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At least 1,171 records · Page 65Linked to original sources
PubMed2005

Barriers to detecting and treating hypercholesterolaemia in patients with ischaemic heart disease: primary care perceptions.

BACKGROUND: Treating hypercholesterolaemia in patients with ischaemic heart disease can significantly reduce vascular deaths and events. Many such patients, however, do not receive effective treatment for hypercholesterolaemia. AIM: To ascertain the barriers to the detection and treatment of hypercholesterolaemia in patients with ischaemic heart disease as seen by primary care teams. DESIGN OF STUDY: Qualitative study using the nominal group technique. SETTING: General practice teams in the North Thames region of the Medical Research Council General Practice Research Framework. METHOD: The main outcomes measures used were identification of the barriers to the detection and treatment of hypercholesterolaemia together with relative rankings. RESULTS: Fourteen individual barriers were identified. The main barriers were: organisational barriers within general practices; confusing and conflicting guidelines from external sources; errors and omissions by GPs; communication problems at the interface between secondary and primary care; and reluctance by patients to take medication. CONCLUSIONS: The reasons for suboptimal detection and treatment of hypercholesterolaemia are complex and act at various levels. Interventions to improve the management of this condition must address these barriers in order to be successful.

Attitude of Health Personnel↗
PubMed2005

Stormwater quality models: sensitivity to calibration data.

Stormwater quality modelling is a useful tool in sewer systems management. Available models range from simple to detailed complex ones. The models need local data to be calibrated. In practice, calibration data are rather lacking. Only few measured events are commonly used. In this paper, the effect of the number and the variability of calibration data on models of various levels of complexity are investigated. The study is carried out on "Le Marais" catchment for suspended solids where 40 reliable measured events and good knowledge of the sewer system are available. The method used is based on resampling subsets of measured events among the 40 available ones. Three types of models were calibrated using subsets of events of different sizes and characteristics resampled among the 40 available ones. For each calibration, the model was validated against the remaining events to stand upon the quality of the model. It was found that the models are quite sensitive to calibration data, a problem neglected in practical studies. The use of more complex models does not necessarily improve modelling results since more problems and error sources are to be expected. The findings are specific to "Le Marais" catchment and the models used.

Calibration↗
PubMedDate not supplied

[The correlation between NT-proBNP plasma levels and heart failure syndrome].

UNLABELLED: proBNP represents the precursor of the brain natriuretic peptide (BNP) and is released by the cardio-myocytes as a result of the myocardial stretch. It is fractioned into two components, BNP and NT-proBNP. We use more often the determination of NT-proBNP levels in laboratory tests because of its prolonged biological half-time (60-120 minutes, much longer than the BNP half-life). AIM: To determine a link between the plasmatic levels of NT-proBNP and heart failure syndrome (HFS). MATERIAL AND METHOD: We studied 40 patients admitted in the Internal Medicine Clinic of the Western University "Vasile Goldiş" Arad, during a two years period (2004-2005). Every patient had a clinical examination, an echocardiography and the determination of NT-proBNP levels. For the determination of the BNP plasmatic levels we used a special kit Elecsys proBNP, which is now largely available. The NT-proBNP levels were correlated with the HFS diagnosis (the presence of dyspnea and the ejection fraction). RESULTS: In 29 patients the NT-proBNP levels were above the upper limit of 125 pg/ml, 86% of them being clinically diagnosed with HFS. 11 patients had BNP levels in the normal values range and 4 of them were clinically diagnosed with HFS. Correlating the NT-proBNP plasma levels and NYHA class of HF we could establish some guidelines regarding the critical BNP values upon which the diagnostic of HFS is almost certain. The minimum level of BNP at which a patient was diagnosed with HF was 89.9 pg/ml. Levels above 125 pg/ml predicts o risk six times higher for HFS. DISCUSSIONS: The BNP plasma values may be modified in hepatic or renal failure, which can cause false high levels of hormone. These situation should be considered possible error sources of diagnosis if the HFS is evaluated only by the means of NT-proBNP plasma levels. CONCLUSIONS: The dosage of plasma levels of NT-proBNP is useful into patients with suspected HFS, if the other methods of diagnosis are not reliable. There is a link between the NT-proBNP plasma levels and the NYHA HFS class. However only the dosage of BNP is not sufficient for a correct diagnosis of HFS.

