Journal of School of Public Health and

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Considering the importance of the mass campaign for measles-rubella vaccination in the elimination of measles and Congenital Rubella Syndrome, and also the necessity of the accurate quantitative and qualitative assessment of the process of this program and the estimation of the information coverage regarding the passive launch of the program, this assessment has been carried out within the population covered by Tehran University of Medical Sciences using a standard method. This study is descriptive- analytical. The necessary sample size was defined as 390 people for the estimation of the immunization coverage, 190 people in each step of the information coverage (and a total of 570 people for the overall three steps), and finally 24 executive teams for the assessment of the quality of the service. Lot Quality Assurance Sampling and subsequent analysis were used for the assessment of service quality, with the upper threshold set at 80% and the lower threshold at 30%. Each lot was defined acceptable or unacceptable based on the quality of the vaccination, the cold chain, the competence of the human resource, and the availability of the necessary materials and equipment. Data analysis was done using the Chi Square and Fisher’s exact tests. 96.4% (95% CI: between 94.6% and 98.2%) of the people between 5 and 25 years old had received the MR vaccine. 7 people (1.8%) of the vaccinated people were not in the target group of vaccination. From the total 190 people who were studied on the basis of information coverage, 152 people (80.9%), 184 people (96.8%) and 190 people (100%) were informed about the mass campaign for MR vaccination in the first, second, and the third steps respectively. More than 80% of the people were informed about the program through TV. The quality of the vaccination was acceptable in 19 executive teams (79.1%) and unacceptable in the other 5 executive teams (20.9%). In this study, the quality of the cold chain was acceptable in 23 executive teams (95.8%) and unacceptable in one team (4.2%). The competence of the human resource, the necessary materials and equipment for MR vaccination was acceptable in all 24 executive teams under study (100%). The enforcement of the mass campaign in such short period of time compared to similar programs in other countries demonstrated the success of the collaborators in the execution of this program. Overall it seems that regarding the quality of vaccination, information coverage, and the provision of materials and equipment in health centers of the districts, the program has achieved its goals.

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In recent years the patterns of mortality have changed in Iran, and cancers are playing a greater role in this regard in this country. Various reports indicate that gastric cancer is highly prevalent it is the second most common cancer in men, and fourth in the general population. The purpose of this study was to determine the five-year survival rate of gastric cancer patients who had undergone surgical treatment at one of the most important cancer treatment centers, the Iran Cancer Institute, and to assess its associated factors. Three hundred and 30 patients with gastric cancer who had been admitted to and operated on at the Iran Cancer Institute between January 1996 and April 2000 were enrolled in this study. The patients’ life expectancy after surgery was determined, and its relationship with variables of age at the time of surgery, gender, and factors related to the disease such as the cancer site, pathologic type, stage, presence of metastasis, and sites of metastases were assessed. The five-year survival rate and the median life expectancy in the studied patients were 23.6% and 19.90 months, respectively. Univariate analysis showed that gender, cancer site, and pathologic type did not affect life expectancy significantly. But the five-year survival rate significantly decreases with age. As expected, those involved with metastasis had a significantly lower five-year survival rate, and the disease stage significantly affected the patients’ life expectancy (P<0.001). The Cox proportional hazards model was used to assess the effect of different variables simultaneously, and it showed that age, distance metastasis, and disease stage influenced the rate of survival. Gastric cancer patients in Iran have a low five-year survival rate. One of the most important reasons seems to be delayed consultation and diagnosis. Most patients are seen first with the disease in the late stages. At this point, most have lymph node and liver metastasis which makes treatment even more complex. Thus, it is necessary to employ mass media for extensive public education about the early warning signs of the disease and performing periodic examinations.

