SEARCH · PubMed Health

Results for “Bayesian analysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources

PubMed2006

Efficacy and safety of endovascular cooling after cardiac arrest: cohort study and Bayesian approach.

BACKGROUND AND PURPOSE: Recently 2 randomized trials in comatose survivors of cardiac arrest documented that therapeutic hypothermia improved neurological recovery. The narrow inclusion criteria resulted in an international recommendation to cool only a restricted group of primary cardiac arrest survivors. In this retrospective cohort study we investigated the efficacy and safety of endovascular cooling in unselected survivors of cardiac arrest. METHODS: Consecutive comatose survivors of cardiac arrest, who were either cooled for 24 hours to 33 degrees C with endovascular cooling or treated with standard postresuscitation therapy, were analyzed. Complication data were obtained by retrospective chart review. RESULTS: Patients in the endovascular cooling group had 2-fold increased odds of survival (67/97 patients versus 466/941 patients; odds ratio 2.28, 95% CI, 1.45 to 3.57; P<0.001). After adjustment for baseline imbalances the odds ratio was 1.96 (95% CI, 1.19 to 3.23; P=0.008). When discounting the observational data in a Bayesian analysis by using a sceptical prior the posterior odds ratio was 1.61 (95% credible interval, 1.06 to 2.44). In the endovascular cooling group, 51/97 patients (53%) survived with favorable neurology as compared with 320/941 (34%) in the control group (odds ratio 2.15, 95% CI, 1.38 to 3.35; P=0.0003; adjusted odds ratio 2.56, 1.57 to 4.17). There was no difference in the rate of complications except for bradycardia. CONCLUSIONS: Endovascular cooling improved survival and short-term neurological recovery compared with standard treatment in comatose adult survivors of cardiac arrest. Temperature control was effective and safe with this device.

Aged↗

PubMed2002

A Bayesian approach to the stereo correspondence problem.

I present a probabilistic approach to the stereo correspondence problem. Rather than trying to find a single solution in which each point in the left retina is assigned a partner in the right retina, all possible matches are considered simultaneously and assigned a probability of being correct. This approach is particularly suitable for stimuli where it is inappropriate to seek a unique partner for each retinal position--for instance, where objects occlude each other, as in Panum's limiting case. The probability assigned to each match is based on a Bayesian analysis previously developed to explain psychophysical data (Read, 2002). This provides a convenient way to incorporate constraints that enable the ill-posed correspondence problem to be solved. The resulting model behaves plausibly for a variety of different stimuli.

Bayes Theorem↗

PubMed1986

The dead space to tidal volume ratio in the diagnosis of pulmonary embolism.

In order to assess the value of the measurement of the physiologic dead space (VD) to tidal volume (VT) ratio in pulmonary embolism (PE), a prospective study was performed in hospital inpatients suspected to have PE (n = 110; mean age +/- SD, 52.2 +/- 15.5 yr). In 16 of 29 patients in whom the diagnosis of PE was excluded on the basis of a normal radioisotope perfusion scan and/or normal pulmonary angiogram, VD/VT was less than 40%; in the other 13 patients, a VD/VT greater than 40% was associated with an abnormal spirogram. In all patients in whom PE was angiographically diagnosed (n = 16), VD/VT was greater than 40%. In the remaining 65 patients, a high probability of PE was rarely (6%) associated with a normal VD/VT, whereas in patients with a low probability of PE, 71% had normal VD/VT values. These data indicate that a VD/VT value of less than 40% makes the diagnosis of PE extremely unlikely, whereas VD/VT value greater than 40% in the presence of a normal spirogram is highly suggestive of PE. The diagnostic sensitivity of a VD/VT greater than 0.4 with a normal spirogram as a positive test of PE, and a VD/VT less than 0.4 excluding the diagnosis of PE was 100%, whereas the specificity was 94%; applying Bayesian analysis, the probability of a correct diagnosis of PE using these criteria in a similar population would be 90.5%, and of excluding PE, 96.7%. Thus, as a diagnostic test in PE, VD/VT measurement is comparable, in terms of sensitivity and specificity, to radioisotope lung scanning.

Adult↗

PubMed1987

Human recombinant erythropoietin promotes differentiation of murine megakaryocytes in vitro.

To determine if erythropoietin affects megakaryocytopoiesis, we measured acetylcholinesterase (AchE) activity, a marker of the murine megakaryocytic lineage, after the addition of human recombinant erythropoietin to serumless murine bone marrow cultures. Erythropoietin increased AchE activity substantially. Moreover, when the hormone was added to serumless cultures of 426 isolated single megakaryocytes derived from megakaryocytic colonies, erythropoietin induced a significant increase in the diameters of these cells. From a Bayesian analysis of the likelihood that some megakaryocytes increased in DNA content during the culture period, we estimate that 61% of the cells increased in ploidy. These data indicate that the action of erythropoietin is not restricted to the erythroid lineage.

