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At least 1,189 records · Page 66Linked to original sources
PubMed1990

Management of isolated thyroid swellings: a prospective six year study of fine needle aspiration cytology in diagnosis.

OBJECTIVE: To audit the accuracy and impact on the frequency of operation of fine needle aspiration cytology of isolated thyroid swellings. DESIGN: Prospective analysis over six years of cytological predictions compared with histological findings. SETTING: Thyroid clinic serving the Grampian region. PATIENTS: 395 Consecutive patients presenting with an isolated thyroid swelling, 307 of whom underwent surgical excision. Analysis was confined to a subgroup of 283 patients with satisfactory aspirates who were operated on. RESULTS: The positive predictive value of aspiration cytology for detecting malignant disease was 100% and the sensitivity 83%. The sensitivity for the detection of neoplasia (frank malignancy together with follicular adenomas) was 76%. The specificity was 58% and the overall accuracy 69%. Recalculation of data in previous papers with strict criteria showed the accuracy of aspiration cytology to be variable and lower than is widely accepted. Since the introduction of aspiration cytology 21% fewer operations for isolated thyroid swellings have been performed. CONCLUSIONS: As a basis of selection for surgical excision of isolated thyroid swellings according to prediction of neoplasia fine needle aspiration cytology is less reliable than is widely accepted. It is an adjunct to management rather than a definitive test, and negative cytological results do not exclude neoplastic disease. Further study should take account of the implications of repeated clinic attendances for review and aspiration as these may culminate in delayed surgical treatment.

Biopsy, Needle↗
PubMed2004

Profound influence of microarray scanner characteristics on gene expression ratios: analysis and procedure for correction.

BACKGROUND: High throughput gene expression data from spotted cDNA microarrays are collected by scanning the signal intensities of the corresponding spots by dedicated fluorescence scanners. The major scanner settings for increasing the spot intensities are the laser power and the voltage of the photomultiplier tube (PMT). It is required that the expression ratios are independent of these settings. We have investigated the relationships between PMT voltage, spot intensities, and expression ratios for different scanners, in order to define an optimal scanning procedure. RESULTS: All scanners showed a limited intensity range from 200 to 50 000 (mean spot intensity), for which the expression ratios were independent of PMT voltage. This usable intensity range was considerably less than the maximum detection range of the PMTs. The use of spot and background intensities outside this range led to errors in the ratios. The errors at high intensities were caused by saturation of pixel intensities within the spots. An algorithm was developed to correct the intensities of these spots, and, hence, extend the upper limit of the usable intensity range. CONCLUSIONS: It is suggested that the PMT voltage should be increased to avoid intensities of the weakest spots below the usable range, allowing the brightest spots to reach the level of saturation. Subsequently, a second set of images should be acquired with a lower PMT setting such that no pixels are in saturation. Reliable data for spots with saturation in the first set of images can easily be extracted from the second set of images by the use of our algorithm. This procedure would lead to an increase in the accuracy of the data and in the number of data points achieved in each experiment compared to traditional procedures.

Algorithms↗
PubMed2003

Using multiple survey vendors to collect health outcomes information: how accurate are the data?

BACKGROUND: To measure and assess health outcomes and quality of life at the national level, large-scale surveys using multiple vendors to gather health information is becoming the norm. This study evaluates the ability of multiple survey vendors to gather and report data collected as part of the 1998 Medicare Health Outcomes Survey (HOS). METHOD: Four hundred randomly sampled completed mailed surveys were chosen from each of six certified vendors (N = 2397) participating in the 1998 HOS. The accuracy of the data gathered from the vendors was measured by creating a "gold standard" record for each survey and comparing it to the final record submitted by the vendor. RESULTS: Overall rates of agreement were calculated, and ranged from 97.0% to 99.8% across the vendors. CONCLUSION: Researchers may be confident that using multiple vendors to gather health outcomes information will yield accurate data.

Benchmarking↗
PubMed2004

Finding and estimating chemical property data for environmental assessment.

The ability to predict the behavior of a chemical substance in a biological or environmental system largely depends on knowledge of the physicochemical properties and reactivity of that substance. We focus here on properties, with the objective of providing practical guidance for finding measured values and using estimation methods when necessary. Because currently available computer software often makes it more convenient to estimate than to retrieve measured values, we try to discourage irrational exuberance for these tools by including comprehensive lists of Internet and hard-copy data resources. Guidance for assessors is presented in the form of a process to obtain data that includes establishment of chemical identity, identification of data sources, assessment of accuracy and reliability, substructure searching for analogs when experimental data are unavailable, and estimation from chemical structure. Regarding property estimation, we cover estimation from close structural analogs in addition to broadly applicable methods requiring only the chemical structure. For the latter, we list and briefly discuss the most widely used methods. Concluding thoughts are offered concerning appropriate directions for future work on estimation methods, again with an emphasis on practical applications.

