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PubMed2000

Pretest probability assessment for selective rest sestamibi scans in stable chest pain patients.

The objective of this study was to determine whether pretest probability assessments permit more selective testing of chest pain patients with technetium-99m sestamibi scanning. Pretest probabilities of cardiac ischemia were measured both objectively (Acute Cardiac Ischemia Time-Insensitive Predictive Instrument [ACI-TIPI]) and subjectively (physician's estimate of the probability of unstable angina). Two groups were defined: patients whose postsestamibi scan led to a "downgrade" of the intensity of monitoring and those that resulted in no change in monitoring intensity. Sixty-five patients met study criteria; 25 had a disposition downgrade and 40 had no change. Pretest ACI-TIPI scores were similar in the two groups (29% +/- 18% versus 27% +/- 11%, mean +/- standard deviation; P = .95) as were the physician's assessment of unstable angina (39% +/- 22% versus 40% +/- 24%; P = .75). Objective or subjective pretest probabilities are not significantly different in patients who are likely to have their disposition altered by sestamibi scanning.

Aged↗

PubMed2001

Dual-coil vs single-coil active pectoral implantable defibrillator lead systems: defibrillation energy requirements and probability of defibrillation success at multiples of the defibrillation energy requirements.

AIMS: The aim of the study was to compare the defibrillation energy requirements and the probability of successful defibrillation at multiples of the minimum defibrillation energy requirements in active pectoral implantable defibrillators with single- and dual-coil lead systems. METHODS AND RESULTS: Eighty-three consecutive patients undergoing implantation of an active pectoral cardioverter-defibrillator were randomized to receive a dual- or single-coil lead system. Defibrillators of two manufacturers with a fixed tilt biphasic defibrillation waveform were used. Defibrillation energy requirements were determined using a step-down defibrillation testing protocol. According to the randomization protocol, the patients were assigned to three additional consecutive defibrillation attempts during device implantation and during pre-discharge testing of either 1.0, 1.5 or 2.0 times the determined defibrillation energy requirement. Patients presenting defibrillation energy requirements > 15 J were excluded from analysis. Eighty of 83 patients (96%) completed the study protocol. Three patients were excluded due to elevated defibrillation energy requirements. The defibrillation energy requirements in the dual- and single-coil patient groups were 8.0 +/- 3.6 J and 8.4 +/- 3.7 J (ns), respectively. A comparable percentage of study patients showed defibrillation energy requirements <10 J (dual-coil: 88% vs single-coil: 83%). Defibrillation impedance was significantly different (dual-coil: 50 +/- 5.8 Ohm; single-coil: 39.8 +/- 4.2 Ohm). Regarding the probabilities of successful defibrillation, there were no significant differences between the two patient groups. The probabilities of defibrillation at the three multiples of the defibrillation energy requirement using a dual- and single-coil lead system were 82, 89.7 and 93.6 and 77.8, 94.1 and 95.8%, respectively (P=0.88, P=0.42, P=0.62, respectively). CONCLUSIONS: Dual- and single-coil active pectoral defibrillator systems show no difference in defibrillation energy requirements and no difference in the probability of successful defibrillation at multiples of the minimum defibrillation energy requirement. The use of more simplified defibrillator lead systems may contribute to a future lead design focusing on improvement in lead durability.

Aged↗

PubMed2005

Calculating initial-state-selected reaction probabilities from thermal flux eigenstates: a transition-state-based approach.

An approach for the calculation of initial-state-selected reaction probabilities utilizing a transition-state view and the multiconfigurational time-dependent Hartree approach is presented. Using flux correlation functions, wave packets located in the transition-state region are constructed and propagated into the asymptotic region to obtain initial-state-selected reaction probabilities. A complete set of reaction probabilities is obtained from a single set of thermal flux eigenstates. Concepts previously applied with success to the calculation of k(T) or N(E) are transferred to the calculation of state-selected probabilities. The benchmark H+H(2) (J=0) reaction on the LSTH potential-energy surface is used to test the reliability of this approach.

