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PubMed1999

Non steady state and steady state PKS Bayesian forecasting and vancomycin pharmacokinetics in ICU adult patients.

The pharmacokinetics of vancomycin was investigated in adult ICU patients after the first administration and at steady state. Then the predictive performance of a two-compartment Bayesian forecasting program was assessed in these patients by using population-based parameters and three non steady state vancomycin concentrations as feedback information. Finally a prospective investigation was carried out to search potential covariates. At steady state, a significant decrease (around 30%) in clearance (CL) was observed, while creatinine clearance (CLcr) was stable and a significant increase (around 30%) in volume of distribution (V(SS)) was observed. A two-fold increase in elimination half-life was found. CL was weakly correlated with CLcr at onset of therapy and at steady state. The Bayesian program tended to overpredict vancomycin peak and trough concentrations. A larger mean prediction error and a poorer precision were observed when population-based parameter estimates were used (no feedback) compared to feedback prediction, but the differences were not significant. Mechanical ventilation and concurrent opioid therapy may be pertinent covariates of vancomycin pharmacokinetics. The current work has shown that vancomycin pharmacokinetics in ICU patients displayed a significant variability and a significant change in both clearance and distribution during the course of therapy. Further investigation is necessary to clarify these findings. Moreover, the use of the Bayesian forecasting PKS program in our patients led to a prediction with low bias but rather poor precision. This outcome highlights the need to implement a population modeling approach, to determine the vancomycin pharmacokinetic parameters and covariates in our ICU patients, and to apply this information to provide more accurate concentration predictions.

Adolescent↗

PubMed2004

Best linear forecast of volatility in financial time series.

The autocorrelation function of volatility in financial time series is fitted well by a superposition of several exponents. This case admits an explicit analytical solution of the problem of constructing the best linear forecast of a stationary stochastic process. We describe and apply the proposed analytical method for forecasting volatility. The leverage effect and volatility clustering are taken into account. Parameters of the predictor function are determined numerically for the Dow Jones 30 Industrial Average. Connection of the proposed method to the popular autoregressive conditional heteroskedasticity models is discussed.

Journal Article↗

PubMed2000

Forecasting confined spatiotemporal chaos with genetic algorithms.

A technique to forecast spatiotemporal time series is presented. It uses a proper orthogonal or Karhunen-Loève decomposition to encode large spatiotemporal data sets in a few time series, and genetic algorithms to efficiently extract dynamical rules from the data. The method works very well for confined systems displaying spatiotemporal chaos, as exemplified here by forecasting the evolution of the one-dimensional complex Ginzburg-Landau equation in a finite domain.

Algorithms↗

PubMed1988

Forecasts of preserved teeth and denture wearers among Danish adults early in the next century.

To assist in the planning of oral health services, forecasts were made and goals specified with regard to the numbers of preserved teeth and subjects wearing full or partial dentures among Danish adults in 1992 and 2002. Forecasting was based on existing data, viz. a survey in 1982, including clinical examination, of a representative sample of 20-80-yr-olds (n = 2548), on register data from the National Health Insurance, and survival rates. By combining information from these sources, an increase was estimated in number of preserved teeth among 20-99-yr-olds from 68 million in 1982 to 82 and 92 million in 1992 and 2002, respectively. Correspondingly, a 28% increase in the mean number of remaining teeth was proposed as a goal for the year 2002. A decrease was estimated in the number of denture wearers, from 1.4 million in 1982 to 1.07 and 0.74 million in 1992 and 2002, respectively. The corresponding goal was specified as a 50% reduction in the proportion of denture wearers in 2002. In the middle aged and older part of the population the increasing number of remaining teeth may be expected to imply considerable needs for professional care even in the beginning of the next century.

Adult↗

PubMed2003

Stratospheric memory and skill of extended-range weather forecasts.

We use an empirical statistical model to demonstrate significant skill in making extended-range forecasts of the monthly-mean Arctic Oscillation (AO). Forecast skill derives from persistent circulation anomalies in the lowermost stratosphere and is greatest during boreal winter. A comparison to the Southern Hemisphere provides evidence that both the time scale and predictability of the AO depend on the presence of persistent circulation anomalies just above the tropopause. These circulation anomalies most likely affect the troposphere through changes to waves in the upper troposphere, which induce surface pressure changes that correspond to the AO.

