Appraisal of advanced sample tabulation of 1982 census of Shanghai.
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Asia↗
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Results for “Error Sources”
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Sampling errors for selected variables from the 1988 Turkish Population and Health Survey.
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Asia↗
[Coverage and quality of the registration of perinatal deaths occurring in health institutions in the Federal District].
"This paper presents the results of the first direct attempt at evaluating the coverage of the perinatal death registration in the Distrito Federal [of Mexico]; this study is based on the information gathered from 574 deaths which took place in 23 hospitals in the Distrito Federal during a three month period in 1984. Both the causes of the failure to register many of these deaths and the quality of the information presented in perinatal death certificates are pointed out and discussed here. According to the evidence analyzed, it is clear that underregistration in the Distrito Federal is extremely marked.... The paper suggests the possibility of establishing a hospital registration system which would keep a record of both deaths and births. It also stresses the need for establishing rules to detect fetal deaths plus the need for unifying criteria regarding the definition of 'live birth'." (SUMMARY IN ENG)
Americas↗
Analysis of unlinked infant death certificates from the NIMS project.
The National Infant Mortality Surveillance (NIMS) project used linked birth and infant death certificates to calculate birth weight-specific infant mortality risks for the 1980 U.S. birth cohort. Record linkage depends on complete registration of vital events, interstate exchange of vital records, accurate information on certificates, and a comprehensive linkage system. States reported 2,604 unlinked infant death certificates for 1980, ranging from 0 to 397 per State. Age at death for these infants ranged from 1 minute to 11 months. More than 41 percent of the unlinked death certificates were for postneonates, compared with 32.5 percent found in the cohort's total infant death experience. Only 38.2 percent of the unlinked infant death certificates showed strictly intrastate events (birth and death occurrence, and residence at death all in one State), compared with 92.9 percent in the cohort's total infant death experience. Estimates of the percentage successfully linked by State ranged from 86.0 to 100.0. After adjusting for the certainly unlinked infant death certificates, nine States' infant mortality risks increased by more than 0.2 per 1,000 live births. Improvements are needed both within and between States to ensure more complete birth and infant death certificate linkage.
Birth Certificates↗
Reader error during CT colonography: causes and implications for training.
This study investigated the variability in baseline computed tomography colonography (CTC) performance using untrained readers by documenting sources of error to guide future training requirements. Twenty CTC endoscopically validated data sets containing 32 polyps were consensus read by three unblinded radiologists experienced in CTC, creating a reference standard. Six readers without prior CTC training [four residents and two board-certified subspecialty gastrointestinal (GI) radiologists] read the 20 cases. Readers drew a region of interest (ROI) around every area they considered a potential colonic lesion, even if subsequently dismissed, before creating a final report. Using this final report, reader ROIs were classified as true positive detections, true negatives correctly dismissed, true detections incorrectly dismissed (i.e., classification error), or perceptual errors. Detection of polyps 1-5 mm, 6-9 mm, and > or =10 mm ranged from 7.1% to 28.6%, 16.7% to 41.7%, and 16.7% to 83.3%, respectively. There was no significant difference between polyp detection or false positives for the GI radiologists compared with residents (p=0.67, p=0.4 respectively). Most missed polyps were due to failure of detection rather than characterization (range 82-95%). Untrained reader performance is variable but generally poor. Most missed polyps are due perceptual error rather than characterization, suggesting basic training should focus heavily on lesion detection.
Clinical Competence↗
Errors in measuring blood gases in the intensive care unit: effect of delay in estimation.
