Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Logistics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed1998

Estimating relative risk of disease from outputs of logistic regression when the disease is not rare.

Many epidemiologic studies in the veterinary field aim to quantify the relationships between risk factors and the occurrence of diseases. The strength of the association between a factor and a disease can be measured by (i) a relative risk (RR), or (ii) an odds ratio (OR) which is widely used because it is directly derived from the estimates of logistic regression. RR directly provides the relative increase in the probability of disease occurrence in case of exposure. OR is often interpretated as a multiplicative factor of the risk of disease occurrence when exposed, although it is not a good approximation of RR when the disease is not rare. The objective of this paper is to propose a method to estimate RR of disease from adjusted odds ratios derived from logistic regression when the disease is not rare. The method of estimation is developed for three different cases: (i) the factor and the outcome are dichotomous; (ii) the factor has more than two classes, and the outcome is dichotomous; and (iii) the factor and the outcome both have more than two classes. In all cases, the principles of estimation are the same: in a subpopulation including individuals diseased at level j (Dj) and not diseased (Do), when exposed to level i (Fi) or not exposed to the factor (Fo), RRij can be calculated with adjusted ORij, and the frequencies of individuals exposed to level i (ni&j), of those not exposed (no&j) and of those diseased (ni&j) among the individuals exposed to level i and not exposed. RRij is the positive solution of the formula: [formula: see text] Simulations were done to assess the relative weight of the exposure rate, disease risk and value of ORij in the difference between RRij and ORij. The difference between ORij and RRij depends upon (i), first of all, the disease risk in the population, but also (ii) the value of ORij, and to a less extent (iii) the exposure rate. Simulations also showed that ranking of the risk-factor levels according to their effect cannot always rely on OR.

Animal Diseases↗
PubMed1999

An integrated logistics support system for training crew medical officers in advanced cardiac life support management.

The purpose of this paper is to present an approach for the development of an integrated logistics support system for training space flight crew medical officers in advanced cardiac life support (ACLS). The most practical approach to deal with this problem has been determined to be the training of one or more of the crew members on the mission as crew medical officers (CMO's). If this approach is taken, there are a number of problems that must be addressed. The basic approach presented in this paper is to develop a performance quality index for ACLS tasks and use this index to monitor and control the performance of crew members throughout their tenure as CMO's. The control tool of the system is based on an integrated learning and forgetting model used to forecast CMO performance level at a given point during flight training. The model represents an aid for trainers in determining a training regime and maintaining the performance standards. A performance evaluator and trainer is also developed to help in the establishment of trainee performance level during training or retraining. All of these tools were evaluated using either expert opinion questionnaires or experimental results. In conclusion, the results presented provide the tools required for an integrated logistics support system for training ACLS personnel.

Aerospace Medicine↗
PubMed2005

[Logistical regression of success factors in the former internship examination for medical students].

