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PubMed1989

Prediction of individual dosage requirements for lignocaine: a validation study for Bayesian forecasting in Japanese patients.

The performance of the Bayesian feedback method for predicting lignocaine dosage developed by Vozeh et al. was evaluated in 53 Japanese patients, treated for either suppression or prophylaxis of ventricular arrhythmias, with respect to accuracy, precision, efficiency, and safety. The lignocaine serum concentrations at 12 h (C12) and 24 h (C24) after continuous infusion was started were predicted and compared retrospectively using the early concentration at 2-4 h (C2-4). The mean of the prediction error (PE) and the root mean-squared error (RMSE) were used as a measure of accuracy and precision. The 95% confidence interval of PE for C12 included zero, but those of PE for C24, whether C2-4 was used alone or in combination with C12, were less than zero, meaning that the prediction of C24 was significantly biased. The RMSE for C12 (13.2%) was less than that for C24 (16.2%), but the difference was not statistically significant. The fraction of measurements lying within the statistically approximate 68% prediction interval (+/- 1 SD) was used to evaluate the estimate of the SD of prediction. The fraction of measurements inside the prediction interval was significantly larger than the expected 68% for both C12 and C24 (p less than 0.05), showing that the estimate of the size of the PE is biased on the safer side. The clinical effects of lignocaine were also evaluated from the viewpoints of suppression of number of ventricular premature beats, prevention of more severe grades of arrhythmias, and toxicity. At least the appearance of toxicity, which four patients exhibited, was related to the lignocaine serum concentration (greater than 6 micrograms/ml).

Adult↗
PubMed1995

Efficient sampling strategies for forecasting pharmacokinetic parameters of irinotecan (CPT-11): implication for area under the concentration-time curve monitoring.

A linear two-compartment Bayesian pharmacokinetic model was developed using a standard two-stage population method for the novel anti-cancer agent CPT-11 from 11 adult patients with refractory cancer. The accuracy and efficiency of this Bayesian model for estimating pharmacokinetic parameters including the area under the concentration-time curve (AUC) was then evaluated using two different sampling strategies in a new study cohort of 13 patients with cancer. Sampling strategies included either one, two, or three nonsteady-state feedback levels determined empirically and from optimal sampling theory (D-optimality). All 24 patients in this study received CPT-11 (60 mg/m2) as a 90-min infusion. Pharmacokinetic parameters derived from the Bayesian model combined with these limited sampling strategies were compared with those parameters obtained from the full sample data sets (n = 10) analyzed by weighted nonlinear least squares regression (reference method). The least-bias and most precise sampling times for estimating AUC were 3.5; 3.5 and 9.5; and 0.5, 3.5, and 9.5 h, respectively. At these times, only marginal improvement in precision of the AUC estimate was observed using two versus three samples. However, the precision of the estimate of clearance was not improved using two versus three samples. The sampling times derived from optimal sampling theory were 0.25, 3.5, 8.5, and 24 h and correlated closely to the actual and best empirical sampling times of 0.5, 3.5, 9.5, and 24 h. These results strongly suggest that Bayesian estimation combined with only two optimally timed samples accurately predicts the AUC of CPT-11 and should be useful for implementing adaptive control dosing for monitoring CPT-11 systemic exposure in patients with cancer.

Adult↗
PubMed2004

Fetal bladder sagittal length: a simple monitor to assess normal and enlarged fetal bladder size, and forecast clinical outcome.

PURPOSE: We examined if the parameter of fetal bladder sagittal length (FBSL) could serve as a monitor of normative and enlarged fetal bladder size. MATERIALS AND METHODS: There were 76 consecutive cases examined between 1984 and 2000 that included measurement of fetal bladder size as FBSL and postnatal urological followup. Fetal images used to assess normal bladder size were derived from cases in which the bladder was normal on prenatal imaging and postnatal testing. An enlarged bladder was categorized as being greater than the 95% CI for a given gestational age (GA). The presence and extent of renal pelvic dilatation were also noted and correlated with FBSL. RESULTS: Measuring normal FBSL in 39 fetuses showed an exponential growth pattern (r = 0.76), which could be represented by the approximate linear formula FBSL = GA in weeks -5 (+/- 95% upper/lower CI = 7). An enlarged bladder was diagnosed in 37 fetuses. A dilated bladder in 9 fetuses, defined as FBSL greater than the 95% upper CI of normal (ie between GA + 2 and GA + 12), showed outcomes of posterior urethral valves, vesicoureteral reflux or a normal outcome. Megacystis in 28 fetuses, defined as FBSL greater than 10 mm larger than that of a dilated bladder (ie greater than GA + 12), showed additional outcomes of megacystis megaureter/vesicoureteral reflux or prune-belly syndrome. A normal outcome was significantly more likely in fetuses with a dilated bladder than in those with megacystis (p < or = 0.05). The incidence of azotemia in those with a dilated bladder or megacystis and pyelectasis was significantly lower than that in those with megacystis with hydronephrosis (p < or = 0.03). CONCLUSIONS: Postnatal diagnosis of fetuses that show an enlarged bladder is predicted based on whether the bladder is enlarged as a dilated bladder or megacystis and if the renal pelvis is enlarged as pyelectasis or hydronephrosis.