Acetylcholinesterase↗

PubMedDate not supplied

Medical decision making with incomplete evidence--choosing a platelet glycoprotein IIbIIIa receptor inhibitor for percutaneous coronary interventions.

BACKGROUND: Medical decision making must often be performed despite incomplete evidence. An example is the choice of a glycoprotein IIb/IIIa (GP2b3a) inhibitor, a class of potent antiplatelet medications, as adjunctive therapy during percutaneous coronary interventions (PCIs). GP2b3a inhibitor efficacy in reducing adverse outcomes has been well documented with multiple placebo-controlled randomized trials, but there is a paucity of comparative data about their individual equivalency. Substantial cost differentials are also present between the drugs. METHODS: A systematic review of the literature was performed to identify all randomized placebo-controlled trials of GP2b3a inhibitors as adjunctive therapy for PCI. Three complimentary methods were used to assist in decision making regarding drug equivalency. First, the data from the single direct comparative trial are analyzed from a Bayesian perspective. Next, prior information from other GP2b3a inhibitor trials in similar but not identical patient populations is incorporated. In the 3rd method, indirect comparisons of GP2b3a inhibitors are carried out using a hierarchical meta-analytic model of the placebo-controlled trials identified by the systematic review. RESULTS: A total of 12 randomized trials were identified involving 3 agents (abciximab, eptifibatide, tirofiban), but only 1 involved a direct comparison of 2 drugs (abciximab v. tirofiban). In contradiction to the original publication, the authors' Bayesian analysis both without (method 1) and with (method 2) the inclusion of some prior information suggests a reasonable probability of equivalency. The indirect comparisons from all randomized placebo-controlled trials (method 3) also failed to provide support for superiority of any agent over the others. CONCLUSION: Decision making with incomplete evidence is a difficult but frequently occurring medical dilemma. The authors propose 3 methods that may elucidate the process and illustrate them in the context of the choice of GP2b3a inhibitor for adjunctive therapy during PCI. Further data may or may not eventually lead to a different conclusion, but based on the evidence available to date, the authors' 3 methods suggest clinical equivalency between GP2b3a inhibitors, in contrast to the initial conclusions from the single comparative randomized trial.

Angioplasty, Balloon, Coronary↗

PubMedDate not supplied

Prediction of individual patient prognosis: value of computer-aided systems.

Physicians take both diagnosis and prognosis into account when allocating treatment. However, by "prognosis" physicians usually imply a somewhat vague impression concerning large groups of patients. One possible task for decision support studies is to design and construct systems that accurately predict individual patient prognoses. The authors constructed and tested such systems in three areas of medicine (inflammatory bowel disease, upper gastrointestinal tract hemorrhage, and acute chest pain). In each area, the individual patient's symptoms were compared with a computer-held database of information via a Bayesian analysis, prior and conditional probabilities being derived from large-scale real-life surveys. Prospective trials designed to test these predictive systems by reference to test series comprising over 4,000 patients indicate that a firm prognostic prediction can generally be made; where made, the accuracy of prediction is over 90%. Ways in which this type of prediction may be of clinical value are discussed.

Adult↗

PubMedDate not supplied

Intermediate, indeterminate, and uninterpretable diagnostic test results.

Diagnostic tests do not always yield positive or negative results; sometimes the results are intermediate, indeterminate, or uninterpretable. No consensus exists for the incorporation of such results into data assessment. Conventional Bayesian analysis leads investigators to either exclude patients with non-positive, non-negative results from their studies or categorize such results into inappropriate cells of the standard four-cell decision matrix. The authors propose a standardized method for reporting results in studies dealing with diagnostic test use and discuss how researchers should expand the four-cell matrix to six cells when non-positive, non-negative results occur. They suggest that the six-cell matrix with new operational definitions of sensitivity, specificity, likelihood ratios, and test yield should be adopted routinely. In addition, they define the different types of non-positive, non-negative results and demonstrate how clinicians can use tree-structured decision analysis from the six-cell matrix. While their method does not solve all problems posed by non-positive, non-negative results, it does suggest a standard method for reporting these results and utilizing all the data in decision making.

Bayes Theorem↗

PubMedDate not supplied

Efficacy and safety of trazodone versus clorazepate in the treatment of HIV-positive subjects with adjustment disorders: a pilot study.