INTRODUCTION: The French competitive internship examination for medical students was replaced in 2004 by a national-ranking exam. The profile of students successful at the internship exam, although more or less stereotypical, was never methodically analyzed. AIMS: To determine the factors that influenced success in the internship exam. METHODS: Records of 242 students from four successive entering classes (1989-1992) at the Saint-Etienne Faculty of Medicine underwent logistical regression analysis. Factors studied were: gender; occupation of the head of household; details about their General Certificate of Education test (age attest, core subject, overall grade); repeating any first-cycle medical studies (PCEM1); PCEM1 grade; number of certificates resat at the end-of-year make-up session or the following year during second-cycle medical studies (DCEM), known as "debts"; and the ranking obtained in the five faculty certificate tests deemed representative of the overall competitive test and on the clinical and therapeutic summary certificate (CSCT). RESULTS: The 95 students (59%) who did not take the internship exam differed from those who did. The former typically: (1) were older when they began studying medicine (p = 0.003); (2) had passed the General Certificate of Education with the lowest or next lowest pass levels (p = 0.023); (3) re-did their PCEM1 studies (p = 0.001); (4) were ranked in the lower two-thirds of their PCEM1 class (p = 0.001); (5) had more PCEM1 certificates to resit during DCEM (p = 0.007); (6) were ranked in the lower two-thirds of their class for the certificates (including the CSCT) (p < 0.001). Of the 147 students who did take the internship exam, 102 (69%) passed. Logistical regression identified three predictive factors in their success: (1) took the General Certificate of Education at an average or younger than average age (adjusted odds ratio (OR) 7.79, confidence interval (CI) 95% [1.59-38.13]); (2) had at most one "debt" (adjusted OR 16.51 [1.88-144.78); (3) ranked in the top third of their class for certificates (including the CSCT) (adjusted OR 7.84 [2.42-25.41]). CONCLUSION: Our study objectively confirmed that consistent work and effective learning strategies, acquired early during education and applied throughout medical studies, strongly promoted success in the previous internship exam. It is likely--but should be verified--that medical students who choose this strategy of constant effort will also do best on the new national-ranking examination.

Educational Measurement↗
PubMed1998

How to move things around a hospital: transport logistics at St. Michael's.

Ongoing fiscal restraint challenges hospitals to focus their resources primarily on core services. Support services receive much less attention. This article describes the experience of Toronto's St. Michael's Hospital when it re-engineered its transport logistics by consolidating centralized support services into a logistics department and creating new roles and processes to enhance patient care.

Central Supply, Hospital↗
PubMed2003

Analysis of the logistic function model: derivation and applications specific to batch cultured microorganisms.

Mathematical models are useful for describing microbial growth, both in natural ecosystems and under research conditions. To this end, a rate expression that accounted for depletion of nutrients was used to derive the logistic function model for batch cultures. Statistical analysis was used to demonstrate the suitability of this model for growth curve data. Two linear forms of the model and two procedures for calculating growth rate constants were derived to facilitate statistical evaluation of growth curves. The procedures for calculating growth rate constants were found to be useful for calculation of growth rate constants at each time point, or for estimating growth rate constants from early growth curve data. The utility of the logistic function model and its alternative forms is discussed with respect to planning experiments, analyzing growth curves for the effects of factors other than nutrient limitation, and developing more complete descriptions of cell proliferation.

Bacteria↗
PubMedDate not supplied

Panel 2.18: logistics, information technology (IT), and telecommunications in crisis management.

This is a summary of the presentations and discussion of Panel 2.18, Logistics, Information Technology, and Telecommunications in Crisis Management of the Conference, Health Aspects of the Tsunami Disaster in Asia, convened by the World Health Organization (WHO) in Phuket, Thailand, 04-06 May 2005. The topics discussed included issues related to logistics, information technology (IT), and crisis communication pertaining to the responses to the damage created by the Tsunami. It is presented in the following major sections: (1) issues; (2) lessons learned; (3) what was done well; (4) what could have been done better; and (5) conclusions and recommendations. Each major section is presented in four sub-sections: (1) needs assessments; (2) coordination; (3) filling the gaps; and (4) capacity building.

Disasters↗
PubMed1997

Logics and logistics of community intervention against osteoporosis: an evidence basis.

Under designations like small areas action research and intervention, directed 'ground-up' health promotion and prevention in the population form an important part of the ongoing medical systems development. There is recent evidence of the success of community intervention against cardiovascular disease. In osteoporosis, however, there is still a lack of conclusive data on both the logics and logistics of such an approach. Since 1988, a county health policy program has been formulated and implemented in Ostergötland, Sweden, following the principles and guidelines of the WHO HFA 2000 declaration. Vadstena (n approximately 7,600) was chosen for a local and generalizable osteoporosis prevention project mediated by the primary care organization by means of health promotion and education in the community. In the present report we emphasize that community intervention is an important new advancement of the medical systems, where the basic research questions include operational and management aspects as equally vital and measurable requisites and results as other performance and outcome variables. We found that a community intervention trial against osteoporosis is both motivated and feasible and in this report wish to provide evidence on these crucial issues of logics and logistics.

