Determining relative importance of variables in developing and validating predictive models

<p>Abstract</p> <p>Background</p> <p>Multiple regression models are used in a wide range of scientific disciplines and automated model selection procedures are frequently used to identify independent predictors. However, determination of relative importance of potential predictors and validating the fitted models for their stability, predictive accuracy and generalizability are often overlooked or not done thoroughly.</p> <p>Methods</p> <p>Using a case study aimed at predicting children with acute lymphoblastic leukemia (ALL) who are at low risk of Tumor Lysis Syndrome (TLS), we propose and compare two strategies, bootstrapping and random split of data, for ordering potential predictors according to their relative importance with respect to model stability and generalizability. We also propose an approach based on relative increase in percentage of explained variation and area under the Receiver Operating Characteristic (ROC) curve for developing models where variables from our ordered list enter the model according to their importance. An additional data set aimed at identifying predictors of prostate cancer penetration is also used for illustrative purposes.</p> <p>Results</p> <p>Age is chosen to be the most important predictor of TLS. It is selected 100% of the time using the bootstrapping approach. Using the random split method, it is selected 99% of the time in the training data and is significant (at 5% level) 98% of the time in the validation data set. This indicates that age is a stable predictor of TLS with good generalizability. The second most important variable is white blood cell count (WBC). Our methods also identified an important predictor of TLS that was otherwise omitted if relying on any of the automated model selection procedures alone. A group at low risk of TLS consists of children younger than 10 years of age, without T-cell immunophenotype, whose baseline WBC is < 20 × 10⁹/L and palpable spleen is < 2 cm. For the prostate cancer data set, the Gleason score and digital rectal exam are identified to be the most important indicators of whether tumor has penetrated the prostate capsule.</p> <p>Conclusion</p> <p>Our model selection procedures based on bootstrap re-sampling and repeated random split techniques can be used to assess the strength of evidence that a variable is truly an independent and reproducible predictor. Our methods, therefore, can be used for developing stable and reproducible models with good performances. Moreover, our methods can serve as a good tool for validating a predictive model. Previous biological and clinical studies support the findings based on our selection and validation strategies. However, extensive simulations may be required to assess the performance of our methods under different scenarios as well as check their sensitivity to a random fluctuation in the data.</p

Electrolytes and Interphases in Sodium-Based Rechargeable Batteries: Recent Advances and Perspectives

For sodium (Na)-rechargeable batteries to compete, and go beyond the currently prevailing Li-ion technologies, mastering the chemistry and accompanying phenomena is of supreme importance. Among the crucial components of the battery system, the electrolyte, which bridges the highly polarized positive and negative electrode materials, is arguably the most critical and indispensable of all. The electrolyte dictates the interfacial chemistry of the battery and the overall performance, having an influence over the practical capacity, rate capability (power), chemical/thermal stress (safety), and lifetime. In-depth knowledge of electrolyte properties provides invaluable information to improve the design, assembly, and operation of the battery. Thus, the full-scale appraisal of both tailored electrolytes and the concomitant interphases generated at the electrodes need to be prioritized. The deployment of large-format Na-based rechargeable batteries also necessitates systematic evaluation and detailed appraisal of the safety-related hazards of Na-based batteries. Hence, this review presents a comprehensive account of the progress, status, and prospect of various Na+-ion electrolytes, including solvents, salts and additives, their interphases and potential hazards

Rapid Assessment as an Evaluation Tool for Polio National Immunisation Days in Brong Ahafo Region, Ghana