Data Collection↗
PubMed1995

[Morphometry of protuberant changes of the optic nerve head].

For objective evaluation of elevated changes in the optic nerve head, volumetric measurement of optic nerve heads in normal eyes, and in eyes with optic neuritis and papilledema was performed using a three-dimensional computerized digital image analyzer. To determine the reliability of the data, both intraphotographic and interphotographic error variance was studied. The reproducibility of the data was good, because the coefficient variation of elevated volume was small, 1.0 to 8.3% (mean; 4.5%) on intraphotographic study and 0.8 to 11.5% (mean; 6.5%) on interphotographic study in the optic neuritis and papilledema. The accuracy of the data was good enough for clinical use, presuming a change of less than 0.05 mm as measuring error.

Adult↗
PubMed1997

The effects of automated encoders on coding accuracy and coding speed.

Encoded data on diagnoses and procedures are put to a broad range of uses. Coding accuracy and speed are imperative. One method that coding experts have recommended to improve coding accuracy and speed is automated encoders. The article describes the effect of automated encoders on coding accuracy and speed when used by trained coding staff. A study involving six Veterans Administration medical centers found that, overall, coding accuracy improved 19.4 percent after implementation of encoding software. The effect on coding speed, however, depended on the system set-up, with some set-ups actually reducing the number of discharges coded per day.

Abstracting and Indexing↗
PubMed1997

Decoupled automated rotational and translational registration for functional MRI time series data: the DART registration algorithm.

A rapid, in-plane image registration algorithm that accurately estimates and corrects for rotational and translational motion is described. This automated, one-pass method achieves its computational efficiency by decoupling the estimation of rotation and translation, allowing the application of rapid cross-correlation and cross-spectrum techniques for the determination of displacement parameters. k-space regridding and modulation techniques are used for image correction as alternatives to linear interpolation. The performance of this method was analyzed with simulations and echo-planar image data from both phantoms and human subjects. The processing time for image registration on a Hewlett-Packard 735/125 is 7.5 s for a 128 x 128 pixel image and 1.7 s for a 64 x 64 pixel image. Imaging phantom data demonstrate the accuracy of the method (mean rotational error, -0.09 degrees; standard deviation = 0.17 degrees; range, -0.44 degrees to +0.31 degrees; mean translational error = -0.035 pixels; standard deviation = 0.054 pixels; range, -0.16 to +0.06 pixels). Registered human functional imaging data demonstrate a significant reduction in motion artifacts such as linear trends in pixel time series and activation artifacts due to stimulus-correlated motion. The advantages of this technique are its noniterative one-pass nature, the reduction in image degradation as compared to previous methods, and the speed of computation.

Adult↗
PubMed1999

Accurate charge densities in days - use of synchrotrons, image plates and very low temperatures.

Extensive synchrotron (28 K) and conventional sealed-tube (9 K) X-ray diffraction data have been collected on tetrakis(dimethylphosphinodithioato-S,S')thorium(IV), [Th(S(2)PMe(2))(4)]. The use of very low temperatures, well below those obtained with liquid-nitrogen cooling, is crucial for the accuracy of the data. This is due to minimization of temperature-dependent systematic errors such as TDS and anharmonicity, and extension and intensification of the data in reciprocal space. Comparison of structural parameters derived separately from the sealed-tube data and the synchrotron data shows good agreement. The synchrotron data are markedly superior when comparing refinement residuals, standard uncertainties (s.u.'s) of the data and s.u.'s of the derived parameters. However, the study suggests that there are still small uncorrected systematic errors in the data. The very large extent [(sinstraight theta/lambda)(max) = 1.77 Å(-1)] of the synchrotron data and the very low temperature at which they were collected makes it possible to separate anharmonic effects from electron-deformation effects even with only an X-ray data set at a single temperature. The electron density shows a large polarization of the outer Th core of d-type symmetry. This deformation is successfully modelled with contracted multipolar functions, which are only slightly correlated with anharmonic expansions in reciprocal space when using the full extent of the data. In the data collection more than a factor of 100 in speed is gained by use of image-plate area detectors at the synchrotron source compared with conventional sequential measurements. Thus accurate, very low temperature synchrotron-radiation diffraction data can now be measured within days, which makes electron-density studies of compounds beyond the first transition series more frequently within reach.

