1,688 research outputs found
Multi-State Models for Panel Data: The msm Package for R
No full textPanel data are observations of a continuous-time process at arbitrary times, for example, visits to a hospital to diagnose disease status. Multi-state models for such data are generally based on the Markov assumption. This article reviews the range of Markov models and their extensions which can be fitted to panel-observed data, and their implementation in the msm package for R. Transition intensities may vary between individuals, or with piecewise-constant time-dependent covariates, giving an inhomogeneous Markov model. Hidden Markov models can be used for multi-state processes which are misclassified or observed only through a noisy marker. The package is intended to be straightforward to use, flexible and comprehensively documented. Worked examples are given of the use of msm to model chronic disease progression and screening. Assessment of model fit, and potential future developments of the software, are also discussed.
Mapping of the EQ-5D index from clinical outcome measures and demographic variables in patients with coronary heart disease
No full textThe official published version of the article can be found at the link below.Background: The EuroQoL 5D (EQ-5D) is a questionnaire that provides a measure of utility for cost-effectiveness analysis. The EQ-5D has been widely used in many patient groups, including those with coronary heart disease. Studies often require patients to complete many questionnaires and the EQ-5D may not be gathered. This study aimed to assess whether demographic and clinical outcome variables, including scores from a disease specific measure, the Seattle Angina Questionnaire (SAQ), could be used to predict, or map, the EQ-5D index value where it is not available.Methods: Patient-level data from 5 studies of cardiac interventions were used. The data were split into two groups approximately 60% of the data were used as an estimation dataset for building models, and 40% were used as a validation dataset. Forward ordinary least squares linear regression methods and measures of prediction error were used to build a model to map to the EQ-5D index. Age, sex, a proxy measure of disease stage, Canadian Cardiovascular Society (CCS) angina severity class, treadmill exercise time (ETT) and scales of the SAQ were examined.Results: The exertional capacity (ECS), disease perception (DPS) and anginal frequency scales (AFS) of the SAQ were the strongest predictors of the EQ-5D index and gave the smallest root mean square errors. A final model was chosen with age, gender, disease stage and the ECS, DPS and AFS scales of the SAQ. ETT and CCS did not improve prediction in the presence of the SAQ scales. Bland-Altman agreement between predicted and observed EQ-5D index values was reasonable for values greater than 0.4, but below this level predicted values were higher than observed. The 95% limits of agreement were wide (-0.34, 0.33).Conclusions: Mapping of the EQ-5D index in cardiac patients from demographics and commonly measured cardiac outcome variables is possible; however, prediction for values of the EQ-5D index below 0.4 was not accurate. The newly designed 5-level version of the EQ-5D with its increased ability to discriminate health states may improve prediction of EQ-5D index values.Funding for this project by EuroQoL grou
IMS LD Author Schemas
No full textMany XML tools encounter problems with the modular XML schemas of the IMS LD specification. Therefore non-modular XML schemas have been created for each of the levels of IMS LD. The only normative XML schemas for the IMS LD specification can be found at the IMS website
IMS LD Author Schemas
No full textMany XML tools encounter problems with the modular XML schemas of the IMS LD specification. Therefore non-modular XML schemas have been created for each of the levels of IMS LD. The only normative XML schemas for the IMS LD specification can be found at the IMS website
IMS LD Author Schemas
No full textMany XML tools encounter problems with the modular XML schemas of the IMS LD specification. Therefore non-modular XML schemas have been created for each of the levels of IMS LD. The only normative XML schemas for the IMS LD specification can be found at the IMS website
Multi-state modelling of repeated hospitalisation and death in patients with heart failure: The use of large administrative databases in clinical epidemiology.
No full textIn chronic diseases like heart failure (HF), the disease course and associated clinical event histories for the patient population vary widely. To improve understanding of the prognosis of patients and enable health care providers to assess and manage resources, we wish to jointly model disease progression, mortality and their relation with patient characteristics. We show how episodes of hospitalisation for disease-related events, obtained from administrative data, can be used as a surrogate for disease status. We propose flexible multi-state models for serial hospital admissions and death in HF patients, that are able to accommodate important features of disease progression, such as multiple ordered events and competing risks. Fully parametric and semi-parametric semi-Markov models are implemented using freely available software in R. The models were applied to a dataset from the administrative data bank of the Lombardia region in Northern Italy, which included 15,298 patients who had a first hospitalisation ending in 2006 and 4 years of follow-up thereafter. This provided estimates of the associations of age and gender with rates of hospital admission and length of stay in hospital, and estimates of the expected total time spent in hospital over five years. For example, older patients and men were readmitted more frequently, though the total time in hospital was roughly constant with age. We also discuss the relative merits of parametric and semi-parametric multi-state models, and model assessment and comparison
Contemporary roles of registries in clinical cardiology: When do we need randomized trials?
