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PubMed2005

The role of second opinion pathology in the management of lesions of the head and neck.

PURPOSE OF REVIEW: Medical error is a common problem, and its human cost in terms of disability, suffering, and death is stunning. Steps toward reducing medical error will require the identification of mistake-prone practices within a complex health care system. Erroneous pathologic diagnosis has been identified as one source of error. This review was undertaken to assess the magnitude of diagnostic imprecision in lesions of the head and neck, and to address the validity of mandatory review of pathology material for patients who are referred from one institution to another for management of tumors involving the head and neck. RECENT FINDINGS: Mandatory second opinion pathology consistently uncovers discrepancies across all major organ systems and has a profound impact on management and prognosis. Site-specific studies have implicated the head and neck as a high-risk area that is prone to diagnostic error. Diagnostic discrepancy rates have ranged from 1 to 53% for surgical pathology studies and from 17 to 60% for cytopathology studies. Major changes (affecting treatment or prognosis) occur in 5 to 7% of surgical pathology cases. The thyroid is consistently identified as a site that is particularly prone to diagnostic discrepancies; and no specific head and neck sites are immune to diagnostic error. SUMMARY: Limited studies addressing the site-specific impact of second opinion pathology implicate the head and neck as a high-risk area that is prone to major changes in diagnoses. Accordingly, mandatory second opinion pathology makes good clinical and risk management sense for all patients referred to head and neck surgery or oncology services before a major therapeutic endeavor is undertaken.

Head and Neck Neoplasms↗
PubMed1977

A new method for internal calibration of left ventricular cineangiography.

Previous methods of internal calibration for cineangiography have made use of reference objects such as catheters or wires of known length or diameter. Such devices have either insufficient X-ray resolution, or require a specific orientation within the ventricle which is difficult to confirm. External calibration methods, while eliminating these errors, can only estimate actual position of the left ventricle. The use of a Swan-Ganz balloon catheter as a calibration object diminishes these problems. When positioned within the left ventrical and filled with a radiopaque medium, the balloon is of sufficient size and density to avoid errors induced by previously employed objects. The inflated balloon geometry is simple and reproducible. The use of this internal calibration catheter markedly diminishes major sources of errors in the determination of ventriculograms for both dogs and humans.

Animals↗
PubMed1997

Pointing at memorized targets during prolonged microgravity.

BACKGROUND: Watt et al. (15) and Young et al. (17) have demonstrated that during prolonged microgravity, large errors can be made when pointing at memorized targets in the absence of vision. However, those experiments could not distinguish between errors caused by not knowing where the arm was pointed and errors caused by not knowing target location. The primary goal of this study was to determine the relative contribution of each of these potential sources of error. HYPOTHESIS: It was hypothesized that pointing errors would be greater than pre-flight controls if vision was continuously absent during testing, but not greater than pre-flight if vision was restricted only while pointing. METHODS: Five subjects on Spacelab SLS-2 (Part A) pointed at targets while keeping their eyes closed continuously; (Part B) touched various body parts and estimated the position of their arms while the eyes remained closed; and (Part C) pointed at the same targets as in A but closed their eyes only while pointing. RESULTS: On the ground, if the eyes were closed only while pointing, pointing errors averaged 4.5 degrees. After several days n space, errors averaged 7.0 degrees (p < 0.05). Again on the ground, if the eyes were closed continuously while pointing, an additional error of 4.0 degrees was measured. However, after several days in space, the additional error was 10.5 degrees (p < 0.0005). CONCLUSIONS: The results of this study suggest that the major problem encountered when pointing at memorized targets in microgravity is a lack of knowledge of target, not limb, position.

Adaptation, Physiological↗
PubMed1984

Quantitation and the elimination of errors in bile reflux tests using a gamma camera.

Entero-gastric reflux may be assessed quantitatively using 99mTc HIDA and a gamma camera. We have devised a computer program which applies corrections for several sources of error. The technique was validated using naso-gastric aspiration and phantom experiments. In 23 patient studies, 13 patients considered not to show reflux by visual assessment had a mean percentage injected dose (PID) in the stomach of 1.9% before correction and less than 1% after correction. The 10 patients with reflux showed a fall of PID from 5.8% to 1.7% as a result of the correction. In 14 patients the mean PID in the stomach after computer correction (3%) was not significantly different from that (3.5%) measured by aspiration. Computer correction of bile reflux data is essential when attempting to quantify the amount of entero-gastric reflux using a gamma camera.