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Background and Aim: The purpose of this study was to assess the accuracy of the bootstrap method in logistic regression and to explore the method's use in logistic regression models in cases where the sample size is insufficient.
Materials and Methods: We use data from 150 patients who had undergone surgery at the Cancer Institute, Emam Khomeini hospital during from 1999 to 2001. Then we drew repeated samples of size 50 from these 150 patients.
Results: Applying ordinary logistic regression, an appropriate model we fitted to the initial data. Then confidence intervals and standard errors were computed for all regression coefficients. There are many situations where the sample size is insufficient and conditions for using ordinary logistic regression are not met. In these cases the use of the bootstrap method not only produces more accurate estimations of regression coefficients, but with repeated sampling, produces estimates very close to the true values. This holds for the estimation of regression coefficients, confidence intervals and standard errors of coefficients.
Conclusion: In this study we show the optimal number of replications and the optimal sample size when using the bootstrap method in studies involving relatively small sample sizes.

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Background and Aim: Nowadays, community health and different methods for health service delivery are among the most important public health issues in many countries. Most developing nations are trying to establish a health care system capable of meeting their basic needs.Hospitals are the most important service delivery points, and they need skilled manpower and adequate equipment for efficient performance of their medical care and educational functions. Today, the health of the mankind is facing greater hazards and challenges than at any other time in history, and within this context, hospitals are supposed to provide service of the highest standards and with minimum delay. Emergency wards are the sections where these principles apply more than anywhere else. These are rightly regarded as the "heart" of any hospital and a quick, efficient workflow in the emergency room can literally save lives.
Material and Methods: This was a cross–sectional (descriptive/analytic) performed in 2005 to assess the structure, process & performance in the emergency wards of 12 teaching hospitals affiliated to Tehran University of Medical Sciences.
Results: 33.3% of the ward chiefs were women the rest were men they were all more than 30 years of age. The average rate for implementing proper managerial standards was 90.6%. The "manpower index" was 69.1%, and the "facilities & equipment" index was 44/5%. The "directions index" and "activities index" were 66.97% and 93.5%, respectively.
Conclusion: The findings show that there is a positive and significant relationship between standards of management at the emergency department and the facilities and equipment index. Also, there are positive correlations between the emergency department's "manpower and rules" index instructions, activities, and years of service in hospitals.

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Background and Aim: Yersinia is an important water- and food-borne bacterium causing gastroenteritis in humans.
Material and Methods: From December 2002 to July 2003, a total of 250 samples -including 158 meat samples and 92 chicken samples- were taken from butcheries and poultry shops operating under the supervision of Tehran University of Medical Sciences. We used a two-step enrichment procedure: phosphate buffer saline was used as primary enrichment within 3 weeks in refrigerator (cold enrichment). Then we applied KOH treatment as secondary enrichment and performed cultures on CIN agar.
Results: In this study, 44.4% of all samples showed Yersinia contamination. The prevalence of Yersinia was 29.1% in meat and 70.7% in poultry. Of the 155 Yersinia isolates, 53 (34.2%) were identified as Y. enterocolitica, 47(30.3%) as Y. intermedia, 42 (27%) as Y. fredriksenii and one (0,6%) as Y. kristensenii. Biotyping of Y. enterocolitica showed that 51 strains (39.7%) corresponded to biotype 1A, 13 strains (24.6%) to biotype 1B, one (1.8%) to biotype 2, three (5,7%) to biotype 3 and one (1.8%) to biotype 4. Fourteen strains (26.4%) could not be classified.
Conclusion: The high prevalence rates in meat and poultry implies that these products could be widely contaminated with Yersinia, thus serving as important vehicles for transmission to humans.

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Background and Aim: Hospitals are among the most important health and medical institutions responsible for promoting health, and provision of appropriate health services requires a healthy, hygienic and safe environment. This research was done with the aim of assessing the environmental health situation Qom hospitals in 2005.

Materials and Methods: This research is an applied descriptive - analytic study on hospitals in QOM Province. Data were gathered using survey and observation methods and a two-part questionnaire. The first part of the questionnaire consisted of 45 items covering demographic data on hospitals and hospital managers. The second part comprised 363 questions about the environmental health situation as well as diagnostic, treating and support services. The questionnaires were filled after validity and reliability tests in eight hospitals in Qom Province. For statistical analysis, we performed Mann-Whitney and Kruskal-Wallis tests and calculated Spearman's coefficient, using the software package SPSS.