Biomarkers↗
PubMed1991

[Automated measurement of retinal vascular diameter].

We describe a new unit of the Jena retinal camera for automatic measurement of retinal vessel diameter. The brightness profile perpendicular to the vessel is registered by CCD line sensor and the signal is transmitted to the computer. An adaptive computer program recognizes the edges of vessels and estimates the vessel diameters automatically. Applying several measurements per vessel, the intraindividual standard deviation may be smaller than 3%. By using the same objective measuring edge criterion, the measuring results are comparable between different observers and methods. Error sources are discussed. Measured vessel reactions to oxygen breathing and reduced perfusion pressure are presented to demonstrate the efficiency of this new method.

Adult↗
PubMed1991

[Hospital morbidity statistics: the accuracy of the diagnosis reported in the discharge registry book].

BACKGROUND: The registry book of admission and discharges (RBD) is operative in most public and private hospitals of this country. Currently its reformation is contemplated, consisting in a modification of the minimal set of basic data and its computerization. The aim of the present study was to evaluate the accuracy of the discharge diagnosis recorded in the RBD and to analyze the possible factors implicated in the current quality level. METHODS: In a sample of 9 hospitals from the Seville province, 2,634 discharges were selected with a stratified sampling process which was proportional to the number of discharges in each stratum during 1985. The accuracy of the diagnosis recorded in the RBD was estimated by comparing it with that in the clinical record (CR). RESULTS: The accuracy indexes showed that, for the large diagnostic groups, only in 45% of discharges the diagnosis coincided in both documents. The accuracy increased to 89% when the estimation was made after excluding those discharges where the diagnosis was not recorded in the RBD and/or in the CR (n = 1303). CONCLUSIONS: The fulfillment of the RBD appears as the main error source, followed by the selection of the major diagnosis and its transcription in the different documents of the circuit. It is concluded that a precondition for the success of a reformed RBD is to guarantee the fulfillment of data.

Diagnosis↗
PubMed1989

[Chromosome analysis for determining paternity using the AMBA/R-Chro-H image evaluation system].

A version of the software package AMBA/R-CHRO developed by the Institute of Breeding Research Quedlinburg and by the Institute of Forensic Medicine, Friedrich-Schiller-University Jena, which is suited for the evaluation of banded human chromosomes, is presented. The parameter which are required for paternity diagnostics (absolute length of the chromosomes, absolute and relative length of the heterochromatin block near the centromere) were automatic registrated and calculated. The way of presenting the chromosomes of interest (A 1, C 9, E 16, Y), their grey-value profiles and their schematic representation make understanding, especially for nonexpert clients, easy. The present software package rationalizes work in the cytogenetic laboratory by reducing objectively and personally conditioned error sources. In addition to this, considerable saving in time is reached. The software package for the interactive automatic microscope image analysis primary developed for using in analysis of vegetable chromosomes finds a new range of application in the field of settlement of paternity cases.

Child↗
PubMed1981

[The validity of self assessment scales (personality questionnaires)].

Departing from the increasing use of personality questionnaires for psychodiagnosis, the limits of these measuring instruments are critically pointed out. Methodical ways for the overcoming of error sources are discussed. A large part of the paper is concerned with the problems of control scales. Further necessary steps with regard to the determination of the validity of self-assessments are presented in outlines.

Diagnosis, Differential↗
PubMed1995

Reproducibility of semi-automated cell cycle analysis of flow cytometric DNA-histograms of fresh breast cancer material.

