[Evaluation of the survival time of the patients with colorectal cancer using exponential model]

Background: colorectal cancer is one of the important causes of death due to cancer worldwide. Survival time in this cancer should be controlled to decrease the risk of mortality. In this study survival time and factors that could affect it are evaluated

Materials and Methods: in the present study, the files of 446 patients afflicted with colorectal cancer who had referred to Taleghani Hospital, Tehran from 1985 to 2013 were chosen as the study group. The exponential model was used here, for the purpose of investigating the survival of patients with colorectal cancer and finding proper variables affecting this survival and longevity

Results: in this study, the subjects had the mean [standard deviation] survival time 4.52 [0.182] year. The patients' age at the time of diagnosis [P=0.002] and tumor size [P=0.032] were the only significant variables affecting the survival of patients in the exponential model. Sex, the family history of colorectal cancer, the tumor site, and body mass index had no significant effect on the survival time of the patients with colorectal cancer

Conclusions: the results of the study show that to improve the survival chance of the patients with colorectal cancer or decrease the mortality rate, due attention should be paid to the age of the patient at the time of diagnosis

How to test normality distribution for a variable: a real example and a simulation study

Many commonly used statistical methods require that the population distribution be nearly normal. Unfortunately, in some papers the one-sample Kolmogorov-Smirnov test has been used for testing normality while the assumptions of applying this test are not satisfied. To conduct this test, it is assumed that the population distribution is fully specified. In practical situation where the mean and SD of population distribution is not specified in advance, one can use a modification of the K-S test for checking the normality assumption which is called, Lilliefors test. In this paper, we explain the method of computing this test with some common statistical softwares such as SPSS, S-PLUS, R and StatXact and utilize a dermatology dataset from Skin Research Center of Shohada-e-Tajrish hospital to illustrate how the use of the one-sample K-S [with the mean and SD estimated from the sample] instead of its modification can be misleading in practice. We also use Monte Carlo simulation to compare the approximate power of the one-sample K-S test [with the estimated population mean and SD] with Lilliefors test in some common specified continuous distributions. The result indicates that one should not use the one-sample K-S test for assessing the normality assumption in practical situation

effect of core stability training with and without whole body vibration in chronic low back pain patients

The subjective of this study was to explore and compare the effects of Whole Body Vibration [WBV] and conventional spinal stabilization exercises on persons with non-specific chronic low back pain [CLBP]. Thirty patients with non-specific chronic low back pain randomly received 6 sessions of spinal stabilization therapy with and without whole body vibration over 2 weeks. The severity of pain, functional disability, abdominal and lumbar multifidus muscle endurance were assessed prior to, midway and after two week WBV or spinal stabilization intervention program sequentially by using VAS score, Oswestry disability index and stabilizer pressure biofeedback unit. Repeated measure ANOVA was used for data analysis. A p-value <0.05 was considered as statistically significant. Findings show that multifidus muscle endurance and general functionality increase significantly over time in both groups [P <0/05]. Both groups didn't show any statistically significant change in perception of pain, supine and prone time after the treatment period [P>0/05] .Neither of the two exercise interventions wasn't superior in producing more significant results except for multifidus and transverse abdominus muscles endurance where the vibration group showed significant improvement over the non-vibration group. Findings revealed that a slight difference existed in favor of the vibration training group, but not sufficient enough to conclude that it is more effective than core muscle exercises alone

Analysis of longitudinal binary outcomes in clinical trials with low percentage of missing values

