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PubMedDate not supplied

Interpreter accuracy and informed consent among Spanish-speaking families with cancer.

Language interpreters mediate a growing number of health care communication events, including the informed consent process, which underlies the ethical conduct of clinical research. This article explores a key interpretive outcome, accuracy, in 21 Spanish/English informed consent consultations. Discussions were transcribed, translated, and coded according to established techniques. Most (74%) discussion was accurately interpreted (range: 47%-98%; std. deviation: .137). Accuracy was lower in the more technical portions of the discussion when compared with nontechnical portions such as discussion of coping and quality-of-life issues (p = .024). The concept of "randomization" often was poorly communicated and interpreted. These differences may be due in part to the use of long, uninterrupted, and jargon-filled sentences by clinicians explaining research, among other factors. The article concludes that accuracy may be promoted if clinicians used less technical language and shorter sentences, and are more "process driven." Interpreters may need to be better informed about research-related concepts such as randomization. Further research is needed to determine the effects of interpretive accuracy on the informed consent process, the decision to participate in research, and other outcomes.

Adolescent↗
PubMed2005

Completeness and accuracy of WWW-based catalogues of medical E-learning modules.

Catalogues of medical E-learning modules offer easy access to learning material that is available on the World Wide Web (WWW) free of charge. Therefore, a study was conducted on the retrieval performance of four WWW-based catalogues: CAL reviews, KELDAmed, LMU, and LRSMed. LRSMed is run by the authors. Completeness was calculated pairwise. Two reviewers checked the availability of 80 modules independently. Five criteria were chosen to calculate accuracy: gynaecology and microbiology as medical fields; case study as type of learning resource; diabetes mellitus and AIDS as free-text diagnoses. Also, two reviewers evaluated independently whether the module is really an appropriate resource for that criterion or not. The analysis is based on a consensual decision about the correct votes. From the URLs, 93% were available at the evaluation of completeness, 92% at the evaluation of accuracy. The kappa values for inter-rater reliability were 0.83 and 0.36. The best service offers 60.8% of the pooled E-learning resources. The resources retrieved by the five criteria were rated as correct in 69.3% (LRSMed), 76.6% (KELDAmed), and 82.7% (CAL reviews). The overall accuracy was 76.7%. Medical students and other potential users of E-learning modules should be aware that the completeness of WWW-based catalogues in this area is not satisfying. The retrieval accuracy is better; four of five resources offered correspond with the search criterion. Up to now, most of the services miss an application-programming interface that could be used for a meta-search to improve completeness.

Computer-Assisted Instruction↗
PubMed1999

Comparison of the power and accuracy of biallelic and microsatellite markers in population-based gene-mapping methods.

Because of their great abundance and amenability to fully automated genotyping, single-nucleotide polymorphisms (SNPs) and simple insertion/deletion are emerging as a new generation of markers for positional cloning. Although the efficiency and cost associated with the markers are important in the mapping of human disease genes, the power to detect the linkage between the marker and the disease locus, as well as the accuracy of the estimation of the map location of the disease gene, dictate the selection of the markers. Both the power and the accuracy depend not only on the type of the markers but also on other factors, such as the age of the disease mutation, the magnitude of the genetic effect, the marker-allele distribution in the population, mutation rates of marker loci, the frequency of the disease allele, the recombination fraction, and the methods for mapping the human disease genes. In this article, we develop a mathematical framework and the analytical formulas for calculation of the power and the accuracy and investigate the impact that the aforementioned factors have on the power and the accuracy, by using two population-based gene-mapping methods-likelihood-based linkage-disequilibrium mapping and the transmission/disequilibrium test, for both biallelic SNPs and microsatellites. These studies provide not only guidance in selection of the markers and in the design of the sample scheme for positional cloning but also insight into the biological bases of the mapping of human disease genes.

Alleles↗
PubMed2000

Accuracy of haplotype frequency estimation for biallelic loci, via the expectation-maximization algorithm for unphased diploid genotype data.

