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PubMed1980

Methodologic problems of exercise testing for coronary artery disease: groups, analysis and bias.

To determine why exercise testing remains controversial as a diagnostic test for coronary artery disease, a methodologic review was undertaken of 33 studies comprising 7,501 patients who had undergone both exercise tests and coronary angiography. Of seven methodologic standards for research design, only one received general compliance: the requirement for an adequate variety of anatomic lesions. Less than half of the studies complied with any of the remaining six standards: adequate identification of the groups selected for study; adequate analysis for relevant chest pain syndromes; avoidance of a limited challenge group; and avoidance of work-up bias, diagnostic review bias and test review bias. Only one study met as many as five standards. These methodologic problems may explain the wide range of sensitivity (35 to 88 percent) and specificity (41 to 100 percent) found for exercise testing, because the variations could not be attributed to the usual explanations: definition of anatomic abnormality, stress test technique or definition of an abnormal test. Determining the true value of exercise testing requires methodologic improvements in patient selection, data collection and data analysis.

Coronary Disease↗

PubMed1994

Critical pathway methodology: effectiveness in congenital heart surgery.

Critical pathway methodology has been demonstrated to provide producible reduction in average length of stay (ALOS) in adults in certain diagnostic-related groups and operations such as coronary artery bypass grafting. The efficacy of this approach in congenital heart surgery was explored. Two hundred eighty-six consecutive patients from a health maintenance organization treated by a single surgeon since the institution of diagnostic-related group coding at that health maintenance organization constituted the study group. One hundred fourteen patients were treated at a university hospital without critical pathway methodology (group 1) and 172, subsequently at the health maintenance organization institution using the methodology (group 2). Operation/lesion, age, and diagnostic-related group matching was possible in 61 pairs. Examination of the ALOS Hospital (operative and postoperative days) for the entire cohort revealed a 43.8% reduction in ALOS Hospital (p < 0.0001) and a 39.0% reduction in ALOS Intensive Care Unit (p < 0.0001). There was also significant reduction in ALOS Hospital and ALOS Intensive Care Unit in the operation/lesion-matched subsets. Outcome measures including operative and late mortality, readmission, unscheduled emergency room and clinic visits, and health maintenance organization family assessment survey demonstrated no improvement in outcome with increased hospital stay. Thus, critical pathway methodology when used in patients undergoing a congenital heart operation produces a significant reduction in hospital stay and intensive care unit stay as well as quality patient care with uniformity of outcome.

Adolescent↗

PubMed1981

A mutagenicity methodology for assessing the formation of N-dimethylnitrosamine in vivo.

The mutagenicity test methodology in vitro has been extensively used during recent years in the identification of potential carcinogenic agents. Mutagenic analyses have been applied to the study of chemical reaction products for the demonstration of the formation of mutagenic agents. Recent studies have indicated that secondary and tertiary amines, when reacted with nitrite in acidic conditions, yield N-nitroso compounds, including the potent carcinogen N-dimethylnitrosamine (NDMA). This finding raises the problem of risk evaluation of several food components of human diets for the presence of potential carcinogenic compounds. By combining a mutagenicity test procedure with yeast cells inoculated into the blood system of mice and incubated in the liver for various times (minutes or hours) we have devised a model methodology which allows the detection of the formation of N-dimethylnitrosamine (NDMA) at a level lower than 1 mg/kg. The methodology has been examined for its use in the study of activators of the nitrosation, such as thiocyanate, and of inhibitors of the nitrosation, such as ascorbic acid and tannic acid. Other food components of the human diet, such as red wine, have also been investigated by this methodology.

Animals↗

PubMed1996

Using PBPK modeling and comprehensive realism methodology for the quantitative cancer risk assessment of butadiene.