Female↗
PubMed1989

A process of events with notification delay and the forecasting of AIDS.

Analysis and prediction of a point process are studied when there is delay in notifying the occurrence of events. A primarily parametric approach is taken to studying the rate of the underlying process and to predicting future properties of the system. Data on AIDS are used in illustration.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Short-term forecasting of life-threatening cardiac arrhythmias based on symbolic dynamics and finite-time growth rates.

Ventricular tachycardia or fibrillation (VT-VF) as fatal cardiac arrhythmias are the main factors triggering sudden cardiac death. The objective of this study is to find early signs of sustained VT-VF in patients with an implanted cardioverter-defibrillator (ICD). These devices are able to safeguard patients by returning their hearts to a normal rhythm via strong defibrillatory shocks; additionally, they store the 1000 beat-to-beat intervals immediately before the onset of a life-threatening arrhythmia. We study these 1000 beat-to-beat intervals of 17 chronic heart failure ICD patients before the onset of a life-threatening arrhythmia and at a control time, i.e., without a VT-VF event. To characterize these rather short data sets, we calculate heart rate variability parameters from the time and frequency domain, from symbolic dynamics as well as the finite-time growth rates. We find that neither the time nor the frequency domain parameters show significant differences between the VT-VF and the control time series. However, two parameters from symbolic dynamics as well as the finite-time growth rates discriminate significantly both groups. These findings could be of importance in algorithms for next generation ICD's to improve the diagnostics and therapy of VT-VF.

Algorithms↗
PubMed2006

Making forecasts for chaotic physical processes.

Making a prediction for a chaotic physical process involves specifying the probability associated with each possible outcome. Ensembles of solutions are frequently used to estimate this probability distribution. However, for a typical chaotic physical system and model of that system, no solution of remains close to for all time. We propose an alternative. This Letter shows how to inflate or systematically perturb the ensemble of solutions of so that some ensemble member remains close to for orders of magnitude longer than unperturbed solutions of . This is true even when the perturbations are significantly smaller than the model error.

Journal Article↗
PubMed1999

Forecasting chaotic cardiovascular time series with an adaptive slope multilayer perceptron neural network.

A multilayer perceptron (MLP) network architecture has been formulated in which two adaptive parameters, the scaling and translation of the postsynaptic function at each node, are allowed to adjust iteratively by gradient-descent. The algorithm has been employed to predict experimental cardiovascular time series, following systematic reconstruction of the strange attractor of the training signal. Comparison with a standard MLP employing identical numbers of nodes and weight learning rates demonstrates that the adaptive approach provides an efficient modification of the MLP that permits faster learning. Thus, for an equivalent number of training epochs there was improved accuracy and generalization for both one- and k-step ahead prediction. The applicability of the methodology is demonstrated for a set of monotonic postsynaptic functions (sigmoidal, upper bounded, and nonbounded). The approach is computationally inexpensive as the increase in the parameter space of the network compared to a standard MLP is small.

Algorithms↗
PubMed2005

Deep depression: mapping, weather forecasting and The Beagle.

This paper traces the voyage of HMS Beagle under the command of Robert FitzRoy, in which Charles Darwin travelled as naturalist. It examines FitzRoy's subsequent career and the coincidence that he, and two other hydrographers connected with the vessel, fell prey to depression.

Depression↗
PubMed1994

Forecasting sibling relationships in early adolescence from child temperaments and family processes in middle childhood.

We developed a model to account for variation in the quality of sibling relationships across a 4-year span from middle childhood to early adolescence. We tested this model on a sample of 71 families, in which older siblings' ages ranged from 6 to 11 years, and those of younger siblings ranged from 4 to 9 years. We also assessed continuity and discontinuity over time in sibling relationship quality. The descriptive analyses revealed an increase of negative sibling relationship qualities and a decrease in positive qualities. The hypothesized paths involving children's temperaments, interparental conflict, positivity in parent-child relationships, and differential negativity in parent-sibling relationships were supported, accounting for 27% to 34% of the variation in sibling relationship quality.

Child↗
PubMed1975

Forecasting the antimalarial activities of arylamidinoureas from their measured physicochemical properties.

1 The octanol : water partition coefficient (PC), protein binding coefficients to albumin (Ba) and haemoglobin (Bh), proton magnetic resonance (PMR) chemical shifts and pKa of 8 arylamidinoureas have been measured. 2 There were statistically significant correlations for 7 of the 8 compounds between the predicted lipophilicity parameter eta and log PC, Ba and Bh, and also between Hammett's electronic parameter sigma and the PMR and pKa observations. 3 3-Chloro,4-nitrophenylamidinourea showed a larger deviation from these correlations than any other compound. Geometric calculations based on the covalent radii and bond angles of the molecule suggested that the neighbouring chloro and nitro substituents were interacting sterically. 4 Molecular orbital calculations and the observed ultra-violet spectrum provided further evidence for such an interaction, and suggested that the nitro group is twisted out of the plane of the benzene ring in this molecule. 5 Such steric interactions can introduce an additional source of error when attempts are made to correlate the biological and predicted physicochemical properties of compounds. 6 Generalized parameters such as eta and sigma cannot be used with confidence to predict the properties of compounds in which such steric interactions occur.

Amidines↗