[show abstract][hide abstract] ABSTRACT: Competing risks, which are particularly encountered in medical studies, are an important topic of concern, and appropriate analyses must be used for these data. One feature of competing risks is the cumulative incidence function, which is modeled in most studies using non- or semi-parametric methods. However, parametric models are required in some cases to ensure maximum efficiency, and to fit various shapes of hazard function.
We have used the stable distributions family of Hougaard to propose a new four-parameter distribution by extending a two-parameter log-logistic distribution, and carried out a simulation study to compare the cumulative incidence estimated with this distribution with the estimates obtained using a non-parametric method. To test our approach in a practical application, the model was applied to a set of real data on fertility history.
The results of simulation studies showed that the estimated cumulative incidence function was more accurate than non-parametric estimates in some settings. Analyses of real data indicated that the proposed distribution showed a much better fit to the data than the other distributions tested. Therefore, the new distribution is recommended for practical applications to parameterize the cumulative incidence function in competing risk settings.
Theoretical Biology and Medical Modelling 11/2011; 8:43. · 1.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: Background & aims
Measuring MUAC has several advantages. The measuring can be taken quickly and at little cost. It is an excellent indictor of nutritional status and is frequently used for screening purposes.
New reference values and charts for mid upper arm circumferences (MUAC) of 2237 healthy primary school children (1163 boys and 1074 girls) aged 6–12 years living in Shiraz (Iran) are presented and their relationships to our previous study carried out 15 years earlier as well as other studies explored. The data were sampled in a multistage scheme and collected through a large-scale cross-sectional growth study.
The results showed that MUAC measurements centiles of girls lied above that of boys in all age groups, which is generally significant (p = 0.006).
Comparison of our data with their peers born 15 years apart indicated that our children get longer MUAC measurements than previous study (p < 0.001), which may be attributed to the post Iran–Iraq war (1980–1988) developments. Also, as compared to Tanzania, Seychelles and Vietnam our children have enjoyed thicker MUAC measurements. However, median of MUAC of our children lie below their peers in the Netherlands and USA for both sexes. The paper, therefore, concludes that the reference values for MUAC values differ from country to country and supports local standards in this regard, which concurs with our previous study. However, it is suggested that these standards be updated every other decade.
e-SPEN the European e-Journal of Clinical Nutrition and Metabolism 01/2008; 3(2).
[show abstract][hide abstract] ABSTRACT: This study aimed to evaluate reliability and validity of the Dermatology Life Quality Index (DLQI) in Iranian burned patients and to examine this question, "Does burn severity or other demographical characteristics affect the patient's perception of his or her quality of life after burn injury?" In this study, we used the Persian version of DLQI questionnaire; its reliability and validity has been confirmed earlier in vitiligo patients. The questionnaire was administered to a group of patients with burn scars after revival. The internal consistency of the questionnaire was assessed by Cronbach's alpha coefficient. Validity was performed using convergent validity. In all, 109 patients (mean age, 28.94) enrolled in the study. The scores of DLQI ranged from 4 to 28 (mean +/- SD, 17.76 +/- 5.55). Reliability analysis showed satisfactory result (Cronbach's alpha, 0.75). Cronbach's alpha coefficient in the patients with a Burn Index >or=15% was greater than those with <15%, which is an acceptable result. The Persian version of the DLQI is a reliable and valid instrument for assessing the impacts of burn scars on quality of life. The life quality index of all the patients irrelevant to age and sex were significantly impaired.
Journal of burn care & research: official publication of the American Burn Association 01/2007; 28(2):312-7. · 1.54 Impact Factor
[show abstract][hide abstract] ABSTRACT: The measurements of head circumference (HC) of 2228 healthy school children (1160 boys and 1068 girls) aged 6.5-11.5 years are presented for the first time. The data were sampled in a multistage scheme and collected through a large-scale cross-sectional growth study carried out in Shiraz, the capital of Fars province of Iran. The results indicated that the HC measurements centiles of the girls lied below that of the boys in all age groups. Comparison of our data of the children with their peers in Turkey, Ireland, Japan and USA showed that on average, girl, HC measurements in Shiraz are larger that of their Turkish counterparts up to the age of 10 years and lie on that later on, but smaller than that of their peers from other mentioned studies. However, boys' HC measurements of Shiraz are lower than that of their peers at all ages. The article, therefore, concludes that the standards for HC will differ from country to country and supports local standards in this regard.
Journal of Tropical Pediatrics 01/2007; 52(6):406-10. · 1.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this paper is to describe and discuss a significant secular trend in stature, weight and mid-arm circumference (MAC) of school children of the same age (6.5-11.5 years) and sex in representative samples from primary schools of Shiraz (southern Iran) at an interval of 15 years (1988 vs 2003). Both samples include children of various socio-economic backgrounds. For both males and females of each age-class, there are significant positive secular trends in stature, weight and MAC. The results suggest that post-war born children sampled in 2003 are generally taller, heavier and larger than their peers of 15 years earlier born pre- and during the war period of Iraq against Iran. Furthermore, the 2003 sample shows less growth deficits in relation to the Center for Disease Control (CDC) reference data. The positive trend can be explained as the result of economic development and improvement of social and health indicators in the post-war Iran reconstruction period.
Annals of Human Biology 01/2006; 33(4):510-4. · 1.48 Impact Factor