Bile Reflux↗
PubMed1977

Radiation scattering and the determination of regional cerebral blood flow by radioisotope clearance.

The sources of error involved in the measurement of regional cerebral blood flow (rCBF) with radioactive tracers in man have been studied. This report shows that one of the main sources is the weakness of the energy emitted by the tracers used. Clearance curves obtained with scalp detectors are subject to interference: the radiation measured originates not only in the region studied but also, by scattering, from the rest of the brain. Because of the weak energy levels involved, the scattered radiation contributes significantly to the total measured radiation, and for the same reason it is impossible to distinguish clearly the scattered radiation from that arriving directly. These systematic errors in rCBF measurements were studied quantitatively by in vitro tests and computer simulation, and limits were established for resulting alterations of all varialbes determined (grey and white matter flow, mean flow, compartment weight). It was concluded that the biologic origin of a modification of rCBF can be affirmed only in the case of changes of at least 10%.

Cerebrovascular Circulation↗
PubMed1990

Errors in DNA synthesis: a source of spontaneous mutations.

Spontaneous mutations in somatic cells may engender several pathologic processes, including cancer. The sources of these mutations remain to be established. We present a conceptual framework in which to analyze the sources of spontaneous mutations and focus here on 3 endogenous processes that have the potential to generate spontaneous sequence alterations in DNA. These are: replication errors, depurination of DNA, and damage to DNA by the generation of active-oxygen species. Each of these processes occurs more frequently than the rate of mutagenesis in somatic cells, but are repaired by different and overlapping mechanisms. Model systems are being developed to determine the spectrum of mutations produced by each of these processes in vitro. A comparison of these spectra with the overall spectrum of spontaneous mutations in somatic cells may help to determine the contribution of each of these processes to spontaneous mutation.

Animals↗
PubMed1984

Is peripheral arterial pressure a satisfactory substitute for ascending aortic pressure when measuring aortic valve gradients?

Substitution of peripheral arterial pressure for ascending aortic pressure is a common but poorly validated practice in the assessment of aortic valve gradients by catheterization. The accuracy of this practice was assessed by comparing the left ventricular-ascending aortic mean gradient in 26 cases of aortic stenosis with the left ventricular-femoral artery gradient, both with and without compensation for temporal delay in femoral artery pressure. Aligned left ventricular-femoral artery gradients (matching upstrokes to compensate for peripheral time delay) underestimated the left ventricular-ascending aortic gradient by 10 mm Hg (range 0 to -17). Unaltered simultaneous left ventricular-femoral artery gradients overestimated the left ventricular-ascending aortic gradient by an average of 9 mm Hg (range +1 to +18). For both peripheral techniques, the error was relatively constant throughout the range of aortic valve gradients. The most accurate estimate of both aortic valve gradient and area was obtained by averaging the gradients and areas derived from aligned and unaltered left ventricular-peripheral arterial simultaneous tracings. Although only occasionally critical for clinical decision-making, these errors may be overwhelming in certain types of research applications, such as comparisons of valve prosthesis gradients and serial evaluations of aortic stenosis. An additional source of error is a coexistent peripheral arterial gradient that was present in 21% of otherwise technically suitable patients in the screened study group.

Aorta↗
PubMed1993

IOL power mislabelling.

Prompted by four cases of IOL power mislabelling, a method was developed which allowed the measurement of the IOL power using a keratometer. The principle of operation was to measure the curvature of the steepest surface of the IOL through a minus lens by which the size of the mires was brought into the measuring range of the keratometer. With this method the IOL power was checked in three random IOL samples from three companies. Although no large errors in IOL power labelling were encountered in these samples, the error of labelling was found to differ significantly between the companies. It was concluded, that poor manufacturing control of IOL power may add to the sources of error in IOL power prediction.

Aged↗
PubMed1987

Reconstructing the rate of appearance of subcutaneous insulin by deconvolution.

In this paper a deconvolution scheme is presented to reconstruct the rate of appearance of subcutaneously injected insulin. Relevant aspects of experiment design are briefly described. Intravenous insulin kinetics are modeled to determine the impulse response of the system. The deconvolution problem is not ill conditioned and is solved using a least-squares method without imposing constraints on the input. An estimate of the error of the reconstructed input is provided. The reliability of the deconvolution scheme is tested by means of an independent validation study. Finally, the different sources of error that affect the method are discussed, and a figure of the global error is derived.

Humans↗
PubMed1990

Automated differentials in the hematology laboratory.