Journal Article↗
PubMed2004

Quality and reliability of data collected in a regional hospital intensive care unit.

OBJECTIVE: To examine the accuracy of the existing data collection system in an intensive care unit (ICU). METHODS: Prospective audit of data collection for APACHE II in a six-bedded general ICU in a region-al hospital for consecutive ICU admissions over a 12 month period. The existing resident medical officer (RMO) data collection system continued unaltered while concurrent collection of APACHE II data completed by one senior medical officer (SMO) was also performed. RMO-APACHE scores were compared to SMO-APACHE scores. RESULTS: The median (interquartile range) APACHE II scores were: 15 (9-21) for RMO data; 17 (12 - 22) for SMO data (p = 0.0001), with a mean difference (SD) of 4.2 (4.2) (p < 0.0001). A rapid survey of New Zealand ICU's indicated that only 4 of 11 APACHE II users employed substantial medical specialist involvement in APACHE II data collection and/or scrutiny prior to database entry. CONCLUSIONS: The existing APACHE II data collection is often imperfect and requires further attention as it is not yet reliable enough to allow for accurate SMR calculations, or for external use for comparative purposes.

Journal Article↗
PubMedDate not supplied

A comparison of three-dimensional interpolation techniques for plume characterization.

Interpolation of contaminant data can present a significant challenge due to sample clustering and sharp gradients in concentration. The research presented in this paper represents a study of commonly used interpolation schemes applied to three-dimensional plume characterization. Kriging, natural neighbor, and inverse distance weighted interpolation were tested on four actual data sets. The accuracy of each scheme was gauged using the cross-validation approach. Each scheme was compared to the other schemes and the effect of various interpolation parameters was studied. The kriging approach resulted in the lowest error at three of the four sites. The simpler and quicker inverse distance weighted approach resulted in a lower interpolation error on the other site and performed well overall. The natural neighbor method had the highest average error at all four sites in spite of the fact that it has been shown to perform well with clustered data. Another unexpected result was that the computationally expensive high order nodal functions resulted in reduced accuracy for the inverse distance weighted and natural neighbor approaches.

Cluster Analysis↗
PubMed1993

Estimating hospital admission patterns using Medicare data.

It is often necessary in health services research and strategic planning to simultaneously describe the geographic pattern of admissions to multiple hospitals. Obtaining the data necessary to accomplish this can often be problematic. In some states discharge abstract data on all admissions to all hospitals in the state are compiled and maintained by a government agency, but in 23 states these data are not available. Furthermore, problems arise when a substantial fraction of admissions cross state borders, such that data from more than one state is required for description of 'patient flows'. Individual hospitals typically maintain data on the geographic source of their own admissions, but are not likely to have access to such data regarding other hospitals in their area. Patient flow data on Medicare admissions are available for all states and are readily accessible, but heretofore it has not been known how closely the admission patterns of Medicare patients approximate those of other types of patients. We examine the accuracy of using data on Medicare admissions to estimate, at the hospital level, the admission patterns of other types of patients. Using zip code-to-hospital patient flow data for all non-federal hospitals in California, we calculated the correlation between Medicare admission patterns and those of three other groups of patients (other adults, pediatrics and obstetrics) for each hospital. For the majority of hospitals, Medicare data predict the admissions of other adults quite well, and the admissions of pediatric and obstetric admissions moderately well.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Lessons from in vitro models of small, irregular, multiple and tunnel-like stenoses relevant to clinical stenoses of valves and small vessels.

This review examines data on the accuracy of the simplified Bernoulli equation for quantitation of pressure drops across small, irregular, multiple and tunnel-like stenoses. This information is drawn from in vitro models of such cardiovascular stenoses and explores the limits of this simplification as they affect accuracy in special situations. Within the physiologic range, discrete small and irregular stenoses present no problems for the measurement of pressure drops using the simplified Bernoulli equation. Multiple side by side orifices of different dimension also give reasonable data using this approach. Tunnel-like stenoses of very small diameter and finite length produce underestimation of the true pressure drop through the stenosis when the simplified Bernouli equation is used. This underestimation is primarily due to neglect of the energy consumed by viscous friction in this situation. These considerations are especially pertinent to the problem of measuring pressure gradients across coronary vessels to assess their clinical significance as well as the adequacy of angioplasty and other intravascular interventional techniques. Because this area needs further exploration, some discussion of in vitro models as such as included.