Haplotype analyses have become increasingly common in genetic studies of human disease because of their ability to identify unique chromosomal segments likely to harbor disease-predisposing genes. The study of haplotypes is also used to investigate many population processes, such as migration and immigration rates, linkage-disequilibrium strength, and the relatedness of populations. Unfortunately, many haplotype-analysis methods require phase information that can be difficult to obtain from samples of nonhaploid species. There are, however, strategies for estimating haplotype frequencies from unphased diploid genotype data collected on a sample of individuals that make use of the expectation-maximization (EM) algorithm to overcome the missing phase information. The accuracy of such strategies, compared with other phase-determination methods, must be assessed before their use can be advocated. In this study, we consider and explore sources of error between EM-derived haplotype frequency estimates and their population parameters, noting that much of this error is due to sampling error, which is inherent in all studies, even when phase can be determined. In light of this, we focus on the additional error between haplotype frequencies within a sample data set and EM-derived haplotype frequency estimates incurred by the estimation procedure. We assess the accuracy of haplotype frequency estimation as a function of a number of factors, including sample size, number of loci studied, allele frequencies, and locus-specific allelic departures from Hardy-Weinberg and linkage equilibrium. We point out the relative impacts of sampling error and estimation error, calling attention to the pronounced accuracy of EM estimates once sampling error has been accounted for. We also suggest that many factors that may influence accuracy can be assessed empirically within a data set-a fact that can be used to create "diagnostics" that a user can turn to for assessing potential inaccuracies in estimation.

Algorithms↗
PubMed2000

Accuracy of the phase space evolution dose calculation model for clinical 25 MeV electron beams.

The phase space evolution (PSE) model is a dose calculation model for electron beams in radiation oncology developed with the aim of a higher accuracy than the commonly used pencil beam (PB) models and with shorter calculation times than needed for Monte Carlo (MC) calculations. In this paper the accuracy of the PSE model has been investigated for 25 MeV electron beams of a MM50 racetrack microtron (Scanditronix Medical AB, Sweden) and compared with the results of a PB model. Measurements have been performed for tests like non-standard SSD, irregularly shaped fields, oblique incidence and in phantoms with heterogeneities of air, bone and lung. MC calculations have been performed as well, to reveal possible errors in the measurements and/or possible inaccuracies in the interaction data used for the bone and lung substitute materials. Results show a good agreement between PSE calculated dose distributions and measurements. For all points the differences--in absolute dose--were generally well within 3% and 3 mm. However, the PSE model was found to be less accurate in large regions of low-density material and errors of up to 6% were found for the lung phantom. Results of the PB model show larger deviations, with differences of up to 6% and 6 mm and of up to 10% for the lung phantom; at shortened SSDs the dose was overestimated by up to 6%. The agreement between MC calculations and measurement was good. For the bone and the lung phantom maximum deviations of 4% and 3% were found, caused by uncertainties about the actual interaction data. In conclusion, using the phase space evolution model, absolute 3D dose distributions of 25 MeV electron beams can be calculated with sufficient accuracy in most cases. The accuracy is significantly better than for a pencil beam model. In regions of lung tissue, a Monte Carlo model yields more accurate results than the current implementation of the PSE model.

Air↗
PubMed2003

Neuronavigation accuracy dependence on CT and MR imaging parameters: a phantom-based study.

Clinical benefits from neuronavigation are well established. However, the complexity of its technical environment requires a careful evaluation of different types of errors. In this work, a detailed phantom study which investigates the accuracy in a neuronavigation procedure is presented. The dependence on many different imaging parameters, such as field of view, slice thickness and different kind of sequences (sequential and spiral for CT, T1-weighted and T2-weighted for MRI), is quantified. Moreover, data based on CT images are compared to those based on MR images, taking into account MRI distortion. Finally, the contributions to global accuracy coming from image acquisition, registration and navigation itself are discussed. Results demonstrate the importance of imaging accuracy. Procedures based on CT proved to be more accurate than procedures based on MRI. In the former, values from 2 to 2.5 mm are obtained for 95% fractiles of cumulative distribution of Euclidean distances between the intended target and the reached one while, in the latter, the measured values range from 3 to 4 mm. The absence of imaging distortion proved to be crucial for registration accuracy in MR-based procedures.