The white blood cell differential continues to be one of the most widely performed clinical laboratory procedures. However, its clinical usefulness is affected by sampling error and, to some extent, by classification criteria. It is also labor intensive and expensive to perform. Automated leukocyte differential instrumentation addresses many of the sources of error that occur with the manual differential. Current state-of-the-art instrumentation will give results that equal or exceed the routine manual differential. Because these instruments also examine red blood cell and platelet parameters, as well as providing white blood cell information, they can better screen for significant abnormalities as well as greatly reduce the expensive and time-consuming manual differential procedures.

Automation↗
PubMedDate not supplied

Prenatal diagnosis of sickle cell anemia and beta-thalassemia by amniocentesis.

Prenatal diagnosis by amniocentesis alone is possible for about 90% of pregnancies at risk for sickle cell anemia and about 70-75% of pregnancies at risk for beta-thalassemia. It should be stressed that to obtain these percentages, a previous homozygous normal or affected child or, alternatively, the couple's parents are needed to confirm the linkage of variant genes to respective DNA markers (polymorphic restriction sites). Families at risk should be studied prior to or early in pregnancy to determine whether these methods will be applicable to their specific case. If appropriate markers are identified and their linkage to the genes being studied is verified, then prenatal diagnosis by amniocentesis can be done at 16-18 weeks; and for these couples, fetoscopy, with its increased risk of fetal loss, can be avoided. The change of errors in diagnosis due to crossing-over between the mutant gene and the linked marker is small. The probability of such a recombination between the beta-globin gene and the polymorphic G gamma Hind III or the 3' Hpa I site is 1/3,000 and 1/14,000 per generation, respectively (13). A more serious problem is non-paternity because of the errors caused in linkage analysis. Improved methods to enable direct detection of the beta S and/or beta thal mutations would remove both of these potential sources of error.

Amniocentesis↗
PubMed1976

[The influence of training on the accuracy of roentgenographic cephalometric tracings (author's transl)].

The accuracy in landmark identification and in the determination of angular and linear measurements used in cephalometric analysis on lateral head film were statistically evaluated comparing operators with different levels of competence. The observed magnitude of methodological error was depending on - prior experience of the investigator - individual radiographic anatomical knowledge - rigour of landmark definition and - accuracy of the tracing procedure. Considering these sources of error some of the variability in the present investigation might be avoided by systematic instructions. In order to decrease the variation in landmark location the reproducibility of some points must be further improved by redefining them in their verbal assessments. From an educational point of view the correlation between individual radiographic anatomical knowledge and the magnitude of error in cephalometric analysis should be considered with particular emphasis.

Cephalometry↗
PubMed1983

Optimum fourier filtering of cardiac data: a minimum-error method: concise communication.

Random fluctuations limit the accuracy of quantities derived from cardiac time-activity curves (TACs). To overcome this problem, TACs are often fitted with a truncated Fourier series giving rise to two sources of error: (a) the truncated series may not adequately describe the TAC shape, causing errors in parameters calculated from the fit: and (b) successive TACs acquired from the same subject under identical circumstances will fluctuate due to limited counts, causing the Fourier fits (and parameters derived from them) to fluctuate. These two errors, respectively, decrease and increase as the number of harmonics increases, suggesting the existence of a minimum in total error. This number of harmonics for minimum error (NHME) was calculated for each of six common parameters used to describe LV TACs. The "true" value of each parameter was determined from TACs of very high statistical precision. Poisson noise was added to simulate lower count rates. For low-count TACs, use of either a smaller or a larger number of harmonics resulted in significantly greater error. NHME was found to occur at two harmonics for the systolic parameters studied, regardless of the noise level present in the TAC. For diastolic parameters, however, NHME was a strong function of the noise present in the TAC, varying from three harmonics for noise levels typical of regional TACs, to five or six harmonics for high-count global TACs.

Diastole↗
PubMed1975

[Serum dixogin determination. Clinical significance, results and error consideration based on comparative studies with different radioimmunoassays].

In order to compare 5 different radioimmunoassays (RIA's) and their results we determined the digoxin concentration in the serum of 186 patients and point out some sources of error. We consider the following points important: 1. There were found varying results in the determination of digoxin concentration in patient's sera using different RIA's. 2. One of the essential reasons for these differences are discrepancies of the RIA standards which belong to each kit. 3. It should be required that the control standard is equal to all RIA's. 4. Each laboratory which carries out digoxin determinations should, in collaboration with the clinic, work out and announce its own guide-line values for the RIA used in regard to the optimal therapeutic range and also to overdoses.

