Em Approach on Influence Measures in Competing Risks Via Proportional Hazard Regression Model

In a conventional competing risk s model, the time to failure of a particular experimental unit might be censored and the cause of failure can be known or unknown. In this thesis the analysis of this particular model was based on the cause-specific hazard of Cox model. The Expectation Maximization (EM) was considered to obtain the estimate of the parameters. These estimates were then compared to the Newton-Raphson iteration method. A generated data where the failure times were taken as exponentially distributed was used to further compare these two methods of estimation. From the simulation study for this particular case, we can conclude that the EM algorithm proved to be more superior in terms of mean value of parameter estimates, bias and root mean square error. To detect irregularities and peculiarities in the data set, the residuals, Cook distance and the likelihood distance were computed. Unlike the residuals, the perturbation method of Cook's distance and the likelihood distance were effective in the detection of observations that have influenced on the parameter estimates. We considered both the EM approach and the ordinary maximum likelihood estimation (MLE) approach in the computation of the influence measurements. For the ultimate results of influence measurements we utilized the approach of the one step . The EM one-step and the maximum likelihood (ML) one-step gave conclusions that are analogous to the full iteration distance measurements. In comparison, it was found that EM one-step gave better results than the ML one step with respect to the value of Cook's distance and likelihood distance. It was also found that Cook's distance i s better than the likelihood distance with respect to the number of observations detected

Artificial Neural Network versus Linear Models Forecasting Doha Stock Market

The purpose of this study is to determine the instability of Doha stock market and develop forecasting models. Linear time series models are used and compared with a nonlinear Artificial Neural Network (ANN) namely Multilayer Perceptron (MLP) Technique. It aims to establish the best useful model based on daily and monthly data which are collected from Qatar exchange for the period starting from January 2007 to January 2015. Proposed models are for the general index of Qatar stock exchange and also for the usages in other several sectors. With the help of these models, Doha stock market index and other various sectors were predicted. The study was conducted by using various time series techniques to study and analyze data trend in producing appropriate results. After applying several models, such as: Quadratic trend model, double exponential smoothing model, and ARIMA, it was concluded that ARIMA (2,2) was the most suitable linear model for the daily general index. However, ANN model was found to be more accurate than time series models. Published under licence by IOP Publishing Ltd.Scopu

Editorial Problem based learning in medical education, where we are?

No Abstract. Sudan Journal of Medical Sciences Vol. 1(1) 2006: 11-1

Evaluation of student assessment practices in a medical college

Background: The importance of students’ assessment and its role in driving students learning are well recognized. Guidelines for good assessment practice have been developed. The GMC issued important recommendations related to assessment of students’ performance to be followed by medical schools in UK. The Liaison Committee on Medical Education (LCME) developed standards emphasizing the importance of documenting students’ performance. The utility concept of an assessment tool had been proposed by Van der Vleuten stating a number of weighted criteria. Assessment of clinical competence was proposed to be well covered by the model of Miller. No single method of assessment can be recommended to be appropriate for all assessment purposes and all domains of competence. Therefore, multiple methods of assessment are required.Methods: There are 35 courses included in the MBBS program in the college of medicine, KKU. these are taught over five years in addition to a preparatory year and the internship year. the curriculum can still be described as discipline based. a survey was planned to study the current assessment situation. this is a cross-sectional descriptive study. the data collection methods used were survey and study of the documents of the courses. an online questionnaire was developed. the responses were analyzed using descriptive statistics to determine frequencies, averages and percentages. the study was conducted during the period January-May 2014.Results: Twenty course coordinators responded to the survey (57%). Eleven of the courses covered were basic and nine were clinical. Multiple tests as well as multiple methods of continuous assessment were used in the courses studied. Some of the methods used for summative assessment are no longer recommended in current assessment practices in medical education. Real OSCE was used only in one clinical course. Standard setting methods were not used and a fixed pass mark was used instead.Conclusions: Important shortcomings in student assessment system in many of the courses studied were identified. Less educationally desirable assessment methods and practices are still used in some courses such as unattended single long case examination. More attention should be given to technical aspects of assessment

Parametric Model Based on Imputations Techniques for Partly Interval Censored Data

The term 'survival analysis' has been used in a broad sense to describe collection of statistical procedures for data analysis. In this case, outcome variable of interest is time until an event occurs where the time to failure of a specific experimental unit might be censored which can be right, left, interval, and Partly Interval Censored data (PIC). In this paper, analysis of this model was conducted based on parametric Cox model via PIC data. Moreover, several imputation techniques were used, which are: midpoint, left & right point, random, mean, and median. Maximum likelihood estimate was considered to obtain the estimated survival function. These estimations were then compared with the existing model, such as: Turnbull and Cox model based on clinical trial data (breast cancer data), for which it showed the validity of the proposed model. Result of data set indicated that the parametric of Cox model proved to be more superior in terms of estimation of survival functions, likelihood ratio tests, and their P-values. Moreover, based on imputation techniques; the midpoint, random, mean, and median showed better results with respect to the estimation of survival function. Published under licence by IOP Publishing Ltd.Scopu

