Some considerations regarding international comparisons of infant mortality.
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Cause of Death↗
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Statistical characterization of the random errors in the radioimmunoassay dose--response variable.
We have developed practical methods for evaluating the magnitude of the random errors in radioimmunoassay dose--response variables, and the relationship between this error and position on the dose--response curve. This is important: to obtain appropriate weights for each point on the dose--response curve when utilizing least-squares curve-fitting methods; to evaluate whether the standards and the unknowns are subject to error of the same magnitude; for quality-control purposes; and to study the sources of errors in radioimmunoassay. Both standards and unknowns in radioimmunoassays for cAMP and cGMP were analyzed in triplicate. The same mean (Y), sample standard deviation, sy, and variance (2-y) of the response variable were calculated for each dose level. The relationship between s 2-y and y was calculated utilizing several models. Results for standards and unknowns from several assays were pooled, and a curve smoothing procedure was used to minimize random sampling errors. This pooling increased the reliability of the analysis, and confirmed the presence of the theoretically predicted nonuniformity of variance. Thus, the calculation of results from these radioimmunoassays should utilize a weighted least-squares curve-fitting program. These analyses have been computerized, and can be used as a "pre-processor" for programs for routine analysis of results of radioimmunoassay.
Analysis of Variance↗
Comparison of the errors due to the use of gauze and the use of filter paper in the gravimetric chloride titration sweat test.
Potential sources of error in the Gibson and Cooke method of sweat testing using gauze and filter paper as collection media as described. The absolute chloride content of gauze was higher than that of filter paper; however, the variability of chloride contents between the two was insignificant. Complete chloride elution from filter paper requires more time than elution from gauze. A method of determining probability of a clinically acceptable measurement based on sweat sample size, chloride determination, and variability of chloride in collection media is also described.
Chlorides↗
The active site of hemerythrin as determined by X-ray absorption fine structure.
Extensive X-ray absorption fine structure measurements and analysis have been made on azidomet- and methemerythrin and on the native forms of oxy- and deoxyhemerythrin. Due to the availability of models that have been synthesized to mimic the active site of hemerythrin, it was possible to make a thorough assessment of the various errors in the structural parameters determined by the analysis. It is found that the largest source of error is the lack of complete transferability of amplitude and phase between the standards and hemerythrin. This is of particular importance in distinguishing the contributions of the second-shell low-Z atoms and, thus, has a substantial influence on the determination of the iron-iron distance. The internal consistencies of the various checks and a new formulation of error analysis for the structural parameters give us confidence in the structure determined for the active site. The main result is that as O2 is released from oxyhemerythrin, the mu-oxo bridge between the two iron atoms in the active site with an Fe-O distance of 1.8 A converts to a mu-hydroxo bridge in deoxyhemerythrin, expanding the Fe-O distance to 2.0 A. The Fe-Fe distance expands proportionally from 3.24 A in oxyhemerythrin to 3.57 A in deoxyhemerythrin so as to keep the Fe-O-Fe bridging angle approximately constant. These conclusions provide experimental support for the structures of oxy- and deoxyhemerythrin proposed previously on the basis of spectroscopic and preliminary X-ray crystallographic data.
Animals↗
A method to assess predominant energies of exposure in a nuclear research centre--Saclay (France).
A study of dosimetric errors is under way within an international collaborative study of cancer risk among workers in the nuclear industry. The objective is to quantify errors in the estimated photon doses to individual organs used for cancer risk estimation. One source of errors is the response of old dosemeters in workplace exposure conditions. As these conditions are not well known, the International Study must rely on expert estimations. This paper describes a method to assess the proportion of the dose from photons in three energy ranges (< 100, 100-300, > or = 300 keV) using the responses under filters of a multi-element dosemeter. The method was tested on experimental and simulated data and provides a good estimate of the proportion of dose from photons below 100 keV, the most critical for dosemeter response. It was applied to personnel readings in one facility, confirming the experts' estimation. Beyond the International Study, the method has implication for the monitoring and protection of workers.
Female↗
Problems in home monitoring of blood glucose.
Two hundred and forty blood glucose readings were made on 5 Glucochek machines by 2 different operators. The results on all machines correlated poorly with equivalent results from an automatic glucose analyser with major discrepancies at all glucose concentrations. There was a wide gap in performance between the 2 operators. Analysis of variance suggested that errors were not only due to inter-operator and inter-machine differences. Possible sources of error were shown to include time of reaction and the amount of blood on Dextrostix. Dextrostix colour changes measured by eye were as accurate as those by Glucochek without the rogue values found at higher glucose concentrations with Glucochek.
