Search results for " Statistical"
showing 10 items of 1649 documents
Impact of intravascular enhancement, heart rate, and calcium score on diagnostic accuracy in multislice computed tomography coronary angiography.
2005
PURPOSE: To assess the effect of intravascular enhancement, heart rate, and calcium score on diagnostic accuracy in the detection of significant coronary artery stenosis using 16-row multislice computed tomography (MSCT). MATERIALS AND METHODS: One hundred patients (88 males; 59+/-11 years) with suspected coronary artery disease who had undergone conventional coronary angiography (CA) and MSCT-CA were retrospectively enrolled for the study. Patients underwent a MSCT-CA, with the following protocol: collimation 16x0.75 mm, gantry rotation time 420 ms, feed/rotation 2.8 mm, kV 120, mAs 400-500. The protocol for contrast material administration was 100 ml of Iodixanol 320 mgI/ml at 4 ml/s and …
Some findings on zero-inflated and hurdle Poisson models for disease mapping
2018
Zero excess in the study of geographically referenced mortality data sets has been the focus of considerable attention in the literature, with zero-inflation being the most common procedure to handle this lack of fit. Although hurdle models have also been used in disease mapping studies, their use is more rare. We show in this paper that models using particular treatments of zero excesses are often required for achieving appropriate fits in regular mortality studies since, otherwise, geographical units with low expected counts are oversmoothed. However, as also shown, an indiscriminate treatment of zero excess may be unnecessary and has a problematic implementation. In this regard, we find …
Empirical study of the dependence of the results of multivariable flexible survival analyses on model selection strategy
2008
Flexible survival models, which avoid assumptions about hazards proportionality (PH) or linearity of continuous covariates effects, bring the issues of model selection to a new level of complexity. Each ‘candidate covariate’ requires inter-dependent decisions regarding (i) its inclusion in the model, and representation of its effects on the log hazard as (ii) either constant over time or time-dependent (TD) and, for continuous covariates, (iii) either loglinear or non-loglinear (NL). Moreover, ‘optimal’ decisions for one covariate depend on the decisions regarding others. Thus, some efficient model-building strategy is necessary. We carried out an empirical study of the impact of the model …
Spatial Interaction between Neighbouring Counties: Cancer Mortality Data in Valencia (Spain)
1995
The statistical analysis of geographical mortality data has usually been approached via regression models that include appropriate covariates. These models assume stochastic independence of mortality counts for neighbouring sites, a questionable assumption that spatial automodels (Besag, 1974, Journal of the Royal Statistical Society, Series B 36, 192-236) make unnecessary. This paper presents the use of the autopoisson distribution in order to detect spatial interaction between neighbouring sites. If this interaction results in being nonsignificant, the auto-Poisson distribution reduces to a usual Poisson regression model, a particular case of generalized linear models (McCullagh and Nelde…
Comment on ‘Estimating average annual per cent change in trend analysis’ by Clegg LX, Hankey BF, Tiwari R, Feuer EJ, Edwards BK, Statistics in Medici…
2010
Trends in incidence or mortality rates over a specified time interval are usually described by the conventional annual per cent change (cAPC), under the assumption of a constant rate of change. When this assumption does not hold over the entire time interval, the trend may be characterized using the annual per cent changes from segmented analysis (sAPCs). This approach assumes that the change in rates is constant over each time partition defined by the transition points, but varies among different time partitions. Different groups (e.g. racial subgroups), however, may have different transition points and thus different time partitions over which they have constant rates of change, making co…
Measuring elderly people's quality of life through the Beck Hopelessness Scale: a study with a Spanish sample.
2016
Hopelessness is a key element of suicidal intent. It can instill a pessimistic outlook on the future, leading an individual to believe that suicide is the only answer to their problems. Hopelessness operates as a modulating variable between depression and suicidal behavior. The aim of this study was to confirm the factor structure of the Beck Hopelessness Scale (BHS) in a non-clinical sample.Three hundred and sixty-two Spanish individuals, aged over 60, free of cognitive impairment and depressive symptoms, completed the BHS scale. Participants were tested using confirmatory factor analysis (CFA), using one-, two- and three-factor models.The one- and two-factor models presented adequate fit …
Patterns of objectively measured sedentary time in 10- to 12-year-old Belgian children: an observational study within the ENERGY-project
2017
Background This study examined the frequency of and differences in sedentary bouts of different durations and the total time spent in sedentary bouts on a weekday, a weekend day, during school hours, during after-school hours and in the evening period in a sample of 10- to 12-year-old Belgian children. Methods Accelerometer data were collected as part of the ENERGY-project in Belgium (n = 577, 10.9 ± 0.7 years, 53% girls) in 2011. Differences in total sedentary time, sedentary bouts of 2–5, 5–10, 10–20, 20–30 and ≥30 min and total time accumulated in those bouts were examined on a weekday, a weekend day, during school hours, during after-school hours and in the evening period, using multile…
Prevalence of fatigue in Parkinson disease and its clinical correlates
2014
Objective: To assess in a noninterventional setting the prevalence and severity of fatigue in patients with Parkinson disease (PD). Methods: This was a cross-sectional study conducted in Italian patients with PD. Objectives included the evaluation of the current prevalence and severity of fatigue in patients with PD measured using the 16-item Parkinson Fatigue Scale (PFS-16), distressing fatigue (defined as a PFS-16 mean score $3.3), and assessment of its clinical correlates. Results: A total of 402 patients were enrolled and 394 patients completed the PFS-16 questionnaire with a PFS-16 mean (6SD) score of 2.87 6 0.99. Of these, 136 patients (33.8%) reported distressing fatigue (PFS-16 mean…
Factor structure and measurement invariance across various demographic groups and over time for the phq-9 in primary care patients in spain
2018
The Patient Health Questionnaire (PHQ-9) is a widely-used screening tool for depression in primary care settings. The purpose of the present study is to identify the factor structure of the PHQ-9 and to examine the measurement invariance of this instrument across different sociodemographic groups and over time in a sample of primary care patients in Spain. Data came from 836 primary care patients enrolled in a randomized controlled trial (PsicAP study) and a subsample of 218 patients who participated in a follow-up assessment at 3 months. Confirmatory factor analysis (CFA) was used to test one- and two-factor structures identified in previous studies. Analyses of multiple-group invariance w…
Effects of work-interval duration and sport specificity on blood lactate concentration, heart rate and perceptual responses during high intensity int…
2018
The aim of this study was to examine the impacts on blood lactate concentration, measured heart rate and assessment of perceived exertion during split sessions of equal relative load, as also their relationship to the specific sport practised. Nineteen regional-level athletes (nine middle and long-distance runners (cyclic group) and ten field-sport team players (acyclic group)) performed four high-intensity interval training (HIIT) sessions with work-interval durations of 10 s, 50 s, 90 s and 130 s. The sessions were carried out at their usual training sites with a separation of at least 48 hours. Blood lactate concentration was measured at rest and 3 min after the completion of each protoc…