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At least 145 records · Page 8Linked to original sources
PubMed1999

Carotid arterial ultrasound scan imaging: A direct approach to stenosis measurement.

PURPOSE: Management decisions regarding carotid artery disease are critically dependent on stenosis but have been made difficult because of conflicting methods used to determine such stenosis. The increasing use of duplex ultrasound scanning has conventionally depended on Doppler velocity measurement, an indirect method for calculating carotid stenosis. Recent technical advances have improved the quality of B-mode/color-flow ultrasound scan imaging (USI). We tested prospectively whether USI was clinically effective as the primary criterion for estimating carotid stenosis. METHODS: Transverse and longitudinal USI, Doppler velocity, and arteriography data were obtained sequentially and independently for 713 carotid bifurcations. The internal carotid artery (ICA) residual lumen, the local outer diameter at the stenotic site, and the diameter distal to the bulb were measured in a representative USI longitudinal section. The peak systolic velocity and the end diastolic velocity (EDV) were measured at the stenosis. Local stenosis as determined with USI was compared with the x-ray arteriographic clinical radiology interpretation (XRI). As the primary method, radiologists compared the residual lumen with the distal ICA diameter, as recommended by the North American Symptomatic Carotid Endarterectomy Trial and the Asymptomatic Carotid Atherosclerosis Study. Analysis was by means of the USI positive predictive value (PPV) and negative predictive value (NPV) of the XRI findings, with the assumption that 80%, 70%, and 60% local stenosis with USI related to 70%, 60%, and 50% stenosis with XRI, respectively. RESULTS: All 56 ICA occlusions as determined with USI were confirmed with XRI. When the USI showed 80% to 99% stenosis, the PPV of the XRI showing 70% to 99% stenosis was 94% (116/123). Two ICAs that were shown to be severely diseased with USI appeared to be occluded with XRI. For <50% stenosis shown with USI, the prediction of <50% stenosis shown with XRI was 94% (253/269). For borderline stenosis in the 50% to 79% range with USI, the addition of velocity criteria to USI data improved both the PPV and the NPV. In the range of 70% to 79% stenosis with USI, the PPV improved from 82% (76/93) to 91% (53/58) for the subgroup with an EDV of more than 80 cm/s. For the range of 60% to 69% stenosis with USI, the PPV improved from 75% (71/95) to 95% (21/22) for the subgroup with an EDV of more than 80 cm/s. In the range of 50% to 59% stenosis with USI, the NPV improved from 69% (53/77) to 93% (14/15) for the subset with a peak systolic velocity of less than 100 cm/s. CONCLUSION: On the basis of the USI data alone, a prediction of arteriographic findings was possible at the 95% level for occlusion and severe stenosis and for ruling out hemodynamically significant stenosis. The addition of velocity data improved prediction in borderline degrees of stenosis. USI was effective for quantifying clinically significant degrees of stenosis.

Adult↗
PubMed2003

Bioavailability versus bioequivalence: the cyclosporine model.

The quest for a fixed-dose immunosuppressive drug continues. Experience with cyclosporine, tacrolimus and mycophenolate mofetil has taught us that there is no correlation between dose and clinical events. These data indicate that the concentration of the drug at the site of action (bioavailability) of each of these agents differs from one patient to the next. In addition, the bioequivalence (concentration of intact drug at the site of action resulting in a measurable response [effect]) may differ among individuals. Technically, it is very difficult to measure the drug concentration at a particular site, especially in organs or tissues that are not directly accessible. Therapeutic drug-blood-level monitoring is a simple indirect method that is used to estimate both bioavailability and bioequivalence. However, the immunosuppressive effect of all these drugs is initiated by binding to receptors on the surface of lymphocytes, which leads to inhibition of cytokine production and proliferation of activated lymphocytes. Thus, it would be more advantageous to monitor the level and effect of these drugs at the site of action (bioequivalence), the lymphocyte. This report describes an assay of this type that was developed for monitoring transplant patients at one center. The assay is based on measuring drug levels in the cytoplasm of lymphocytes. It is quick and easy to perform (20 samples per hour), inexpensive, and reproducible. The between-run Coefficient of Variance (CV) is 5.4 and a within-run CV is 3.1. For this study, blood and lymphocyte drug levels in transplant patients were determined and correlated with graft function and clinical events (biopsy-proven rejection and/ or toxicity).

Adult↗
PubMed1982

Clinical determination of energy cost and walking velocity via stopwatch or speedometer cane and conversion graphs.

Work rate and relative exercise intensity are basic considerations in developing optimal exercise training prescriptions in cardiopulmonary rehabilitation. Velocity and energy cost of walking are directly related to work rate and indirectly related to exercise intensity. This article describes two methods of measuring walking velocity and estimating oxygen uptake. The validity and accuracy of the methods are discussed. We believe both methods are clinically useful. Because one method uses a specially instrumented speedometer cane, technical information concerning its design and construction is also included.

Canes↗
PubMed1990

Clinical development of aromatase inhibitors for the treatment of breast and prostate cancer.