Minimally Invasive Surgery: Can We See Inside the Future

The substantial developments in surgery, over the last century with the advent of antiseptic substance, anesthetic agents, antibiotics, surgical nutrition, and organ transplantation, haven’t  changed neither the basic surgical tools nor the surgical techniques. Minimally invasive surgery (MIS), was first proposed by Wickham in 1986 because of the radical changes in the treatment of kidney stones between 1979 and 1983. This new concept of (MIS) has revolutionized the management of surgical disorders in a very short period of time.  It has moved the focus of surgery towards reducing the morbidity without compromising on the quality of healthcare(1). (MIS) is getting in more and more in all fields of surgery, laparoscopic and endoscopic surgery are no exception(2). It basically entailed entering the body cavities or lumina through the skin or through a natural orifice incurring the least damage to those organs or structures. . Collectively called minimal access surgery it has developed so much to the extent of being impossible to halt or withdraw it back. Recently computerized designing of laparoscopic instrument is introduced and microprocessor controlled safety features are added.  MIS has proved a boom for patients over the last 25 years. It has significantly reduced  hospital stay, grossly reduced the  patients’ recovery time, and greatly improved the cosmetic consequences of operations with less pain and  less strain of the organism. Despite the improvement in outcomes with laparoscopy, the technique still has some limitations.  Apart from grand cost and training needs, there is definite loss of tactile perception and of course the surgeon’s eyesight is limited by the two dimensional view(3)

Regression analysis of masked competing risks data under cumulative incidence function framework

In the studies that involve competing risks, somehow, masking issues might arise. That is, the cause of failure for some subjects is only known as a subset of possible causes. In this study, a Bayesian analysis is developed to assess the effect of risks factor on the Cumulative Incidence Function (CIF) by adopting the proportional subdistribution hazard model. Simulation is conducted to evaluate the performance of the proposed model and it shows that the model is feasible for the possible applications

Effects of time-lagged meteorological variables on attributable risk of leishmaniasis in central region of Afghanistan

Background: Leishmaniasis remains one of the world's most neglected vector-borne diseases, affecting predominantly poor communities mainly in developing countries. Previous studies have shown that the distribution and dynamics of leishmaniasis infections are sensitive to environmental factors, however, there are no studies on the burden of leishmaniasis attributable to time-varying meteorological variables. Methods: This study used data from 3 major leishmaniosis afflicted provinces of Afghanistan, between 2003 and 2009, to provide empirical analysis of change in heat/cold-leishmaniosis association. Non-linear and delayed exposure-lag-response relationship between meteorological variables and leishmaniasis were fitted with a distributed lag non-linear model applying a spline function which describes the dependency along the range of values with a lag of up to 12 months. We estimated the risk of leishmaniasis attributable to high and low temperature. Results: The median monthly mean temperature and rainfall were 16.1 °C and 0.6 in., respectively. Seasonal variations of leishmaniasis were consistent between males and females, however significant differences were observed among different age groups. Temperature effects were immediate and persistent (lag 0–12 months). The cumulative risks were highest at cold temperatures. The cumulative relative risks (logRR) for leishmaniasis were 6.16 (95% CI: 5.74–6.58) and 1.15 (95% CI: 1.32–1.31) associated with the 10th percentile temperature (2.16 °C) and the 90th percentile temperature (28.46 °C). The subgroup analysis showed increased risk for males as well as young and middle aged people at cold temperatures, however, higher risk was observed for the elderly in heat. The overall leishmaniasis-temperature attributable fractions was estimated to be 7.6% (95% CI: 7.5%–7.7%) and mostly due to cold. Conclusion: Findings in this study highlight the non-linearity, delay of effects and magnitude of leishmaniasis risk associated with temperature. The disparity of risk between different subgroups can hopefully advise policy makers and assist in leishmaniasis control program

The Perception of Stakeholders towards Services Provided By Primary Health Care in Khartoum State, Sudan

Background: Sudan is a signatory country to Alma Ata Declaration and Primary Health Care (PHC) had been established since 1979. Although a lot of improvement is claimed to be achieved in PHC, some of the areas might be still far below the expectations. The objective of this study was to investigate the perception of the PHC stakeholders in Khartoum State about the PHC services provided and the adequacy of facilities used.Materials and Methods: This is a cross-sectional descriptive study conducted in Khartoum State, Sudan, between June and October 2015. A structured questionnaire was administered to a sample of PHC stakeholders. A 3-point Likert scale was used to indicate the quality of the different services provided and the facilities present. SPSS version 20 was used for analysis to calculate relevant descriptive statistical parameters.Results: Vaccination and care for pregnant ladies were perceived by respondents as present and adequate (100% and 95%, respectively). The other services that are perceived as adequate include: child health care, health education, chronic illness, drugs availability and the referral system. In sanitation services and feedback about patients referred to hospitals, only 20% and 4% were satisfied, respectively.Conclusion: Most of the PHC services were perceived as adequate by the respondents from Khartoum State. The services and facilities that were perceived as inadequate include sanitation services, communicable diseases, the referral system and provision of dental services.Key words: primary health care (PHC), stakeholders