The National Academy of Sciences and many others have noted the need for quantitative health risk assessment methodology that goes beyond a simple screening analysis based on upper bounds on risk. The Academy recommended adoption of methodologies which provide a higher-tier analysis based on realistic estimates of risk which reflect more of the available biological information. In recent years, scientists have challenged the assumption of low-dose linearity and other default assumptions in cancer risk assessment. These challenges have stimulated the continued evolution of quantitative risk assessment methodologies, because effective risk management requires accurate characterizations of uncertainty and greater utilization of cost-benefit analyses for decision making. "Comprehensive Realism" is an emerging quantitative weight-of-evidence based risk assessment methodology for both cancer and noncancer health effects which utilizes probability distributions and decision analysis techniques to reflect more of the available human and animal dose-response data. The current state of knowledge about the relative plausibility of alternative dose-response analyses is also addressed in this approach. The framework discussed here should lead to a higher-tier assessment of butadiene.

Butadienes↗

PubMedDate not supplied

Alcoholism treatment outcome studies, 1980-1992: methodological characteristics and quality.

We examine the methodological characteristics and provision of study information in 339 alcoholism treatment outcome studies reported between 1980 and 1992. We consider factors in four methodological domains: sampling and description of patients, specification of treatments, outcome variable assessment and follow-up, and treatment effect estimates; we also consider the methodological quality of the studies. Although methodological quality has improved over time, there remains room for improvement. Of special concern is the low statistical power of many studies. Multiple treatment group studies had an average .54 probability of detecting a treatment effect of medium size.

Adult↗

PubMedDate not supplied

Analog baselines: a critical review of the methodology.

Analog baselines are an experimental methodology for identifying the functions of maladaptive behavior in the naturally occurring environment (Iwata, Dorsey, Slifer, Bauman, & Richman, 1982; Iwata et al., 1994). This article identifies a number of potential limitations in this methodology. These include: (a) procedural problems inherent in the use of multielement designs, (b) the fidelity of analog baseline design conditions, (c) the relation of the analog conditions to the naturally occurring environment, (d) a narrow analysis of behavior limited by an implicit adherence to an ABC model of behavior, (e) a limited acknowledgement of multifunction and idiosyncratically motivated behaviors, (f) problems in the definition of response classes, and (g) difficulties in the use of analog baselines to design interventions. Future research should attend to three main questions. First, the convergent validity of different assessment methodologies, including analog baselines, should be evaluated. Future research should attend to procedures that can integrate the entire clinical process of referral, identifying the functions of the target behavior, including other methods of identifying the functions of behavior, treatment design, and implementation. Second, assessment failures could be examined carefully to identify ways of developing this methodology further. Third, the process of designing an intervention depends upon input from many sources of information. The use of analog baselines will be enhanced by a greater understanding of the process of clinical decision making.

Behavior Therapy↗

PubMed2004

Evaluation of glucose controllers in virtual environment: methodology and sample application.

OBJECTIVE: Adaptive systems to deliver medical treatment in humans are safety-critical systems and require particular care in both the testing and the evaluation phase, which are time-consuming, costly, and confounded by ethical issues. The objective of the present work is to develop a methodology to test glucose controllers of an artificial pancreas in a simulated (virtual) environment. MATERIAL AND METHODS: A virtual environment comprising a model of the carbohydrate metabolism and models of the insulin pump and the glucose sensor is employed to simulate individual glucose excursions in subjects with type 1 diabetes. The performance of the control algorithm within the virtual environment is evaluated by considering treatment and operational scenarios. RESULTS: The developed methodology includes two dimensions: testing in relation to specific life style conditions, i.e. fasting, post-prandial, and life style (metabolic) disturbances; and testing in relation to various operating conditions, i.e. expected operating conditions, adverse operating conditions, and system failure. We define safety and efficacy criteria and describe the measures to be taken prior to clinical testing. The use of the methodology is exemplified by tuning and evaluating a model predictive glucose controller being developed for a wearable artificial pancreas focused on fasting conditions. CONCLUSION: Our methodology to test glucose controllers in a virtual environment is instrumental in anticipating the results of real clinical tests for different physiological conditions and for different operating conditions. The thorough testing in the virtual environment reduces costs and speeds up the development process.