Results: Poor environmental health was observed in 25% of the radiology wards, kitchens and laundries. The situation was assessed as "appropriate" in 12.5% of laboratories and central sterilization (CSR), 25% of emergency services, 50% of ICU wards and 71% of surgery and recovery rooms, and it was intermediate of the other wards. Overall, the level of compliance with the principles of environmental health was average, i.e. about 72.5 percent. Further analysis of data showed that the situation was better in private, non-teaching hospitals compared to government-run and teaching hospitals. However, environmental health was found to improve with an increase in the number of active hospital beds and the managers' experience in their current job. It declined with increasing hospital age and increasing age of the hospital managers.

Conclusion: Overall, the environmental health situation in Qom hospitals was found to be at an intermediate level. Hence, these hospitals have a long way to go before they can achieve the appropriate level of environmental health

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Backgrounds and Aim: One of the remuneration methods in the hospital system in Iran is per case, based on a classification system termed Global system (GS). The GS, supported by Iran's Ministry of Health and Medical Education (MOHME), was established in 1999 and is now used for cost reimbursement in the second- and third-levels of health care services. In this system, patients are classified into 60 categories, based on the most frequent surgical operations. However, it now appears, that there are many questions about this system. This study aims to compare the global operations reimbursement rates with actual costs in the Cancer Institute, Tehran, in 2003 and 2004.
Materials and Methods: This survey was a retrospective, analytical-descriptive one aiming at comparing the global operations reimbursement rates with actual costs in 646 global operations carried out in the Cancer Institute in 2003 and 2004. The global-operations and actual-costs data were gathered from Hospital Information Systems (HIS) and High Council of Insurance annual regulations, respectively, and analyzed using SPSS 11.5 software and the Wilcoxon non-parametric test.
Results: The differences between the cost reimbursement rates of global operations and their actual costs were lower in 2004 as compared to those in 2003. Also, the actual costs of operations were higher than the global operations reimbursement rates in both years and the difference was significant statistically in either year (P<0/001).
Conclusion: Some of the MOHME and Cancer Institute's authorities and experts believe that the decrease in differences between the cost reimbursement rates of global operations and their actual costs in 2003 compred to 2004 is due to increased awareness of physicians and the accounting and discharge units' personnel of the global operations and related regulations, as well as increasing global operations reimbursement rates. Also, they believe that the differences between the global operations reimbursement rates and their actual costs in either year could be attributed to not considering the actual inflation rate, hospital types, patients' co-morbidities, etc. in calculating the global operations reimbursement rates. It is suggested to make more realistic calculations, taking into account such variables as the actual inflation rate, hospital types, patient co-morbidities, etc.

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Background and Aim: One of the most prevalent occupational diseases and conditions is musculo-skeletal disorders (MSDs) that impose expensive medical-recompense expenses, organic damages, and work-time wasting. The aim of this study was to detect spine curvatures (cervical, back/ low back, lumbar) and prevalence of musculo-skeletal disorders in assembly workers of Bahman automobile company, Tehran, Iran.

Materials and Methods: In this cross-sectional, descriptive-analytical study 160 assembly workers of Bahman Automobile Manufacturing Company (vans, cars), Tehran, Iran were included. In the descriptive part data were collected on the demographic characteristics of the subjects. In the analytical section associations among the dependent variables, as well as between the dependent and independent variables, were determined. The Nordick Questionnaire, a scale, and a flexible ruler were used for data collection. The SPSS software was used for data analysis.

Results: Although the mean age of the participants was low (30.89 yrs), the prevalence of MSDs was high (69.4% 1.58). The most prevalenct of the MSDs was in the lumbar part (n=83 %51.9) and the least in the hip and femoral region (n=9: %5.6). Significant associations (p < 0.05) were found between MSDs prevalence and independent factors (age, years of working, marital status). However, cervical, back, lumbar curvatures and the Delmax index were not statistically related with MSDs.