Journal Article↗

PubMed1996

[Bayesian forecasting of plasma vancomycin concentration using time-dependent pharmacokinetics].

A new prediction method of vancomycin (VCM) pharmacokinetics has been developed using the modified Bayesian forecasting method involved in time-dependent pharmacokinetics in clearance. We investigated to evaluate the usefulness of this new prediction method compared with that of the ordinary Bayesian forecasting method. Serum samples, obtained from 4 patients at least 3 different days during the period for the VCM treatment were assayed by fluorescence polarization immunoassay. VCM pharmacokinetic parameters and predicted serum VCM concentrations were calculated using this new method and the ordinary one according to the one-compartment model. The precision of the predicted serum VCM concentrations by these two methods at the third experimental day were evaluated with the mean prediction error (ME), mean absolute prediction error (MAE) and root mean squared error (RMSE). The most precise and least-bias prediction of serum VCM concentrations were observed using this new prediction method (ME: -0.36 +/- 1.40, MAE: 1.13 +/- 0.82 and RSME: 1.37). The time-dependent decrease of VCM clearance was observed in all patients. Therefore, the fitting of the actual serum VCM concentrations obtained using the ordinary method produced less precise results than that using this new method. These results suggest the usefulness of this new prediction method considering time-dependent changes in VCM clearance.

Aged↗

PubMed2004

Forecasting model for the incidence of hepatitis A based on artificial neural network.

AIM: To study the application of artificial neural network (ANN) in forecasting the incidence of hepatitis A, which had an autoregression phenomenon. METHODS: The data of the incidence of hepatitis A in Liaoning Province from 1981 to 2001 were obtained from Liaoning Disease Control and Prevention Center. We used the autoregressive integrated moving average (ARIMA) model of time series analysis to determine whether there was any autoregression phenomenon in the data. Then the data of the incidence were switched into [0,1] intervals as the network theoretical output. The data from 1981 to 1997 were used as the training and verifying sets and the data from 1998 to 2001 were made up into the test set. STATISTICA neural network (ST NN) was used to construct, train and simulate the artificial neural network. RESULTS: Twenty-four networks were tested and seven were retained. The best network we found had excellent performance, its regression ratio was 0.73, and its correlation was 0.69. There were 2 input variables in the network, one was AR(1), and the other was time. The number of units in hidden layer was 3. In ARIMA time series analysis results, the best model was first order autoregression without difference and smoothness. The total sum square error of the ANN model was 9 090.21, the sum square error of the training set and testing set was 8 377.52 and 712.69, respectively, they were all less than that of ARIMA model. The corresponding value of ARIMA was 12 291.79, 8 944.95 and 3 346.84, respectively. The correlation coefficient of nonlinear regression (R(NL)) of ANN was 0.71, while the R(NL) of ARIMA linear autoregression model was 0.66. CONCLUSION: ANN is superior to conventional methods in forecasting the incidence of hepatitis A which has an autoregression phenomenon.

China↗

PubMed2004

[A study on the variables forecasting male adolescents' sexual intercourse].

PURPOSE: This study was designed to identify the variables affecting male adolescents' sexual intercourse through a comprehensive analysis of individual and environmental factors. METHOD: The subjects of this descriptive survey on causal relations were 462 subjects enrolled in liberal and vocational high schools selected on a convenience sampling basis. The data collected from May-July 2002 was put to logistic regression analysis to build a forecast model. FINDINGS: 1) Individual factors such as school record, experience seeking, non-inhibition and sexual permissiveness, 2) family factors such as parental living arrangement, 3) school factors such as career tract and 4) peer factors such as having a boy/girl friend were identified as significant variables forecasting sexual intercourse. CONCLUSION AND RECOMMENDATION: The theoretical model built on the basis of the major findings of this study will hopefully help promote a wholesome youth culture related to sexual intercourse. It is recommended that a program be developed that can help control the variables identified in this study along with a follow-up study to verify the model.

