Journal of Biostatistics and Epidemiology
Volume:1 Issue: 1, Winter 2014

The excess hazard rate proposed by Andersen and Vaeth may underestimate the long-term excess hazard rate for cancer survival. Zahl explained the phenomenon by continuous selection of the most robust individuals after diagnosis. He applied correlated inverse Gaussian and gamma frailty models to estimate excess intensity and reached a better estimate of the rate and called it the corrected excess hazard. The compound Poisson distribution has more parameters and therefore owns more flexibility and includes gamma and inverse Gaussian distributions as special cases. Therefore, the aim of this study was to estimate the excess hazard using compound poisson frailty model.Methods & Materials: Both shared and correlated frailty (CF) variables based on compound Poisson distribution were used to model unobserved common covariates. A data set of patients diagnosed with localized or regional gastrointestinal tract cancer collected at the Mazandaran province of Iran was studied. As registration systems in Iran are so affected by omission and various errors, a number of five West Coale–Demeny life tables for men and four for women were constructed corresponding to each birth cohort, which was considered as the reference life tables. Thus, population-based mortality rates [h1(t)] were simply replaced by the appropriate values of the West tables depending on the sex (male or female) and birth cohort of the patient. The CF model with unequal variances could best estimate the long-term excess hazard. This study advocates the CF models can best estimate the long-term excess hazard rates regardless of the distribution of the frailty variable.

Following the Bam earthquake, relief teams and individual volunteers’ influx in the scene. We conducted this survey to determine the needs and health status of relief workers when they were in the scene.Methods & Materials: This was a concurrent nested mixed-method survey that the qualitative nested in a quantitative approach. Interviews were through an open-ended semi-structural questionnaire three weeks after Bam earthquake. Respondents were from the relief team who had been staying in Bam at least for one week at the time of interview. We surveyed 235 relief workers and majority of them (75%) were in the scene since the1st or 2nd week of earthquake. Twenty-eight of them experienced illness, and the most common complaint was respiratory track illness. One hundred eighty five of them (79%) expressed their need to a psychology consultation. The results of thematic analysis of qualitative phase of survey were about the 19 themes expressed by the subjects. The results of this study revealed that all relief workers should be trained for self- protection. Preparing the basic needs by him/her-self may maximize the performance of relief workers in disaster regions. The study method design applied was appropriate for the similar situations.

It is very helpful to classify and predict the clinical category of a sample based on its gene expression profile. This study was conducted to predict tissues of colorectal adenoma, adenocarcinoma, and paired normal in colon based on microarray data using nearest shrunken centroid method.Methods & Materials: In this study, the colon cancer dataset were used including, 18 adenocarcinoma, 4 colorectal adenoma, and 22 paired normal colon samples with 2360 common gene expression measurements. In order to predict categories of colon cancer was used nearest shrunken centroid method. R software was used for data analysis. Based on our findings, performance of nearest shrunken centroid method was successful to reduce 2360 genes to a set of eleven genes containing rig, BIGH3, GLI3, Homo sapiens guanylin, p78, 54KDa, XBP-1, CO-029, desmin, MLC-2, and HMG-1. This method predicted three classes. It predicted two classes’ colorectal adenoma and adenocarcinoma with error of zero and normal class with error of 4.5%. Nearest shrunken centroid method succeeded to reduce several 1000 genes to 11 genes that were able to characterize colon tissue samples to one of the three classes of adenocarcinoma, colorectal adenoma and normal with 97.7% accuracy.

Due to lack of a unique and acceptable classification scheme for occupation in Iran, the role of this measure has been ignored in many health researches. We aimed to find a suitable classification. Methods & Materials: In-depth interviews with expert health professionals were done through purposeful sampling. They expressed their opinions on five commonly used occupational based socio-economic measures in the world to develop a consensus draft for Iranian occupational classification. The main themes were identified by content analysis. The experts agreed that the National Statistics Socio-economic Classification was the most compatible job classification for Iran’s health researches. Some of the problems in occupation assessment in health research were also clarified through interviews. Job classification would better consist of more than one job dimension; the economic parameters are not stable and accurately measurable, so more social aspects of occupation such as the authority and control over workforce should be considered.

