PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “predictive modelling”

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 1,081 records · Page 60Linked to original sources
PubMed2000

Lower limb skeletal muscle mass: development of dual-energy X-ray absorptiometry prediction model.

Although magnetic resonance imaging (MRI) can accurately measure lower limb skeletal muscle (SM) mass, this method is complex and costly. A potential practical alternative is to estimate lower limb SM with dual-energy X-ray absorptiometry (DXA). The aim of the present study was to develop and validate DXA-SM prediction equations. Identical landmarks (i.e., inferior border of the ischial tuberosity) were selected for separating lower limb from trunk. Lower limb SM was measured by MRI, and lower limb fat-free soft tissue was measured by DXA. A total of 207 adults (104 men and 103 women) were evaluated [age 43 +/- 16 (SD) yr, body mass index (BMI) 24.6 +/- 3.7 kg/m(2)]. Strong correlations were observed between lower limb SM and lower limb fat-free soft tissue (R(2) = 0.89, P < 0.001); age and BMI were small but significant SM predictor variables. In the cross-validation sample, the differences between MRI-measured and DXA-predicted SM mass were small (-0.006 +/- 1.07 and -0.016 +/- 1.05 kg) for two different proposed prediction equations, one with fat-free soft tissue and the other with added age and BMI as predictor variables. DXA-measured lower limb fat-free soft tissue, along with other easily acquired measures, can be used to reliably predict lower limb skeletal muscle mass.

Absorptiometry, Photon↗
PubMed1991

Stroke rehabilitation: a model predicting return home.

We undertook this study to describe the changes in functional status for patients in a rehabilitation program for acute stroke and to identify the variables that best predict discharge home. Of 282 patients, 75% were discharged home. Increases in functional status were found for all 18 activities of the Functional Independence Measure from admission to discharge. Significant predictors of discharge disposition in a logistic regression model were the admission and discharge functional status scores, length of stay, and living arrangement before the stroke. The functional status at discharge was the most important predictor. Knowledge of these predictors can contribute to more appropriate treatment and discharge planning.

Adolescent↗
PubMed1998

Assessment of outcome prediction models for patients with localized prostate carcinoma managed with radical prostatectomy or external beam radiation therapy.

BACKGROUND: A clinical staging system for localized prostate carcinoma that provides reliable information on which management decisions regarding an individual patient can be based is lacking. This study compared the abilities of all published proposed clinical staging systems to predict time to prostate specific antigen (PSA) failure after radical prostatectomy or external beam radiation therapy for clinically localized prostate carcinoma. METHODS: A total of 1441 clinically localized prostate carcinoma patients who were managed with radical prostatectomy at the University of Pennsylvania in Philadelphia (n = 688) or the Brigham and Women's Hospital in Boston (n = 288) or with external beam radiation therapy at the Joint Center for Radiation Therapy in Boston (n = 465) were entered into this study. Patients who received adjuvant or neoadjuvant hormonal or radiation therapy were excluded. Akaike's Information Criterion (AIC) and Schwartz Bayesian Criterion (SBC) estimates, which are comparative measures, were calculated for each clinical staging system. Pairwise comparisons of the AIC and SBC estimates for the most predictive clinical staging systems were performed using a formal bootstrap technique with 2000 replications. RESULTS: Both the staging system based on the risk score and the staging system based on the calculated volume of prostate carcinoma and PSA (cVCa-PSA) optimized the prediction of time to posttreatment PSA failure. The cVCa-PSA system, however, provided a more clinically useful stratification of outcome. CONCLUSIONS: Improved clinical staging for patients with localized prostate carcinoma may be possible with parameters obtained during routine evaluation. Validation by other investigators is underway.

Aged↗
PubMed2006

The delivery of drugs to patients by continuous intravenous infusion: modeling predicts potential dose fluctuations depending on flow rates and infusion system dead volume.