DNA-variables such as DNA-ploidy, DNA-index and %S-phase cells have been proven to have prognostic value for breast cancer patients. These variables can be obtained by interpreting DNA-histograms by cell cycle analysis. Since there are a number of potential error sources, the aim of this study was to determine the intra- and inter-observer reproducibility of semi-automated cell cycle analysis with the emphasis on DNA ploidy and %S-phase assessments. The 149 DNA-histograms we used were randomly selected from the Multicentre Morphometric Mammary Carcinoma Project, a nationwide prospective study in The Netherlands on the reproducibility and prognostic power of quantitative assessments. These DNA-histograms were obtained by flow cytometry of fresh frozen breast cancer material. Cell cycle analysis was performed according to a strict protocol with the semi-automated computer program 'MultiCycle', using the background correction option; 68 histograms were analyzed in duplicate by the same observer, and 81 histograms were analyzed by two observers. Assessment of DNA-ploidy showed an intra-observer concordance of 99% (kappa-value 0.98) and an inter-observer concordance of 94% (kappa-value 0.91). The disagreement could be attributed to overlooking a DNA-tetraploid cell cycle in one case, some difficult histograms and varying opinions about small peaks between the observers in a few cases. Intra-observer %S-phase correlation coefficients varied between 0.72 for the %S-phase of the second aneuploid cell cycle and 0.99 for the %S-phase of the diploid cell cycle. Inter-observer correlation coefficients varied between 0.81 for the %S-phase of the second cell cycle and 0.95 for the %S-phase of the diploid cell cycle and the average %S-phase cells. As for DNA-index, intra- and inter-observer correlation coefficients were 0.97 and 0.94, respectively. In conclusion, intra- and inter-observer reproducibility of semi-automated cell cycle analysis of flow cytometric DNA-histograms from fresh breast cancer material using the Multi-Cycle program, following a strict protocol, is in principle high. The results of this study may help us to decide which of the different %S-phases provided by cell cycle analysis software should be used in daily practice.

Breast Neoplasms↗
PubMed1994

Retest reliability of the temporal and distance characteristics of hemiplegic gait using a footswitch system.

Using a footswitch system, the retest reliability of the temporal and distance parameters of gait was investigated within a session for 22 stroke patients in the early phase of rehabilitation. High to very high reliability was found for the temporal and distance parameters of gait, and the temporal symmetry index based on the difference in single-limb support duration between each leg (r = 0.85 to 0.98; intraclass correlation coefficients (ICC)(2,1) = 0.82 to 0.98). Significant differences were found between the two trials for velocity, stride length, and total double support (p < .05). Despite the high reliability coefficients, 95% confidence intervals, which take into account the random and systematic error, were wide for all parameters. These wide confidence intervals indicate that the use of two consecutive measurements for interpreting an individual patient's change would not be a sensitive method for monitoring progress or deterioration during rehabilitation. Strategies that may improve the clinical usefulness of temporal and distance gait measures in stroke rehabilitation are discussed. These include further reducing error sources, increasing data collection per measurement, using serial measurements on each patient, or using less rigorous confidence intervals.

Aged↗
PubMed1995

Analysis of errors due to assigned model constants in pharmacokinetic calculations based on functional optimization.

Mathematical models in pharmacokinetic studies frequently include, in addition to model parameters that are estimated from experimental data, model constants that are directly measured or derived from standardized, anthropometric formulae. Although these assigned constants are usually considered as error-free, uncertainties in their values affect the estimation precision of the remaining model parameters as well as the reliability of other derived quantities such as predictions of drug concentration levels or prescriptions of drug dosage. The present paper addresses the problem of quantifying the effects of errors in assigned model constants on the outcome of pharmacokinetic calculations. The error analysis is performed starting from the general assumption that the optimization of some objective function, such as encountered in parameter estimation, is involved. The proposed approach is based on the linearization of theoretical conditions that must be satisfied by the optimal solution of the problems. It requires quite complex mathematical calculations which can be however performed automatically by specific software based on symbolic computer algebra. Examples of applications are reported showing the usefulness of this kind of error analysis, in particular for detecting potentially critical error sources in the modeling of physiological systems and for suggesting improvements to experimental protocols for increasing the confidence in diagnostic and therapeutic decisions.

Administration, Oral↗
PubMed1996

Measuring hospital use without claims: a comparison of patient and provider reports.

