Non-parametric inference on calibration of predicted risks

Moderate calibration, the expected event probability among observations with predicted probability z being equal to z, is a desired property of risk prediction models. Current graphical and numerical techniques for evaluating moderate calibration of risk prediction models are mostly based on smoothing or grouping the data. As well, there is no widely accepted inferential method for the null hypothesis that a model is moderately calibrated. In this work, we discuss recently-developed, and propose novel, methods for the assessment of moderate calibration for binary responses. The methods are based on the limiting distributions of functions of standardized partial sums of prediction errors converging to the corresponding laws of Brownian motion. The novel method relies on well-known properties of the Brownian bridge which enables joint inference on mean and moderate calibration, leading to a unified 'bridge' test for detecting miscalibration. Simulation studies indicate that the bridge test is more powerful, often substantially, than the alternative test. As a case study we consider a prediction model for short-term mortality after a heart attack, where we provide suggestions on graphical presentation and the interpretation of results. Moderate calibration can be assessed without requiring arbitrary grouping of data or using methods that require tuning of parameters

Closed-Form Solution of the Unit Normal Loss Integral in Two-Dimensions

In Value of Information (VoI) analysis, the unit normal loss integral (UNLI) frequently emerges as a solution for the computation of various VoI metrics. However, one limitation of the UNLI has been that its closed-form solution is available for only one dimension, and thus can be used for comparisons involving only two strategies (where it is applied to the scalar incremental net benefit). We derived a closed-form solution for the two-dimensional UNLI, enabling closed-form VoI calculations for three strategies. We verified the accuracy of this method via simulation studies. A case study based on a three-arm clinical trial was used as an example. VoI methods based on the closed-form solutions for the UNLI can now be extended to three-decision comparisons, taking a fraction of a second to compute and not being subject to Monte Carlo error. An R implementation of this method is provided as part of the predtools package (https://github.com/resplab/predtools/).Comment: 1 table, 1 figure, will be submitted to MDM - technical not

An Empirical Study of the Interface between Healthcare Facility Design and Human Resource Management

Expected growth in healthcare needs resulting from the Affordable Care Act and growing population of older citizens is challenging owners and operators of hospitals to improve quality of care and reduce operational costs. Although many factors drive hospital operating expenses, this study looked specifically at human resource-related expenses. Previous studies have shown that implementing human resource practices improves performance outcomes at individual and organizational levels. Organizational psychologists suggest that human resource practices improve employee motivation and performance because they convey the message that an organization values employees’ contributions and cares about their well-being, which can be reciprocated with higher levels of motivation and commitment toward the organization. Healthcare environmental studies also suggest that a safe and high-quality work environment sends a similar message to employees. More than 700 healthcare professionals from 10 acute-care hospitals participated in this cross-sectional study. Structural equation modeling found that employees’ satisfaction with their physical work environment and human resource practices reduced their job-related anxiety and improved their job satisfaction and organizational commitment. Perceived organizational support mediated part of these relationships. The author also found a small but positive interaction effect between the physical work environment and human resource practices. Examination of different spaces within a facility showed that work spaces and staff rest areas had a considerable influence on job attitudes of employees, while the impact of patient areas was negligible. Multigroup analysis indicated that the influence of the physical work environment on employees newer to the facility and the organization and on nightshift staff members was stronger. Results also highlighted the importance of attention to caregiver needs for a safe and comfortable work environment. Among the 27 different environmental features investigated in this study, finishing materials and indoor air quality had the highest levels of association with employees’ overall evaluation of their environment, regardless of their individual characteristics. Additionally, employees highly valued furniture design and thermal comfort. In comparison, features that addressed the visual quality of the work environment, such as window views and pieces of artwork, were found to have smaller associations with employee evaluations

Evolution of a Project Based Organization, a Case study

Little research has been conducted on how project-based organizations navigate internal and external pressures to develop and improve project competences over time. Using a cases study approach, this paper examines the development and implementation of project based organization over a period of 30 years. Overall, the evolution of project management competencies in the organization broadly followed the prevailing approaches in improving organizational management practices uncovered in review of literature. The organization’s capability to adopt and implement project management frameworks improved over time as senior managers became more masterful at matching improvement actions into the organizational context. This research also presents how a systematic approach of project management maturity models for identifying and implementing project management practices and processes can increase the effectiveness and comprehensiveness of overall management practices. The study concludes with a series of recommendations in further improving project management practices and processes in project-based organizations

The Association Between Rate and Severity of Exacerbations in Chronic Obstructive Pulmonary Disease: An Application of a Joint Frailty-Logistic Model.

Exacerbations are a hallmark of chronic obstructive pulmonary disease (COPD). Evidence suggests the presence of substantial between-individual variability (heterogeneity) in exacerbation rates. The question of whether individuals vary in their tendency towards experiencing severe (versus mild) exacerbations, or whether there is an association between exacerbation rate and severity, has not yet been studied. We used data from the MACRO Study, a 1-year randomized trial of the use of azithromycin for prevention of COPD exacerbations (United States and Canada, 2006-2010; n = 1,107, mean age = 65.2 years, 59.1% male). A parametric frailty model was combined with a logistic regression model, with bivariate random effects capturing heterogeneity in rate and severity. The average rate of exacerbation was 1.53 episodes/year, with 95% of subjects having a model-estimated rate of 0.47-4.22 episodes/year. The overall ratio of severe exacerbations to total exacerbations was 0.22, with 95% of subjects having a model-estimated ratio of 0.04-0.60. We did not confirm an association between exacerbation rate and severity (P = 0.099). A unified model, implemented in standard software, could estimate joint heterogeneity in COPD exacerbation rate and severity and can have applications in similar contexts where inference on event time and intensity is considered. We provide SAS code (SAS Institute, Inc., Cary, North Carolina) and a simulated data set to facilitate further uses of this method

Frequency of myasthenic crisis in relation to thymectomy in generalized myasthenia gravis: A 17-year experience

BACKGROUND: Myasthenic crisis is the most serious life-threatening event in generalized myasthenia gravis (MG) patients. The objective of this study was to assess the long-term impact of thymectomy on rate and severity of these attacks in Iranian patients. METHODS: We reviewed the clinical records from 272 myasthenic patients diagnosed and treated in our neurology clinic during 1985 to 2002. Fifty-three patients were excluded because of unconfirmed diagnosis, ocular form of MG, contraindication to surgery, concomitant diseases and loss to follow-up. The Osserman classification was used to assess the initial severity of the disease. Frequency and severity of the attacks were compared between two groups with appropriate statistical tests according to the nature of variables. Multivariate logistic regression analysis was used to assess the predictors of myasthenic crisis in the group of patients without thymoma. RESULTS: 110 patients were in thymectomy group and the other 109 patients were on medical therapy. These two groups had no significant differences with respect to age at onset, gender, Osserman score in baseline and follow up period. 62 patients (28.3% of all 219 patients) had reported 89 attacks of myasthenic crisis. 20 patients of 62 (32%) were in thymectomy group and 42 (68%) were in the other group. There was significant difference between the two groups in number of patients with crisis (P = 0.001; odds ratio = 2.8 with 95% CI of 1.5 to 5.2). In addition, these attacks were more severe in group of non-thymectomized patients as the duration of ICU admission was longer and they needed more ventilatory support during their attacks. Regression model showed thymectomy and lower age at onset as two predictors of decrement in myasthenic crisis rate in non-thymomatous MG patients. CONCLUSIONS: It is suggested that frequency and severity of myasthenic attacks as important endpoints in evaluation of MG patients. Thymectomy seems to have a preventive role on rate and severity of these attacks