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PubMed1998

Validation of home blood glucose meters with respect to clinical and analytical approaches.

OBJECTIVE: To evaluate the clinical and analytical accuracy of home blood glucose meters. RESEARCH DESIGN AND METHODS: Six blood glucose meters--Reflolux S (Boehringer Mannheim, Mannheim, Germany), One Touch II (LifeScan, Milpitas, CA), Glucocard Memory (Menarini, Florence, Italy), Precision QID (Medisense, Cambridge, U.K.), HaemoCue (HaemoCue, Angelholm, Sweden), and Accutrend alpha (Boehringer Mannheim, Mannheim, Germany)--were compared with a reference method (Beckman Glucose Analyzer II) under controlled conditions (glucose clamp technique). Validation of the blood glucose meters was accomplished by clinically oriented approaches (error grid analysis), statistical approaches (variance components analysis), and by the criteria of the American Diabetes Association (ADA), which recommend a target variability of < 5%. RESULTS: A total of 1,794 blood glucose monitor readings and 299 reference values ranging from 2.2 to 18.2 mmol/l were analyzed (705 readings < 3.89 mmol/l, 839 readings between 3.89 and 9.99 mmol/l, and 250 readings > 9.99 mmol/l). According to error grid analysis, only Reflolux S and Glucocard M had 100% of estimations within the clinically acceptable zones A and B. Assessment of analytical accuracy revealed substantial differences between the glucose meters after separation of the data into defined glycemic ranges. None of the devices met the ADA criteria. CONCLUSIONS: To evaluate accuracy of blood glucose meters, error grid analysis, as well as statistical models, are helpful means and should be performed together. Analytical performance of currently available home blood glucose meters differs substantially within defined glycemic ranges.

Blood Glucose Self-Monitoring↗

PubMed1985

Analytical approaches for biomedical elemental analysis.

Several different analytical systems are available for biomedical elemental analysis related to human nutrition. The principle, detection limits, analytical artifacts, and applications are presented for the following analytical systems for elemental analysis classified by sample volume: macro volume systems--flame atomic absorption spectroscopy (FAAS) and inductively coupled plasma (ICP); micro volume systems--electrothermal atomization (graphite furnace) atomic absorption spectroscopy (ETA-AAS) and x-ray fluorescence (XRF); and ultramicro volume systems--electron probe x-ray microanalysis (EPX) and laser microprobe mass analysis (LAMMA).

Electron Probe Microanalysis↗

PubMed1998

Optimal design of planar-concave collimators for SPECT--an analytical approach.

In this paper we present an analytical tool for the design and optimization of planar-concave collimators for SPECT. We conclude that a single general planar-concave collimator that eliminates the non-isotropic blurring for all SPECT applications does not exist. On the other hand, it is possible to achieve pseudo-optimal collimators for different clinical applications by a careful choice of the design parameters. By classifying the clinical applications into two groups, for instance body and brain studies, the non-isotropic blurring for most SPECT situations may be dramatically reduced by means of planar-concave collimators. The results based on Monte Carlo simulations show that the shape of the point source response function of the reconstructed image obtained from the planar-concave collimator is more isotropic than that obtained from a conventional parallel-hole collimator. Specifically, the ratio of the FWHM of the reconstructed point response function in the radial and tangential direction is increased from 0.5 for the parallel-hole to 0.85 for the planar-concave collimator for sources 200 mm away from the centre of rotation.

Algorithms↗

PubMed1980

A decision analytic approach to cleft palate treatment evaluation.

An analytic methodology, developed from the field of decision analysis, is presented for the evaluation of treatment alternatives. The management of velopharyngeal incompetence illustrates the method. Nasal quality is utilized as a primary means of measuring outcome. Results indicate that treatment alternatives can be preferentially ordered using analytic methods which incorporate costs, benefits, and probabilities of successful and unsuccessful outcomes. Extensions of the mathematical formulations are discussed in relationship to treatment outcomes.

Cleft Palate↗

PubMed2001

An accurate analytical approach to electron crystallography.