Algorithms↗

PubMed2006

The relationship of theory and methodology in EEG studies of mental activity.

Due to the multidisciplinary character of psychophysiology, the problem of comparability of psychological and physiological phenomena of different natures and levels of organization has always been raised. This requires the interaction of theory and methodology to appropriately address the specifics of the psychophysiological paradigm, all the while maintaining their grounding in the actual psychological and physiological concepts. The history of EEG studies of mental activity shows that a weak theoretical basis at certain stages can result not only in methodological crises but can also affect empirical data collection and interpretation. An adequate theory can lend strong support to the methodology with "brain-oriented" structuring of psychological tasks and such a theory improves the neurophysiological informative value of the EEG parameters referring to the psychological characteristics of mental processes etc. On the other hand, the great importance of the EEG recording and processing techniques can result in overrating technological progress, hence frequently holding back meaningful interpretation and construction of a comprehensive psychophysiological conceptual framework. This in turn causes demands for higher material and intellectual outlays, due to overspecialization in research, and results in work duplication as well as the creation of a fragmentary knowledge structure. This article illustrates how the multidisciplinary interaction of theory and methodology, when focused on theoretical problems, can yield a series of concepts with escalating levels of integration, bringing together such different branches of psychophysiology as the study of functional states and of individual differences. As a result, this extends the theoretical model based on normal material to encompass borderline constitutional psychopathology.

Electroencephalography↗

PubMed2005

Methodology for biologically-based treatment planning for combined low-dose-rate (permanent implant) and high-dose-rate (fractionated) treatment of prostate cancer.

PURPOSE: The combination of permanent low-dose-rate interstitial implantation (LDR-BRT) and external beam radiotherapy (EBRT) has been used in the treatment of clinically localized prostate cancer. While a high radiation dose is delivered to the prostate in this setting, the actual biologic dose equivalence compared to monotherapy is not commonly invoked. We describe methodology for obtaining the fused dosimetry of this combined treatment and assigning a dose equivalence which in turn can be used to develop desired normal tissue and target constraints for biologic-based treatment planning. METHODS AND MATERIALS: Patients treated with this regimen initially receive an I-125 implant prescribed to 110 Gy followed, 2 months later, by 50.4 Gy in 28 fractions using intensity-modulated external beam radiotherapy. Ab initio methodology is described, using clinically derived biologic parameters (alpha, beta, potential doubling time for prostate cancer cells [T(pot)], cell loss factor), for calculating tumor control probability isoeffective doses for the combined LDR and conventional fraction EBRT treatment regimen. As no such formalism exists for assessing rectal or urethral toxicity, we make use of semi-empirical expressions proposed for describing urethral and rectal complication probabilities for specific treatment situations (LDR and fractionation, respectively) and utilize the notion of isoeffective dose to extend these results to combined LDR-EBRT regimens. RESULTS: The application to treatment planning of the methodology described in this study is illustrated with real-patient data. We evaluate the effect of changing LDR and EBRT prescription doses (in a manner that remains isoeffective with 81 Gy EBRT alone or with 144 Gy LDR monotherapy) on rectal and urethral complication probabilities, and suggest that it should be possible to improve the therapeutic ratio by exploiting joint LDR-EBRT planning. CONCLUSIONS: We describe new methodology for biologically based treatment planning for patients who receive combined low-dose-rate brachytherapy and external beam radiotherapy for prostate cancer. Using relevant mathematical tools, we demonstrate the feasibility of fusing dose distributions from each treatment for this combined regimen, which can then be expressed as isoeffective dose distributions. Based on this information, dose constraints for the rectum and urethra are described which could be used for planning such combination regimens.

Algorithms↗

PubMed2006

Use of methodological search filters to identify diagnostic accuracy studies can lead to the omission of relevant studies.