IV drug infusion has the potential for dosing errors, which arise from complex interactions between carrier flows and the infusion set dead volume. We computed the steady-state mass of drug stored in the infusion set dead volume, using phenylephrine as a model compound. The mass of drug in the dead volume increases with stock drug concentration and desired dose but decreases with carrier flow rate. We also modeled the dynamic perturbations in drug delivery when a carrier is abruptly stopped. Rapid initial carrier flow rates lead to greater depression in drug delivery rate after carrier flow ceases. Rapid drug infusion rates lead to faster restoration of desired drug delivery. Finally, the time to reach a new steady-state after a change in drug delivery or carrier rate was computed. This time is longest for large stock-drug concentrations, larger dead volumes, and slower final carrier rates. These computations illustrate that (a) the dead volume may contain a large mass of drug available for inadvertent bolus, (b) cessation of carrier flow can profoundly reduce drug delivery, and (c) after a change in carrier flow or drug dosing, a significant lag is possible before drug delivery achieves steady state. Although computed for phenylephrine, the concepts are generic and valid for any drug administered by IV infusion.

Aged↗
PubMed1984

Percutaneous absorption: a new physicochemical predictive model for maximum human in vivo penetration rates.

A diffusion model for stratum corneum-limited percutaneous absorption based on the interaction of the diffusate with the stratum corneum was derived. Two types of interactions were proposed, ion-dipole and lipid-lipid, based on current knowledge of the stratum corneum and on irreversible thermodynamic arguments. The resulting flux equations predict a linear dependence of flux on the dipole moment and ln X of the diffusates , where X is the mole fraction solubility. These flux equations were tested on 21 different diffusates whose human percutaneous absorption rates in vivo had been previously determined. A solubility method was used to classify the interaction pathway for each diffusate . Correlation of the maximum absorption rate for the lipid and polar pathways give correlation coefficients of 0.946 and 0.998, respectively. It is believed that these studies provide a starting point for the ultimate goal of percutaneous absorption research: to be able to bypass in vivo and in vitro studies and to predict absorption solely on the basis of the physicochemical properties of the diffusates .

Chemical Phenomena↗
PubMed1998

Intersegmental coordination of limb movements during locomotion: mathematical models predict circuits that drive swimmeret beating.

Normal locomotion in arthropods and vertebrates is a complex behavior, and the neural mechanisms that coordinate their limbs during locomotion at different speeds are unknown. The neural modules that drive cyclic movements of swimmerets respond to changes in excitation by changing the period of the motor pattern. As period changes, however, both intersegmental phase differences and the relative durations of bursts of impulses in different sets of motor neurons are preserved. To investigate these phenomena, we constructed a cellular model of the local pattern-generating circuit that drives each swimmeret. We then constructed alternative intersegmental circuits that might coordinate these local circuits. The structures of both the model of the local circuit and the alternative models of the coordinating circuit were based on and constrained by previous experimental results on pattern-generating neurons and coordinating interneurons. To evaluate the relative merits of these alternatives, we compared their dynamics with the performance of the real circuit when the level of excitation was changed. Many of the alternative coordinating circuits failed. One coordinating circuit, however, did effectively match the performance of the real system as period changed from 1 to 3.2 Hz. With this coordinating circuit, both the intersegmental phase differences and the relative durations of activity within each of the local modules fell within the ranges characteristic of the normal motor pattern and did not change significantly as period changed. These results predict a mechanism of coordination and a pattern of intersegmental connections in the CNS that is amenable to experimental test.

Animal Structures↗
PubMed1999

A predictive model for the non-thermal inactivation of Salmonella enteritidis in a food model system supplemented with a natural antimicrobial.

Home-made taramasalad, a traditional Greek appetizer, was inoculated with Salmonella enteritidis supplemented with different concentrations of oregano essential oil (0.0, 0.5, 1.0, 2.0% v/w) and stored at different temperatures (5, 10, 15, 20 degrees C). The product's pH was adjusted from 4.3 to 5.3 with lemon juice. At each combination of the environmental factors, the bacterial counts were modelled as a function of time in order to estimate the kinetic parameters of the pathogen. For comparison, two different models were used. A reduction of Salmonella enteritidis was observed in all cases and its death rate depended on the pH, the storage temperature and the essential oil concentration. Death responses as a function of pH, storage temperature and concentration of oregano essential oil were described using a quadratic function which was then used to predict the death of Salmonella enteritidis in home-made taramasalad of different compositions.

Food Microbiology↗
PubMedDate not supplied

A single mathematical model predicts physicians' recommendations and postmenopausal women's decisions to participate in a clinical trial to prevent breast cancer or coronary heart disease.