No full textClinical registries are established as tools for auditing clinical standards and benchmarking quality improvement initiatives. They also have an emerging role (as electronic health records) in cardiovascular research and, in particular, the conduct of RCTs. While the RCT is accepted as the most robust experimental design, observational data from clinical registries has become increasingly valuable for RCTs. Data from clinical registries may be used to augment results from RCTs, identify patients for recruitment and as an alternative when randomization is not practically possible or ethically desirable. Here the authors appraise the advantages and disadvantages of both methodologies, with the aim of clarifying when their joint use may be successful
Clinical and cost-effectiveness analysis of an open label, single-centre, randomised trial of spinal cord stimulation (SCS) versus percutaneous myocardial laser revascularisation (PMR) in patients with refractory angina pectoris: The SPiRiT trial
No full textBackground: Patients with refractory angina have significant morbidity. This study aimed to
compare two of the treatment options, Spinal Cord Stimulation (SCS) and Percutaneous
Myocardial Laser Revascularisation (PMR) in terms of clinical outcomes and cost-effectiveness.
Methods: Eligible patients were randomised to PMR or SCS and followed up for exercise
tolerance time (ETT), Canadian Cardiovascular Society (CCS) classification and the quality of life
measures SF-36, Seattle Angina Questionnaire and the EuroQoL at 3, 12 and 24 months. Utilities
were calculated using the EQ-5D and these and costs were compared between groups. The
incremental cost-effectiveness ratio (ICER) per QALY for SCS compared to PMR was also
calculated.
Results: At 24 months post-randomisation, patients that had SCS and PMR had similar ETT (mean
difference 0.05, 95% CI -2.08, 2.18, p = 0.96) and there was no difference in CCS classification or
quality of life outcomes. The difference in overall mean costs when comparing SCS to PMR was
GBP5,520 (95% CI GBP1,966 to GBP8,613; p < 0.01) and the ICER of using SCS was GBP46,000
per QALY.
Conclusion: Outcomes after SCS did not differ appreciably from those after PMR, with the former
procedure being less cost-effective as currently applied. Larger studies could clarify which patients
would most benefit from SCS, potentially increasing cost-effectiveness.
Trial registration: Current Controlled Trials ISRCTN0964895
Advances in Editors for IMS LD in the TENCompetence Project
No full textThe TENCompetence project has made the first release of IMS LD tools which provide significant improvements in usability and integration. The project and the user group are introduced, and the principal improvements described. The results of initial evaluation are outlined, and the direction of future work is indicated
Using Widgets to Provide Portable Services for IMS Learning Design
No full textSharples, P., Griffiths, D., & Scott, W. (2008). Using Widgets to Provide Portable Services for IMS Learning Design. In R. Koper, K. Stefanov & D. Dicheva (Eds.), Proceedings of the 5th International TENCompetence Open Workshop "Stimulating Personal Development and Knowledge Sharing" (pp. 57-60). October, 30-31, 2008, Sofia, Bulgaria: TENCompetence Workshop. [For the whole proceedings please see also http://hdl.handle.net/1820/1961 ]Since the publication of the IMS LD specification it has been recognised that the lack of a rich set of runtime
services is a major barrier to adoption. The approaches taken to resolving this problem are reviewed, and their
strengths and limitations identified. A generic widget server developed by the authors is described. Integration of
the widget server with the IMS LD runtime system provides an extensible set of services. This has been demonstrated
with the creation of widgets for forums, messaging, vote, and Google maps which are provided for users within the
context of their role and activities in a Unit of Learning. Authoring and administration are described, showing how
the system is both extensible and portable.The work on this publication has been sponsored by the TENCompetence Integrated Project that is funded by the European Commission's 6th Framework Programme, priority IST/Technology Enhanced Learning. Contract 027087 [http://www.tencompetence.org
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