1,721,025 research outputs found
Meta-analysis and meta-modelling for diagnostic problems
No full textBackgroundA proportional hazards measure is suggested in the context of analyzing SROC curves that arise in the meta–analysis of diagnostic studies. The measure can be motivated as a special model: the Lehmann model for ROC curves. The Lehmann model involves study–specific sensitivities and specificities and a diagnostic accuracy parameter which connects the two.MethodsA study–specific model is estimated for each study, and the resulting study-specific estimate of diagnostic accuracy is taken as an outcome measure for a mixed model with a random study effect and other study-level covariates as fixed effects. The variance component model becomes estimable by deriving within-study variances, depending on the outcome measure of choice. In contrast to existing approaches – usually of bivariate nature for the outcome measures – the suggested approach is univariate and, hence, allows easily the application of conventional mixed modelling.ResultsSome simple modifications in the SAS procedure proc mixed allow the fitting of mixed models for meta-analytic data from diagnostic studies. The methodology is illustrated with several meta–analytic diagnostic data sets, including a meta–analysis of the Mini–Mental State Examination as a diagnostic device for dementia and mild cognitive impairment.ConclusionsThe proposed methodology allows us to embed the meta-analysis of diagnostic studies into the well–developed area of mixed modelling. Different outcome measures, specifically from the perspective of whether a local or a global measure of diagnostic accuracy should be applied, are discussed as well. In particular, variation in cut-off value is discussed together with recommendations on choosing the best cut-off value. We also show how this problem can be addressed with the proposed methodology
Outcomes research and cost-effectiveness analysis in radiology
No full textThe decision to implement a new medical technology requires that it not only increases survival or quality of life, but that it is also economically sound. The unique feature in the assessment of diagnostic tests is that the results of such tests are intermediate outcomes. Both randomized controlled clinical trials and decision analysis have an important role to play in the assessment of diagnostic tests. Important points to consider when performing a cost-effectiveness study are what perspective to take; comparing the technology with the next best strategy; including both effectiveness and costs; the distinction between describing and valuing the quality of life; intangibles such as the value of information; and the incremental cost-effectiveness ratio.</p
Outcomes research and cost-effectiveness analysis in radiology
No full textThe decision to implement a new medical technology requires that it not only increases survival or quality of life, but that it is also economically sound. The unique feature in the assessment of diagnostic tests is that the results of such tests are intermediate outcomes. Both randomized controlled clinical trials and decision analysis have an important role to play in the assessment of diagnostic tests. Important points to consider when performing a cost-effectiveness study are what perspective to take; comparing the technology with the next best strategy; including both effectiveness and costs; the distinction between describing and valuing the quality of life; intangibles such as the value of information; and the incremental cost-effectiveness ratio
The relationship between descriptive and valuational quality-of-life measures in patients with intermittent claudication
No full textThe study objective was to assess the relationship between descriptive and valuational quality-of-life measures in patients with intermittent claudication. in telephone interviews, 68 patients completed a questionnaire consisting of a descriptive health status measure (RAND 35-Item Health Survey 1.0), and several valuational measures (standard gamble, time tradeoff, rating scale, and McMaster health utility index). All measures demonstrated reduced quality of life in the patients. Scores on the RAND-36 dimensions correlated moderately well with the rating scale and McMaster health utility index (R = 0.37-0.67) but less well with the standard gamble and the time tradeoff (R = 0.10-0.46). Multiple regression analysis demonstrated that 28% of the variance in the time-tradeoff values and 14% of the variance of the standard-gamble utilities could be Explained by the best combination of RAND dimensions. These results suggest that answers to descriptive health-status questions cannot reliably predict standard-gamble utilities or time-tradeoff values
The DAMASK trial protocol: a pragmatic randomised trial to evaluate whether GPs should have direct access to MRI for patients with suspected internal derangement of the knee
Get PDFBackground: Though new technologies like Magnetic Resonance Imaging (MRI) may be accurate, they often diffuse into practice before thorough assessment of their value in diagnosis and management, and of their effects on patient outcome and costs. MRI of the knee is a common investigation despite concern that it is not always appropriate. There is wide variation in general practitioners (GPs) access to, and use of MRI, and in the associated costs. The objective of this study was to resolve uncertainty whether GPs should refer patients with suspected internal derangement of the knee for MRI or to an orthopaedic specialist in secondary care. Methods/Design: The design consisted of a pragmatic multi-centre randomised trial with two parallel groups and concomitant economic evaluation. Patients presenting in general practice with suspected internal derangement of the knee and for whom their GP was considering referral to an orthopaedic specialist in secondary care were eligible for inclusion. Within practices, GPs or practice nurses randomised eligible and consenting participants to the local radiology department for an MRI examination, or for consultation with an orthopaedic specialist. To ensure that the waiting time from GP consultation to orthopaedic appointment was similar for both trial arms, GPs made a provisional referral to orthopaedics when requesting the MRI examination. Thus we evaluated the more appropriate sequence of events independent of variations in waiting times. Follow up of participants was by postal questionnaires at six, twelve and 24 months after randomisation. This was to ensure that the evaluation covered all events up to and including arthroscopy. Discussion: The DAMASK trial should make a major contribution to the development of evidence-based partnerships between primary and secondary care professionals and inform the debate when MRI should enter the diagnostic pathway
- …