Few eligible postmenopausal women participate in clinical trial research to prevent breast cancer or coronary heart disease, making it impossible to adequately assess the efficacy of tested interventions for this vulnerable group. To elucidate the causal factors and decision model underlying participation behavior, 180 white, African American, and Hispanic postmenopausal women judged their likelihood of participation in a breast cancer or coronary heart disease prevention clinical trial in scenarios with varied cost/remuneration, perceived risk, doctor's recommendation, and expected toxicity. In addition, 293 white, African American, and Hispanic male and female physicians judged the strength of their participation recommendation in scenarios with varied cost/remuneration, expected toxicity, patient's age, and the source of the information about the clinical trial. An additive and constant-weight-averaging model were rejected. The same configural-weight-range model accounted for judgments in both breast cancer and coronary heart disease scenarios, with different parameter values for each group. According to this model, white and Hispanic women under 70 years of age are most likely to participate, even under somewhat adverse conditions; costs and high toxicity levels act as severe barriers to physicians' positive recommendations and women's participation. Perceived risk was the most important factor for women, yet only 8% and 15% reported ever having received risk information from their doctor for breast cancer and coronary heart disease, respectively. For these two diseases, respectively, 75% and 48% of women rated their risk of the disease as low and 76% and 88% reported they had never heard of a randomized clinical trial or of a prevention clinical trial being conducted. These results have implications for education, information dissemination, and prevention clinical-trial planners.

Aged↗
PubMed2002

Predictive modelling for packaging design: equilibrium modified atmosphere packages of fresh-cut vegetables subjected to a simulated distribution chain.

The impact of temperature fluctuations in a simulated cold distribution chain, typical of commercial practice, was investigated on both the microbial and sensorial quality of equilibrium modified atmosphere (EMA) packaged minimally processed vegetables. The internal O2 concentration of the designed packages could be predicted for the different steps of the simulated distribution chain by applying an integrated mathematical system. The internal atmosphere in the packages remained in its aerobic range during storage in the chain due to the application of high permeable packaging films for O2 and CO2. Spoilage microorganisms were proliferating fast on minimally processed bell peppers and lettuce. Yeasts showed to be the shelf-life limiting group. Visual properties limited the sensorial shelf-life. Listeria monocytogenes was able to multiply on cucumber slices, survived on minimally processed lettuce and decreased in number on bell peppers due to the combination of low pH and refrigeration. Aeromonas caviae was multiplying on both cucumber slices and mixed lettuce, but was as well inhibited by the low pH of bell peppers. Storage temperature control was found to be of paramount importance for the microbial (spoilage and safety) and sensorial quality evaluation of EMA-packaged minimally processed vegetables.

Bacteria↗
PubMed2002

[Advance in researches on vegetation cover and management factor in the soil erosion prediction model].

Vegetation cover and land management are the main limiting factors of soil erosion, and quantitative evaluation on the effect of different vegetation on soil erosion is essential to land use and soil conservation planning. The vegetation cover and management factor (C) in the universal soil loss equation (USLE) is an index to evaluate this effect, which has been studied deeply and used widely. However, the C factor study is insufficient in China. In order to strengthen the research of C factor, this paper reviewed the developing progress of C factor, and compared the methods of estimating C value in different USLE versions. The relative studies in China were also summarized from the aspects of vegetation canopy coverage, soil surface cover, and root density. Three problems in C factor study were pointed out. The authors suggested that cropland C factor research should be furthered, and its methodology should be unified in China to represent reliable C values for soil loss prediction and conservation planning.

China↗
PubMed2006

Prediction models for rheumatoid arthritis during diagnostic investigation: evaluation of combinations of rheumatoid factor, anti-citrullinated protein/peptide antibodies and the human leucocyte antigen-shared epitope.