Algorithms↗
PubMed2005

Direct navigation on 3D rotational x-ray data acquired with a mobile propeller C-arm: accuracy and application in functional endoscopic sinus surgery.

Recently, three-dimensional (3D) rotational x-ray imaging has been combined with navigation technology, enabling direct 3D navigation for minimally invasive image guided interventions. In this study, phantom experiments are used to determine the accuracy of such a navigation set-up for a mobile C-arm with propeller motion. After calibration of the C-arm system, the accuracy is evaluated by pinpointing divots on a special-purpose phantom with known geometry. This evaluation is performed both with and without C-arm motion in between calibration and registration for navigation. The variation caused by each of the individual transformations in the calibration and registration process is also studied. The feasibility of direct navigation on 3D rotational x-ray images for functional endoscopic sinus surgery has been evaluated in a cadaver navigation experiment. Navigation accuracy was approximately 1.0 mm, which is sufficient for functional endoscopic sinus surgery. C-arm motion in between calibration and registration slightly degraded the registration accuracy by approximately 0.3 mm. Standard deviations of each of the transformations were in the range 0.15-0.31 mm. In the cadaver experiment, the navigation images were considered in good correspondence with the endoscopic images by an experienced ENT surgeon. Availability of 3D localization information provided by the navigation system was considered valuable by the ENT surgeon.

Algorithms↗
PubMed2007

Influence of dose engine accuracy on the optimum dose distribution in intensity-modulated proton therapy treatment plans.

Analytical dose computation algorithms like pencil beam algorithms (PB) are presently used for clinical treatment planning in intensity-modulated proton therapy. PB offer fast computation times, but are based on substantial approximations. Monte Carlo algorithms (MC) offer better accuracy, but are slower. We present a comparison of optimized treatment plans for six patients computed either with PB or MC. Both PB and MC are used during optimization, plus MC is used to recompute PB results. PB is used with different accuracy settings that define the coarseness of approximation. We evaluate the errors of PB optimized treatment plans via comparison with MC optimized plans (convergence errors) and MC recomputed plans (systematic errors) occurring for different accuracy settings of the PB. The level of lateral heterogeneities, being one of the main sources of inaccuracies of the PB, is quantified by a formula. In geometries with high levels of lateral heterogeneities, the shortcomings of PB are most obvious. For these geometries, simple PB lead to clinically significant differences and more accurate PB settings have to be used to diminish the error. The most accurate PB settings lead however to longer computing times by approximately a factor of 2 to 4 compared to PB with simple settings. Although the errors can be diminished, they cannot be fully eliminated even with sophisticated PB. Further gain in accuracy can therefore only be reached with MC in optimization. The use of MC in optimization is technically feasible, the computing times are however about 25 to 50 times longer compared to PB with most accurate settings.

Algorithms↗
PubMed2002

The accuracy of fine-needle aspiration biopsy and frozen section in patients with thyroid cancer.