OBJECTIVE: We compared the validity of hospital admission and length of stay reports from patients, outpatient providers, and hospitals, and we examined possible sources of error. DATA SOURCES: Data were collected from people enrolled in a randomized trial of treatment for severe mental illness and substance use disorders, from community mental health centers (CMHCs), and from hospitals. Reports for each of the 74 study participants covered two-year time periods beginning and ending at various times between 1989 and 1993. STUDY DESIGN: We compared reports from the various sources and constructed a hybrid with data from all three sources. Using parametric and non-parametric statistics, we compared patient, CMHC, and hospital reports with each other and with the hybrid source. In subsequent regression analyses we explored correlates of reporting accuracy. PRINCIPAL FINDINGS: Single-source reports underestimated hospital use, but when patient and CMHC reports were combined, results were very similar to those obtained by the more laborious hybrid method. Patient reports became less accurate as the time between discharge and reporting increased; people with bipolar disorders reported admissions with greater accuracy than did people with schizophrenia. CMHC reporting accuracy decreased as the distance to the admitting hospital increased and were less accurate for people with more severe psychiatric symptoms. CONCLUSIONS: Reports from single sources are likely to underestimate hospital use for different reasons. Combining carefully collected data from patients and outpatient providers produces estimates of hospital use that are substantially the same as those developed through methods that are more laborious and costly.

Adult↗
PubMed1977

[Antiglobulin test -- preparation and evaluation of antiglobulin sera].

After demonstrating the principle of antiglobulin reaction, preparation and evaluation of antiglobulin sera as well as the procedure of the antiglobulin test (agT) are described. Possible error sources are indicated and a central preparation of a highquality antiglobulin serum and its examination by government authorities is suggested,

Agglutination Tests↗
PubMed1996

Bioelectrical impedance techniques in medicine. Part III: Impedance imaging. First section: general concepts and hardware.

Measurement accuracy is a key point in impedance imaging and is mainly limited by factors that take place in the acquisition system. This part is a review of hardware solutions developed in acquisition systems for electrical impedance tomography (EIT). The general principles of EIT along with the changes that have taken place in the last decade, in terms of measurement strategy, and a certain number of definitions are introduced. The major hardware error sources that occur in the front end of EIT systems are presented. A review of the various alternatives published in the literature that are used to drive current, including current and voltage approaches, and the main solutions recommended in the literature to overcome the key point drawbacks of voltage measurement systems, including voltage buffers, instrumentation amplifiers, and demodulators, are provided. Some calibration procedures and approaches for the evaluation of the performance of EIT systems are also presented.

Computers↗
PubMed1990

Antibodies as a source of analytical errors.

This review discusses the interference in clinical chemical analysis caused by autoantibodies and by antibodies to foreign antigens. The nature of these disturbances, their occurrence, prevalence, and detection, the different ways in which they are manifested, the clinical consequences of the failure to recognize such interference, and finally methods for avoiding these disturbances are discussed. Interference by cold agglutinins in the automatic determination of the erythrocyte count, interference by cryoglobulins in the determination of the leukocyte count, and EDTA-induced thrombocyte agglutination are well documented as sources of error in the analysis of haematological parameters. Enzyme determinations may be affected by the occurrence of macro-complexes of the measured enzyme with immunoglobulins. This type of interference, for example, may occur in the determination of amylase and creatine kinase. Immunoassays for the determination of hormones or tumour markers are sensitive to autoantibodies and heterophilic antibodies. The former are particularly important in the determination of thyroid hormones, where the interference is method-dependent. In several immunoassays, interference by heterophilic antibodies can be abolished by the addition of non-immune serum. Finally, rheumatoid factors, antibodies administered for therapeutic purposes, and monoclonal gammopathies are possible sources of interference in the determination of various analytes.

Antibodies↗
PubMed1998

Condom use as a dependent variable: measurement issues relevant to HIV prevention programs.

The value of condoms in efforts to slow the spread of HIV infection has been well established in the literature. Behavioral science faces the challenge of promoting condom use through intervention programs. As these programs are evaluated, multiple issues should be considered in relation to measuring participant use of condoms for the purposes of preventing HIV infection. Lack of attention to these issues is likely to create a large number of Type I and Type II errors. Ten common sources of error are described and corresponding recommendations for eliminating these errors are offered. A review of published studies shows that there is little consistency relevant to controlling for these sources of error. Incorporation of standardized methodology will allow for more accurate program evaluation and benefit researchers by facilitating comparisons across studies.