Arterial blood gas measurement is subject to a number of potential sources of error. We investigated some of these in the intensive care unit (ICU). We audited samples for adequate volume and the presence of air and found that all samples were of adequate volume, but 40% contained bubbles or froth. We compared pulse oximeter estimations of oxygen saturation (SpO(2)) with laboratory estimates (SO(2)) from arterial blood samples, and found that there was less than a 5% chance of a difference of 5% or more. We audited the delay between sampling and processing and looked for errors arising as a result. We found that 4% of samples waited longer than 30 minutes to be analyzed in the laboratory, but that there was no correlation between delay and error in partial pressure of oxygen (PO(2)), carbon dioxide (PCO(2)), or SO(2). We performed a bench study to document the changes in PO(2) and PCO(2) over time with samples stored at room temperature and on ice. We found that samples in 1.5-mL PICO 70 syringes (Radiometer Medical A/S, Bronshoj, Denmark) were stable for PO(2) and SO(2) for up to 30 minutes either at room temperature or kept in iced water, and that changes after 60 minutes were small and unlikely to be clinically significant. PCO(2) showed a statistically significant increase after 20 minutes at room temperature, but the changes were not clinically significant.
Analysis of Variance↗
Tanner-Whitehouse method of assessing skeletal maturity: problems and common errors.
The Tanner-Whitehouse method of assessing skeletal maturity has been in use for more than three decades. Problems in assigning bone ages arise from many sources. The most significant sources of error are poor positioning of the hand when the radiograph is taken, which alters the radiographic appearance of the epiphysis and makes interpretation unnecessarily difficult, and the lack of consistency in repeat ratings of the same film by one or more observers (intra- and inter-observer error). In addition, use of the system outside the limits of its design is a common error seen in clinical practice. Computer systems are now being developed with the aim of reducing many of the inconsistencies associated with radiographic investigations of normal children.
Age Determination by Skeleton↗
Volumetric measurement of human calf muscle from magnetic resonance imaging.
Muscle mass is a determining factor in skeletal muscle function and is affected by inactivity, immobilization, disease, and aging. The aim of this study was to develop an objective and time-efficient method to quantify the volume and cross-sectional area of human calf muscles using three-dimensional magnetic resonance images. We have estimated the errors incurred in muscle volume measurements arising from artifacts known to occur in magnetic resonance imaging (MRI). The largest source of error was due to partial volume effects, which resulted in overestimation of phantom volumes ranging from 145 to 900 cc by 6% to 13%. The magnitude of this effect has been shown to increase with decreasing object size and decreasing spatial resolution. We have presented a straightforward correction for this effect, which has reduced the volume measurement error to less than 4% for all cases. Through the use of computer simulations, the correction algorithm has been shown to be independent of object shape and orientation. To reduce user subjectivity, a semiautomated computer program has been developed to segment MRI data for particular muscle groups. Images from seven human subjects were analyzed by the program, yielding muscle volumes of 154.2 +/- 23.2, 281.2 +/- 35.8, and 432.2 +/- 83.7 for the lateral gastrocnemius, medial gastrocnemius, and soleus, respectively.
Adult↗
The tangential breast match plane: practical problems and solutions.
The three-field breast set-up, in which tangential oblique opposed fields are joined to an anterior supraclavicular field, has been the method of choice for treatment of breast cancer for many years. In the last several years many authors have suggested refinements to the technique that improve the accuracy with which fields join at a match plane. The three-field breast set-up, using a rotatable half-beam block is the technique used at our institution. In instituting this procedure, several practical problems were encountered. Due to the small collimator rotation angles used it is possible to clinically reverse the collimator angle without observing an error noticeable on fluoroscopy. A second error can occur when the table base angle is used to compensate for the incorrect collimator rotation. These potential sources of error can be avoided if a programmable calculator or computer program is used to assist the dosimetrist during the simulation. Utilization of fluoroscopy, digital table position displays and a caliper provide accurate input for the computer program. This paper will present a hybrid procedure that combines practical set-up procedures with the mathematical calculation of ideal angles to result in an accurate and practical approach to breast simulation.
Breast Neoplasms↗
Importance of potency in typing by colicine production.
Six colicinogenic strains, producing colicine A, B, D, K, S(4), and V, showed a variation in the reproducibility of the potency of their crude extracts, although a standard technique was used. The importance of this variation on typing was shown by the effect of different colicine potencies on the patterns of inhibition of the Abbott and Shannon indicators. Using a diffusion technique, 3,004 assays were performed and it was found that the patterns of inhibition depended mainly on the strength of the colicine.A further source of error in typing by production patterns was the sensitivity of the indicator strain. Two sets of indicators from different sources were compared, and though there was agreement in most strains, there were differences which varied from slightly more resistant to totally resistant. It is suggested that the potency of the colicine produced by the colicinogenic strain should be known before typing is performed in order that standard comparisons may be achieved. The precise sensitivity of the indicators should also be confirmed periodically.