Adult↗
PubMed2005

Fast recruiting clinical trials--a utopian dream or logistical nightmare?

Randomised clinical trials that exceed anticipated recruitment rates will by definition have the necessary precision to answer the research question within the expected time, thus ensuring the timely release of data that will inform future clinical practice. In addition, the national or international momentum generated brings with it a collective sense of achievement. Such trials, however, may also identify logistical and scientific problems that researchers should be aware of and for which provision needs to be made. The logistical problems relate to the rapid identification of the extra resources required to allow continued excellence in day-to-day management and monitoring of trial governance (both in participating centres and in coordinating trials units). The scientific/clinical problems include managing issues such as unexpected toxicities and suboptimal compliance, and the lack of time available in a rapidly recruiting trial to address them. A related issue concerns the lack of time available to initiate substudies (e.g. biological substudies), the relevance of which may only become apparent as the trial progresses. Many of these challenges were highlighted by recent experience with the Cancer Research UK Taxotere as Adjuvant Chemotherapy trial.

Clinical Trials as Topic↗
PubMed2002

DNA profiling: a valuable tool for quality control of sample logistics including occurrences of suspected sample confusion in a blood donation centre.

BACKGROUND AND OBJECTIVES: A molecular method for analysing whole-blood samples should be established for quality control of plasma sample logistics. MATERIALS AND METHODS: DNA profiles of retention samples (plasma) were compared to profiles of recent donations (whole blood). DNA extraction, amplification and detection were performed using the Qiagen DNA Blood Mini kit, the AmpFFISTR Profiler Plus Kit and capillary electrophoresis, respectively. RESULTS: Matched pairs of full profiles were obtained for all samples investigated, therefore no deviation from the standardized procedures was detected. CONCLUSIONS: Modified extraction and amplification protocols enabled DNA profiling to be used for the quality control of plasma samples. Hence, DNA profiling can be used in the blood bank as a safe and easy method for quality control of sample logistics.

Blood Banks↗
PubMed1997

Sonographic prediction of malignancy in adnexal masses using multivariate logistic regression analysis.

The aim of the study was to assign a probability of malignancy for any patient with an adnexal tumor by the application of multivariate logistic regression analysis to variables recorded at the time of pelvic sonography. Sixty-seven women with known adnexal masses were examined using transvaginal B-mode and color Doppler imaging. For each patient the variables included: (1) age, (2) maximum tumor diameter, (3) tumor volume, (4) unilocularity (presence (0) or absence(1)), (5) papillary projections (presence (1) or absence (0)), (6) random echogenicity (presence (1) or absence (0)), (7) highest peak systolic velocity (PSV), (8) time-averaged maximum velocity (TAMXV), (9) pulsatility index (PI) and (10) resistance index (RI). The TAMXV, PI and RI were those associated with the highest PSV. These ten independent variables and the final histological diagnosis for each patient (the dependent variable) were used for the regression analysis. Approximately 75% of the entire dataset was randomly selected for generating the regression model. The remaining 25% was used as the testing set for cross-validation of the model. In the entire dataset there were 52 women with benign, three with borderline and 12 with invasive ovarian tumors. Regression analysis on the ten variables resulted in the retention of only 'age', 'papillary projection score' and 'TAMXV' as significantly contributing to predicting the presence or absence of malignancy. The probability of malignancy for any patient was given by solving the equation: Probability = 1/(1 + e-z) where e is the base value for natural logarithms and z = (0.1273 x Age) + (0.2794 x TAMXV) + (4.4136 x Papillary projections score) - 14.2046. Cross-validation of the model on the test set of data gave a 100% sensitivity and specificity. However, for the entire dataset the best sensitivity and specificity were 93.3 and 90.4%, respectively, at a cut-off value of 25% probability of malignancy. In conclusion, multivariate logistic regression analysis enables the calculation of probability of malignancy for any patient with a known adnexal mass. The accuracy of this prediction appears to be better than that of morphological or Doppler criteria when the latter are used independently. The value of this model needs to be tested prospectively.