Journal Article↗

PubMed2006

A full dimensional time-dependent wave packet study for the H4 four-center, collision induced dissociation, and single exchange reactions: reaction probabilities for J=0.

A time-dependent initial state selected wave packet method has been developed to study the H2(v(1)=10-11,j1=0)+H2'(v2=0,j2=0)-->HH'+HH' four-center (4C) reaction, and two other competing reactions: the H2+H2'-->H+H+H2' collision induced dissociation (CID) and the H2+H2'-->H+HH'+H' single exchange (SE) reaction, in full six dimensions. Initial state-specific total reaction probabilities for these three competing reactions are presented for total angular momentum J=0 and the effects of reagent vibration on reactions are examined. It is found that (a) the CID process is the dominant process over the whole energy range considered in this study, but the 4C and SE processes also have non-negligible probabilities; (b) the SE process has a lower threshold energy than the 4C process, but the SE probability increases slower than the 4C probability as collision energy increases; (c) the vibrational excitation of H2(v1) is much more efficient than translational motion for promoting these processes, in particular to the CID process.

Journal Article↗

PubMed2006

Statistical mechanical theory for steady state systems. V. Nonequilibrium probability density.

The phase space probability density for steady heat flow is given. This generalizes the Boltzmann distribution to a nonequilibrium system. The expression includes the nonequilibrium partition function, which is a generating function for statistical averages and which can be related to a nonequilibrium free energy. The probability density is shown to give the Green-Kubo formula in the linear regime. A Monte Carlo algorithm is developed based upon a Metropolis sampling of the probability distribution using an umbrella weight. The nonequilibrium simulation scheme is shown to be much more efficient for the thermal conductivity of a Lennard-Jones fluid than the Green-Kubo equilibrium fluctuation method. The theory for heat flow is generalized to give the generic nonequilibrium probability densities for hydrodynamic transport, for time-dependent mechanical work, and for nonequilibrium quantum statistical mechanics.

Journal Article↗

PubMed2002

Lévy laws in free probability.

This article and its sequel outline recent developments in the theory of infinite divisibility and Lévy processes in free probability, a subject area belonging to noncommutative (or quantum) probability. The present paper discusses the classes of infinitely divisible probability measures in classical and free probability, respectively, via a study of the Bercovici-Pata bijection between these classes.

Journal Article↗

PubMed1981

Immigration and extinction probabilities for individual species: relation to incidence functions and species colonization curves.

We develop a dynamic model of island biogeography based on immigration and extinction probabilities of individual species rather than on the usual biogeographic parameters of the number of species immigrating or going extinct per unit time. In the real world, these probabilities vary enormously among species, and three field studies suggest lognormal distributions. Based on such distributions of individual probabilities, our model proceeds by calculating the conditional probability of species occurrence--the likelihood that a given species will occur on a given island--as a function of total species number on the island. The model succeeds in predicting two observed features of species communities; (i) staggered, sigmoidally-shaped incidence functions ("differing area requirements of different species") and (ii) concave immigration and extinction curves.

Animals↗

PubMed1987

Selecting the highest of three binomial probabilities.

A sequential elimination procedure for selecting the highest probability in binomial trials, proposed by Levin and Robbins [Levin, B. & Robbins, H. (1981) Proc. Natl. Acad. Sci. USA 78, 4663-4666], is examined further in the special case of trials involving three probabilities. A conjectured inequality relating ratios of selection probabilities to odds ratios is shown to hold only under certain necessary and sufficient conditions. Weaker conjectured inequalities involving the probability of correct selection are shown to hold without restriction.

Journal Article↗

PubMed2004

Comparison of patients fulfilling criteria for confirmed and probable human granulocytic ehrlichiosis.