Conclusion: This study shows that associations exist between muscleo-skeletal disorders and age, years of working, height, and marital status. The findings also reveal that there is no relation between MSDs and the vertebral curvatures (cervical, back, lumbar), except the neck curvature in the car (not van) assembly workers. It may be concluded that genetics and environmental conditions can adversely affect the musculo-skeletal health. We cannot control the genetic factors. However, one can provide more favorable environmental conditions. For example, employing younger workers may help decrease the musculo-skeletal disorders.

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Background and Aim: Like other cancers, gastric cancer is due to uncontrolled growth of tissues. Although there are different therapy methods to treat it, such as surgery, radiation therapy, chemotherapy, and multimodality therapy, relapse and death may occur. Reports show that in Iran gastric cancer is the first cause of death among deaths due to cancers. The purpose of this study was to determine the two-year survival rate after relapsing and its associated factors among gastric cancer patients who had undergone surgical treatment in Iran Cancer Institute, one of the most important cancer treatment centers in Iran.

Methods and Materials: A total of 330 patients with gastric cancer who had been admitted to and operated on at the Iran Cancer Institute between January 1996 and April 2000 were enrolled in this study. The patients' life expectancy after relapse was determined. Survival was defined as the elapsed time between the two successive events, relapse and death, neither of which can be determined exactly therefore the data are doubly censored failure time data. Thus, the relationships between life expectancy at relapse and such variables as age, gender, and factors related to the disease, such as the cancer site, pathologic type, stage, and sites of metastases were determined using the Cox proportional hazards model.

Results: The two-year survival rate after relapsing and the median life expectancy after relapsing were 15% and 10.15 months, respectively. Univariate analysis showed that except disease stage, no other variable (age, gender, cancer site, pathologic type and sites of metastases) affected life expectancy after relapsing significantly. The Cox proportional hazards model for doubly censored failure time data showed that age, gender, and pathologic type had the highest influence, in a decreasing order, on the rate of survival after relapsing.

Conclusion: Two-year survival rate after relapsing is very low in gastric cancer patients. One of the most important reasons seems to be delayed consultation and diagnosis. Most patients seek medical advice first with the disease in the late stages, when most have lymph node, liver or even distant metastasis which makes treatment even more complex, and when the risk of relapse and death would be increased. Thus, early diagnosis and therapy for a common stomach illness could help prevent a potential gastric cancer.

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Background and Aim: Organizational centralization, an important concept/system in management, relates to hierarchy of authority and degree of participation in decision-making. In this study we aimed to determine the extent of organizational centralization in hospitals affiliated with Tehran University of Medical Sciences (TUMS), Tehran, Iran and identify factors affecting the organizational centralization at the level of executive managers.

Methods and Materials: All the managers and head nurses of 13 TUMS hospitals (26 subjects) were included in this cross-sectional study in 2005. Data, collected using questionnaires, were analyzed using the following tests: t-test, ANOVA, Pearson and Spearman, the software being the SPSS. The extent of organizational centralization was categorized into centralized, semi-centralized, and uncentralized.

Results: Five of the 5 variables studied were statistically significantly associated with organizational centralization. They were gender (p=0.001), organizational position (p=0.005), attending management courses (p=0.001), and financial burden of decisions (p=0/03) in the hospital managers group, and possibility of controlling the decision (p=0.014) in the head-nurses group.

Conclusion: The average organizational centralization in the hospitals was 75.38% it was 76.3% and 73.38% for hospital managers and head-nurses, respectively. On the whole, the management system of TUMS hospitals is a semi-centralized system.

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Background and Aim: The large volume of reports and statistics in the literature on the prevalence of musculoskeletal disorders (MSDs) in Iran and other countries indicates that it is essential to assess the ergonomic situation in different occupations. These disorders can be caused by long-term exposure to different agents or by trauma to the musculoskeletal system. A large part of the work force in Iran is engaged in general construction and dam construction workshops. The postures of these workers while working in the workshops are unsuitable postures. The objective of this study was to assess the ergonomic situation of workers in dam construction workshops.

Methods and Materials: This was a cross-sectional study conducted in 2008. The sample included 110 randomly selected male-workers in a dam construction workshop in Takab City, Iran, engaged in 25 different jobs. Data were collected using the Nordic Musculoskeletal Questionnaire and the National Institute of Occupational Health-Center to Protect Worker Rights Checklist (NIOSH-CPWR), both developed by the National Institute of Occupational Health-Center to Protect Workers Rights. The software used to analyze data was SPSS.