Adult↗
PubMed2002

Development of a model for prediction of survival in pediatric trauma patients: comparison of artificial neural networks and logistic regression.

BACKGROUND/PURPOSE: There is a paucity of outcome prediction models for injured children. Using the National Pediatric Trauma Registry (NPTR), the authors developed an artificial neural network (ANN) to predict pediatric trauma death and compared it with logistic regression (LR). METHODS: Patients in the NPTR from 1996 through 1999 were included. Models were generated using LR and ANN. A data search engine was used to generate the ANN with the best fit for the data. Input variables included anatomic and physiologic characteristics. There was a single output variable: probability of death. Assessment of the models was for both discrimination (ROC area under the curve) and calibration (Lemeshow-Hosmer C-Statistic). RESULTS: There were 35,385 patients. The average age was 8.1 +/- 5.1 years, and there were 1,047 deaths (3.0%). Both modeling systems gave excellent discrimination (ROC A(z): LR = 0.964, ANN = 0.961). However, LR had only fair calibration, whereas the ANN model had excellent calibration (L/H C stat: LR = 36, ANN = 10.5). CONCLUSIONS: The authors were able to develop an ANN model for the prediction of pediatric trauma death, which yielded excellent discrimination and calibration exceeding that of logistic regression. This model can be used by trauma centers to benchmark their performance in treating the pediatric trauma population.

Calibration↗
PubMed2004

Trial logistics, implementation, and conduct of the OCTAVE mega study in Germany. Prospective, randomised, double-blind study to compare the efficacy and tolerability of omapatrilat and enalapril.

Using the example of the largest clinical trial so far conducted to obtain marketing approval (OCTAVE--Omapatrilat Cardiovascular Treatment Assessment Versus Enalapril) this paper describes the way the trial was conducted in Germany and the set-up of the trial logistics. OCTAVE was a prospective, randomised, double-blind study in which the efficacy and tolerability of omapatrilat (CAS 167305-00-2) compared to enalapril (CAS 75847-73-3) were studied in 25 302 patients with uncontrolled blood pressure. Patient recruitment was completed on schedule in just under four months in this global study. An appropriate study design, tailor-made logistics, a special monitoring system and effective project and data management allowed the selection and initiation of 430 study centres in Germany. As a result 4868 patients were randomised within about six months of finalising the study protocol.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

Estimation of the operative risk of mitral valve replacement by multivariate logistic regression analysis.

The knowledge of factors determining the risk of postoperative myocardial failure (MF) should allow a more rational approach to the timing and the management of mitral valve replacement (MVR). Using multivariate logistic regression analysis the influence of 41 preoperative and perioperative variables on MF was assessed in a training group of 353 consecutive patients undergoing isolated primary MVR between 6/76 and 12/82. Early MF mortality was 4.2%. Strongest independent preoperative predictors of MF were advanced NYHA functional class (p less than 0.001), hepatomegaly (p = 0.001), and reduced body weight (p = 0.01). Amongst preoperative and perioperative variables independent determinants of MF were NYHA functional class (p less than 0.001), hepatomegaly (p = 0.002), hypotension during extracorporeal circulation (ECC) (p = 0.005), body weight (p = 0.007), ECC duration (p = 0.008), female sex (p = 0.061) and the absence of cardioplegia (p = 0.065). From the combination of these determinants estimates of the probability of MF were calculated and adjoined to low or high risk by means of an optimum cutoff point. The sensitivity of this test performed before and after operation was 0.80 and 0.93, the specificity 0.92 and 0.94, respectively. The reliability of this prognostic test was prospectively evaluated on data of 107 consecutive MVR patients between 1/83 and 12/84. The observed diagnostic characteristics of the test group were comparable to those predicted from the training group. Multivariate logistic regression analysis selects independent determinants, estimates the risk of MF or other modes of postoperative events and identifies patients with low or high risk with a definable validity as an objective aid for medical decision-making.