In order to assess the validity of definitions for human granulocytic ehrlichiosis (HGE), epidemiological, clinical and laboratory findings for 13 patients with confirmed HGE and 21 patients fulfilling criteria for probable HGE were compared. The patients were identified during a prospective study on the aetiology of febrile illness occurring after a tick bite, performed in Slovenia from 1995 to 2002. Significant differences between the 2 groups were found for age of patients, duration of fever before the first examination, and several clinical and laboratory parameters including the occurrence of chills, myalgia, arthralgia, leukopenia, thrombocytopenia, abnormal liver function tests results, and elevated concentration of C-reactive protein. All the abnormalities were established more often in patients with confirmed HGE than in those with probable HGE. Patients with confirmed HGE exhibited higher geometric mean titre values and higher peak antibody titres to Anaplasma phagocytophilum that developed later in the course of their illness. The differences indicate that in some patients fulfilling criteria for probable HGE the signs and symptoms most probably are not the result of a recent infection with A. phagocytophilum.

Adult↗

PubMed2005

Prevalence of probable mental disorders among pediatric asthma patients in an inner-city clinic.

OBJECTIVE: To determine the screen-positive prevalence of anxiety disorders and depression among pediatric asthma patients in an inner-city asthma clinic and to investigate the association between probable diagnoses of anxiety disorders and depression and medical service use among inner-city pediatric asthma patients. METHOD: In this pilot study, a consecutive sample of pediatric asthma patients aged 5-11 in the waiting room of an inner-city asthma clinic was screened for mental disorders using the DISC Predictive Scales (DPS), which produces probable DSM-IV diagnoses. In addition, data on health service use for asthma were collected. Statistical analyses were performed to examine the relationship between probable anxiety disorders and depression and health service use for asthma among pediatric asthma patients. RESULTS: Approximately one in four (25.7%) pediatric asthma patients in an inner-city asthma clinic met criteria for a probable diagnosis of current anxiety disorders or depression (past 4-week prevalence). Specifically, childhood separation anxiety disorder was common among 8.1%, panic among 14.9%, generalized anxiety disorder among 4.1%, agoraphobia among 5.4%, and 2.7% had depression. Having more than one anxiety disorder or depression diagnosis was associated with higher levels of inpatient and outpatient medical services, compared with patients who were negative on screening for anxiety or depressive disorders, although differences failed to reach statistical significance. CONCLUSIONS: These findings are the first to provide preliminary evidence suggesting that mental health problems are common among pediatric asthma patients in an inner-city clinic. The results also suggest that mental health problems in pediatric asthma patients may be associated with elevated levels of medical service use for asthma. Replication of this pilot study is needed with a larger sample, more precise diagnostic methodology, and a comparison group with chronic medical illness.

Ambulatory Care Facilities↗

PubMed1997

Anomalous effect of permeant ion concentration on peak open probability of cardiac Na+ channels.

Human heart Na+ channels were expressed transiently in both mammalian cells and Xenopus oocytes, and Na+ currents measured using 150 mM intracellular Na+. Decreasing extracellular permeant ion concentration decreases outward Na+ current at positive voltages while increasing the driving force for the current. This anomalous effect of permeant ion concentration, especially obvious in a mutant (F1485Q) in which fast inactivation is partially abolished, is due to an alteration of open probability. The effect is only observed when a highly permeant cation (Na+, Li+, or hydrazinium) is substituted for a relatively impermeant cation (K+, Rb+, Cs+, N-methylglucamine, Tris, choline, or tetramethylammonium). With high concentrations of extracellular permeant cations, the peak open probability of Na+ channels increases with depolarization and then saturates at positive voltages. By contrast, with low concentrations of permeant ions, the open probability reaches a maximum at approximately 0 mV and then decreases with further depolarization. There is little effect of permeant ion concentration on activation kinetics at depolarized voltages. Furthermore, the lowered open probability caused by a brief depolarization to +60 mV recovers within 5 ms upon repolarization to -140 mV, indicative of a gating process with rapid kinetics. Tail currents at reduced temperatures reveal the rapid onset of this gating process during a large depolarization. A large depolarization may drive a permeant cation out of a site within the extracellular mouth of the pore, reducing the efficiency with which the channel opens.