A total of 1076 patients with thyroid nodules were reviewed. The accuracy of fine needle aspiration biopsy (FNAB) and frozen section (FS) were compared and clinical risk factors were analyzed. Our results indicate that 67.9% are benign and 32.1% are malignant with the predominance of papillary thyroid cancer (75.1%). Overall diagnostic accuracy for FNAB and FS were 90.8%-91.2% and 89.1%-90.5%, respectively. There were no significant differences between the diagnostic accuracy on FNAB and FS in all tumors except the follicular adenoma and carcinoma. The diagnostic accuracy of FS was higher than FNAB in patients with follicular adenoma (89.3% vs. 58.9%, p < 0.001) and but lower than FNAB in patients with follicular carcinoma (46.2% vs. 92.3%, p < 0.001). In conclusion, FNAB is cost effective in the preoperative evaluation of thyroid nodule. FS could be eliminated in most cases except with follicular and Hürthle cell neoplasms. FS is valuable when result of FNAB is suspicious or unavailable. FS is more appropriate in deciding the extent of thyroidectomy in follicular neoplasm and FNAB is more reliable initial approach to surgery in patients with Hürthle cell neoplasm. Clinical risk factors may help in selecting patients for surgery but cannot exceed FS in deciding the extent of thyroidectomy in patients with follicular and Hürthle cell neoplasms.

Adolescent↗
PubMed2000

Effect of acetaminophen on the accuracy of glucose measurements obtained with the GlucoWatch biographer.

BACKGROUND: Improved glycemic control significantly reduces long-term microvascular complications of diabetes mellitus associated with chronic hyperglycemia. The GlucoWatch biographer is designed to facilitate intensive diabetes management by providing automatic, frequent, and noninvasive glucose readings up to three times per hour for as long as 12 hours. METHODS: The device extracts glucose through intact skin using reverse iontophoresis and measures the extracted glucose with an electrochemical biosensor. A clinical trial was performed to assess the effect of acetaminophen, a potential interference for traditional blood glucose meters, on the accuracy of the GlucoWatch biographer in adult subjects with diabetes (n = 18). One thousand milligram doses of acetaminophen were administered to subjects in two groups: one to achieve Cmax (peak acetominophen concentration) at the time of biographer calibration and the other to achieve Cmax during the measurement period. The biographer readings were compared to serial fingerstick blood glucose measurements. RESULTS: Time profiles over 9 hours show close tracking of the biographer glucose results with fingerstick blood glucose measurements for all groups. The mean difference between the two measurements is between 8 and 12 mg/dL for all groups. The mean absolute value of the relative difference is less than 20%, and more than 93% of the points were in the clinically acceptable (A+B) region of the Clarke Error Grid. No statistically significant differences were found for any accuracy measurement across all groups. CONCLUSIONS: The GlucoWatch Biographer provides frequent measurements of glucose over a 12-hour period with high accuracy. No effect of therapeutic dosage of acetaminophen on the accuracy of the glucose readings was found.

Acetaminophen↗
PubMed2001

Dose accuracy testing of the humalog/ humulin insulin pen device.

The primary purpose of the study was to determine whether pen users would challenge the insufficient remaining dose (IRD) stop mechanism with sufficient force to affect the dose accuracy of the final dose. The secondary purpose was to determine the participant's positive and negative impressions of the Humalog/Humulin pen and the likelihood of using the new prefilled pen. Three different modifications to the prefilled pen's IRD stop feature were made. These three pen models then underwent environmental dose accuracy testing at various temperatures and humidities, and user dose accuracy testing by 64 patients with diabetes. Evaluation also involved challenging the IRD stop at various dialing torques. Thirty pens from each model were tested to failure of the IRD stop. A model of the prefilled pen was selected for commercialization that met the dose accuracy targets of +/- 1 unit (U) for insulin doses less than 20 U and +/- 5% of dose volume for doses equal to or over 20 U. The selected pen model was superior at the minimum (1 unit), median (30 unit) and maximum (60 unit) dose volumes. Also 92% (n = 59) of patients interviewed felt that the stop mechanism for the final dose was clear. Extensive testing in the development of a prefilled insulin delivery device demonstrates an accurate and reliable medical device.

Diabetes Mellitus↗
PubMed2005

Accuracy of prediction models in the context of disease management.