Colicins↗
Generalized algebraic scene-based nonuniformity correction algorithm.
A generalization of a recently developed algebraic scene-based nonuniformity correction algorithm for focal plane array (FPA) sensors is presented. The new technique uses pairs of image frames exhibiting arbitrary one- or two-dimensional translational motion to compute compensator quantities that are then used to remove nonuniformity in the bias of the FPA response. Unlike its predecessor, the generalization does not require the use of either a blackbody calibration target or a shutter. The algorithm has a low computational overhead, lending itself to real-time hardware implementation. The high-quality correction ability of this technique is demonstrated through application to real IR data from both cooled and uncooled infrared FPAs. A theoretical and experimental error analysis is performed to study the accuracy of the bias compensator estimates in the presence of two main sources of error.
Algorithms↗
Development of milk powder reference materials certified for aflatoxin M1 content (Part I).
The development of 3 full-cream milk powder reference materials, certified for their aflatoxin M1 content, is described. The materials were prepared and certified within the Reference Material Programme of the Community Bureau of Reference (BCR). The 3 reference materials, RMs 282, 284, and 285, contain aflatoxin M1 at concentrations of less than 0.05, 0.31 +/- 0.06, and 0.76 +/- 0.05 micrograms/kg, respectively. The preparation, testing for homogeneity, stability of the reference materials, and the certification exercise, which was preceded by 2 intercomparisons of methods, are discussed. Particular emphasis was placed on the independence of the measurements in the certification exercise and the control of errors associated with extraction efficiency and the aflatoxin M1 calibrant. Finally, some guidance is given on avoiding the principal sources of errors in the determination of aflatoxin M1. Details concerning the supply of the reference materials will be provided by BCR on request.
Aflatoxin M1↗
Audit of death certificates.
Information on the number and causes of death is one of the basic components of a country's health information system. Data are usually derived from death certificates and health facility discharge summaries. There are usually several causes of error in the routine collection of this information. A criteria audit of death certificates is presented to assess these sources of error in Papua New Guinea. This procedure involved the systematic and critical analysis of hospital mortality as reported in death certificates. The audit is simple, cheap and useful for monitoring the quality of the mortality information which will be used in health planning and management. Quality criteria are defined and the completeness and relevance of the data audited are discussed. Recommendations for the improvement of the health information system are made.
Adolescent↗
Assessing glycemia in diabetes using self-monitoring blood glucose and hemoglobin A1c.
CONTEXT: With the increasing prevalence of diabetes, successful management of blood glucose control is increasingly important. Current approaches to assessing glycemia include the use of self-monitoring of blood glucose (SMBG) and hemoglobin A1c (HbA1c). OBJECTIVES: To assess the evidence underlying the use of these 2 modalities, to evaluate confounders and sources of error in each test, to describe upcoming developments, and to reach evidence-based conclusions on their optimal use. DATA SOURCES, STUDY SELECTION, AND DATA EXTRACTION: Reports identified from MEDLINE searches (1976-2005) using relevant terms were selected for quality and relevance to the stated questions. Particular attention was paid to larger cohort studies, clinical trials, meta-analyses, and established recommendations. DATA SYNTHESIS: If used properly SMBG gives an acceptably accurate reflection of immediate plasma glucose levels. Study results vary, but in general, the evidence supports a positive effect of regular SMBG for improving glycemia, particularly in individuals treated with insulin. The best timing of SMBG and its frequency are controversial issues, but the clinical recommendation is for regular monitoring with frequency depending on the treatment and the instability of glycemia. In the relatively near term, SMBG could gradually be replaced by continuous glucose monitoring. HbA1c measures long-term glycemic control, reflecting a time-weighted mean over the previous 3 to 4 months. There are a number of physiologic and methodologic confounders that can affect HbA1c, but standardization of assays has been well established. The main value of HbA1c is its use as a predictor of diabetic complications and the proven effect of improved control of HbA1c on complication risk. A reasonable target value for HbA1c is less than 7%. A new method for measuring HbA1c may cause significant changes in the recommended levels, the numbers reported, and even the name of the test. CONCLUSION: Assessing glycemia in diabetes can be a challenge, but approaches are available that promote successful management of blood glucose and may thereby lead to a significant reduction in morbidity and mortality related to diabetes.