A much more accurate analytical expression of dynamical electron diffraction than the phase object approximation (POA) formula has been derived in this paper which decreases the restriction of sample thickness up to almost one order of magnitude compared to POA theory. The importance of the new expression is twofold. First, a sample with such a thickness that new expression remains valid can be prepared experimentally. Second, the new expression reveals a clear and straightforward relationship between the wave function and crystal potential. In the expression, the effect of dynamical diffraction on wave function can be simply attributed to two factors TP(D) = (sin(lambda pi zg2))/(4pi2g2) and TA(D) = [1 - cos(lambda pi zg2)]/4pi2g2. Compared to the effect of transfer functions of an electron microscope on wave function, we found that TP(d) and TA(d) play the same role as transfer function but are independent of the instrument. For this reason, we here call the former as "extrinsic transfer functions" and the latter as "intrinsic" ones. In principle, one should correct not only extrinsic transfer functions but also intrinsic ones if one desires to achieve higher resolution.

Journal Article↗

PubMed1998

Force regulation is deficient in patients with parietal lesions: a system-analytic approach.

By means of a quantitative system-analytic investigation strategy, the postural motor control of the fingers was evaluated, to characterise the possible deficit of force regulation in patients with parietal lesions. In spite of a normal response to short torque pulses, the parietal-lesion patients had difficulties in returning to the preload level after the application of an additional step torque load to fingers II-IV of their left or right hands. The control offset (measured 500 ms after step torque application) was significantly larger in the patient group. This deficit in the investigated patients with parietal lesions to compensate for step torque loads was not due to a paresis, but rather resulted from a disturbance in the generation of a sufficient counterforce against the applied step torque within an adequate time window and motor pattern. This distinct force-regulation deficit was found in patients with left- and right-sided parietal lesions.

Adult↗

PubMed1981

Operability of nuclear instruments for medical use in developing countries. A decision-analytic approach.

Nuclear technology in diagnostic medicine has become a world-wide phenomenon. One of the problems encountered in implementing this technology in developing countries is predicting the operability of nuclear instruments under local conditions of maintenance and use. Our approach to this problem employs an analytic method often applied in medical decision making, and which can be incorporated into schemes for evaluating the total diagnostic process which utilizes nuclear technology. A recent survey of nine types of nuclear instruments in medical use in eight countries in Southeast Asia provided comprehensive information on the application and maintenance of these instruments, as well as a detailed record of actual operability and use of these instruments over a six-month period. A multivariate statistical analysis for predicting the operability of these instruments was carried out with some of the survey data. Responses to a set of 14 potentially important attributes of instrument use and maintenance obtained from the survey data were used to estimate the posterior probabilities of an instrument being inoperable for more than a given total number of hours in the six-month period during which operability was required. The posterior probabilities were determined by means of both Bayesian and discriminant analysis and summarized in the form of receiver operating characteristic (ROC) curves. Among a number of possible interpretations of the results, the analysis suggests that attributes generally involving installation, documentation, environment, and personnel training appear to be particularly important in predicting the operability of the instruments surveyed.

Decision Making↗

PubMed1999

Analytical approach to time lag in binary nucleation.

We present an analytical formula for the time required to establish steady state in a nucleating binary system. To test our solution, we evaluate the time lag for a range of activities of both components at the vapor-liquid transition, and show that our result is in much better agreement with a purely numerical simulation than other available analytical formulas, which overestimate the time lag by factors of from 2 to 200.

Journal Article↗

PubMed1984

An analytic approach to resolving problems in medical ethics.

Education in ethics among practising professionals should provide a systematic procedure for resolving moral problems. A method for such decision-making is outlined using the two classical orientations in moral philosophy, teleology and deontology. Teleological views such as utilitarianism resolve moral dilemmas by calculating the excess of good over harm expected to be produced by each feasible alternative for action. The deontological view focuses on rights, duties, and principles of justice. Both methods are used to resolve the 1971 Johns Hopkins case of a baby born with Down's syndrome and duodenal atresia.

Decision Making↗

PubMed1994

[Integration of geographic and analytical approach in environmental epidemiology].

Some developments of research in environmental epidemiology are reviewed, with special emphasis on the limitations of currently adopted methods. At the light of causal criteria commonly used in the evaluation of epidemiologic studies, an approach based on the integration of geographic and analytic studies is suggested, in order to obtain results relevant in terms of public health.