Background: Despite reported high coverage of National Immunization Days (NIDs) campaign in many countries children are still being missed during these campaigns. This is a study of a rapid assessment done to determine OPV coverage during an immunization campaign. Methods: In this descriptive cross-sectional study, regional supervisors in Brong Ahafo region of Ghana visited randomly selected houses during the first round of the Polio NIDs in October 2004 to identify under-5 children that were reached with OPV vaccines in the households and those missed during the campaign. Results: In the 13 districts a 1607 houses visited by regional supervisors for rapid assessment, volunteers did not visit 4 (0.24%) houses. There were 3737 under five in all the houses visited by the supervisors for rapid assessment out which 42 (1.2%) were missed and unvaccinated and the reason was that the children were not at home. The assessment showed that the main sources of information to mothers / caretakers on NIDs were Gong-gong and radio. The assessment provided opportunities to identify proportion of children missed and ensure necessary intervention to reach them. Conclusion: Rapid assessment is a valuable tool for evaluation of NIDs; it enables timely intervention in covering missed children and helps in careful interpretation of the usual over 100% coverage often recorded during NIDs. It is recommended that this be practiced widely to improve quality of NIDs for early global eradication of poliomyelitis.Contexte : Malgr\ue9 la haute couverte rapport\ue9e lors des campagnes nationales d'immunisation, dans plusieurs pays des enfants sont toujours rat\ue9s par ces campagnes. Nous proposons une estimation rapide de la couverture durant une campagne d'immunisation. M\ue9thodes : Dans cette \ue9tude descriptive sur un \ue9chantillon repr\ue9sentatif, des maisons choisies au hasard ont \ue9t\ue9 visit\ue9 par les superviseurs r\ue9gionaux de la r\ue9gion de Brong Ahafo, Ghana lors du premier passage des journ\ue9es nationales d'immunisation contre la Polio en Octobre 2004. Il s'agissait d'identifier les enfants de moins de 5 ans ayant re\ue7u le vaccin dans ces maisons et d'identifier ceux qui n'ont pas \ue9t\ue9 vaccin\ue9s dans cette campagne. R\ue9sultats : Dans 13 districts, un total de 1607 maisons visit\ue9es par les superviseurs r\ue9gionaux, pour estimation rapide. Quatre maisons (0,24%) n'avaient pas \ue9t\ue9 visit\ue9es par les volontaires. Il y'avaient 3737 enfants de moins de 5 ans dans l'ensemble des maisons visit\ue9es par les superviseurs, parmi eux 42 (1,2%) n'avaient pas \ue9t\ue9 vaccin\ue9s et la raison \ue9taient que ces enfants \ue9taient absents de la maison. L'\ue9valuation avait montr\ue9 que les principales sources d'information des mamans/gardiens lors des journ\ue9es nationales d'immunisation \ue9taient les Gong-gong et la radio. L'estimation avait donn\ue9 des opportunit\ue9s pour la d\ue9termination de la proportion d'enfants non vaccin\ue9s et des interventions \ue0 faire afin d'atteindre ces enfants. Conclusion : L'estimation rapide est un instrument important pour l'\ue9valuation des journ\ue9es nationales d'immunisation, elle permet des interventions opportunes pour couvrir les enfants manqu\ue9s. Elle permet aussi de faire une interpr\ue9tation prudente du taux de couverture de 100% habituellement rapport\ue9 durant ces journ\ue9es nationales d'immunisation. Il est recommand\ue9 de vulgariser cette v\ue9rification afin d'am\ue9liorer la qualit\ue9 de ces journ\ue9es nationales d'immunisation pour une \ue9radication globale de la poliomy\ue9lite

A NSFD method for the singularly perturbed Burgers-Huxley equation

This article focuses on a numerical solution of the singularly perturbed Burgers-Huxley equation. The simultaneous presence of a singular perturbation parameter and the nonlinearity raise the challenge of finding a reliable and efficient numerical solution for this equation via the classical numerical methods. To overcome this challenge, a nonstandard finite difference (NSFD) scheme is developed in the following manner. The time variable is discretized using the backward Euler method. This gives rise to a system of nonlinear ordinary differential equations which are then dealt with using the concept of nonlocal approximation. Through a rigorous error analysis, the proposed scheme has been shown to be parameter-uniform convergent. Simulations conducted on two numerical examples confirm the theoretical result. A comparison with other methods in terms of accuracy and computational cost reveals the superiority of the proposed scheme

Studi Volume Lalu Lintas di Jalan Raya Narogong Cileungsi, Kabupaten Bogor, Periode Agustus 2011