Blood Glucose Self-Monitoring↗
Distortion of intravascular ultrasound images because of nonuniform angular velocity of mechanical-type transducers.
The purpose of this study was to quantify nonuniform rotation in a current mechanical intravascular ultrasound (IVUS) instrument and its effect on arc, area, and diameter measurements. The accurate reconstruction of IVUS two-dimensional images is dependent on uniform rotation of the catheter tip. Prior investigations suggested that bends in the catheter driveshaft may be responsible for poor torque transmission, nonuniform rotation, and consequent errors in IVUS measurements. Eight 30 MHz mechanically driven IVUS catheters were evaluated in a model simulating the catheter course through the aorta and coronary ostium in a clinical study. Angular velocity and posi-ion profiles of the transducer, image angle, and diameter and area measurement errors were obtained from each catheter by imaging a vascular phantom with eight equispaced echogenic markers from concentric and eccentric positions. Six catheters also were tested for comparison in a simple curvature model. Rotational error was found in all catheters tested and worsened in the aortic model. Maximal angular error, defined as the largest angle between actual and presumed transducer direction, increased when measured in the aortic model as compared with the simple curvature model (17 +/- 12 degrees to 45 +/- 25 degrees; p < 0.05). Angles of 45 degrees were misrepresented with a mean range of values of 26 to 63 degrees. With eccentric catheter placement, area and diameters had average maximal absolute errors of 26% +/- 7.8% and 23% +/- 10%, respectively. In conclusion, nonuniform rotation of mechanical IVUS transducers constitutes a significant potential source of error in IVUS measurement of arcs of calcification, and lumen shape, area, and diameter.
Humans↗
Memory for facts, source, and context: can frontal lobe dysfunction explain age-related differences?
Age-related differences in memory for facts, source, and contextual details were examined in healthy young (18-35 years old) and old (65-80 years old) volunteers. In all tested memory functions, decline over time was greater in the elderly than in the young. A time-dependent increase in the prevalence of source amnesia errors was clearly associated with old age. Contrary to several recent reports, measures of frontal lobe functions did not predict source memory. Nevertheless, some of these putative frontal function measures were related to memory for contextual details. The number of perseverative responses on the Wisconsin Card Sorting Test was inversely related to performance on both factual and contextual memory tests, but the association with contextual memory was stronger. Difficulties with response selection on a Stroop task predicted poor contextual memory in young but not in old adults.
Adolescent↗
Overview of bioelectrical impedance analyzers.
Six commercial bioelectrical impedance analyzers were evaluated to determine their accuracy as impedance meters, their sensitivity to contact impedance, and other operating parameters such as maximum current amplitude and test wave-form. Over a range of impedances that simulate human body impedance, analyzer errors varied from < 1% to nearly 20%. Larger errors were observed when the contact impedance was at the limits of the operating range of the analyzer. Body models, sources of error, and several simple tests that the user can perform are also discussed.
Calibration↗
Enhanced x-ray phase determination by three-beam diffraction.
For decades, solving the phase problem of x-ray scattering has been a goal that, in principle, could be achieved by means of n-beam diffraction (n-BD). However, the phases extracted by the actual n-BD phasing techniques are not very precise, mainly due to systematic errors that are difficult to estimate. We present an innovative theoretical approach and experimental procedure that, combined, eliminate two major sources of error. It is a high precision phasing technique that provides the triplet-phase angle with an error of about 2 degrees.
Journal Article↗