course of their genetic evolution. In this paper, we analyzed correlated cell-by-cell measurements of cell DNA content, HER-2/neu protein content, and ras protein content obtained by multiparameter flow cytometry studies of primary breast cancers from 92 patients. These laboratory findings were correlated with established clinical prognostic factors for each patient at the time of diagnosis, using a stepwise multiple analysis of variance (MANOVA). The stepwise MANOVA successively splits a group of patients into two mutually exclusive dissimilar groups, selecting the clinical prognostic factor that is most effective in doing so. Using this criterion, formation of the first three groups that were judged most dissimilar on the cytometry parameters was based on the number of positive nodes at the time of diagnosis. We show that ploidy, HER-2/neu protein content, and ras protein content, as measured by multiple parameter flow cytometry, are correlated with nodal status and other known clinical prognostic factors. The cell-by-cell multiparameter data suggest that for some individual tumors there are multiple genetic evolutionary pathways. Multiple genetic evolutionary pathways are also suggested by the MANOVA analysis. Focusing on the identification and analysis of genetic evolutionary pathways within individual tumors and across patients appears to offer a promising approach for defining the prognosis of early cancers.

Aged↗
PubMed1999

Expression of delta F508 cystic fibrosis transmembrane conductance regulator protein and related chloride transport properties in the gallbladder epithelium from cystic fibrosis patients.

Cystic fibrosis transmembrane conductance regulator (CFTR), the cystic fibrosis (CF) gene product, functions as an adenosine 3', 5'-cyclic monophosphate (cAMP)-regulated chloride channel in the apical membrane of biliary epithelial cells, including gallbladder epithelial cells. It has been shown that triangle upF508, the most common CF mutation, impedes CFTR trafficking to the apical surface of epithelial cells. To elucidate the mechanisms of CF biliary disease, we examined structural features, CFTR expression, and chloride transport properties in gallbladder epithelial cells from nine triangle upF508 homozygous liver transplant recipients. Three CF patients had microgallbladders, characterized by severe histological abnormalities. Microgallbladder epithelial cells displayed aberrant immunolocalization of CFTR and of other normally apical proteins in the lateral domain of their plasma membrane and in their cytoplasm. This pattern was mimicked by chronic cholecystitis in non-CF patients. In the 6 remaining CF patients, CFTR was predominantly apical in the gallbladder epithelium, consistent with the detection of a fully glycosylated form by Western blot. In CF as compared with non-CF gallbladder epithelial cells in primary culture, chloride efflux was lower in response to cAMP and tended to be higher in response to exogenous adenosine 5'-triphosphate (ATP). The CF cells exhibited a residual cAMP-dependent chloride secretion that was inversely correlated with ATP-induced chloride secretion, and almost completely blunted in the cells derived from microgallbladders. Our results suggest that epithelial structural alterations aggravate triangle upF508 CFTR mislocalization in the gallbladder epithelium. The associated decrease in residual cAMP-dependent chloride secretion may contribute to biliary damage despite the up-regulation of alternative chloride transport pathways.

Adolescent↗
PubMedDate not supplied

An analytic approach to quantifying pain scores.

Statistical problems in clinical trials frequently involve fitting regression lines when the underlying data are categorical or ordinal response variables. Usually an ad hoc a priori quantification is used to assign values to these ordinal responses. For pain intensity data collected in analgesic trials, the usual approach is to set none equal to 0, mild equal to 1, moderate equal to 2, and severe equal to 3. While this scheme has been generally accepted, on the basis that for similar clinical trials reasonably similar results are obtained by different investigators, concern exists that the distances between pain scores are probably not equal. A method is presented for quantifying categorical responses so that the resulting scores maximize the simultaneous fit of the dose-response regression lines. The optimal scores derived by this technique may then be used in a bioassay analysis to estimate the relative potency of 2 compounds. As illustrative examples, this method was applied to data from 2 clinical trials and the results were compared to the usual method.

Analysis of Variance↗