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PubMed2003

User-friendly programs for easy calculations in paternity testing and kinship determinations.

Four computer programs are developed for easy calculations of likelihood ratios (LRs) for paternity testing and kinship determinations. The programs are constructed based on the concepts of Bayes Theorem, conditional probability and pedigree analysis. Computer enumeration is used for handling the calculations. The programs have wide applicability, and users can save and check the results easily. The programs employ the distinctive pull-down manual, making them very easy to use. In this paper, we explain the theory and describe various features of the software.

Alleles↗
PubMed1989

Optimal use of literature knowledge to improve the Bayesian diagnosis of coronary artery disease.

Bayes' theorem with the independence assumption is applied to a test sample of 141 subjects, using two sets of test sensitivities and specificities. The first set is derived by averaging over literature reports on the accuracy of the exercise electrocardiogram, exercise thallium scintigraphy, and carciac fluoroscopy. The second set of indices is derived by applying multivariate regression to the technical, population, and methodologic attributes obtained from the same literature by the use of meta-analysis. The meta-analytically corrected sensitivities and specificities resulted in significant improvement in the discriminatory power of the Bayes model. (Area under ROC curve increased, p = less than 0.01). However, the corrected model was not as accurate as a data-derived logistic regression model of the same test variables. Meta-analysis may be useful for modest improvement in the accuracy of literature-derived Bayesian models for predicting disease probabilities.

Adult↗
PubMed2005

Bayesian inference applied to macromolecular structure determination.

The determination of macromolecular structures from experimental data is an ill-posed inverse problem. Nevertheless, conventional techniques to structure determination attempt an inversion of the data by minimization of a target function. This approach leads to problems if the data are sparse, noisy, heterogeneous, or difficult to describe theoretically. We propose here to view biomolecular structure determination as an inference rather than an inversion problem. Probability theory then offers a consistent formalism to solve any structure determination problem: We use Bayes' theorem to derive a probability distribution for the atomic coordinates and all additional unknowns. This distribution represents the complete information contained in the data and can be analyzed numerically by Markov chain Monte Carlo sampling techniques. We apply our method to data obtained from a nuclear magnetic resonance experiment and discuss the estimation of theory parameters.

Bayes Theorem↗
PubMed2004

A breast cancer prediction model incorporating familial and personal risk factors.

Many factors determine a woman's risk of breast cancer. Some of them are genetic and relate to family history, others are based on personal factors such as reproductive history and medical history. While many papers have concentrated on subsets of these risk factors, no papers have incorporated personal risk factors with a detailed genetic analysis. There is a need to combine these factors to provide a better overall determinant of risk. The discovery of the BRCA1 and BRCA2 genes has explained some of the genetic determinants of breast cancer risk, but these genes alone do not explain all of the familial aggregation of breast cancer. We have developed a model incorporating the BRCA genes, a low penetrance gene and personal risk factors. For an individual woman her family history is used in conjuction with Bayes theorem to iteratively produce the likelihood of her carrying any genes predisposing to breast cancer, which in turn affects her likelihood of developing breast cancer. This risk was further refined based on the woman's personal history. The model has been incorporated into a computer program that gives a personalised risk estimate.

Adult↗
PubMed2004

[Diagnosis and early diagnosis of ankylosing spondylitis].

Ankylosing spondylitis (AS) is often diagnosed not before 5-10 years after onset of clinical symptoms. The main reason for this delay is the late appearance of unequivocal radiographic sacroiliitis which is a prerequisite for making the diagnosis. It is important to realize that both the early stage without radiographic sacroiliitis and the late stage with radiographic sacroiliitis are part of the same disease and, therefore, should be considered as a disease continuum. The term axial spondyloarthritis (SpA) appears appropriate to describe this disease continuum. Diagnosing axial SpA without radiographic sacroiliitis, however, is difficult and associated with diagnostic uncertainties since there are no diagnostic criteria available. Considering all SpA features which are relevant for the diagnosis of axial SpA (with and without radiographic sacroiliitis), we have recently proposed a diagnostic algorithm based on calculations using Bayes' theorem to be applied in individual patients. This diagnostic algorithm enables the physician to diagnose or to exclude axial SpA with a high degree of confidence. An early and reliable diagnosis is relevant to both the patient and the physician since an early diagnosis allows the best therapy to be introduced and consequently maintained.

Algorithms↗
PubMed1985

[Risk indicators].

The notion of risk indicator depends on the background of its application. The search for a better understanding of pathological processes implies a rigorous methodology in order to establish a link between the indicator and the risk. Today, the clinician often resorts the Bayes' theorem without taking in account the etiological role of each diagnostic indicator. In the field of public health, the risk indicator is often useful for descriptive or evaluative purposes. Its predictive use implies that it has been built on experimental epidemiological data. In most instances, the use of a multivariate model does not properly solve the problem of the interactions between variables.

Adult↗
PubMed2006

Population pharmacokinetics of higher-dose mizoribine in healthy male volunteers.