Survey of traffic volume is one of the simplest methods to obtain traffic data in order to better understand optimalisation andefficiency so that it can minimize vehicle traffic congestion problems on the highway. The method used is based on descriptive andanalytical methods, which is done is to classify the vehicles in classes manually by counting the number of vehicles per time unitbased on class - class. The purpose of the volume of traffic surveys carried out in the classified Narogong Cullinan Road, Bogorregency during the period August, 2011, results that can be found is the degree of saturation of the highway is still in an acceptablelevel. Analysis of traffic flow at the study site is still under the limit congestion. It is suggested that to reduce the traffic density, thetype of heavy vehicles such as out of the factory operates around the study site between the hours of 10:00 pm to 3:00 am

Past eight-year malaria data in Gedeo zone, southern Ethiopia: trend, reporting-quality, spatiotemporal distribution, and association with socio-demographic and meteorological variables.

BACKGROUND: Informed decision making is underlined by all tiers in the health system. Poor data record system coupled with under- (over)-reporting of malaria cases affects the country's malaria elimination activities. Thus, malaria data at health facilities and health offices are important particularly to monitor and evaluate the elimination progresses. This study was intended to assess overall reported malaria cases, reporting quality, spatiotemporal trends and factors associated in Gedeo zone, South Ethiopia. METHODS: Past 8 years retrospective data stored in 17 health centers and 5 district health offices in Gedeo Zone, South Ethiopia were extracted. Malaria cases data at each health center with sociodemographic information, between January 2012 and December 2019, were included. Meteorological data were obtained from the national meteorology agency of Ethiopia. The data were analyzed using Stata 13. RESULTS: A total of 485,414 suspected cases were examined for malaria during the previous 8 years at health centers. Of these suspects, 57,228 (11.79%) were confirmed malaria cases with an overall decline during the 8-year period. We noted that 3758 suspected cases and 467 confirmed malaria cases were not captured at the health offices. Based on the health centers records, the proportions of Plasmodium falciparum (49.74%) and P. vivax (47.59%) infection were nearly equivalent (p = 0.795). The former was higher at low altitudes while the latter was higher at higher altitudes. The over 15 years of age group accounted for 11.47% of confirmed malaria cases (p < 0.001). There was high spatiotemporal variation: the highest case record was during Belg (12.52%) and in Dilla town (18,150, 13.17%, p < 0.001) which is located at low altitude. Monthly rainfall and minimum temperature exhibited strong associations with confirmed malaria cases. CONCLUSION: A notable overall decline in malaria cases was observed during the eight-year period. Both P. falciparum and P. vivax were found at equivalent endemicity level; hence control measures should continue targeting both species. The noticed under reporting, the high malaria burden in urban settings, low altitudes and Belg season need spatiotemporal consideration by the elimination program

Patterns of treatment seeking behavior for mental illnesses in Southwest Ethiopia: a hospital based study