Cross Reactions↗
PubMed1975

A critical evaluation of sonar "crown-rump length" measurements.

In a study to evaluate the reproducibility and accuracy of the sonar technique of measurement of the in vivo fetal crown-rump length (Robinson, 1973), a series of in vivo and in vitro experiments was performed in which the random and systematic errors inherent in the technique were assessed. The potential sources of random error were those of operator judgement, movement of the fetus and mother, machine sensitivity settings and measurement from the photograph; while the sources of systematic error were those of oscilloscope scale factor, and velocity calibration inaccuracies, and the effect of beam width. The overall effect of the random errors, that is, the reproducibility of the technique, was assessed in an in vivo blind trial in which three independent measurements were made of the fetus. In a series of 30 experiments the average standard deviation of the three readings was found to be 1.2 mm. Evaluation of the systematic errors by in vivo experimentation, on the other hand, showed that the basic sonar measurements were in error by an overestimate of 1 mm for the beam width effect and 3.7 per cent for the scale factor and velocity calibration errors. A weighted non-linear regression analysis of 334 measurements was performed in order to obtain a "curve of best fit" for the period covering 6 to 14 weeks of menstrual age. The values obtained were corrected for the systematic errors and compared with widely quoted anatomical figures. In the second part of this investigation the original data was further analyzed to determine on a statistical basis the accuracy of the technique as a method of estimating maturity. It was shown that such an estimate could be made to within 4.7 days with a 95 per cent probability on the basic of a single measurement, and to within 2.7 days if three independent measurements were made.

Anthropometry↗
PubMed1995

Quantitative endoscopic classification of esophagitis by means of computerized image processing. Part 1: Theoretical background.

The potential sources of error for quantitative mapping of pathological areas in tubular organs are investigated mathematically and discussed. The first of the main errors stems from a predominance of red in the illuminating light reflected and re-reflected from the side wall of the tubular organ as compared with the white illuminating light coming directly from the light source in the endoscope. A mathematical model for this has been constructed to define an allowed interval of observation distance. The second error is due to geometrical projection, and results from the fact that more distant parts of the inside of a tube subtends a smaller solid angle than closer parts.

Esophagitis↗
PubMed1992

Amniotic fluid volume assessment: comparison of ultrasonographic estimates versus direct measurements with a dye-dilution technique in human pregnancy.

OBJECTIVE: The purpose of our study was to compare the accuracy of clinical ultrasonographic techniques of amniotic fluid volume assessment with a dye-dilution technique. STUDY DESIGN: We compared amniotic fluid volume as measured by ultrasonographic techniques with a dye-dilution method in 50 women undergoing amniocentesis during the third trimester. Thirteen separate ultrasonographic techniques, including the amniotic fluid index, were evaluated with regression analysis. RESULTS: Amniotic fluid volumes as determined by dye-dilution ranged between 129 and 4444 ml. The amniotic fluid index overestimated the actual volume by as much as 88.7% at lower volumes and underestimated the actual volume by as much as 53.9% at higher volumes. CONCLUSIONS: Differences in measurement error between the other ultrasonographic methods and the amniotic fluid index did not appear to be sufficient to warrant changes in current clinical practice. A major source of error in ultrasonographic amniotic fluid volume assessment is that one-dimensional measurements are used to estimate the volume of a complex, three-dimensional object.

Amniotic Fluid↗
PubMed1999

Pitfalls in Doppler evaluation of diastolic function: insights from 3-dimensional magnetic resonance imaging.

Ultrasound-Doppler assessment of diastolic function is subject to velocity errors caused by angle sensitivity and a fixed location of the sample volume. We used 3-dimensional phase contrast magnetic resonance imaging (MRI) to evaluate these errors in 10 patients with hypertension and in 10 healthy volunteers. The single (Doppler) and triple (MRI) component velocity was measured at early (E) and late (A) inflow along Doppler-like sample lines or 3-dimensional particle traces generated from the MRI data. Doppler measurements underestimated MRI velocities by 9.4% +/- 8.6%; the effect on the E/A ratio was larger and more variable. Measuring early and late diastolic inflows from a single line demonstrated the error caused by their 3-dimensional spatial offset. Both errors were minimized by calculating the E/A ratio from maximal E and A values without constraint to a single line. Alignment and spatial offset are important sources of error in Doppler diastolic parameters. Improved accuracy may be achieved with the use of maximal E and A velocities from wherever they occur in the left ventricle.

Adult↗