Environmental Health↗

PubMed1998

A decision analytic approach to commissioning ambulance cardiac services.

The paper discusses how a decision analytic framework has been used by an English health authority in relation to the commissioning of ambulance cardiac services. Strategies for the management by ambulance personnel of victims of cardiac arrest and persons with acute chest pain of cardiac origin were modelled in a decision-event tree, and a bibliographic database established. The international research literature prior to 1997 was searched in order to derive probability values for the tree. However, after checking whether the subgroupings of results in the papers were in accordance with the variables in the tree, the number of useful papers on acute chest pain was found to be only two. In the almost complete absence of information--even from small observational studies--on the management of the great majority of patients with cardiac symptoms transported by ambulance, the local ambulance service and the main providers of hospital services in the district are now collaborating in field studies of cardiac care in order to improve the inputs into the model.

Algorithms↗

PubMedDate not supplied

Decision analytic approach to the management of gonorrhea contacts.

We used a combination of decision analytic and modeling techniques in constructing a model for study of the management of an asymptomatic woman presenting to a sexually transmitted disease clinic as a contact of a man with gonorrhea. Total cost (physical, emotional, and economic) is expressed in units of dysutility. Initially the probabilities and "costs" of anogenital gonorrhea, incubating syphilis, carriage of the agents of nongonococcal urethritis, and coincident pharyngeal gonorrhea are considered; complications and sequelae are then accounted for. The best strategy is to culture for Neisseria gonorrhoeae, treat immediately with tetracycline, and follow up sexual partners if the culture is positive. Dysutility values calculated for the strategies of just treating with standard regimens of tetracycline, procaine penicillin, or amoxicillin are 288, 310, and 560, respectively. Sensitivity analyses show that the most important factors in determining optimal strategy are the probabilities and costs associated with the patient's carriage of the agents of nongonococcal urethritis. In order for this decision to change, the dysutility value for nongonococcal urethritis would have to decrease to 17% of our best estimate, or the overall prevalence of nongonococcal urethritis would have to be reduced to 16% of our best estimate.

Costs and Cost Analysis↗

PubMed2002

Analytical approach to viscous fingering in a cylindrical Hele-Shaw cell.

We report analytical results for the development of the viscous fingering instability in a cylindrical Hele-Shaw cell of radius a and thickness b. We derive a generalized version of Darcy's law in such cylindrical background, and find it recovers the usual Darcy's law for flow in flat, rectangular cells, with corrections of higher order in b/a. We focus our interest on the influence of the cell's radius of curvature on the instability characteristics. Linear and slightly nonlinear flow regimes are studied through a mode-coupling analysis. Our analytical results reveal that linear growth rates and finger competition are inhibited for an increasingly larger radius of curvature. The absence of tip-splitting events in cylindrical cells is also discussed.

Journal Article↗

PubMed2002

Estimation of heat transfer and temperature rise in partial-body regions during MR procedures: an analytical approach with respect to safety considerations.

In order to assess thermal response to RF exposure during MR procedures at the tissue level, simple analytical solutions to the non-stationary Pennes' bio-heat equation were obtained using the Green's function approach. Two thermal models appropriate for partial-body exposure were analyzed: In the first model, the temperature field at the periphery of an idealized volume RF resonator was modeled. The analytical solution reveals that tissue response to RF heating is characterized by an equilibration time and length. Both parameters are inversely related to tissue perfusion and vary for the soft-tissues considered between 0.27-25 min and 1.5-12 mm, respectively. None of the tissues investigated increase in temperature more than 0.5 degrees C for each W/kg of power dissipated. Secondly, a homogeneous tissue solution was derived that predicts the temperature-time course to an MR examination with time-varying specific absorption rates (SAR). Since SAR limits indicated in current MR safety standards relate to running SAR averages computed over an appropriate period of time, an expression was formulated that gives an upper limit for the temperature rise averaged over the same period of time, as a function of both the upper limit of running SAR averages and the duration of the MR examination. The analysis revealed that the partial-body SAR limits indicated in the IEC standard may not guarantee under all circumstances compliance with the basic restrictions concerning temperature rise.