<p>Abstract</p> <p>Background</p> <p>Early recognition of the signs and symptoms of mental health disorders is important because early intervention is critical to restoring the mental as well as the physical and the social health of an individual. This study sought to investigate patterns of treatment seeking behavior and associated factors for mental illness.</p> <p>Methods</p> <p>A quantitative, institution-based cross sectional study was conducted among 384 psychiatric patients at Jimma University Specialized Hospital (JUSH) located in Jimma, Ethiopia from March to April 2010. Data was collected using a pretested WHO encounter format by trained psychiatric nurses. Data was analyzed using SPSS V.16.</p> <p>Result</p> <p>Major depression disorder 186 (48.4%), schizophrenia 55 (14.3%) and other psychotic disorders 47 (12.2%) were the most common diagnoses given to the respondents. The median duration of symptoms of mental illness before contact to modern mental health service was 52.1 weeks. The main sources of information for the help sought by the patients were found to be family 126 (32.8%) and other patients 75 (19.5%). Over a third of the patients 135 (35.2%), came directly to JUSH. Half of the patients sought traditional treatment from either a religious healer 116 (30.2%) or an herbalist 77 (20.1%) before they came to the hospital. The most common explanations given for the cause of the mental illness were spiritual possession 198 (51.6%) and evil eye 61 (15.9%), whereas 73 (19.0%) of the respondents said they did not know the cause of mental illnesses. Nearly all of the respondents 379 (98.7%) believed that mental illness can be cured with modern treatment. Individuals who presented with abdominal pain and headache were more likely to seek care earlier. Being in the age group 31-40 years had significant statistical association with delayed treatment seeking behavior.</p> <p>Conclusions</p> <p>There is significant delay in modern psychiatric treatment seeking in the majority of the cases. Traditional healers were the first place where help was sought for mental illness in this population. Most of the respondents claimed that mental illnesses were caused by supernatural factors. In contrast to their thoughts about the causes of mental illnesses however, most of the respondents believed that mental illnesses could be cured with biomedical treatment. Interventions targeted at improving public awareness about the causes and treatment of mental illness could reduce the delay in treatment seeking and improve treatment outcomes.</p

Chemical exchange saturation transfer MRI in central nervous system tumours on a 1.5 T MR-Linac

Purpose: To describe the implementation and initial results of using Chemical Exchange Saturation Transfer (CEST) for monitoring patients with central nervous system (CNS) tumours treated using a 1.5 tesla MR-guided radiotherapy system. Methods: CNS patients were treated with up to 30 fractions (total dose up to 60 Gy) using a 1.5 T Elekta Unity MR-Linac. CEST scans were obtained in 54 subjects at one or more time points during treatment. CEST metrics, including the amide magnetization transfer ratio (MTRAmide), nuclear Overhauser effect (NOE) MTR (MTRNOE) and asymmetry, were quantified in phantoms and CNS patients. The signal was investigated between tumour and white matter, across time, and across disease categories including high- and low-grade tumours. Results: The gross tumour volume (GTV) exhibited lower MTRAmide and MTRNOE and higher asymmetry compared to contralateral normal appearing white matter. Signal changes in the GTV during fractionated radiotherapy were observed. There were differences between high- and low-grade tumours, with higher CEST asymmetry associated with higher grade disease. Conclusion: CEST MRI using a 1.5 T MR-Linac was demonstrated to be feasible for in vivo imaging of CNS tumours. CEST images showed tumour/white-matter contrast, temporal CEST signal changes, and associations with tumour grade. These results show promise for the eventual goal of using metabolic imaging to inform the design of adaptive radiotherapy protocols

Duration and determinants of birth interval among women of child bearing age in Southern Ethiopia

<p>Abstract</p> <p>Background</p> <p>Longer intervals between consecutive births decrease the number of children a woman can have. This results in beneficial effects on population size and on the health status of mothers and children. Therefore, understanding the practice of birth interval and its determinants is helpful to design evidence based strategies for interventions. The objective of this study was to determine duration and determinants of birth interval among women of child bearing age in Lemo district, southern Ethiopia in March 2010.</p> <p>Methods</p> <p>A community based cross sectional study design with stratified multistage sampling technique was employed. A sample of 844 women of child bearing age were selected by using simple random sampling technique after complete census was conducted in selected kebeles prior to data collection. Structured interviewer administered questionnaire was used for data collection. Actual birth interval was measured with the respondents' memory since majority of the women or their children in the area had no birth certificate.</p> <p>Results</p> <p>Majority (57%) of women were practicing short birth interval length with the median birth interval length of 33 months. Actual birth interval length is significantly shorter than preferred birth interval length. Birth interval showed significant variation by contraceptive use, residence, wealth index, breast feeding and occupation of husbands.</p> <p>Conclusion</p> <p>low proportion of optimal birth spacing practices with short actual birth interval length and longer preferred birth interval lengths were evident among the study subjects. Hence interventions to enhance contraceptive utilization behaviors among women in Lemo district would be helpful to narrow the gap between optimal and actual birth spacing.</p