OBJECTIVE: To determine the usefulness of methodological filters in search strategies for diagnostic studies in systematic reviews. STUDY DESIGN AND SETTING: We made an inventory of existing methodological search filters for diagnostic accuracy studies and applied them in PubMed to a reference set derived from 27 published systematic reviews in a broad range of clinical fields. Outcome measures were the fraction of not identified relevant studies and the reduction in the number of studies to read. RESULTS: We tested 12 search filters. Of the studies included in the systematic reviews, 2%-28% did not pass the sensitive search filters, 4%-24% did not pass the accurate filters, and 39%-42% did not pass the specific filters. Decrease in number-needed-to-read when a search filter was used in a search strategy for a diagnostic systematic review varied from 0% to 77%. CONCLUSION: The use of methodological filters to identify diagnostic accuracy studies can lead to omission of a considerable number of relevant studies that would otherwise be included. When preparing a systematic review, it may be preferable to avoid using methodological filters.

Biomedical Research↗

PubMed2006

An integrated impact assessment and weighting methodology: evaluation of the environmental consequences of computer display technology substitution.

Computer display technology is currently in a state of transition, as the traditional technology of cathode ray tubes is being replaced by liquid crystal display flat-panel technology. Technology substitution and process innovation require the evaluation of the trade-offs among environmental impact, cost, and engineering performance attributes. General impact assessment methodologies, decision analysis and management tools, and optimization methods commonly used in engineering cannot efficiently address the issues needed for such evaluation. The conventional Life Cycle Assessment (LCA) process often generates results that can be subject to multiple interpretations, although the advantages of the LCA concept and framework obtain wide recognition. In the present work, the LCA concept is integrated with Quality Function Deployment (QFD), a popular industrial quality management tool, which is used as the framework for the development of our integrated model. The problem of weighting is addressed by using pairwise comparison of stakeholder preferences. Thus, this paper presents a new integrated analytical approach, Integrated Industrial Ecology Function Deployment (I2-EFD), to assess the environmental behavior of alternative technologies in correlation with their performance and economic characteristics. Computer display technology is used as the case study to further develop our methodology through the modification and integration of various quality management tools (e.g., process mapping, prioritization matrix) and statistical methods (e.g., multi-attribute analysis, cluster analysis). Life cycle thinking provides the foundation for our methodology, as we utilize a published LCA report, which stopped at the characterization step, as our starting point. Further, we evaluate the validity and feasibility of our methodology by considering uncertainty and conducting sensitivity analysis.

Computer Terminals↗

PubMed2005

"Reference Biospheres" for solid radioactive waste disposal: the BIOMASS methodology.

The BIOMASS Theme 1 project has developed a methodology for the logical and defensible construction of 'assessment biospheres': mathematical representations of biospheres used in the total system performance assessment of radioactive waste disposal. The BIOMASS Methodology provides a systematic approach to decision making, including decisions on how to address biosphere change. The BIOMASS Methodology was developed through consultation and collaboration with many relevant organisations, including regulators, operators and a variety of independent experts. It has been developed to be practical and to be consistent with recommendations from ICRP and IAEA on radiation protection in the context of the disposal of long-lived solid radioactive wastes. The five main steps in the methodology are described in this paper. The importance of a clear assessment context, to clarify intentions and to support a coherent biosphere assessment process within an overall repository performance assessment, is strongly emphasised. A well described assessment context is an important tool for ensuring consistency across the performance assessment as a whole. The use of interaction matrices has been found to be helpful in clarifying the interactions between different habitats within the biosphere system and the significant radionuclide transfer pathways within the biosphere system. Matrices also provide a useful means of checking for consistency.

Program Development↗

PubMed2006

Methodological improvements for measuring eicosanoids and cytokines in exhaled breath condensate.