The population pharmacokinetic parameters of mizoribine in healthy subjects were estimated using a nonlinear mixed effects model (NONMEM) program. Pharmacokinetic data for population analysis were obtained in the previous study, in which 24 healthy Caucasian male subjects participated in a single-dose (3, 6, 9, 12 mg/kg) study, and 12 subjects participated in a multiple-dose (6, 12 mg/kg/d) study. The mean value of the absorption lag time, absorption rate constant (KA), and apparent distribution volume (V/F) was estimated to be 0.349 h, 0.869 h-1, and 0.834 l/kg, respectively. Oral clearance (CL/F) was modeled with creatinine clearance (CLcr), and the mean value was estimated to be 1.93.CLcr l/h. In addition, pharmacokinetic parameters in individual 36 subjects were obtained from population estimates according to Bayes' theorem. Pharmacokinetic parameters (KA, V/F, and CL/F) in the single-dose study were almost constant at a dose range of 3-12 mg/kg, and were similar to those in the multiple-dose study. These findings indicated that the pharmacokinetics of mizoribine is well described by a simple one-compartment model with first-order absorption.

Adult↗
PubMedDate not supplied

Clinical efficacy of rubella vaccine.

In the period October 10, 1980, to January 19, 1981, 83 cases of rash illness compatible with rubella were reported in Sanford, ME. Twenty-two (27%) were confirmed serologically. Forty cases (48%) occurred in Sanford High School students; the overall attack rate was 3.2%. A case-control study was undertaken to determine the effectiveness of rubella vaccine in preventing clinical rubella. Bayes' theorem was used to calculate the attack rates in the vaccinated population (ARV) and the unvaccinated population (ARU). Vaccine efficacy (VE), calculated with use of the formula VE (%) = [(ARU - ARV)/ARU] x 100, was 90%. These results indicate that rubella vaccine is highly effective in preventing clinical rubella and do not support proposals for routine revaccination.

Adolescent↗
PubMed1999

Graphic representation of sequential Bayesian analysis.

Previously undescribed algebraic transforms of Bayes' theorem define families of operating points in the receiver operating characteristic (ROC) space which, at given pre-test probability, produce constant post-test probabilities. These isopredictive operating points form straight lines in the ROC space. The lines can be used to emulate Bayesian sequential analysis in a strictly graphic procedure, which can be applied in clinical work and medical education.

Bayes Theorem↗
PubMedDate not supplied

Sequential test selection in the analysis of abdominal pain.

Numerous decision-making tools exist to assist physicians in diagnosis management. However, the accuracy of available clinical information is often ambiguous or unknown and current analytical models do not explicitly incorporate judgementally defined information. A model encompassing both physician judgment and probability analysis was developed to accommodate such data. A problem requiring sequential diagnostic testing was structured utilizing the analytic hierarchy process (AHP). The case presented involved a patient complaining of upper abdominal pain who, after initial evaluation, did not need immediate surgery. Physicians were faced with identifying the optimal sequence of diagnostic testing. The criteria used for test selection included minimizing risk, patient discomfort, and cost of testing and maximizing diagnostic capability. Although at the onset the "best" test choice was unknown, the clinical picture indicated four test alternatives: upper gastrointestinal series (GI), abdominal ultrasonography (US), abdominal computed tomography (CT), and upper gastrointestinal endoscopy (END). Based upon the relative preferences of the criteria utilized, the AHP analysis indicated that upper GI series was the optimal first test. Given a negative test, posterior probabilities were calculated using Bayes' theorem, resulting in a new estimate of diagnostic capability. The AHP analysis was reiterated, identifying abdominal ultrasonography as the optimal second test. This analysis may be repeated as many times as necessary. Sensitivity analysis demonstrated that changing criteria preferences may alter the choice of tests and/or their sequence.

Abdominal Pain↗
PubMed1987

Differential diagnosis of genetic disease by DNA restriction fragment length polymorphisms.

DNA restriction fragment length polymorphisms (RFLPs) are used for diagnosis of genetic disease in families known to be affected by specific disorders, but RFLPs can be also useful for the differential diagnosis of hereditary disease. An RFLP pattern represents the inheritance of chromosomal markers in a family, and such a pattern may be compatible with the inheritance of a certain disorder in that family. Probabilities to find such a pattern if the disorder were present and if it were absent can be combined with the prior probabilities of disease considered in the differential diagnosis on the basis of previous clinical and laboratory data. Bayes' theorem is used to calculate the posterior probabilities of the diseases in question. This approach is illustrated in a family suffering from either spinal muscular atrophy (an autosomal recessive disease) or Becker muscular dystrophy (an X-chromosomal disorder). Probabilities to exclude a certain disorder can be calculated in advance, as some RFLP patterns are not compatible with the presence of that disorder.

Bayes Theorem↗
PubMed1986

Estimating the probability of malignancy in solitary pulmonary nodules. A Bayesian approach.