The efficacy of trazodone and clorazepate to relieve anxiety and depressive symptoms in 21 HIV-positive subjects with adjustment disorders was determined in a 28-day single-centre, randomized, double-blind study. Subjects were evaluated using the Hospital Anxiety and Depression Scale, the Revised Symptom Checklist, the European Organization for Research and the Treatment of Cancer Quality of Life Questionnaire, and a binary criterion based on the Clinical Global Impression. The incidence of successful treatment was 80% for trazodone compared with 64% for clorazepate; the sample number was too small to establish a significant difference. Bayesian analysis revealed the probability of making a wrong decision in prescribing trazodone rather than clorazepate reduced from 35% to 18% in this small sample. Clinical evaluations using the different scales suggest some benefit from trazodone, although this was not significant. Safety of both treatments was similar. Trazodone is devoid of the risk of abuse and dependence, and may be a valuable alternative to benzodiazepines for the treatment of HIV-related adjustment disorders.

Adjustment Disorders↗

PubMed1999

Comparative study of the efficacy and safety of trazodone versus clorazepate in the treatment of adjustment disorders in cancer patients: a pilot study.

The efficacy of trazodone (mean once-daily dose 111.5 +/- 36.3 mg) versus clorazepate (mean once-daily dose 17.5 +/- 7.5 mg) to relieve anxious and depressive symptoms in 18 patients undergoing treatment for breast cancer was investigated in a 28-day randomized, double-blind study. Efficacy was evaluated using the Hospital Anxiety and Depression Scale, the Revised Symptom Checklist and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire. A successful response to treatment was achieved in 91% (10/11) of patients who received trazodone and 57% (four of seven) of patients who were administered clorazepate (P = 0.1373). Bayesian analysis revealed that the prior probability of making a wrong decision in prescribing trazodone rather than clorazepate reduced from 26% to 8%. Assessment of the clinical scales suggested a benefit of trazodone compared with clorazepate, although the differences were not significant. Safety of both treatments was similar. Trazodone is devoid of an abuse risk and dependence and, therefore, could be a valuable alternative to clorazepate in the treatment of adjustment disorders in cancer patients.

Adjustment Disorders↗

PubMed2003

What was the cause of Franklin Delano Roosevelt's paralytic illness?

In 1921, when he was 39 years of age, Franklin Delano Roosevelt contracted an illness characterized by: fever; protracted symmetric, ascending paralysis; facial paralysis; bladder and bowel dysfunction; numbness; and dysaesthesia. The symptoms gradually resolved except for paralysis of the lower extremities. The diagnosis at the onset of the illness and thereafter was paralytic poliomyelitis. Yet his age and many features of the illness are more consistent with a diagnosis of Guillain-Barré syndrome, an autoimmune polyneuritis. The likelihoods (posterior probabilities) of poliomyelitis and Guillain-Barré syndrome were investigated by Bayesian analysis. Posterior probabilities were calculated by multiplying the prior probability (disease incidence in Roosevelt's age group) by the symptom probability (likelihood of a symptom occurring in a disease). Six of eight posterior probabilities strongly favoured Guillain-Barré syndrome.

Diagnosis, Differential↗

PubMedDate not supplied

Assessment of heterogeneity of residual variances using changepoint techniques.

Several studies using test-day models show clear heterogeneity of residual variance along lactation. A changepoint technique to account for this heterogeneity is proposed. The data set included 100,744 test-day records of 10,869 Holstein-Friesian cows from northern Spain. A three-stage hierarchical model using the Wood lactation function was employed. Two unknown changepoints at times T1 and T2, (0<T1<T2<tmax), with continuity of residual variance at these points, were assumed. Also, a nonlinear relationship between residual variance and the number of days of milking t was postulated. The residual variance at a time t (sigma2(et)) in the lactation phase i was modeled as: sigma2(et) = t(lambda)(i)sigma2(ei) for (i =1,2,3), where lambda(i) is a phase-specific parameter. A Bayesian analysis using Gibbs sampling and the Metropolis-Hastings algorithm for marginalization was implemented. After a burn-in of 20,000 iterations, 40,000 samples were drawn to estimate posterior features. The posterior modes of T1, T2, lambda1, lambda2, lambda3, sigma2(e1), sigma2(e2), sigma2(e3) were 53.2 and 248.2 days; 0.575, -0.406, 0.797 and 0.702, 34.63 and 0.0455 kg2, respectively. The residual variance predicted using these point estimates were 2.64, 6.88, 3.59 and 4.35 kg2 at days of milking 10, 53, 248 and 305, respectively. This technique requires less restrictive assumptions and the model has fewer parameters than other methods proposed to account for the heterogeneity of residual variance during lactation.