Animals↗

PubMed2006

Regulation of CRAC channel activity by recruitment of silent channels to a high open-probability gating mode.

CRAC (calcium release-activated Ca(2+)) channels attain an extremely high selectivity for Ca(2+) from the blockade of monovalent cation permeation by Ca(2+) within the pore. In this study we have exploited the blockade by Ca(2+) to examine the size of the CRAC channel pore, its unitary conductance for monovalent cations, and channel gating properties. The permeation of a series of methylammonium compounds under divalent cation-free conditions indicates a minimum pore diameter of 3.9 A. Extracellular Ca(2+) blocks monovalent flux in a manner consistent with a single intrapore site having an effective K(i) of 20 microM at -110 mV. Block increases with hyperpolarization, but declines below -100 mV, most likely due to permeation of Ca(2+). Analysis of monovalent current noise induced by increasing levels of block by extracellular Ca(2+) indicates an open probability (P(o)) of approximately 0.8. By extrapolating the variance/mean current ratio to the condition of full blockade (P(o) = 0), we estimate a unitary conductance of approximately 0.7 pS for Na(+), or three to fourfold higher than previous estimates. Removal of extracellular Ca(2+) causes the monovalent current to decline over tens of seconds, a process termed depotentiation. The declining current appears to result from a reduction in the number of active channels without a change in their high open probability. Similarly, low concentrations of 2-APB that enhance I(CRAC) increase the number of active channels while open probability remains constant. We conclude that the slow regulation of whole-cell CRAC current by store depletion, extracellular Ca(2+), and 2-APB involves the stepwise recruitment of silent channels to a high open-probability gating mode.

Boron Compounds↗

PubMed2003

Trends of probable post-traumatic stress disorder in New York City after the September 11 terrorist attacks.

The authors investigated trends in probable post-traumatic stress disorder (PTSD) prevalence in the general population of New York City in the first 6 months after the September 11 terrorist attacks. Three random digit dialing telephone surveys of adults in progressively larger portions of the New York City metropolitan area were conducted 1 month, 4 months, and 6 months after September 11, 2001. A total of 1,008, 2,001, and 2,752 demographically representative adults were recruited in the three surveys, respectively. The current prevalence of probable PTSD related to the September 11 attacks in Manhattan declined from 7.5% (95% confidence interval: 5.7, 9.3) 1 month after September 11 to 0.6% (95% confidence interval: 0.3, 0.9) 6 months after September 11. Although the prevalence of PTSD symptoms was consistently higher among persons who were more directly affected by the attacks, a substantial number of persons who were not directly affected by the attacks also met criteria for probable PTSD. These data suggest a rapid resolution of most of the probable PTSD symptoms in the general population of New York City in the first 6 months after the attacks. The psychological consequences of a large-scale disaster in a densely populated urban area may extend beyond persons directly affected by the disaster to persons in the general population.

Adolescent↗

PubMed2006

What is the probability of successive cases of Legionnaires' disease occurring in European hotels?

BACKGROUND: Public health officials will normally take action at accommodation sites following an association with a cluster of cases of Legionnaires' disease. This paper seeks to determine the likelihood of such a cluster occurring at a site once it has been associated with a single case of the disease, and therefore whether more should be done at sites following individual cases. METHODS: Information for UK residents reported to the EWGLINET system between 1993 and 2000 was included in a dataset. The size and country of hotel visited by the cases were divided into six country groups (France, Italy, Spain, Turkey, other Europe and other World), and eight size groups (<20 rooms, 20-49, 50-99, 100-199, 200-299, 300-399, 400-499, 500+). The data were investigated using Cox proportional hazards regression to model the probability of at least one further case following the first. RESULTS: The dataset comprised 793 cases that had stayed at 605 sites in 51 countries between 1993 and the end of 2000. This included 605 cases that were the first case associated with a site, and 188 subsequent cases. Following the first case, 16.6% of sites were associated with at least one subsequent case during the period under study. The probability of a subsequent case occurring within 6 months of the first varied by country and size group, with some combinations returning a probability >30%; the probability of a subsequent case occurring within 2 years of the first reached over 50% in some instances. CONCLUSIONS: There may be support for early intervention at some accommodation sites following a first case of Legionnaires' disease, in specific country and size groups.