In many studies, the survival of patients with chronic kidney disease who are treated with peritoneal dialysis technique has been considered, while this is possible in peritoneal dialysis patients to switch to another treatment. To achieve more accurate estimation of patient survival is necessary to examine all events. The purpose of this study is to estimate the cumulative incidence function (CIF) of events using competing risks method and then calculating the survival of patients treated with peritoneal dialysis.Methods & Materials: This study includes 417 patients with chronic kidney disease who were under peritoneal dialysis between July 1996 and December 2009 in three centers in Tehran. We achieved their survival by 13 years follow-up time. We have collected patient demographic data and clinical characteristics. CIF of death and other events was estimated using the cause-specific hazard approach and direct approach. Parametric regression model was used to adjust the effects of covariates. The data analysis was performed using the R software. In this study, the median follow-up time was 664 days. A total of 112 (26.9%) patients treated with peritoneal dialysis died before completing the study, and before the end of the study. One hundred sixty seven (40.0%) patients treated with peritoneal dialysis changed their dialysis method to hemodialysis or had renal transplantation. The effective risk factors on death CIF and other competing events CIF were diabetes mellitus, albumin, creatinine, diastolic blood pressure, urea and age, creatinine, diastolic blood pressure, respectively.

Quality-of-life (QOL) among human immunodeficiency virus (HIV)-infected people has been the center of focus worldwide. The World Health Organization QOL Group (WHOQOL Group) has developed a 31-item QOL questionnaire, which has been translated and used in many countries. This paper aimed at examining the reliability and validity of Persian version of HIV specific WHOQOL scaleBREF questionnaire (WHOQOL-HIV BREF) in Iranian patients suffering from HIV/acquired immunodeficiency syndrome (AIDS).Methods & Materials: For the purpose of this cross-sectional study, a standard “forward- backward” translation and cognitive debriefing were initially applied. Subsequently, 150 people living with HIV/AIDS visitingTertiary Referral Consultation Center for clients with risky behaviors in Tehran completed the Persian version of the questionnaire. Validity was assessed using “Known Group Comparison” through ANOVA test. Internal reliability was measured by Cronbach’s alpha and Split-Half coefficients. WHOQOL-HIV BREF was capable to discriminate between two groups who were different in their QOL (P< 0.05). Internal consistency analysis was satisfactory for domains (Cronbach’s alpha =0.64–0.85), and whole the instrument (Cronbach’s alpha=0.93). The Persian version of WHOQOL-HIV BREF is a reliable and valid instrument to assess the QOL among Iranian HIV-infected population.

The aim of the current study was to investigate the advantages of Bayesian method in comparison to traditional methods to detect best antioxidant in Freezing of human male gametes.Methods & Materials: Semen samples were obtained from 40 men whose sperm had normal criteria. A part of each sample was separated without antioxidant as fresh and the remaining was freezed with and without antioxidant. Taurine (in concentrations of 25 mm and50mm) and cysteine (5mm and10mm) as antioxidants were prepared as intervention. Traditional results were obtained from randomized incomplete block design and compared with Bayesian results in their ability to find the significant difference among our groups. Using Markov chain Monte Carlo algorithm within the WinBUGS software, we developed a Bayesian approach to estimate the protective effect of antioxidant against inverse effect of freezing on the quality of sperm. Classic method could detect the significant difference just in cycteine10mm for viability which was confirmed by Bayesian method. In Bayesian method, in addition to results from classic method, we could find the significant improvement in abnormality: cysteine 10mm, protamin deficiency: taurine 25 mm and10 mm, viability: cysteine 10mm, DNA fragmentation: cysteine 10mm which all of them was interested in clinically, but could not be proved by the traditional methods. Bayesian approach in sperm biology research can be considered as a good replacement of the traditional methods for estimation. Using this method, we can solve complex and intractable statistical models. Future researches should be done to confirm our suggestion.

Case-crossover studies are the case-control version of crossover studies. In these studies, cases and controls are the same subjects. The term crossover is applied for designs that all subjects pass through both treatment (exposure) and placebo (non-exposure) phases. In fact they are crossover of subjects between periods of exposure and non-exposure. This design is most suitable for outcomes, which their induction time is short. Whatever the onset of outcome is more abrupt, it is more amenable to be studied in case-crossover studies. Case-crossover design can be implemented in a number of ways. In this article some common terms in the literature of case- crossover studies, major concerns in selection of controls, different ways for designing case- crossover studies, some examples for analyzing these data according to different sampling designs and also design and analysis of case-time-control designs with practical examples are being explored.