Body Temperature↗

PubMed1997

The relationship of social environment, social networks, and health outcomes in the Seattle Longitudinal Study: two analytical approaches.

This study examined the relation of social networks and perceived social environment to health outcomes and cost utilization over a 1-year period in a community sample of 387 (173 males, 214 females). Two analytical strategies, a variable-oriented approach and a subject-oriented approach, were used to complement each other: structural equation modeling assessed the direct relationship between social relationships and health, while cluster analysis examined how social relationship patterns were related to health outcomes. Lower levels of perceived social environment were associated with an increased number of hospital visits. For unmarried individuals, increased age was associated with greater medical usage and estimated total health care cost, while low perceived social environment was related to a greater number of doctor visits. Among married individuals, women had more frequent doctor visits, medication usage, estimated outpatient costs, and primary care visits. Married individuals with low levels of social networks had increased total health care costs, outpatient costs, and primary care visits. Cluster analysis was used to group individuals by characteristics of perceived social environment and social networks. Members of the cluster groups with greater health problems were more likely to be isolated, had the least social contact, and had lower levels of education and income. Including subject-oriented approaches is useful in complementing more popular regression methods for data analysis.

Adult↗

PubMed1983

Drugs and driving: a systematic analytical approach.

To collect useful epidemiological data about drug involvement in highway safety, it is essential that sensitive and specific analytical procedures be used to establish the presence of and to determine the concentrations of drugs and metabolites in samples collected from drivers. This paper describes a comprehensive and systematic screening procedure requiring 6 mL of blood, which has been used for the analysis of samples collected from injured and fatally injured drivers. The procedure uses radioimmunoassay, gas chromatography with selective detectors, and high performance liquid chromatography. Drugs and metabolites presumptively identified are then confirmed primarily using gas chromatography--chemical ionization mass spectrometry.

Accidents, Traffic↗

PubMed1990

New in vitro analytical approaches for clinical chemistry measurements in critical care.

The effective management of patients in intensive care units, operating rooms, and emergency rooms requires frequent measurement of a select group of analytes, preferably at or near the patient's bedside. Tests recognized as being essential for such management include blood gases and related variables (pH, pO2, pCO2, HCO3-, hematocrit/hemoglobin, O2 saturation), electrolytes (Na+, K+, Ca2+, Cl-), and in some cases, certain metabolites (glucose, lactate, urea, creatinine). This report describes the measurement principles, practical instrumental designs, analytical performance, and limitations of several newer electrochemical sensor-based approaches useful for in vitro determination of these species in undiluted whole-blood samples. Considerable attention is given to the most recent advances in ion-selective electrode technology as they relate to blood gas and electrolyte determinations. Similar attention is given to modern enzyme-electrode techniques, which are useful for direct measurements of metabolites in whole blood. The challenges of integrating these new analytical methods into convenient, multi-analyte, user-friendly, bedside or stat-lab instruments are also discussed.

Autoanalysis↗

PubMed2002

Heterogeneous nucleation and crowding in sickle hemoglobin: an analytic approach.

Sickle hemoglobin nucleation occurs in solution as a homogeneous process or on existing polymers in a heterogeneous process. We have developed an analytic formulation to describe the solution crowding and large nonideality that affects the heterogeneous nucleation of sickle hemoglobin by using convex particle theory. The formulation successfully fits the concentration and temperature dependence of the heterogeneous nucleation process over 14 orders of magnitude. Unlike previous approaches, however, the new formulation can also accurately describe the effects of adding nonpolymerizing agents to the solution. Without additional adjustable parameters, the model now describes the data of M. Ivanova, R. Jasuja, S. Kwong, R. W. Briehl, and F. A. Ferrone, (Biophys. J. 2000, 79:1016-1022), in which up to 50% of the sickle hemoglobin is substituted by cross-linked hemoglobin A, which does not polymerize, and which substitution causes the rates to decrease by 10(5). The success of this approach provides insight into the polymerization process: from the size-dependence of the contact energy deduced here, it also appears that various contacts of unknown origin are energetically significant in the heterogeneous nucleation process.

Calorimetry↗