Disease Outbreaks↗

PubMed2000

The effect of deviant stimulus probability on the human mismatch process.

The present study addresses the separate activities of frontal and temporal MMN generators which might be differentially affected by a change in the probability of standard stimuli. As the probability of standard stimuli was increased, the frontal MMN component significantly increased in amplitude, while the temporal one was not affected. Correspondingly, the scalp current density (SCD) maps showed that the temporal MMN generator was activated even at low probability of standard stimuli, suggesting that even the weak memory trace could start the automatic mismatch process, whereas the frontal MMN generator was activated only with increased probabilities of standard stimuli, suggesting that the stronger the memory trace is, the easier it might trigger the involuntary switching of attention to stimulus change.

Acoustic Stimulation↗

PubMed1992

Probability of causation for radiation-attributable cancer in the Indian population.

Once a cancer is diagnosed in an individual with a history of radiation exposure, it may be required to know the probability that radiation exposure was the cause of the disease. The National Institute of Health, U.S., has generated radio epidemiological tables giving probability of causation for various radiogenic cancers for the population of the U.S. In this paper, the probability of causation has been calculated for the Indian population using two models: (1) the original National Institute of Health model, and (2) direct use of Japanese constant relative risk coefficients for solid tumors. In both cases, new risk coefficients based on DS86 dosimetry and extended follow-up for 35 y have been used. Calculations with new coefficients, based on the National Institute of Health model have been extended to the American population and compared with the results for the Indian population. These values are generally higher for the Indian population than for Americans because of the lower baseline incidence rates in India. Probability of causation values based on the constant relative risk model are independent of population characteristics.

Adolescent↗

PubMed1983

Conditional probability in the diagnosis of coronary artery disease: a future tool for eliminating unnecessary testing?

Approximately 30% of the 300,000 coronary arteriograms done annually in the United States yield normal results. To see if the use of conditional probability in the diagnosis of coronary artery disease (CAD) could aid in predicting these normal results, we retrospectively assessed 96 patients with chest pain but without prior myocardial infarction. The probability of CAD was calculated by a computer program (CADENZA) using data from the history, exercise electrocardiography, and thallium-201 scintigraphy. All patients had coronary arteriography for definitive diagnosis. Based on preangiogram probabilities, different cutoff points were used to separate patients with angiograms likely to be normal from those likely to be abnormal. A preangiogram probability of 20% appeared to be the best separator. If the computer program, with this cutoff point, had been used to influence the decision to perform angiography, 38 of the 42 patients with negative angiograms would have been advised against it, and only two of the 54 patients who later were found to have CAD would have been missed. In view of the costs and risks of the CAD diagnostic process, the ability to identify the likelihood of positive angiograms could be useful in planning testing strategy, both in terms of avoiding "unnecessary" angiograms and avoiding redundant noninvasive procedures.

Angiography↗

PubMed2001

New methods for estimating pretest probability in the diagnosis of pulmonary embolism.

The clinical assessment of the probability of pulmonary embolism is a key step in proposed diagnostic strategies for pulmonary embolism, because the interpretation of noninvasive test results is conditional on the pretest probability derived from the presence or absence of clinical factors. The past year has brought important progress in the general area of clinical prediction of pulmonary embolism with the publication of two new simple clinical prediction rules. Each of the prediction rules includes a total of seven clinical variables that, when combined, allow for the categorization of patients into categories of low, intermediate, or high pretest probability of pulmonary embolism. Although these clinical prediction rules are perhaps only slightly better than the estimates of experienced clinicians, they provide an explicit method for estimating the probability of PE as an adjunct to diagnostic testing. Further validation work is now needed to assess how well these new prediction rules perform in settings other than the derivation sites.

Algorithms↗