Results:The average service record of the workers was 36.6 ± 86.8 months. The data show that the most common (55.5%) MSDs were in the low back region. There were statistically significant positive associations between prevalence of MSDs and many independent variables, namely, age, weight, education level, service record, smoking, type of job, lengths of time of standing and sitting at work, total duration of work, work pressure, undesirable postures, and surface for walking.

Conclusion: The results of this study generally confirm findings of previous investigators. It can be concluded that ergonomic assessment of jobs may give valuable information to be used by occupational health and safety authorities in planning preventive and educational programs.

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Background and Aim: Domestic violence against women is a serious public health problem and women adopt different solutions to fight against it. This study was carried out to determine the prevalence of intimate partner violence and views of women
on adopting ways to fight against it in Arak city, Iran, year 2008.

Methods and Materials: In a cross-sectional study in Arak city in 2008, a total of 1037 women were interviewed. The data collected were analysed statistically.

Results: Findings showed that the common types of abuse were emotional (64.6%), verbal (57.1%), financial (32.3%), and physical (26.8%). The women mentioned that the most efficient ways they chose to counteract the abuses were as follows: resuming talking after the settlement of quarrels (93%), keeping silent on the part of one of the partners (81%), and seeking advice from the older members of the family (81%). The considered going into a temporary sulk (51%) and reciprocation (46%) ineffective methods. Correlations were found between violence on the one hand and education, job, addiction of the spouse, income of the spouse, mental disorder of the partner, and number of children on the other hand (p<0.05).

Conclusion: Results of this study show that a large number of women are subjected to different types of violence. It seems that increasing awareness of married women and girls concerning effective counteractive methods can be an effective step in solving this social problem.

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Background and Aim: The most common cancer in Iran is digestive system cancer, the highest incidence of which is reported from the Caspian Sea littoral. This study aimed to determine factors affecting the survival of patients with gastrointestinal cancer using the Cox and parametric models the 2 models were compared.

Materials and Methods: This survey was a prospective study conducted between 1990 and 1991. Data were collected through the Cancer Registry Center in Babol, which functions under supervision of the School of Public Health and Institute of Public Health Research, Tehran University of Medical Sciences. We tried to identify cases of gastrointestinal cancers. The individual characteristics of 484 patients, namely, age, sex, family history, marital status, smoking status, occupation, ethnicity, medication status, education, residence (urban, rural), and type of cancer were recorded. The patients were followed up for a period of 15 years, i.e., until 2006 year. To determine the effective factors on survival of patients, the Cox model and parametric models such as exponential, weibull, log-normal, log-logistic, and the AIC criteria and residuals were used to compare the effectiveness of the models. The SAS and STATA software were used for data analysis, with a significant level of 0.05.

Results: Sixty-six percent of the patients (total n=484) were males and 34% females, with a mean age of 59 and 55 years, respectively. Their distribution according to type of cancer was as follows: esophageal cancer, 359 (74.2%) stomach cancer, 110 (22.7%) colorectal cancer, 15(3.1%). Estimated one-, three-, and five-year survival rates were 24%, 16% and 15%, respectively.

Conclusion: The results of this study reveal that gender and family history can be strong risk factors for GI cancer. Log-normal and log-logistic models in multivariate and univariate analyses gave almost similar results. However, based on AIC criteria and residuals analysis, the log-logistic model gives the best fit as compared to other parametric models and can be used instead of the Cox model for determining factors affecting survival of patients with gastrointestinal tract cancer.

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Background and Aim: Length of stay (LOS) in a hospital is one of the best hospital indicators that can be used for various purposes. In this survey, we studied the hospital LOS and its associated factors in Tehran University of Medical Sciences Women's Hospital (a teaching hospital) in Tehran using the Cox proportional hazards semi parametric model and compared the results with the results obtained using the multiple linear regression.