Blood Flow Velocity↗
PubMed2004

Communicable-disease surveillance in New Jersey.

The DHSS and federal agencies have expanded their surveillance efforts to improve existing methods of reporting notifiable communicable diseases and to include additional data sources that might provide a more comprehensive view of disease activity in New Jersey. Currently, the DHSS is evaluating these efforts and recognizes several issues that need to be addressed, including: assessment of the timeliness, completeness, and accuracy of surveillance data; validation of surveillance data through comparison with hospital uniform billing data; characterization of the sensitivity of alerts through examination of reasons for identified aberrations in disease activity; evaluation of DHSS staffs and LINCS epidemiologists' follow-up efforts in response to alerts; evaluation of cumulative data trends to determine patterns in baseline disease activity (e.g., variations in disease activity attributed to seasonality); development of methods to integrate data from all surveillance efforts to provide timely, comprehensive, and coordinated summaries of disease activity and to distribute these summaries regularly to all New Jersey public health partners to better inform public health and clinical management; and development of a coordinated multi-agency response plan in conjunction with adjacent states. Though the DHSS hopes that these surveillance efforts will contribute to the early detection of sentinel events that might represent possible bioterrorist or emerging infectious disease threats, the DHSS will also need to engage the medical community more fully in surveillance activities. In previous experiences, astute clinicians were responsible for the identification of the first cases of West Nile virus, anthrax, and SARS. Therefore, to further ensure the success of its surveillance efforts, the DHSS will also need to continue educating clinicians about its surveillance activities and the importance of timely reporting of patients with illness patterns that might suggest an unusual infectious disease outbreak associated with bioterrorism or emerging infectious diseases.

Communicable Disease Control↗
PubMed1999

Calculating photon beam characteristics with Monte Carlo techniques.

This study describes the results from a simulation of a 10 MV photon beam from a medical linac using the BEAM code. To check the quality of the generated photon beam, the characteristics of this beam (depth dose curve, cross profiles, and output factors) have been calculated and compared to measured data. By splitting up the radiation head in two parts, the target section and the collimator section calculation times were long, but acceptable when aiming at phase space files containing some 5 million particles. Given the number of particles evaluated, the accuracy of all data was around 2%. Analysis of the phase space files for different field size supports results from previous studies about contaminant particles and sources for scattered radiation for photon beams from medical linacs. The total scatter output factor Scp as well as the collimator scatter output factor Sc have been calculated within 2% of measurements. Also, the ratio between dose at a reference point for the full scatter situation and the no-scatter situation has been calculated correctly. All depth dose curves and cross profiles have also been calculated correctly, although with only moderate statistics. Improvements are possible by increasing the number of particles in the simulations (up to 50 million for the largest field size) at least 4-8 times, although calculation times will increase with the same factor. Nevertheless, the method proved itself as reliable. Still, the accuracy should be improved to 1% or better. This is necessary as we plan to use Monte Carlo simulations to benchmark three-dimensional radiotherapy planning systems. By increasing the number of particles in the phase space files and subsequently increasing the number of particles in each simulation, this 1% accuracy will be achieved. The easy way to increase the number of particles in a simulation by increasing the number of times phase space files, which were already recycled ten times, are reused from ten times (this study) to 40 times or more will not work, as it introduces artifacts, especially in the cross profiles.

Biophysical Phenomena↗
PubMed1999

Measuring protein synthesis by mass isotopomer distribution analysis (MIDA).