Adolescent↗

PubMed1999

Possibilities of See5 software in forecasting of life expectancy not achieving.

Results of application of See5 to epidemiological domain were presented. The aim of this paper is to find out if See5 can be used for forecasting whether life expectancy will be achieved or not. The basis for forecasting are data-attributes, predictors (anthropological data, living habits, laboratory data, blood pressure measured in years 1970/71, and the status of examinee--class (alive or dead) in 1990. Data were split at random into 10 blocks with approximately the same number of cases and the same distribution of classes. Results were given in the form of decision trees and rulesets, and tested through crossvalidation. The most interesting question--what are prediction-candidates for not achieving life expectancy estimated in the year of examination--did not give a satisfactory result: the accuracy of classification was about 70%. However, a very interesting fact is that each rule consists of at least one candidate predictor, usually considered as risk factor (e.g. high diastolic blood pressure and animal fat consumption).

Adult↗

PubMed2002

[Research on the forecast of intraocular lens power after excimer laser keratorefractive operation].

OBJECTIVE: To study the accuracy of different formulas forecasting intracellular lens (IOL) power after excimer laser keratorefractive operation. METHODS: One hundred and twenty eyes (60 cases) underwent LASIK surgery. Before and after the surgery, the IOL powers were calculated to correct the myopia to emmetropia by experiential SRK II formula, theoretical SRK/T formula and Binkhoist II formula respectively. Then we calculated the IOL power equal to original lens power by F, and analyzed the results before and after surgery by SPSS statistical software. RESULTS: 1. The IOL powers were not obviously different by different formulas between pre-operative and post-operative results in low myopia (P > 0.05). In middle and high myopia there were obvious differences (P < 0.01), the postoperative results were smaller than the preoperative ones. 2. The differences of equal IOL power by different formulas were highly related to the practical corrective refractive values of the surgery. Regression formula: The difference of equal IOL power = a + b x the practical corrective refractive value of the surgery. (SRK II: a = -l.23, b = 0.72; SRK/T: a = -l.03, b = 0.52; Binkhoist II: a = -1.44, b = 0.5). CONCLUSION: The IOL powers forecasted by different formulas are smaller in middle and high myopia after excimer laser keratorefractive operation than that before the operation, and can be corrected by regression formula.

Adolescent↗

PubMed2002

[Blood gases values forecasting by artificial neural network in prematurely born infants with respiratory distress].

Artificial Neural Networks (ANN) are modern tools for data analysis. They can compete with commonly used statistical methods. Till the date they were not used for modeling continuous parameters in medicine. The aim of this paper is to assess accuracy of ANN in forecasting blood gases values in preterm infants with respiratory distress. The study was conducted with the use of the data from Neonatal Information System (NIS) describing first 30 days of the hospital stay of 19 newborns with birthweight < or = 1500 g admitted to the unit before second day of life in 1997. Separate ANN was created for prognosis of 4 parameters of arterial blood gases (pH, pCO2, pO2, HCO3) and oxygenation index (pO2/FiO2) for 1 hour in advance. For each forecasted parameter input set of parameters was established. The ANN was taught with back propagation algorithm using data of 18 patients, the accuracy of prognosis was tested on the data of the remaining patient. This procedure was repeated 19 times. The error of prognosis was assessed in comparison to predefined curves of the maximal error. The accuracy of achieved prognoses was respectively for pH, pCO2, pO2, HCO3, pO2/FiO2 98.9, 99.7, 97.1, 98.3, 95%.

Blood Gas Analysis↗

PubMed2004

Forecasting of life threatening arrhythmias using the compression entropy of heart rate.