There has been a significantly increased interest in the adoption of prediction modeling by many disease and case management programs to risk stratify members in order to optimize the utilization of available clinical resources. Before adopting any prediction model, it is critical to understand how to evaluate the model's accuracy. This paper explains the basic concepts of prediction accuracy, the relevant parameters, their drawbacks, and their interpretations. It also introduces a new accuracy parameter termed "cost concentration," which indicates the model accuracy more explicitly in the context of disease management.

Disease Management↗
PubMed1999

Diagnostic accuracy in fine-needle aspiration of soft tissue and bone lesions. Influence of clinical history and experience.

Interpretation of soft tissue and bone lesions with fine-needle aspiration (FNA) is difficult. We determined whether clinical history or experience improves diagnostic accuracy of FNA interpretation of these lesions. Four cytopathologists with varying degrees of experience retrospectively reviewed 89 soft tissue and bone lesions, initially without knowledge of clinical history and subsequently with knowledge of clinical history. Each time, the pathologist rendered a precise diagnosis (histogenetic classification, e.g., angiosarcoma, lipoma) for each case and classified the lesion into one of 4 categories: benign, probably benign, probably malignant, or malignant. The proportion of correct precise diagnoses was calculated. Also, the numbers of correct and incorrect classifications of malignancy were used in standard relative operating characteristic (ROC) curve analysis. The area under the ROC curve was estimated to give an indicator of diagnostic accuracy. Knowledge of clinical history increased the proportion of correct diagnoses and the accuracy of the classification for all observers. Experienced observers more accurately classified lesions, and knowledge of clinical history particularly improved the diagnostic accuracy of less experienced observers.

Biopsy, Needle↗
PubMed1992

A method for the independent assessment of the accuracy of hematology whole-blood calibrators.

An independent assessment of the accuracy with which a large manufacturer assigned values to hematologic calibrators was performed. Data were collected from 1,767 hospitals and clinics distributed over North America. Statistical analysis of the mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration of these patient data confirmed the accuracy of the values for hemoglobin, erythrocyte count, hematocrit, and erythrocyte indices for the calibrators manufactured and released during a 9-month period. This approach proved both workable and effective in detecting inaccuracies of less than 1%. Few technologist-users have the time or the equipment to verify independently the accuracy of hematologic calibrators. The manufacturers should perform ongoing, independent assessments of the accuracy of their products. The statistical analysis of patient data provides manufacturers with a suitable method.

Calibration↗
PubMedDate not supplied

Combining carbohydrate-deficient transferrin and gamma-glutamyltransferase to increase diagnostic accuracy for problem drinking.

AIM: To examine methods for combining quantitative results for serum carbohydrate deficient transferrin (CDT), gamma-glutamyltransferase (GGT) and/or aspartate aminotransferase (AST), and refining these by inclusion of patient characteristics. METHODS: Data from 1684 subjects, recruited from the general population, abstainer groups and alcohol treatment centres (participants in the five nations WHO/ISBRA study of biological markers of alcohol use), were used to develop clinical rules for combining results of GGT, AST and CDT. The algorithm derived by Sillanaukee and Olsson was tested, and compared with new algorithms derived by logistic regression and discriminant analysis. Diagnostic accuracy was assessed by area underneath the receiver operator characteristic curve. Effects of adding gender and clinical information to the algorithm were estimated. RESULTS: The predictive ability of combination rules derived from the two studies and by two different statistical techniques was remarkably consistent. For men, combining lnCDT and lnGGT provided the best accuracy for detecting daily consumption of 60 g ethanol or more in the past 30 days. For women, GGT alone provided the best accuracy for that consumption level. Clinical variables added significantly to the diagnostic accuracy of the models for both men and women, and conversely the test results modified the probability of problem drinking as assessed from clinical data alone. A graphic method was produced to help clinicians estimate probabilities for consumption of 60 g or more per day. CONCLUSIONS: Combining biochemical markers enhances detection of problem drinking in men but not in women. Information on clinical variables increases the ability to correctly detect problem drinking.

Adolescent↗
PubMed1998

Comparative accuracy of methods for protein sequence similarity search.