Blood Glucose↗
Pitfalls in clinical staging of bladder tumors.
Errors in clinical staging of bladder carcinoma occur in about 50 per cent of patients. Sources of error include (1) a variable assortment of diagnostic studies performed, (2) inexactitudes inherent in the diagnostic measures employed, (3) insufficient corroboration by surgical and pathologic staging, (4) the lack of a satisfactory means for detecting micrometastases, and (5) a generalized confusion regarding the multiple classifications available for clinical staging. More precise clinical staging will be influential in treatment decision-making and in prognosis. Minimum requirements for clinical staging of the primary tumor currently include complete examination, excretory urography, cystoscopy, bimanual examination under anesthesia, and transurethral resection or biopsy. Polycystography, triple contrast cystograpy and arteriography may be helpful occasionally to document muscle invasion. Pedal lymphangiography and lymphography can in selected cases be helpful in detecting otherwise silent nodal involvement in spite of its inability to demonstrate many primary or regional lymph nodes. Familiarity with the above diagnostic options and the advantages and limitations of each is essential for each physician caring for a patient with bladder carcinoma. Conversion to TNM classification for bladder carcinoma that is similar to that of the UICC seems appropriate (1) because of its more rational approach to extent of involement by primary tumor, lymph node and distant sites, and (2) in order for our western hemisphere urologists to communicate better with our colleagues from around the globe. Such a system is now under consideration by a subcommittee of the American Joint Committee on Staging and End Result Reporting.
Aged↗
Errors in the certification of neonatal death.
OBJECTIVE: To examine the precision of the perinatal death certificate (PDC) and ascertain the possible sources of error in the certification of neonatal deaths. METHODS: The 'Main' and 'Other' causes of death recorded on the PDC were obtained from the Registry of Births, Deaths and Marriages and compared with those from a clinicopathological summary (CPS) completed after all pending laboratory results and/or autopsy information were available. RESULTS: There were 179 neonatal deaths during the 7 year period under review. The PDC and CPS main causes of death were concordant in 103 of 179 infants (58%) and discordant in the remaining 76 infants (42%). The PDC main cause of death was incorrectly classified in 61 of 76 infants (80%) with discordant findings and was incompletely classified in the remaining 15 infants (20%). The following discordancies were recorded for the 61 infants with an incorrect classification: (i) transposition of the 'Main' and 'Other' causes of death, resulting in a sequencing discordancy in 14 infants (23%); (ii) recording a non-pathological condition as the main cause of death in 40 infants (66%); and (iii) recording an incorrect pathological condition as the main cause of death in seven infants (11%). Eight of the 61 (13%) incorrect classifications and four of the 15 (27%) incomplete classifications were associated with laboratory and/or autopsy data being unavailable when the PDC was completed. CONCLUSIONS: The concordancy between the PDC and CPS would have increased from 58 to 91% if the 'Main' and 'Other' causes of death had been sequenced correctly, if the main cause of death had been ascribed to a pathological disease rather than a non-pathological condition and if corrective information from pending laboratory tests and/or autopsy examination had been made available to the Registry of Births, Deaths and Marriages.
Cause of Death↗
Potential errors and their prevention in operating room teamwork as experienced by Finnish, British and American nurses.
This study describes how the potential sources of errors and error prevention in operating room (OR) teams are experienced by Finnish, American and British nurses. The data were collected by interviews and analysed using a qualitative content analysis. Results consisted of categories demanding teamwork practice, shared responsibility in teams and organized teamwork. The demanding practice category included fear of errors, turnover in teams, overtime work and emotional distress as potential factors leading to errors in OR teamwork. Shared responsibility emphasized how the familiar teams, safety control and formal documentation of errors prevented errors. At the organizational level, the prevention of errors required scheduling of work, good management, competency and a reasonable physical environment. In order to improve safety in OR teams, recognition should be given to the balance of error-making and learning from them. More effective ways in reporting incidents should be adopted and overall reporting systems should be developed in Finnish OR teams.
Adult↗
The effect of the evanescent wave upon acoustic measurements in the human ear canal.