In interventional or observational longitudinal studies, the issue of missing values is one of the main concepts that should be investigated. The researcher's main concerns are the impact of missing data on the final results of the study and the appropriate methods that missing values should be handled. Regarding the role and the scale of the variable that missing values have been occurred and the structure of missing values, different methods for analysis have been presented. In this article, the impact of missing values on a binary response variable, in a longitudinal clinical trial with three follow up sessions has been investigated Propensity Score, Predictive Model Based and Mahalanobis imputation strategies with complete case and available data methods have been used for dealing with missing values in the mentioned study. Three models; Random intercept, Marginal GEE and Marginalized Random effects models were implemented to evaluate the effect of covariates. The percentage of missing responses in each of the treatment groups, throughout the course of the study, differs from 6.8 to 14.1. Although, the estimate of variance component in random intercept and marginalized random effect models were highly significant [p <0.001] the same results were obtained for the effect of independent variables on the response variable with different imputation strategies. In our study according to the low missing percentage, there were no considerable differences between different methods that were used for handling missing data

Efficacy of group obstetric consultation in mild to moderate anxiety of pregnancy

Anxiety is a common mental disorder of pregnancy leading to adverse maternal and fetal pregnancy outcomes. Hence, preparation of effective approaches for reduction of anxiety is an issue of importance. Accordingly, this study was performed to determine the efficacy of group obstetric consultation on anxiety control in pregnant women in non-severe cases. In this randomized clinical trial, 90 pregnant women attending to a Health Care Center in Tehran, Iran from April 2010 to March 2012 with first pregnancy aging from 18 to 35 years and gestational age of eight to eighteen weeks were evaluated. They were randomly assigned into consultation and control groups. The consultation group was designed according to the different needs of pregnancy for five sessions in five weeks [each session 60 to 90 minutes] and the control group only received routine perinatal care. There was statistically significant difference between after-intervention scores in anxiety state [P=0.014]; but the anxiety trait showed no difference [P=0.19]. Also the changes in trait anxiety scores was more in consultation group compared with control group [P=0.002] that was also seen for anxiety state scores [P=0.0001]. Totally, it may be concluded that group consultation is effective in reduction of state and trait anxiety in pregnant women with non-severe non-pathological cases of anxiety

Comparison of the precision of measurements in three types of micropipettes according to NCCLS EP5-A2 and ISO 8655-6

Micropipettes or piston pipettes are used to make most volume measurements in fields such as health, chemistry, biology, pharmacy and genetics. Laboratories must ensure that results obtained using these instruments are reliable; therefore, it is necessary to calibrate micropipettes. Before the start of the calibration process, we must check the precision of measurements. The objective of this work is to compare several methods for calculating the precision of three kinds of micropipettes according to the reference value in ISO 8655-6. The medical tests will not have accurate results, if the volume of the liquid doesn't transfer precisely by micropipettes. Thus, the physician might potentially face problems in the disease diagnosis and its control. In the NCCLS EP5-A2, there is a method to specify and assess the precision of micropipettes by using CV [Coefficient of Variation]. Also there are other methods to estimate and test the CV theory, in the formal statistics texts which could be applied to assess the micropipettes precision. In this research we evaluate the precision of lab micropipettes. Three brands of micropipettes, A, B and C are assigned to measure the distilled water mass by using accurate scale which is accurate up to 10-6 to measure 50-gram weights. The experimental environment is a metrology lab which is approved by Iran Standard and Industrial Researches Organization. A technician sampled at the beginning of the experiment and then after 2 hours, the same technician repeated the sampling. Overall, each micropipette is used to measure 40 times with 10-repeat times for single measurement in 28 work days. Common statistical methods are used to estimate and test the CV. Point estimation of CV for micropipettes A, B and C were 0.50%, 0.64% and 1.56%, respectively. Furthermore, the upper limit of 95% confidence bounds for these three micropipettes using the exact method were 0.53%, 0.69% and 1.65%, respectively. Micropipette A met the ISO 8655-6 standard level, but micropipettes B and C did not. On average, measurement errors in micropipettes B and C were respectively 30% and 3.11 times more than micropipette A. By using the approach of CLS EP5-A2 and confidence interval for CV, precision of the three micropipettes were compared. Only one of them met the ISO 8655-6 standard level, but the others failed