Materials and Methods: This was a descriptive-analytical study in which we reviewed 3421 files of inpatients hospitalized in, and those discharged from, the oncology, surgery and obstetrics units in 2008. The required data were collected using a data collection sheet and inpatient interviews. A P<0.05 was considered statistically significant.

Results: The median of patients' LOS in the hospital was 50.8 hours, that in the obstetrics, surgical and oncology units being 48.5, 54.4 and 94.2 hours, respectively. Of all the patients, 2632 (76.9%) had been discharged with a recovery status and the rest (23.1%) with a no-recovery status. Results of the Cox proportional hazards model showed that the following variables had increased LOS: a distance longer than 200 km between a patent's residence and the hospital, hospitalization in the surgery and oncology units, admission on a Thursday, admission by an internist, hospitalization for neoplastic, endocrine, nutritional, or genitourinary system diseases (P<0.005), as well as a high number of diagnostic laboratory tests, radiographies or sonographies (P<0.001). Patients admitted and hospitalized as an emergency case had a shorter LOS (P<0.001) than others. On the other hand, based on the multiple linear regression model results, some occupations (being a worker, a farmer, a stockbreeder, or a retired spouse) admission on a Thursday, (The first day of the weekend in Iran), suffering from a neoplastic disease, and a high number of diagnostic tests or radiographies or sonographies increased, and admission by a resident decreased, patients' LOS (P<0.05).

Conclusion: Considering having censored data, the Cox proportional hazards model is a more suitable model than the multiple linear regression models for identifying factors influencing patients' LOS in a hospital. From among the LOS Cox model's associated factors as identified in this study, policy-makers and managers can only change admission days and the number of diagnostic tests. That is to say, they should try to prevent admission on a Thursday (unless emergency cases) and also perform the required primary diagnostic tests before admitting a patient into the hospital, which would lead to a more effective utilization of hospital beds and other resources.

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Background and Aim: Many researchers have studied survival (time to death) of gastric cancer patients. Although gastric cancer diagnosed in early stages can be cured by surgery, chance of relapse still exists after operation. Hence, we should consider both events, that is, relapse of the disease and death, in order to be able to make a more precise estimation for survival of the patients. The purpose of this study was to use the competing risks method to estimate the cumulative incidence functions (CIF) of the relapse of disease and death and consequently to estimate the postoperative disease-free survival.
Materials and Methods: A total of 330 patients admitted to Iran Cancer Institute and operated between March 1995 and March 1999 were enrolled in the study. They were followed up for at least 5 years to estimate their 5-year disease-free survival. Information on their demographic, clinical, and therapeutic characteristics, as well as on the type and time of occurrence of the first event (relapse of disease or death) after surgery was collected from their medical records. The direct parametric method was applied to estimate CIFs of relapse of the disease and death, while to adjust the effects of some covariates the parametric regression model was used. Data analysis was done using the R software and a p-value <0.05 was considered statistically significant. The findings were compared with the results obtained on the basis of data analysis in which the competing events were not considered.
Results: The median follow-up time was 37.9 months. Of all the patients 13% experienced relapse and 60.9% death as the first event after surgery. The CIFs of relapse of disease and death 5 years after operation, with due consideration of covariates, were estimated at 11.0% and 68.6%, respectively. Age, stage of disease, and complementary treatment were statistically associated with the CIF of death, while only complementary treatment was related to the CIF of relapse. Older patients and those in more advanced stages of disease were more likely to die after operation. Moreover, while complementary treatment after operation decreased the CIF of relapse of disease, it increased the CIF of death. The disease-free survival of patients 5 years after surgery was 20.(consideringtheeffectsofsomecovariates).
Conclusion: The competing risks method is recommended for analyzing survival data because of its capability in considering different events and, therefore, making it possible to make more precise estimations. By using this method, considering smaller variance estimates for model parameters and also narrow confidence intervals for the cumulative incidence functions of competing events, it is expected to obtain more precise results. Unfortunately, the results have revealed that the disease-free survival of gastric cancer patients is low in Iran.