Bioprosthesis↗
PubMed1992

Logistical and ergonomic transportation capacity for refuse collection workers: a work physiology field study.

In a work physiology field study, the work flow and the electrocardiogram were recorded throughout whole shifts for six male refuse (garbage) collection workers who transported and emptied 1.1 m3 refuse containers. The work rate (WR), indicated by the number of 1.1 m3 containers emptied per unit of time, and the work pulse rate (WPR) were determined in the data evaluation. The work pulse rate increases with the work rate. The functional relationship can be approximated by a linear regression function (WPR = 20.9 + 35.8.WR). The work pulse rate reaches such high values that it must be assumed that the work cannot be performed continuously throughout the whole working day. Consequently, regular breaks should be provided. When determining the necessary duration of the breaks, it was assumed that an equilibrium between fatigue and recovery should be maintained during the working day. The recovery breaks should be at least long enough for the heart rate to return to the resting level. The necessary duration of the breaks was determined on the basis of the present field study and the laboratory investigations described in the literature. A minimum duration of 10 min per working hour results from the calculations. The breaks should be taken regularly at about hourly intervals. A transportation-capacity model is provided for the planning of the deployment of refuse workers. It permits calculation of the number of 1.1 m3 containers a three-man crew, comprising the refuse collection truck driver and two loaders, can empty during one shift. Both the logistical and ergonomic transportation capacities can be determined using the model. The logistical transportation capacity (TCL) indicates the number of containers which can be emptied per shift by a crew when only criteria such as the optimal utilization of the working time are considered. The ergonomic transportation capacity (TCE) is understood as the number of containers which can be emptied per shift taking into consideration the workers' strain and the recovery breaks they require. TCE amounts to between about 140 and 160 containers per shift depending on the type of city district. TCL is higher by between 20 and 30 containers per shift. In order to meet the demand of protecting workers' health, the number of containers to be emptied per shift by a three-man crew should not exceed the ergonomic transportation capacity.

Adult↗
PubMed2006

Relationships between independence level of single motor-FIM items and FIM-motor scores in patients with hemiplegia after stroke: an ordinal logistic modelling study.

OBJECTIVE: To assess the relationships between independence levels of single motor-related Functional Independence Measure (FIM) items and summed FIM-motor scores of patients with hemiplegia after stroke. DESIGN: For each patient FIM scores were assessed 4 times during hospitalization. Ordinal logistic analyses were performed on group data. SUBJECTS: Fifty patients with hemiplegia after stroke staying in a long-term rehabilitation facility. RESULTS: Analyses revealed that FIM-motor scores accounted for much of the variability of independence levels for most of the single FIM items, including dressing upper body, and transfers to bed/chair/wheelchair and to toilet. For these items, the independence levels were proportionally associated with FIM-motor scores. For eating, higher FIM-motor scores (>60) were associated with modified independence and lower FIM-motor scores (<40) correlated with attainment of supervision/set-up levels. For dressing lower body, greater independence was apparent when FIM-motor scores were higher (>60). CONCLUSION: For single FIM items, relative difficulty was comparable with results from previous literatures using Rasch analyses. Moreover, our results revealed that relative difficulty for single items varied greatly between independence levels. With regard to disability task targets, probability of independence evaluated from logistic modelling is an aid to efficient rehabilitation scheduling.

Activities of Daily Living↗
PubMed2005

Metamodels of bias in Cox proportional-hazards and logistic regressions with heteroscedastic measurement error under group-level exposure assessment.