MOTIVATION: Searching a protein sequence database for homologs is a powerful tool for discovering the structure and function of a sequence. Two new methods for searching sequence databases have recently been described: Probabilistic Smith-Waterman (PSW), which is based on Hidden Markov models for a single sequence using a standard scoring matrix, and a new version of BLAST (WU-BLAST2), which uses Sum statistics for gapped alignments. RESULTS: This paper compares and contrasts the effectiveness of these methods with three older methods (Smith-Waterman: SSEARCH, FASTA and BLASTP). The analysis indicates that the new methods are useful, and often offer improved accuracy. These tools are compared using a curated (by Bill Pearson) version of the annotated portion of PIR 39. Three different statistical criteria are utilized: equivalence number, minimum errors and the receiver operating characteristic. For complete-length protein query sequences from large families, PSW's accuracy is superior to that of the other methods, but its accuracy is poor when used with partial-length query sequences. False negatives are twice as common as false positives irrespective of the search methods if a family-specific threshold score that minimizes the total number of errors (i.e. the most favorable threshold score possible) is used. Thus, sensitivity, not selectivity, is the major problem. Among the analyzed methods using default parameters, the best accuracy was obtained from SSEARCH and PSW for complete-length proteins, and the two BLAST programs, plus SSEARCH, for partial-length proteins.

Databases, Factual↗
PubMed2004

A simple statistical method for discriminating outer membrane proteins with better accuracy.

MOTIVATION: Discriminating outer membrane proteins from other folding types of globular and membrane proteins is an important task both for identifying outer membrane proteins from genomic sequences and for the successful prediction of their secondary and tertiary structures. RESULTS: We have systematically analyzed the amino acid composition of globular proteins from different structural classes and outer membrane proteins. We found that the residues, Glu, His, Ile, Cys, Gln, Asn and Ser, show a significant difference between globular and outer membrane proteins. Based on this information, we have devised a statistical method for discriminating outer membrane proteins from other globular and membrane proteins. Our approach correctly picked up the outer membrane proteins with an accuracy of 89% for the training set of 337 proteins. On the other hand, our method has correctly excluded the globular proteins at an accuracy of 79% in a non-redundant dataset of 674 proteins. Furthermore, the present method is able to correctly exclude alpha-helical membrane proteins up to an accuracy of 80%. These accuracy levels are comparable to other methods in the literature, and this is a simple method, which could be used for dissecting outer membrane proteins from genomic sequences. The influence of protein size, structural class and specific residues for discrimination is discussed.

Algorithms↗
PubMed1988

How the rise time of carbon dioxide analysers influences the accuracy of carbon dioxide measurements.

Carbon dioxide measurements are not accurate, especially in children, if the response time of the carbon dioxide analyser is too slow and its output fails to reach the actual carbon dioxide concentration at the end of the breath. The distortion of the carbon dioxide waveform is a function of the "rise time" of the analyser. We have simulated an expired carbon dioxide curve and calculated the rise time required to measure accurately end-tidal carbon dioxide and VCO2 in adults and children. A rise time of 80 ms (10-70%) is sufficient to measure end-tidal carbon dioxide concentration with 5% accuracy in patients with rates of ventilation less than 100 b.p.m. and I:E ratios less than 2:1. We have measured the rise time of 11 commercially available carbon dioxide analysers and found that only six of the 11 responded quickly enough to be accurate for rates up to 100 b.p.m. All 11 responded rapidly enough to measure end-tidal carbon dioxide concentration with 5% accuracy when ventilatory rates were less than 30 b.p.m. To measure VCO2 with 5% accuracy, an analyser should have a rise time of 20 ms. Only one analyser met this specification. An analyser's rise time can be estimated clinically to within 10 (SD 8) ms by a simple breath hold and forced exhalation, thus providing an estimate of the accuracy of carbon dioxide measurements in adults or children.

Anesthesia, Inhalation↗