Numerous aromatase inhibitors are under development for breast cancer treatment. The major aims are to obtain a drug which at its dose of maximum efficacy has no effect on other endocrine systems, has no clinical side-effects and is convenient to administer. During the early clinical stages of development detailed endocrine and pharmacokinetic analyses are a valuable aid in the establishment of a drug's selectivity and its optimum dose, route and frequency of administration. The optimal dose may be defined as the minimum that will achieve maximal and sustained suppression of aromatase activity. This has generally been measured indirectly by comparing the suppression of plasma oestrogen levels at a selection of dosages. This approach has major advantages in speeding dose selection for therapeutic clinical trials. However, it also has some disadvantages including the unproven assumption that clinical response has a direct relationship with the degree of oestrogen suppression. In addition there are technical difficulties of analysis, of wide variability in endocrine response between patients and of demonstrating oestrogen suppression to be equivalent between doses (necessary to show maximal suppression). The direct measurement of aromatase inhibition in vivo by isotopic infusion analysis provides support to these indirect estimates. Its value is shown by our recent results with CGS16949A. The additional value of collating pharmacokinetic and endocrine measurements is apparent from our investigations of 4-hydroxyandrostenedione (4-OHA) and pyridoglutethimide. A consideration of our experience with these inhibitors may be helpful in directing the development of future agents. Whilst the value of aromatase inhibition in breast cancer is established its value in prostatic cancer is in doubt: we have found that 4-OHA is only poorly efficacious in advanced prostatic cancer.

Aminoglutethimide↗
PubMed1980

[Lymphoscanning potentials in the diagnosis of lung cancer metastasis].

Clinical estimation is given of indirect isotope lymphoscanning, performed by intrapulmonary administration of Au-198, for diagnosing lung cancer metastases. The method enables obtaining scannographs of intrathoracic lymphnodes and also, based on the changes in scannograms, judging the presence of lymphogenic metastases. Lymphoscanning is a technically feasible and safe method, it provides comparatively large information for diagnostic purposes and may occupy an important place among other diagnostic technics for ascertaining the extent of lung cancer proliferation.

Bronchial Neoplasms↗
PubMed1994

Technical and scientific developments in exposure marker methodology.

Recent advances in techniques to measure markers of exposure to environmental toxicants in humans are changing the ways in which environmental scientists, epidemiologists, and policymakers characterize and interpret such exposure. In this article we review some major technical and scientific developments in exposure marker methodology for estimating internal dose, with special reference to studies conducted at the US Centers for Disease Control and Prevention. We consider important characteristics of laboratory methods, advances in laboratory technology, analytical standards, and quality assurance of laboratory measurements; comparisons with indirect methods for estimating exposures, such as exposure indices and questionnaires; human pharmacokinetic data; sampling problems; surveillance of human exposures to toxicants; and interpretation of measurements. With a view to increasing the reliability of exposure assessment, we make recommendations for obtaining more data on human exposure to toxicants.

Biomarkers↗
PubMed1994

Costs of illness in cost-effectiveness analysis. A review of the methodology.

Costs of illness are an important input in cost-effectiveness analysis (CEA). Reviews of the literature have found that many CEAs are of low technical quality and fail to take account of costs of illness appropriately. The costs of illness and disease averted by an intervention, indirect costs, and medical care costs in added years of life are topics that present methodological issues and are not handled consistently in CEAs. Costs of illness and disease averted may be estimated by prevalence- or incidence-based methods; the correct conceptual paradigm depends on the nature of the disease. Incidence costs may be estimated by modelling the disease process, or directly from prevalence costs, the choice being determined by the extent and quality of data available. Regardless of the method, in forward-looking CEAs potential technological change must be taken into account so that incidence-based lifetime costs estimated from current treatment practices will not be biased. Whether to include indirect costs is an important issue, because indirect costs may be large and have a significant impact on the cost-effectiveness ratio. In the pure CEA model, indirect costs are excluded on ethical grounds and to prevent incursion of elements of cost-benefit analysis into CEA. The modified CEA model accepts enhanced productivity as an economic benefit made possible by, but distinct from, the health effect of an intervention. Indirect costs are included when appropriate, depending on the perspective of the analysis, the measure of effectiveness, and who bears the costs. When medical care extends life, expenditures will be incurred in the added years for illness and disease unrelated to the intervention. As with indirect costs, the pure CEA considers unrelated 'downstream' costs an indirect consequence of the health benefit of the intervention and excludes them from CEAs with the societal perspective. The modified CEA treats unrelated downstream costs as an economic effect of the change in health due to the intervention and includes them in order to have a more complete accounting of the cost of the intervention.

Cost of Illness↗
PubMed1989

Automated blood pressure measurements during exercise.

