Background & Aim: 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. 
Results: The CF model with unequal variances could best estimate the long-term excess hazard.
Conclusion:  This study advocates  the CF models can best estimate  the long-term  excess hazard rates regardless of the distribution of the frailty variable.

Background & Aim: 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.
Results: We surveyed 235 relief workers and majority of them (75%) were in the scene since the1stor  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.
Conclusion:  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.

Background  & Aim: 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.
Results: 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%.
Conclusion: 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.

Background & Aim: 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.
Results: 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.
Conclusion: 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.

Background & Aim: 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.
Results: 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 .
Conclusion: 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.

Background & Aim: 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.
Results:  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).
Conclusion:  The Persian version of WHOQOL-HIV  BREF is a reliable and valid instrument  to assess the QOL among Iranian HIV-infected population.

Background & Aim: 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.
Results: 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.
Conclusion: 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.

Background & Aim: 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 casecrossover studies, major concerns in selection of controls, different ways for designing casecrossover 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.