OBJECTIVES: To calculate the probabilities for rheumatoid arthritis in a consecutive cohort of patients during diagnostic investigation. Different logistic regression models evaluating the value of human leucocyte antigen (HLA)-shared epitope determination and testing for rheumatoid factor and anti-citrullinated protein/peptide antibodies (ACPA) were fitted. METHODS: 1003 consecutive patients were included in the study, presenting a new diagnostic problem for which rheumatoid arthritis was included in the differential diagnosis. All patients were tested for ACPA, rheumatoid factor and HLA-shared epitope. RESULTS: After 1 year, diagnoses were established: 153 patients had definite rheumatoid arthritis and 629 patients had rheumatoid arthritis excluded. Rheumatoid factor, used as a continuous marker, is useful in evaluating the probability for rheumatoid arthritis. Combined rheumatoid factor and shared epitope testing may provide additional predictive information, but combined ACPA and rheumatoid factor testing is superior. The redundancy of shared epitope testing in a model that includes ACPA testing can be explained by the high association between ACPA and shared epitope both in patients with rheumatoid arthritis and in those with non-rheumatoid arthritis. The value of rheumatoid factor testing increased if patients presented with at least one swollen joint at baseline. CONCLUSION: Valid probabilities for rheumatoid arthritis during routine diagnostic investigation were calculated, and showed that the potential additional value of shared epitope testing disappears when ACPA testing is available. Combined rheumatoid factor and ACPA testing is useful, especially when rheumatoid factor is considered as a continuous parameter reflecting an increasing probability for rheumatoid arthritis at higher rheumatoid factor titres. The value of (continuous) rheumatoid factor testing increases when the a priori chance is higher.

Arthritis, Rheumatoid↗
PubMed1989

A linear muscle model predicts the hyperbolic force-velocity relationship.

A variety of different schemes have been reported in the literature for linearizing the force-velocity relationship observed in muscle, a dominant element in the muscle. This report extends assertions that a linear muscle system has force-velocity characteristics as described by Hill's hyperbolic equation, and that no linearization whatsoever is required. The muscle is modeled as a parallel combination of passive elasticity, and series elasticity connected to the parallel combination of active state tension generator, viscosity and length tension elasticity. Each of the elements are linear. Simulation solutions of this third-order system yield a hyperbolic shaped force-velocity curve using physiologically derived estimates, based on the oculomotor system, for the parameters of the muscle model.

Elasticity↗
PubMed2002

A biotic ligand model predicting acute copper toxicity for Daphnia magna: the effects of calcium, magnesium, sodium, potassium, and pH.

The extent to which Ca2+, Mg2+, Na+, K+ ions and pH independently mitigate acute copper toxicity for the cladoceran Daphnia magna was examined. Higher activities of Ca2+, Mg2+, and Na+ (but not K+) linearly increased the 48-h EC50 (as Cu2+ activity), supporting the concept of competitive binding of these ions and copper ions to toxic action or transport sites at the organism-water interface (e.g. fish gill, the biotic ligand). The increase of the EC50 (as Cu2+ activity) with increasing H+, however, seemed to suggest cotoxicity of CuOH+ rather than proton competition. Based on the biotic ligand model (BLM) concept, we developed a methodology to estimate stability constants for the binding of Cu2+, CuOH+, Ca2+, Mg2+, Na+, and H+ to the biotic ligand, solely based on toxicity data. Following values were obtained: log K(CuBL) = 8.02, log K(CuOHBL)= 7.45, log K(CaBL) = 3.47, log K(MgBL) = 3.58, log K(NaBL) = 3.19, and log K(HBL) approximately 5.4. Further, we calculated that on average 39% of the biotic ligand sites need to be occupied by copper to induce a 50% acute effect for D. magna after 48 h of exposure. Using the estimated constants, a BLM was developed that can predict acute copper toxicity for D. magna as a function of water characteristics. The presented methodology can easily be applied for BLM development for other organisms and metals. After validation with laboratory and natural waters (including DOC), the developed model will support efforts to improve the ecological relevance of presently applied risk assessment procedures.

Animals↗
PubMed1982

A new fallout prediction model.

The standard method for the calculation of nuclear weapon fallout radiation doses and dose rates in operational type studies for the last 20 yr has been the computer algorithm known as WSEG-10. WSEG-10 uses empirical functions rather than numerical analyses and computes fallout dose (rates) in seconds or less on modern computers. WSEG-10 has long been criticized for its inability to allow for variations in the activity-particle size distribution of the fallout, for its inability to account for fractionation and for the absence of realistic settling rates. At the other end of the scale, the Defense Land Fallout Information Code, DELFIC, is currently used for research work and as a comparison standard. DELFIC produces fallout footprints on the ground by numerical integration, employing discrete cells in space, time and particle size. A new fallout prediction method is presented here which, unlike WSEG-10, does allow variations in activity with particle size, does account for fractionation and does model variable settling rates. This new model, like WSEG-10 but unlike DELFIC, computes in seconds or less. Some results are presented and compared to DELFIC and to WSEG results. Additionally, this new model will treat the far-field problem of interest in a massive strategic attack which cannot be easily done using DELFIC.

Forecasting↗