In occupational epidemiology, group-based exposure assessment entails estimating the average exposure level in a group of workers and assigning the average to all members of the group. The assigned exposure values can be used in epidemiological analyses and have been shown to produce virtually unbiased relative-risk estimates in many situations. Although the group-based exposure assessment continues to be used widely, it is unclear whether it produces unbiased relative-risk estimates in all circumstance, specifically in Cox proportional-hazards and logistic regressions when between-worker variance is not constant but proportional to the true group mean. This question is important because (i) between-worker variance has been shown to differ among exposure groups in occupational epidemiological studies and (ii) recent theoretical work has suggested that bias may exist in such situations. We conducted computer simulations of occupational epidemiological studies to address this question and analysed simulation results using 'metamodelling'. The results indicate that small-to-negligible bias can be expected to result from heteroscedastic between-worker variance. Cox proportional-hazards models can produce attenuated risk estimates, while logistic regression may result in overestimation of risk gradient. Bias caused by ignoring the heteroscedastic measurement error is unlikely to be large enough to alter the conclusion about the direction of exposure-disease association in occupational epidemiology.

Computer Simulation↗
PubMed2006

Attenuation in risk estimates in logistic and Cox proportional-hazards models due to group-based exposure assessment strategy.

In occupational epidemiology, it is often possible to obtain repeated measurements of exposure from a sample of subjects (workers) who belong to exposure groups associated with different levels of exposure. Average exposures from a sample of workers can be assigned to all members of that group including those who are not sampled, leading to a group-based exposure assessment. We discuss how this group-based exposure assessment leads to approximate Berkson error model when the number of subjects with exposure measurements in each group is large, and how the error variance approximates the between-worker variability. Under the normality assumption of exposures and with moderately large number of workers in each group, there is attenuation in the estimate of the association parameter, the magnitude of which depends on the sizes of the between-worker variability and the true association parameter. Approximate equations for attenuation have been derived in logistic and Cox proportional-hazards models. These equations show that the attenuation in Cox proportional-hazards models is generally more severe than in logistic regression. Furthermore, when the between-worker variability is large, our simulation study found that the approximation by equation is poor for the Cox proportional-hazards model. If the number of subjects is small, the approximation does not hold for either model.

Environmental Monitoring↗
PubMed2006

The logistic transform for bounded outcome scores.

The logistic transformation, originally suggested by Johnson (1949), is applied to analyze responses that are restricted to a finite interval (e.g. (0,1)), so-called bounded outcome scores. Bounded outcome scores often have a non-standard distribution, e.g. J- or U-shaped, precluding classical parametric statistical approaches for analysis. Applying the logistic transformation on a normally distributed random variable, gives rise to a logit-normal (LN) distribution. This distribution can take a variety of shapes on (0,1). Further, the model can be extended to correct for (baseline) covariates. Therefore, the method could be useful for comparative clinical trials. Bounded outcomes can be found in many research areas, e.g. drug compliance research, quality-of-life studies, and pain (and pain relief) studies using visual analog scores, but all these scores can attain the boundary values 0 or 1. A natural extension of the above approach is therefore to assume a latent score on 0,1) having a LN distribution. Two cases are considered: (a) the bounded outcome score is a proportion where the true probabilities have a LN distribution on (0,1) and (b) the bounded outcome score on [0,1] is a coarsened version of a latent score with a LN distribution on (0,1). We also allow the variance (on the transformed scale) to depend on treatment. The usefulness of our approach for comparative clinical trials will be assessed in this paper. It turns out to be important to distinguish the case of equal and unequal variances. For a bounded outcome score of the second type and with equal variances, our approach comes close to ordinal probit (OP) regression. However, ignoring the inequality of variances can lead to highly biased parameter estimates. A simulation study compares the performance of our approach with the two-sample Wilcoxon test and with OP regression. Finally, the different methods are illustrated on two data sets.

Anticholesteremic Agents↗