When making acoustic measurements in a human ear canal, it is often necessary to monitor the output of a sound source with a microphone positioned within a few millimeters of that sound source. This microphone will not only measure the pressure due to the propagated acoustic wave, which we wish to measure, but also the pressure due to the evanescent wave. The pressure due to the evanescent wave can be viewed as a source of error in the measurement of the propagating acoustic wave. This paper attempts to quantify the magnitude of this error. Theoretical predictions are made of the relative level of the evanescent sound pressure in a number of source and microphone arrangements applicable to ear canal measurements. It is shown that these theoretical predictions represent an upper limit of evanescent sound pressure that can be measured experimentally. The maximum measurement error due to the presence of the evanescent wave in human ear canals below 10 kHz is predicted to be 3 dB in adults and 1.3 dB in 1 month old infants, when the loudspeaker and microphone ports are spaced more than 2 mm apart.
Acoustic Stimulation↗
Optimal control for an above-knee prosthesis with two degrees of freedom.
Our previous research and clinical tests of a self-contained powered above-knee prosthesis (AKP) showed that a knee joint with one degree of freedom (DOF) increases the energy cost of walking with respect to able-bodied subjects. Better symmetry of the gait can improve performance, so we suggest here the integration of a second powered DOF into the knee joint mechanism to control the internal-external rotation of the shank-foot complex. The control for the AKP with two DOFs is based on a method of optimal tracking. The data used for analysis were collected in able-bodied subjects braced with an ankle splint to experimentally duplicate a gait like that of amputees using a two-DOF prosthesis. The simulation showed the following: (1) the technique of optimal programming can be used for simulation of the artificial leg during locomotion; (2) the optimal tracking method is an efficient tool for selection of actuators for the above-knee prosthesis, ensuring that the tracking remains within limits. Limitation of joint torque is desirable in order to reduce the size of the motor, but beyond a certain point limiting maximal torques lead to tracking errors that are associated with higher energy costs and hence the need for a larger power source. The errors are also associated with higher forces at the interface between the socket and the prosthesis. The optimal tracking method allows the optimization of tracking with constraints on the size of the motor used and its energy cost.
Adult↗
Degeneration and height of cervical discs classified from MRI compared with precise height measurements from radiographs.
STUDY DESIGN: Descriptive study comparing MRI classifications with measurements from radiographs. OBJECTIVES: 1. Define the relationship between MRI classified cervical disc degeneration and objectively measured disc height. 2. Assess the level of inter- and intra-observer errors using MRI in defining cervical disc degeneration. SUMMARY OF BACKGROUND DATA: Cervical spine degeneration has been defined radiologically by loss of disc height, decreased disc and bone marrow signal intensity and disc protrusion/herniation on MRI. The intra- and inter-observer error using MRI in defining cervical degeneration influences data interpretation. Few previous studies have addressed this source of error. The relation and time sequence between cervical disc degeneration classified by MRI and cervical disc height decrease measured from radiographs is unclear. METHODS: The MRI classification of degeneration was based on nucleus signal, prolaps identification and bone marrow signal. Two neuro-radiologists evaluated the MR-images independently in a blinded fashion. The radiographic disc height measurements were done by a new computer-assisted method compensating for image distortion and permitting comparison with normal level-, age- and gender-appropriate disc height. RESULTS/CONCLUSIONS: 1. Progressing disc degeneration classified from MRI is on average significantly associated with a decrease of disc height as measured from radiographs. Within each MRI defined category of degeneration measured disc heights, however, scatter in a wide range. 2. The inter-observer agreement between two neuro-radiologists in both defining degeneration and disc height by MRI was only moderate. Studies addressing questions related to cervical disc degeneration should take this into consideration.
Adult↗
A needle tracking device for ultrasound guided percutaneous procedures.
A novel tracking device is proposed for measuring the position and orientation of a needle with respect to an ultrasound probe. This device is intended to guide an operator during a percutaneous needle insertion so that the needle trajectory can be visually aligned with the target before insertion. The tracking device uses a pair of cameras to track the needle location so that a standard needle can be used without attaching a separate sensor to the needle. The main challenge is to calibrate the tracking system with sufficient accuracy. Calibration methods are described for each of the system parameters. A series of tests show that an overall error of 3.1 +/- 1.8 mm is achieved with two commercial cameras and an error of 6.5 +/- 5.7 mm is achieved with two inexpensive consumer cameras. An analysis of the source of errors reveals that the errors arise from all of the calibration steps. Overall system accuracy is therefore determined by both the quality of the cameras and the performance of calibration.
Biopsy, Needle↗
A confirmation of the general relativistic prediction of the Lense-Thirring effect.