Journal Article↗

PubMedDate not supplied

Bayes factors for detection of quantitative trait loci.

A fundamental issue in quantitative trait locus (QTL) mapping is to determine the plausibility of the presence of a QTL at a given genome location. Bayesian analysis offers an attractive way of testing alternative models (here, QTL vs. no-QTL) via the Bayes factor. There have been several numerical approaches to computing the Bayes factor, mostly based on Markov Chain Monte Carlo (MCMC), but these strategies are subject to numerical or stability problems. We propose a simple and stable approach to calculating the Bayes factor between nested models. The procedure is based on a reparameterization of a variance component model in terms of intra-class correlation. The Bayes factor can then be easily calculated from the output of a MCMC scheme by averaging conditional densities at the null intra-class correlation. We studied the performance of the method using simulation. We applied this approach to QTL analysis in an outbred population. We also compared it with the Likelihood Ratio Test and we analyzed its stability. Simulation results were very similar to the simulated parameters. The posterior probability of the QTL model increases as the QTL effect does. The location of the QTL was also correctly obtained. The use of meta-analysis is suggested from the properties of the Bayes factor.

Algorithms↗

PubMedDate not supplied

Genetic parameters of a random regression model for daily feed intake of performance tested French Landrace and Large White growing pigs.

Daily feed intake data of 1 279 French Landrace (FL, 1 039 boars and 240 castrates) and 2 417 Large White (LW, 2 032 boars and 385 castrates) growing pigs were recorded with electronic feed dispensers in three French central testing stations from 1992-1994. Male (35 to 95 kg live body weight) or castrated (100 kg live body weight) group housed, ad libitum fed pigs were performance tested. A quadratic polynomial in days on test with fixed regressions for sex and batch, random regressions for additive genetic, pen, litter and individual permanent environmental effects was used, with two different models for the residual variance: constant in model 1 and modelled with a quadratic polynomial depending on the day on test d(m) as follows in model 2: sigma(epsilon(m))(2) = exp (gamma(0) + gamma(1) d(m) + gamma(2) d(m)(2)). Variance components were estimated from weekly means of daily feed intake by means of a Bayesian analysis using Gibbs sampling. Posterior means of (co)variances were calculated using 800 000 samples from four chains (200 000 each). Heritability estimates of regression coefficients were 0.30 (FL model 1), 0.21 (FL model 2), 0.14 (LW1) and 0.14 (LW2) for the intercept, 0.04 (FL1), 0.04 (FL2), 0.11 (LW1) and 0.06 (LW2) for the linear, 0.03 (FL1), 0.04 (FL2) 0.11 (LW1) and 0.06 (LW2) for the quadratic term. Heritability estimates for weekly means of daily feed intake were the lowest in week 4 (FL1: 0.11, FL2: 0.11) and week 1 (LW1: 0.09, LW2: 0.10), and the highest in week 11 (FL1: 0.25, FL2: 0.24) and week 8 (LW1: 0.19, LW2: 0.18), respectively. Genetic eigenfunctions revealed that altering the shape of the feed intake curve by selection is difficult.

Analysis of Variance↗

PubMedDate not supplied

Multiple trait model combining random regressions for daily feed intake with single measured performance traits of growing pigs.

A random regression model for daily feed intake and a conventional multiple trait animal model for the four traits average daily gain on test (ADG), feed conversion ratio (FCR), carcass lean content and meat quality index were combined to analyse data from 1449 castrated male Large White pigs performance tested in two French central testing stations in 1997. Group housed pigs fed ad libitum with electronic feed dispensers were tested from 35 to 100 kg live body weight. A quadratic polynomial in days on test was used as a regression function for weekly means of daily feed intake and to describe its residual variance. The same fixed (batch) and random (additive genetic, pen and individual permanent environmental) effects were used for regression coefficients of feed intake and single measured traits. Variance components were estimated by means of a Bayesian analysis using Gibbs sampling. Four Gibbs chains were run for 550000 rounds each, from which 50000 rounds were discarded from the burn-in period. Estimates of posterior means of covariance matrices were calculated from the remaining two million samples. Low heritabilities of linear and quadratic regression coefficients and their unfavourable genetic correlations with other performance traits reveal that altering the shape of the feed intake curve by direct or indirect selection is difficult.

Analysis of Variance↗

PubMedDate not supplied

Genetic parameters for litter size in sheep: natural versus hormone-induced oestrus.