The measurement of protein kinetics by isotopic techniques has been hindered by the long-standing difficulty of accurately measuring the isotope content of the biosynthetic precursor pool (aminoacyl-tRNA in tissues). Mass isotopomer distribution analysis (MIDA) is a stable isotope-mass spectrometric (MS) technique for measuring biosynthetic precursor enrichments from measurements on a polymeric product, based on combinatorial probabilities of labeled and unlabeled monomeric subunits. Proteins contain complex isotopomer patterns as a result of their relatively high molecular mass, however, so that resolution of the individual mass isotopomers in the polymeric product (an analytic requirement for MIDA) is technically difficult. An approach for measuring protein synthesis by MIDA is described and tested here: First, in vitro, using a synthetic peptide present in human serum albumin; and then, in vivo, for albumin synthetic rate in rats. A peptide contained in human serum albumin (SVVLLLR) and theoretically recoverable from trypsin/chymotrypsin proteolysis was synthesized by solid-phase peptide synthesis using known mixtures of natural abundance and [5,5, 5-2H3]leucine. Additionally, enriched and natural abundance peptides were mixed in vitro to simulate in vivo biosynthesis and to address problems of instrument accuracy, precision, and data management. The mass isotopomer patterns of the synthetic peptides were analyzed using electrospray ionization (ESI) with both magnetic sector and quadrupole mass analyzers. The resolution of the magnetic sector was superior to that of the quadrupole instrument, but accuracy and precision in the measurement of mass isotopomer abundances and kinetic parameters were comparable and both gave values close to those predicted. Next, rats were infused with [5,5,5-2H3]leucine intravenously, and a leucine-rich peptide was isolated and purified from trypsin-digested rat serum albumin (RHPDYSVSLLLR, 1456 Da) and then analyzed by ESI-MS using a magnetic sector instrument. Precursor pool enrichments and fractional synthetic rates (0.45 +/- 0.03 day-1, t1/2 = 1.53 +/- 0.09 days) were calculated. Biosynthetic rates of rat serum albumin were congruent with previously published values. In summary, measurement of protein synthesis and precursor pool enrichments by MIDA is technically feasible and practical in vivo using proteolytically derived peptides and ESI-MS analysis.

Amino Acid Sequence↗
PubMed2002

Development and evaluation of patient-centered software for a weight-management clinic.

OBJECTIVE: To describe a weight-management clinic software system and to report on its preliminary evaluation. RESEARCH METHODS AND PROCEDURES: The software system standardizes the collection of relevant patient information from an initial medical assessment, weekly clinic visits, and laboratory testing protocol of a medically supervised proprietary meal-replacement program in a university-based referral clinic. It then generates monthly patient feedback reports with graphs of clinical and laboratory parameters to support a patient-centered approach to weight management. After patients and clinic physicians review the data to ensure accuracy, the database is used for subsequent patient feedback reports, reports to referring physicians, quality assurance, and research. Clinic physicians and referring physicians were asked to rate their acceptance of the system. In addition, in a retrospective analysis of data generated by the system, outcomes for patients who received system-generated feedback (n = 620) were compared with those who participated in the program before the introduction of feedback (n = 130). RESULTS: Clinic and referring physicians reported that they had high overall satisfaction with the software and that the system saved them time, and the latter group reported that it decreased laboratory use. Regarding patients, the feedback group had lower dropout rates in the latter half of the program, better rates of attendance, completion of laboratory tests, and weight loss after 8 weeks. DISCUSSION: The software seems to facilitate the effectiveness of the treatment protocol for obesity and generates a high-quality database for patient care, clinic administration, quality assurance, and research purposes.

Ambulatory Care↗
PubMed2001

Implementation of a Victorian Cardiac Surgery Database.

The Victorian Cardiac Surgery Database project will be jointly developed and delivered by Melbourne Information Management and the Baker Medical Research Institute. After a pilot phase involving one hospital, all Victorian public hospitals with cardiac surgery units will provide data for developing and testing the Cardiac Surgery Database. In the initial proposal, the period of data collection is from 1 April 2001 to 31 March 2002. Issues being addressed in preparation for the implementation phase are those of ownership, management and administration of the Database as well as taxation, liability and governance. Completeness and accuracy of the data collection process and the maintenance of confidentiality are prime considerations in the implementation phase of the project.

Journal Article↗
PubMed2005

The systematic component of phylogenetic error as a function of taxonomic sampling under parsimony.

The effect of taxonomic sampling on phylogenetic accuracy under parsimony is examined by simulating nucleotide sequence evolution. Random error is minimized by using very large numbers of simulated characters. This allows estimation of the consistency behavior of parsimony, even for trees with up to 100 taxa. Data were simulated on 8 distinct 100-taxon model trees and analyzed as stratified subsets containing either 25 or 50 taxa, in addition to the full 100-taxon data set. Overall accuracy decreased in a majority of cases when taxa were added. However, the magnitude of change in the cases in which accuracy increased was larger than the magnitude of change in the cases in which accuracy decreased, so, on average, overall accuracy increased as more taxa were included. A stratified sampling scheme was used to assess accuracy for an initial subsample of 25 taxa. The 25-taxon analyses were compared to 50- and 100-taxon analyses that were pruned to include only the original 25 taxa. On average, accuracy for the 25 taxa was improved by taxon addition, but there was considerable variation in the degree of improvement among the model trees and across different rates of substitution.

Classification↗