An important early prediction of Einstein's general relativity was the advance of the perihelion of Mercury's orbit, whose measurement provided one of the classical tests of Einstein's theory. The advance of the orbital point-of-closest-approach also applies to a binary pulsar system and to an Earth-orbiting satellite. General relativity also predicts that the rotation of a body like Earth will drag the local inertial frames of reference around it, which will affect the orbit of a satellite. This Lense-Thirring effect has hitherto not been detected with high accuracy, but its detection with an error of about 1 per cent is the main goal of Gravity Probe B--an ongoing space mission using orbiting gyroscopes. Here we report a measurement of the Lense-Thirring effect on two Earth satellites: it is 99 +/- 5 per cent of the value predicted by general relativity; the uncertainty of this measurement includes all known random and systematic errors, but we allow for a total +/- 10 per cent uncertainty to include underestimated and unknown sources of error.
Journal Article↗
Evaluation of layer decomposition for multiframe quantitative coronary angiography.
Multiframe quantitative coronary angiography is typically performed by averaging measurements of artery diameter over multiple frames. This approach reduces errors attributable to random noise but may not reduce systematic errors caused by background structures, nonlinear system response, and motion blur. We attempt to reduce these sources of error by decomposing the image sequence into moving layers, one of which includes the artery. We embed simulated arteries into clinical angiographic sequences so that the true vessel dimensions are known accurately. The measurement tasks are minimum diameter, geometric percent stenosis, and densitometric percent stenosis. We compare measurements for single and multiple raw images, single images with fixed mask subtraction, single and multiple images with layered background subtraction, and time-averaged layer images. We find that both multiframe averaging and layer decomposition significantly improve geometric and densitometric accuracy compared with single-frame measurements. The best results were obtained by averaging measurements from multiple frames of layered background-subtracted images.
Algorithms↗
Variation in administration of cyclophosphamide and mesna in the treatment of childhood malignancies.
The objective of this study was to describe the variation in preparation and administration of cyclophosphamide, mesna, and hydration for the treatment of childhood malignancies within clinical trial protocol documents. All cyclophosphamide-containing cooperative group (Pediatric Oncology Group) protocols that were open at Dana-Farber Cancer Institute in April 1998 were evaluated. Among the 14 active protocols, there were 23 unique cyclophosphamide regimens. Marked variation existed in infusion rate, fluid type, and volume used for admixing cyclophosphamide and mesna, as defined in the "Treatment" section of the protocols that we evaluated. Further variation was found in the type, amount, and rate of infusion of prehydration and posthydration fluid. Internal inconsistency existed within the protocols pertaining to the administration methods described in the "Agent Information," "Treatment," and "Consent" sections of the written documents. Clinical trial protocol documents serve as reference material for health care providers who prescribe, dispense, and administer protocol chemotherapy. Misinterpretation of protocol documents and clinician orders are contributing factors in serious and deadly medication errors. Internal inconsistency within protocol documents and variation in drug administration across protocols is a potential source of error. We recommend improved accuracy, clarity, and internal consistency of protocol documents to improve patient safety and compliance with protocol specifications. In addition, the use of standard concentrations, volumes, and methods of administration of chemotherapeutic agents and accompanying fluids is recommended.
Antineoplastic Agents, Alkylating↗
Semantic features of an enterprise interface terminology for SNOMED RT.
OBJECTIVE: To evaluate the utility of SNOMED RT in support of a natural language interface for encoding of clinical assessments. METHOD: Using a random sample of clinical terms from the UNMC Lexicon, I mapped the terminology into canonical data entries using SNOMED RT. Working from the source term language, I evaluated lexical mapping to the SNOMED term set, and the function of the SNOMED RT semantic network in support of a language-based clinical coding interface. RESULTS: Ambiguity in the source terms was low at 0.3%. Lexical (language-based) mapping could account for only 48.8% of meaning from the source terms. The RT semantic network accounted for 39.5% of meaning, and supplementing the lexical map this led to 80.2% capture of source content. Error rates in the segment of RT which I reviewed were low at 0.6%. 97.6% of source content could be accurately captured in SNOMED RT. CONCLUSION: SNOMED RT supported an accurate and reliable representation of clinical assessment data in this sample. The semantic network of RT substantially enhanced the encoding of concepts relative to lexical mapping. However these data suggest that natural language encoding with SNOMED RT in an enterprise environment is unlikely at this time.
Natural Language Processing↗
[Sampling problems in the population census of 1990].
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Censuses↗