The litter size in Suffolk and Texel-sheep was analysed using REML and Bayesian methods. Litters born after hormonal induced oestrus and after natural oestrus were treated as different traits in order to estimate the genetic correlation between the traits. Explanatory variables were the age of the ewe at lambing, period of lambing, a year*flock-effect, a permanent environmental effect associated with the ewe, and the additive genetic effect. The heritability estimates for litter size ranged from 0.06 to 0.13 using REML in bi-variate linear models. Transformation of the estimates to the underlying scale resulted in heritability estimates from 0.12 to 0.17. Posterior means of the heritability of litter size in the Bayesian approach with bi-variate threshold models varied from 0.05 to 0.18. REML estimates of the genetic correlations between the two types of litter size ranged from 0.57 to 0.64 in the Suffolk and from 0.75 to 0.81 in the Texel. The posterior means of the genetic correlation (Bayesian analysis) were 0.40 and 0.44 for the Suffolk and 0.56 and 0.75 for the Texel in the sire and animal model respectively. A bivariate threshold model seems appropriate for the genetic evaluation of prolificacy in the breeds concerned.

Animals↗

PubMed2006

OpWise: operons aid the identification of differentially expressed genes in bacterial microarray experiments.

BACKGROUND: Differentially expressed genes are typically identified by analyzing the variation between replicate measurements. These procedures implicitly assume that there are no systematic errors in the data even though several sources of systematic error are known. RESULTS: OpWise estimates the amount of systematic error in bacterial microarray data by assuming that genes in the same operon have matching expression patterns. OpWise then performs a Bayesian analysis of a linear model to estimate significance. In simulations, OpWise corrects for systematic error and is robust to deviations from its assumptions. In several bacterial data sets, significant amounts of systematic error are present, and replicate-based approaches overstate the confidence of the changers dramatically, while OpWise does not. Finally, OpWise can identify additional changers by assigning genes higher confidence if they are consistent with other genes in the same operon. CONCLUSION: Although microarray data can contain large amounts of systematic error, operons provide an external standard and allow for reasonable estimates of significance. OpWise is available at http://microbesonline.org/OpWise.

Algorithms↗

PubMed2004

A survey of current Bayesian gene mapping methods.

Recently, there has been much interest in the use of Bayesian statistical methods for performing genetic analyses. Many of the computational difficulties previously associated with Bayesian analysis, such as multidimensional integration, can now be easily overcome using modern high-speed computers and Markov chain Monte Carlo (MCMC) methods. Much of this new technology has been used to perform gene mapping, especially through the use of multi-locus linkage disequilibrium techniques. This review attempts to summarise some of the currently available methods and the software available to implement these methods.

Bayes Theorem↗

PubMed2026

Emergence of two novel HIV-1 Circulating Recombinant Forms (CRF190_0708 and CRF191_0708): molecular characterization and clinical insights from a five-year study in Yunnan, China.

BACKGROUND: To characterize HIV-1 molecular epidemiology and identify novel circulating recombinant forms (CRFs) among antiretroviral therapy (ART)-naïve heterosexuals in Yunnan, China, and evaluate their clinical impact. METHODS: This study examined 636 HIV-1 pol sequences to analyze genetic diversity, pretreatment drug resistance (PDR), and transmission networks. Near full-length genomes were obtained to identify and characterize novel recombinants, with their evolutionary history inferred by Bayesian analysis. Co-receptor tropism was predicted, and the five-year clinical outcomes (including immune reconstitution and virologic response) of patients infected with the novel CRFs were compared. RESULTS: The most prevalent type identified was CRF08_BC, accounting for 50.16% of cases. The prevalence of drug resistance was 5.97% (38/636), with the K103N mutation being the most common. An analysis of transmission networks revealed that 52.2% (272/521) of clusters were associated with CRF07_BC and CRF08_BC. Two novel second-generation CRFs were identified: CRF190_0708, with an estimated time to the most recent common ancestor (tMRCA) of 1998.9, and CRF191_0708, with a more recent tMRCA ranging from 2009.5 to 2011.6. During the five-year follow-up period, viral rebound was observed in 7 patients in the CRF190_0708 group and in 1 patient in the CRF191_0708 group. Drug-resistance mutations (M184V and K103N) were detected in a subset of rebound cases in the CRF190_0708 group. CONCLUSIONS: This study identifies two novel HIV-1 recombinants, CRF190_0708 and CRF191_0708, highlighting ongoing viral evolution in Yunnan. Preliminary findings suggest possible clinical differences, warranting further investigation. Continued molecular surveillance is needed. TRIAL REGISTRATION: The clinical study was registered at ClinicalTrials.gov under the identifier NCT03852849. The date of registration was March 22, 2019.

Adult↗