One of the critical parameters measured during exercise is blood pressure. However, the accurate measurement of systolic and diastolic blood pressure during exercise is difficult with auscultation and impractical with direct arterial techniques. The purpose of this study was to compare an automated system (Colin, Inc. STBP-680) with auscultation in humans during rest and exercise and to compare the automated system with direct arterial blood pressure measurement in a canine model during pharmacological challenges that resulted in a wide range of blood pressure values. Compared with direct arterial blood pressure taken in the canine model, the STBP-680 gave good estimates of diastolic blood pressure and adequately monitored relative changes in systolic blood pressure, diastolic blood pressure, and mean arterial pressure (mean arterial pressures in all instances were calculated as one-third systolic plus two-thirds diastolic blood pressures). Compared with auscultation methods in humans, the STBP-680 gave similar estimates of resting diastolic blood pressure and monitored relative changes in resting systolic blood pressures, diastolic blood pressures, and mean arterial pressures. During both treadmill and cycle ergometer exercise in humans, the STBP-680 monitored changes in systolic blood pressure, phase IV diastolic blood pressure, and mean arterial pressure. Further, the STBP-680 estimated exactly and noted relative changes in heart rate in every test. However, during exercise, quantitative estimations of systolic blood pressure by the STBP-680 were higher than those found using auscultation. Where exact, quantitative measures of blood pressure are needed, direct arterial measurement continues to be the most accurate method. However, where indirect methods can be used, the STBP-680 may provide a suitable alternative that reduces many of the technical concerns of auscultation in young, healthy individuals.

Adult↗
PubMed1990

[The marginal accuracy of the fit of fixed adhesive ceramic inlays].

48 extracted human molars were restored with MOD inlays using 3 different ceramic systems: Dicor, Mirage and Vitadur N. For the Dicor system both the direct and indirect manufacturing procedures were used and all the necessary technical and clinical steps were performed. After being subjected to a thermal cycling stress test for 100 days, the teeth were ground sectioned for light microscopic examination. Sintered high-strength ceramic systems (Mirage and Vitadur N) displayed significantly better marginal adaptation than casted glass ceramic. In order to estimate the extent of the outer marginal gap, we measured the defective surface where the adhesive composite had disintegrated. The best possible marginal fit will certainly prolong the longevity of inlay restorations.

Ceramics↗
PubMedDate not supplied

The use of subjective rating of exertion in Ergonomics.

In Ergonomics, the use of psychophysical methods for subjectively evaluating work tasks and determining acceptable loads has become more common. Daily activities at the work site are studied not only with physiological methods but also with perceptual estimation and production methods. The psychophysical methods are of special interest in field studies of short-term work tasks for which valid physiological measurements are difficult to obtain. The perceived exertion, difficulty and fatigue that a person experiences in a certain work situation is an important sign of a real or objective load. Measurement of the physical load with physiological parameters is not sufficient since it does not take into consideration the particular difficulty of the performance or the capacity of the individual. It is often difficult from technical and biomechanical analyses to understand the seriousness of a difficulty that a person experiences. Physiological determinations give important information, but they may be insufficient due to the technical problems in obtaining relevant but simple measurements for short-term activities or activities involving special movement patterns. Perceptual estimations using Borg's scales give important information because the severity of a task's difficulty depends on the individual doing the work. Observation is the most simple and used means to assess job demands. Other evaluations integrating observation are the followings: indirect estimation of energy expenditure based on prediction equations or direct measurement of oxygen consumption; measurements of forces, angles and biomechanical parameters; measurements of physiological and neurophysiological parameters during tasks. It is recommended that determinations of performances of occupational activities assess rating of perceived exertion and integrate these measurements of intensity levels with those of activity's type, duration and frequency. A better estimate of the degree of physical activity of individuals thus can be obtained.

Ergonomics↗
PubMedDate not supplied

[Recent methodological advances in measuring mortality differentials].

"Some recent techniques are discussed which facilitate the analysis of differential mortality according to several simultaneous criteria, in situations where small samples impede cross-tabulation by all relevant dimensions. All of these techniques involve the use of regression models." The primary object is to provide an introduction to this topic for the nonspecialist. An extensive bibliography is provided. "The logic behind Cox's proportional hazards method, the most common in present applications, is explained, and its advantages and disadvantages are pointed out. More appropriate alternatives for the analysis of mortality in human population are indicated. Finally, some comments are made on the problem of unexplained heterogeneity and on extensions to indirect estimation, which were inspired by Cox's method." (summary in ENG)

Bibliographies as Topic↗
PubMed1999

[Importance and methods of evaluation of risks of malignant arrhythmias and sudden death].

Malignant arrhythmia and sudden death are one of the greatest challenges in cardiology. In prevention, it is important to correctly select patients under risk. Simple and non-invasive methods, by which we could make selection for invasive testing in wider population, need to get importance. The methods in risk stratification can be divided into classical and those recently accepted. Classical methods, which are mostly indirect methods, are echocardiography, exercise stress testing, Holter-ECG, coronary arteriography and electrophysiological testing. Predictive accuracy of classical methods is not satisfactory. This is the reason why new direct methods are developing. According to preliminary results they have better predictive accuracy. Accepted methods are analysis of late potentials and autonomic imbalance estimation, while in T wave alternans and QT interval dispersion some technical problems need to be resolved before routine application. Considering that these methods show various elements of arrhythmogenesis, the best predictive accuracy should be achieved by combination of all methods. But, before definite recommendation, this needs to be demonstrated in large prospective studies.

Arrhythmias, Cardiac↗