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

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

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

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

CYTOCHROME P450 CYP1B1*2 GENE AND ITS ASSOCIATION WITH T2D IN TABUK POPULATION, NORTHWESTERN REGION OF SAUDI ARABIA

Objective: Cytochrome P450 1B1 (CYP1B1) is involved in the activation of procarcinogens and steroid metabolism. Genetic variants of CYP1B1are associated with altered catalytic activity and disease phenotypes. The purpose of this study was to investigate the role of CYP1B1 (rs1056827) polymorphism in inducing T2D.Methods: This cross-sectional study enrolled 113 subjects of T2D and 120 controls. DNA was isolated from blood. Genotyping of the rs1056827 wasdone by allele-specific polymerase chain reaction. The frequency of alleles and genotype distribution was compared in T2D cases and healthy controls.Statistical analysis was performed with SPSS, Chi-square, and Fisher exact test. Hardy-Weinberg equilibrium was tested by a χ2 test. The associations between rs1056827 variant genotypes and T2D were estimated by computing the odds ratios and their 95% confidence intervals (CI) from univariate and multivariate logistic regression analysis.Results: A significant association of rs1056827 was found between T2D cases and controls (p<0.0001). When GG genotype was compared with GT genotype a significant association was found with odd ration (OD)0.24 (95% CI: (0.131–0.452) and risk ratio (RR) 0.45 (0.30–0.67) times the risk of T2D heterozygous with the G/T allele (p≤0.0002). In a comparison of GG homozygous with the TT homozygous, there was no significant association with the OD 0.38 (95% CI: (0.02–6.51) RR 0.55(0.13–2.35), p<0.49. When G allele was compared with the T allele a highly significant association with OD 0.54 (95% [CI]: (0.37–0.80) RR 0.75(0.630–0.897) < p≤0.003 suggesting a possible dominant effect of this polymorphism on T2D risk.Conclusion: This result suggests a significant association between rs1056827G>T polymorphism and T2D. This finding is limited due to the smaller sample size and can be validated by large sample size studies

A Comparison Between Students’ Performance In Multiple Choice and Modified Essay Questions in the MBBS Pediatrics Examination at the College of Medicine, King Khalid University, KSA

Objectives: To investigate the relation between the students' scores in MCQs and MEQs of the summative assessment in pediatrics at the College of medicine KKU. Introduction: Student assessment is the most difficult task in medicine since it is ultimately related to human life and safety. Assessment can take different types of formats with advantages and disadvantages and there is no single prescribed method of choice. Research Methods: This is a quantitative, observational retrospective study enrolling 50 students who completed the final MBBS examination in pediatrics in 2015.The medical students’ scores in MCQs and MEQs in the final MBBS pediatrics examination were collected and SPSS used for analysis. Results: 52% of the students scored A and B, 46% scored C and 2% scored D and nobody scored F. The mean percentage scores in MCQs, MEQs and the combined are75.03%, 79.99% and 76.68% respectively. The standard deviation (SD) for MCQs, MEQs and combined are 0.0753, 0.0763 and 0.0559 respectively.There are no significant differences in means and SD. The correlation (CR) between MCQs and MEQs is -1.73%. The CR between MCQs and MEQs for those who scored A and B is 7.38% which could indicate a weak but significant +ve CR (p value 0.017), (table3). For those who scored C inverse CR (-74.38%) was observed between MCQs and MEQs. Discussion: The main finding of this study was the weakly negative CR between students' performance on MCQs and MEQs. Good performance in MCQs is not necessary correlated with good performance in LEQs. This is not in agreement with Oyebola et al. and Moqattash et al findings, who reported positive CR in the performance of their students. The discrepancy observed in performance between MCQs and MEQs could be explained by the subjectivity and the difficulty in avoiding bias in setting and marking essay questions.   Key Words: multiple choice questions, Modified long essay questions, correlation

Competing risks for reliability analysis using Cox’s model

Purpose – Cox’s model with Weibull distribution and Cox’s with exponential distribution are the most important models in reliability analysis. This paper seeks to show that, with a large sample size based on expectation maximization (EM) algorithm, both models give similar results. Design/methodology/approach – The parameters of the models have been estimated by method of maximum likelihood based on EM algorithm. The objective of this analysis is to fit the modification of Cox’s model with Weibull distribution and Cox’s with exponential distribution, examine its performance and compare their results with Crowder et al. Findings – A simulation study indicates that the parametric Cox’s model with Weibull distribution gives similar results to Cox’s with exponential distribution, especially for a large sample size. Also, the modification of the two models showed better results compared with Crowder et al., especially for the second causes of failure. Originality/value – A modification of the two competing risk models has mostly been applied in failure time data and simulation data. The results of the simulation study indicate that the Weibull and exponential are suitable for Cox’s model as they are easy to use and it can achieve even higher accuracy compared with other distribution models

The Neoproterozoic Keraf Suture in NE Sudan: Sinistral Transpression along the Eastern Margin of West Gondwana

The Keraf Suture, formed during the Neoproterozoic consolidation of Gondwana, is a ~500 km long, ~50 km wide, N-trending suture between the Neoproterozoic Arabian-Nubian Shield in the east and the older Nile Craton to the west. The Keraf Suture is superimposed on E- and NE-trending structures on both sides. The northern part of the suture is dominated by N-trending, upright folds, whereas the southern part is characterized by N- and NNW-trending, sinistral, strike-slip faults. A major antiform defines a structural divide between the northern and southern parts of the suture. 40Ar/39Ar ages on biotite and hornblendes separated from a deformed granitic body indicate that the sinistral movement along the N- and NNW-trending faults took place at ~580 Ma. The difference in structural styles along strike is due to formation of the Keraf Suture by sinistral transpression, which accompanied early NW-SE oblique collision between East and West Gondwana at ~650-600 Ma and terminal collision at ~580 Ma

BT-201: Investigation of the spider web for antibacterial activity

Spiders build their webs with a material called silk. Spider silk contain protein fiber that have many advantages and functions. One of them is to capture their prey such as flies, insects, and others. The needs on the research of antibacterial activity are important for human health because of importance of finding a new cure for some diseases that occur because of microorganisms. Some of the microorganisms, especially bacteria are becoming resistant to many antibacterial agents. The purpose of this new investigation was to determine if spider webs exhibit antibacterial properties. In order to determine antibacterial properties, the spider webs were extracted using different solvents such as methanol, ethanol, acetone, and water in different conditions (extraction time, and concentration used for optimization). These extracts were screened for antibacterial activity using disc diffusion assay. Two bacteria were used in the antibacterial assay namely Bacillus subtilis, and Escherichia coli. The determination of spider webs exhibiting antibacterial properties was based, at least in this study, solely upon the definite appearance of inhibition zone around the well of plates. In screening, acetone solvent was shown the best for antibacterial activity compare to other solvents with 10 mm of diameter of inhibition zone for Bacillus subtilis and 9 mm of diameter of inhibition zone for Escherichia coli. In optimization, the maximum inhibition zone on the Bacillus subtilis was 15 mm at a time of 48 hours and concentration of 0.035 g/ml. Meanwhile, the maximum diameter of inhibition zone on the Escherichia coli was 12 mm at a time of 48 hours and concentration of 0.035 g/ml. Therefore, this study showed that spider webs could be potential source of new antibacterial agents