OBJECTIVES: Ventricular tachycardia (VT) provoking sudden cardiac death (SCD) are a major cause of mortality in the developed countries. The most efficient therapy for SCD prevention are implantable cardioverter defibrillators (ICD). In this study heart rate variability (HRV) measures were analyzed for short-term forecasting of VT in order to improve VT sensing and to enable a patient warning of forth-coming shocks. METHODS: The last 1000 normal beat-to-beat intervals before 50 VT episodes stored by the ICD were analyzed and compared to individually acquired control time series (CON). HRV analysis was performed with standard parameters of time and frequency domain as suggested by the HRV Task Force and furthermore with a newly developed and optimized nonlinear parameter that assesses the compression entropy of heart rate (Hc). RESULTS: Except of meanNN (p = 0.02) we found no significant differences in standard HRV parameters. In contrast, Hc revealed highly significant (p = 0.007) alterations in VT compared with CON suggesting a decreased complexity before the onset of VT. CONCLUSION: Compression entropy might be a suitable parameter for short-term forecasting of life-threatening tachycardia in ICD.

Arrhythmias, Cardiac↗

PubMedDate not supplied

Health care's financial forecast--2005 and beyond.

Good, bad and ugly may be the best way to describe the financial forecast for health care over the next few years. Take a look at some of the factors affecting the forecast.

Delivery of Health Care↗

PubMed1991

Chest diameters in the body mass forecast.

Two other body mass indices have been studied in the paper, by means of which the density is to measure human body has on the surface and in the volume of the hypothetic cylinder with the height equal to that of stature and with the circumference computed from the transverse and sagittal diameters of the chest. Thus we have to do with a modification of the procedure where the width and depth of chest were given by its circumference (mesosternale). The reason which made this modification interesting for us was in that the measurement of the transverse and sagittal diameter of the chest did not depend--when compared with the chest circumference measurement--so much on the muscular and fat tissue of the human body. Both these body mass indices have been used also to forecast body mass adequate to the respective skeletal space--surface and volume of the cylinder constructed by means of the dimensions of the skeleton: stature and transverse and sagittal diameter of the chest. Prediction efficiency of both these formulas has been verified numerically by means of an extensive data material of the Czechoslovak Spartakiade 1985, in dependence on sex and age. Information contribution of the chest diameters in the adequate body mass forecast proved to be doubtless. Besides it the possibility has been discussed to increase prediction reliability of body mass by combining both procedures under consideration with respect to the values of skeletal dimensions of the respective proband.

Adolescent↗

PubMed1990

Modified allometric function in the body mass forecast.

This paper is a contribution to the problem of an optimum forecast of body mass by means of the skeletal dimensions stature and chest circumference. Application of the basic equation valid for allometric functions made it possible to estimate the power of chest circumference in the forecast formula as approximately 1.7 for males and 1.6 for females. In such a formula the respective body mass index seems to be almost independent of age, for both males and females. Reliability of the procedure under consideration will be the object of an evaluation in another study.

Adolescent↗

PubMed1987

The well-balanced diet and the "at risk" micronutriments: a forecasting nutritional index.

The forecasting nutritional index is the list of micronutrients whose intakes do not amount to 80% of the recommended allowances, this list being determined on the basis of a balanced diet. This kind of diet allows to bring out the micronutriments which are the least likely to be found in the diet. The food and epidemiological studies results allow to confirm the forecasting nature of this index.

Diet↗

PubMed1986

Hospital output forecasts and the cost of empty hospital beds.

This article investigates the cost incurred when hospitals have different levels of beds to treat a given number of patients. The cost of hospital care is affected by both the forecasted level of admissions and the actual number of admissions. When the relationship between forecasted and actual admissions is held constant, it is found that an empty hospital bed at a typical hospital in Michigan has a relatively low cost, about 13 percent or less of the cost of an occupied bed. However, empty beds in large hospitals do add significantly to cost. If hospital beds are closed, whether by closing beds at hospitals which remain in business or by closing entire hospitals, cost savings are estimated to be small.

Bed Occupancy↗

PubMed1985

Forecasting the presence of atmospheric pollens.

The forecasting process includes several aspects. The scientific aspects include (i) a priori observations, like statistics of weather attributes during recent years, variation of earlier atmospheric pollen amounts, and general correlations between weather factors and pollen frequencies. (ii) The present-day observations are made closer to the flowering season, and they include e.g. the development of the present and forecasted weather, the development of the flower buds, and information obtained from other countries. The practical aspects include effective television, radio and newspaper service, necessary education and information, rapid data analysis and transfer systems, and good national and international cooperation.

Air↗