BACKGROUND: Exhaled breath condensate (EBC) is simple to collect and as such a non-invasive method that has attracted substantial interest in the last few years. However, several methodological concerns have been raised and it has been difficult to reproduce results between different centres. Because of low concentrations of inflammatory markers, potential loss in the sampling system may have great influence. The aim of the present study was to se if evaporation and plastic coating could facilitate detection. METHODOLOGY: Through methodological improvements, we have now made it possible to measure EBC concentrations of eicosanoids and cytokines in our system. Due to absorbance of both fatty acid derivates and proteins to several plastics, the first step is coating of all surfaces with bovine serum albumin and Tween 20. Since several assays are sensitive to these factors, the methodology has to be standardised to avoid false results. Secondly, larger amounts of EBC have to be vacuum-dried, and thereafter resolved in the respective assay buffers. The EBCs have to be concentrated 5-10 times, depending on samples and assay sensitivity. RESULTS: Due to these improvements we can measure, for example, cysteinyl-leukotrienes, leukotriene B4, prostaglandin E and 8-isoprostane. High sensitivity assays have also made it possible to measure cytokines, for example, interleukin (IL)-1beta, IL-8 and IL-13. SUMMARY: We are aware of different results from other labs. However, it seems essential to coat and to concentrate the samples in order to achieve reliable and measurable results.

Adult↗

PubMed2005

Siting MSW landfills with a spatial multiple criteria analysis methodology.

The present work describes a spatial methodology which comprises several methods from different scientific fields such as multiple criteria analysis, geographic information systems, spatial analysis and spatial statistics. The final goal of the methodology is to evaluate the suitability of the study region in order to optimally site a landfill. The initial step is the formation of the multiple criteria problem's hierarchical structure. Then the methodology utilizes spatial analysis processes to create the evaluation criteria, which are mainly based on Greek and EU legislation, but are also based on international practice and practical guidelines. The relative importance weights of the evaluation criteria are estimated using the analytic hierarchy process. With the aid of the simple additive weighting method, the suitability for landfill siting of the study region is finally evaluated. The resulting land suitability is reported on a grading scale of 0-10, which is, respectively, from least to most suitable areas. The last step is a spatial clustering process, which is being performed in order to reveal the most suitable areas, allowing an initial ranking and selection of candidate landfill sites. The application of the presented methodology in the island of Lemnos in the North Aegean Sea (Greece) indicated that 9.3% of the study region is suitable for landfill siting with grading values greater than 9.

Environment↗

PubMed2003

Some methodological deficiencies in studies on traffic accident predictors.

The paper discusses some methodological problems in (psychological) research on traffic accident predictors and reviews a convenience sample of the literature. Three methodological aspects are identified as being important: reliability of accident predictors, time period for accidents used as dependent variable, and culpability for accidents. Papers are scrutinized and most are found to be wanting in these aspects. Traffic researchers do not adhere to, or hardly even discuss, these basic methodological problems. It is concluded that the current research into (psychological) accident predictors is fraught with methodological deficiencies. Why most studies seem to be deficient in these aspects is not clear, as several researchers have pointed out these problems.

Accidents, Traffic↗

PubMed1995

Methodologic sources of inconsistent prognoses for post-acute myocardial infarction.