Bias↗
PubMed2003

A simulation study of the error in dipole source localization for EEG spikes with a realistic head model.

OBJECTIVE: We tried to determine the error range of dipole modeling for EEG spikes originating from various clinically important sources by a simulation study employing a realistic head model. The computed error range was also compared with the degree of disturbance of dipole modeling caused by adding background activity to the spike. METHODS: The scalp fields generated by temporal, frontal and rolandic epileptic sources with spatial extent were simulated, and the corresponding 3-dimensional maps of residual variance (RV) were built by computing the RV for a single dipole at each point on a fine imaginary grid in the brain. Single dipole modeling was also performed for the simulated scalp fields after adding real background activity. RESULTS: The brain volume corresponding to a small RV was compact for the frontal sources and the lateral and baso-mesial temporal sources, and large for the anterior and baso-lateral temporal sources. The distribution of dipoles estimated for spikes contaminated with background corresponded to that of the volume of small RV and to spike-amplitude. Estimates were improved by employing inferior temporal electrodes. CONCLUSIONS: When evaluating dipole models of epileptic spikes, error ranges can be estimated and they vary considerably from region to region. SIGNIFICANCE: This study illustrates the variability of the error in dipole modeling of epileptic spikes. This variability is important when considering the clinical interpretation of modeling results.

Brain Mapping↗
PubMed1989

Glare testing in cataract patients: instrument evaluation and identification of sources of methodological error.

This study sought to determine the relative sensitivity of two commercially available glare testers in predicting outdoor acuity in a population of patients with minimal cataracts. Two target optotypes were evaluated: high contrast letters and varying contrast sinusoidal gratings. Although both instruments demonstrated a significant correlation between indoor and outdoor acuity, they showed a significant difference between predicted outdoor acuity and obtained visual acuity. The brightness acuity tester on high intensity was inaccurate in predicting outdoor vision regardless of test optotype, overpredicting glare disability in 76% (average) of the study population. Glare disability overpredictions fell to 8% on the medium setting with +/- 2 lines of vision classified as "no change." Using the same criterion, the Miller-Nadler glare tester overpredicted glare disability in 2% of the cataract population but underpredicted glare disability in 62%. In this study, letter optotypes resulted in less variability than sinusoidal grating stimuli. In addition, we identify several methodological factors to consider before designing a glare experiment. These potential sources of error can influence the outcome of any glare study that compares indoor and outdoor acuity and include the study population, visual stimuli (optotypes), and elements of the outdoor testing situation.

Adolescent↗
PubMed1999

Surgically induced intracranial contrast enhancement: potential source of diagnostic error in intraoperative MR imaging.

BACKGROUND AND PURPOSE: Intraoperative MR imaging is being used increasingly during neurosurgical interventions. The aim of this study was to describe and classify different forms of surgically induced intracranial contrast enhancement observed during intraoperative MR examinations. METHODS: A total of 51 intraoperative MR examinations were performed to assess the extent of brain tumor removal. The intraoperative MR results (T1-weighted images, unenhanced and obtained serially after the IV administration of paramagnetic contrast material) were compared with preoperative and early postoperative MR findings. Animal experiments were conducted to obtain further evidence of the mechanism of surgically induced contrast enhancement. RESULTS: Four different types of surgically induced contrast enhancement were found: meningeal enhancement, increased enhancement of the choroid plexus, delayed enhancement at the resection margins, and immediate intraparenchymal contrast enhancement. The types of surgically induced contrast enhancement differ regarding their location, configuration, and time course. Their potential to be confused with contrast-enhancing, residual tumor also varies. Three of the four types of surgically induced contrast enhancement were reproducible in an animal model. CONCLUSION: Surgically induced contrast enhancement is a potential source of error in intraoperative MR imaging. Careful analysis of the location, configuration, and time course of intraoperatively observed intracranial enhancement is critical to avoid confusing surgically induced contrast enhancement with contrast-enhancing, residual tumor.

Animals↗