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  Background and Aim: In many diagnostic studies, including surveying the survival of patients with gastric cancer where each individual after surgery can experience more than one type of event, and the occurrence of one type of event hinders the occurrence of other types of events, the question of competing risk is raised. For checking the effect of each covariate on the occurrence of any event and estimating the hazard function, Cox and Fine and Gray models are used. In the event that the assumptions of two models do not hold, using them will be an incorrect course of action. One way to overcome this problem is to use models that have higher flexibility.

  Materials and Methods: In this study, the demographic, clinical and therapeutic characteristics of 330 patients with gastric cancer who referred from January 1996 to April 2000 to the Cancer Institute of Iran Imam Khomeini Hospital and underwent surgery, including their type, and the time of occurrence of the first event (locoreginal replace/death) for each patient from medical records were collected and evaluated. Using this information, the cumulative hazard function of relapse of disease was plotted by means of three models Cox, Fine and Gray and the flexible one, and was checked against the observed cumulative incidence function of recurrence of disease and, finally, their performance was evaluated.

  Results: Nearly, for each event, the proportionality assumption holds for all the variables . According to the graph of cumulative incidence function for the event of interest (recurrence), it can be seen that the Cox model, has overestimated the cumulative incidence function and the curves of two other models are very similar and also similar to the observed curve. However, the cumulative incidence function of the flexible model is smoother than the others.

  Conclusion: In the competing risk framework, Cox model is not very useful in practice while it seems that the flexible model is not only a good alternative to the Fine and Gray model but will also be superior to it when the assumption of proportionality does not hold.

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  Background and Aim: One of the most important problems in intensive care unit is high nursing workload. High workload may lead to increased human errors, compromised quality and safety of care, and reducing quality of working life. The purpose of this study provides valid and reliable tools to assess the mental workload of the ICU nurses and also identify inducing factors that will create workload.

  Materials and Methods: This study had two phases. 1- Determine the face validity and reliability of the NASA-TLX (to assess the workload) by Backward Translation method and Cronbach's alpha method. 2–Designing the performance obstacles and facilitators questionnaire by interview and pilot study.

  Results: Face validity and reliability of NASA-TLX method was confirmed (α=0.897). The performance obstacles and facilitators questionnaire for ICU nurses provides in 53 questions and 10 subscales. Relevancy is 97% and Clarity is 96%. Overall, 90% of nurses assessment comprehensiveness of the questionnaire was very comprehensive and comprehensive.

  Conclusion : According to the results, can be used NASA-TLX method and the performance obstacles and facilitators questionnaire to assess workload of ICU nurses.

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Background and Aim: In many medical studies along with longitudinal data, which are repeatedly measured during a certain time period, survival data are also recorded. In these situations, using models such as, mixed effects models or GEE method for longitudinal data and Cox model for survival data, are not appropriate because some necessary assumptions are not met. Instead, the joint models have been introduced, to consider: 1- measurement error in time-dependent covariates 2-monotone and non-ignorable missing data which occurs after an event and 3- relation between longitudinal and survival outcomes, simultaneously. At this paper, joint model Puts longitudinal response (i.e. creatinine) as a time dependent variable, along with other covariates in survival sub model, to investigate dialysis patients survival. Materials and Methods: This research contained information about 417 patients affected to chronic renal failure, under treatment of continuous ambulatory peritoneal dialysis (CAPD) method. Patients were referred to three medical centers in Tehran (Shariati, Modares and Shafa) between 1997 to 2009.In this study longitudinal data and time dependent covariate were used Therefore, different variables for each person at certain time have been measured. In first some information was gathered from patient’s file, and then effective factors on survival of patients have been determined by using joint model. Results were compared with naive analysis (extended Cox model). For data analyzing, R software and significant level of 0.05 have been used. Results: with using joint model sex, age, diabetes, diastolic blood pressure, haemoglobin, urea, LdL, and creatinine covariates were significant. In extended Cox model, only age and Diastolic blood pressure covariates were considered as effective factors on hazard of death in patients. Conclusion: Joint model assess the effective factors on both endpoints simultaneously. Also it considers missing data that appeared due to an event, and covariates which were measured with error. Therefore in these cases, using joint models that led to better results and more knowledge about dieses, are necessary.