PURPOSE: To investigate basic methodologic problems that could explain inconsistent and contradictory results for predictor variables in studies of prognosis after myocardial infarction (MI). MATERIALS AND METHODS: Studies on postinfarct prognosis published in English between 1979 and 1991 were identified with a MEDLINE literature search. The key words used for the computer search were: "prognosis" and "myocardial infarction" in the title and "mortality" or "survival" or "outcome" in the title or abstract. Reference lists in the reports captured by the search were examined for pertinent articles, and additional articles were sought in the index pages of two prominent journals. To be included in the analysis, a study had to fulfill the following eligibility criteria: a cohort study or randomized, controlled trial; sample size > or = 50 patients; a clear identification of the time when follow-up began, after the acute phase of MI and either before or at hospital discharge; follow-up for a minimum of 6 months or median/mean of 1 year; and multivariable analysis for intervals no longer than 2 years after the MI. Eight methodologic standards addressing sources of major problems were established and applied to each study. RESULTS: Of 766 reports identified, 111 fulfilled the eligibility criteria. The median number of standards fulfilled was 3, the highest 6. The proportions of studies complying with each of the 8 methodologic standards were: (1) inception cohort, 60%; (2) total death as an unequivocal outcome, 54%; (3) verification of cause-specific deaths (in 62 studies analyzing cardiac death), 37%; (4) analysis of crucial variables describing baseline severity, 13%; (5) indication of quantitative scope of the spectrum of baseline severity, 20%; (6) reproducible classification of candidate predictor variables, 40%; (7) adequate identification of quantitative importance of and boundaries for statistically significant predictor variables, 39%; and (8) evaluation of impact of treatment on predictor variables, 13%. CONCLUSIONS: The results show that studies on postinfarct prognosis have frequently disregarded basic methodologic principles. Suitable adherence to these principles in future research will allow improved interpretation of results and can reduce inconsistent findings, while improving the applicability of the identified predictors.

Humans↗

PubMed2005

[Methodological recommendations of the Regulatory Agencies].

The suitability of new drugs for use in the general population in terms of risk and benefit is assessed by the health authorities through their drug agencies. These agencies regulate the entry of drugs on the market and their conditions for use according to strict criteria of quality, safety and efficacy. To preserve the principle of transparency, the requirements are previously published as guidelines, which are freely available on the Internet. All these guidelines have the following basic recommendations in common: (a) appropriate methodology for the objective, defined in detail a priori, (b) traceability, (c) verification of the appropriateness of the methodology applied, (d) justification of any deviation from the initial plan and (e) demonstration of the robustness of the results in distinct scenarios. Regulatory guidelines differ from other methodological references in their emphasis on the practical issues of the design and performance of studies, accepted methodological principles, and systems to ensure quality assurance in research. Although these requirements might not be universally applied to all types of research, the guidelines are freely available and are a good reference for the authorship, review and publication of clinical trials. The present article aims to review some of the guidelines that could be especially useful.

Biomedical Research↗

PubMed1998

Economic analyses in obstetrics and gynecology: a methodologic evaluation of the literature.

OBJECTIVE: To evaluate the methodology of the cost-effectiveness and cost-benefit literature in obstetrics and gynecology. DATA SOURCES: We performed a MEDLINE search of the general and subspecialty obstetrics and gynecology journals for the years 1990 through 1996. METHODS OF STUDY SELECTION: Original investigations including cost-effectiveness or cost-benefit were evaluated by two reviewers for adherence to ten minimum methodologic standards derived by a review of guidelines for medical economic analyses. The major criteria considered included: 1) provision of comparative options, 2) statement of analytic perspective, 3) presentation of cost data, 4) identification of outcome measure, 5) use of summary measure of economic effectiveness or benefit, and 6) performance of a sensitivity analysis. The minor criteria evaluated included: 1) statement of source of cost data, 2) inclusion of long-term costs, 3) use of discounting, and 4) calculation of an incremental summary measure. TABULATION, INTEGRATION, AND RESULTS: Ninety-eight articles that included cost-benefit or cost-effectiveness analyses were identified. The mean number of major and minor principles adhered to were 3.6 and 1.0, respectively. Five publications (5.1%) conformed to all ten major and minor criteria, whereas nine (9.2%) articles used all six major criteria. The provision of cost data (94.8%) and statement of comparative options (96.9%) were the major principles most frequently adhered to, whereas the use of discounting (10.2%) and statement of analytic perspective (19.3%) showed the lowest compliance. Agreement between the reviewers was excellent (kappa .87). CONCLUSION: Published economic analyses in the obstetrics and gynecology literature seldom adhere to all recommended methodologic guidelines. Further training in the methodology of cost-effectiveness analysis is needed within the specialty.

Cost-Benefit Analysis↗