Decisions about managing solitary pulmonary nodules often involve estimates of the likelihood that the nodule is malignant. We used Bayes' theorem to devise a simple scheme for estimating the likelihood that a solitary pulmonary nodule is malignant based on the diameter of the nodule, the patient's age and history of cigarette smoking, and data on the overall prevalence of malignancy in solitary nodules. This method may improve the accuracy of estimating the likelihood of malignancy for individual patients with solitary pulmonary nodules.

Age Factors↗
PubMedDate not supplied

Laboratory tests for total and allergen-specific immunoglobulin E.

The principles of measurement of IgE by enzyme-immunoassay are given. A Bayesian approach is taken for the clinical interpretation of serum total IgE. Application of Bayes' Theorem to serum total IgE can significantly influence the probability of a clinical diagnosis of allergy. There is a correlation between allergen-specific IgE measured by enzyme-immunoassay, by radioallergosorbent test and by skin tests for immediate hypersensitivity. However, there is a need to standardize the reagents used for allergy skin testing, as well as the reagents and methods used for the laboratory measurement of allergen-specific IgE.

Allergens↗
PubMed1996

Calculating risk and outcome: The Society of Thoracic Surgeons database.

Various approaches to the calculation of medical risk are reviewed, including univariate analysis, additive methods, use of Bayes' theorem by The Society of Thoracic Surgeons, logistic regression, and neural networks. Strengths and weaknesses of the various approaches are evaluated. The use and importance of observed/expected ratios, the C statistic, and receiver operating curves are discussed. Specific requirements for the building of useful risk-calculation models are discussed, including the importance of the model set/test set method and the role of both numbers of patients and time frames in model building.

Bayes Theorem↗
PubMed1997

Generalized likelihood ratios for quantitative diagnostic test scores.

The reduction of quantitative diagnostic test scores to the dichotomous case is a wasteful and unnecessary simplification in the era of high-speed computing. Physicians could make better use of the information embedded in quantitative test results if modern generalized curve estimation techniques were applied to the likelihood functions of Bayes' theorem. Hand calculations could be completely avoided and computed graphical summaries provided instead. Graphs showing posttest probability of disease as a function of pretest probability with confidence intervals (POD plots) would enhance acceptance of these techniques if they were immediately available at the computer terminal when test results were retrieved. Such constructs would also provide immediate feedback to physicians when a valueless test had been ordered.

Algorithms↗
PubMed1985

57Co-labelled bleomycin scintigraphy for the detection of lung cancer: a prospective study.

The sensitivity and specificity of scanning with 57Co-labelled bleomycin for the diagnosis of lung cancer were determined from a prospective study involving a large group of patients with an abnormal chest roentgenogram. A semi-quantitative analysis of the scintigram was obtained by defining an index in terms of the excess isotope uptake within the tumour. Malignant pulmonary lesions were found in 121/175 patients and 113 had a positive scan. Benign pulmonary disorders were found in 54 patients, 45 of whom had a negative scan. The sensitivity and specificity were therefore 93% and 83% respectively. Bayes' theorem was then used to determine the predictive value of this test, either positive or negative, when the prevalence of disease varied from 10 to 90%. A receiver operating characteristic curve permits the choice of an appropriate value of the tumour uptake index to minimize the false positive fraction without classifying too many true positives as false negatives.

Adenocarcinoma↗
PubMed1988

Use of the competing-hypotheses heuristic to reduce 'pseudodiagnosticity'.

A quasiexperimental research design involving a nonequivalent control group was used to examine the efficacy of a brief educational intervention in teaching medical students to select optimal diagnostic data consistent with the competing-hypotheses heuristic and Bayes' theorem when solving clinical problems. There was no significant difference between intervention (n = 119) and control (n = 89) groups in performance at baseline, but the intervention group performed significantly better (p less than .001) than the control group after training. The results suggest that some problem-solving skills, such as learning to use the competing-hypotheses heuristic, can be enhanced or learned independent of the acquisition of content knowledge.

Bayes Theorem↗
PubMed1985

Differential diagnosis and the competing-hypotheses heuristic. A practical approach to judgment under uncertainty and Bayesian probability.

Evaluating the same diagnostic information across the plausible competing diagnoses is a practical strategy (ie, heuristic) to guide decision making in the face of uncertainty. The prevalence of use of this competing-hypotheses heuristic by 89 first-year house officers was examined in three simulated patient cases. Results indicated that only a minority (24%) of the house officers selected optimal diagnostic information consistent with this Bayesian heuristic across all three cases. Almost all (97%) of the house officers selecting optimal diagnostic information were able to identify the most probable diagnosis specified by Bayes' theorem, while only a chance number (53%) of house officers selecting nonoptimal information were able to identify the most probable diagnosis. The competing-hypotheses heuristic is discussed within the context of diagnostic problem-solving models derived from the literature on medical decision making and clinicopathological conference case records. It is suggested that the heuristic, which does not necessitate any mathematical calculations, may be useful as a complement to clinical judgment.

Bayes Theorem↗