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PubMed1997

Is congruence between data partitions a reliable predictor of phylogenetic accuracy? Empirically testing an iterative procedure for choosing among phylogenetic methods.

The relationship between phylogenetic accuracy and congruence between data partitions collected from the same taxa was explored for mitochondrial DNA sequences from two well-supported vertebrate phylogenies. An iterative procedure was adopted whereby accuracy, phylogenetic signal, and congruence were measured before and after modifying a simple reconstruction model, equally weighted parsimony. These modifications included transversion parsimony, successive weighting, and six-parameter parsimony. For the data partitions examined, there is a generally positive relationship between congruence and phylogenetic accuracy. If congruence increased without decreasing resolution or phylogenetic signal, this increased congruence was a good predictor of accuracy. If congruence increased as a result of poor resolution, the degree of congruence was not a good predictor of accuracy. For all sets of data partitions, six-parameter parsimony methods show a consistently positive relationship between congruence and accuracy. Unlike successive weighting, six-parameter parsimony methods were not strongly influenced by the starting tree.

Animals↗
PubMed1995

Establishing the relative accuracy of three new definitions of the adult respiratory distress syndrome.

OBJECTIVES: Over the last few years, new definitions of the adult respiratory distress syndrome (ARDS) have been introduced that potentially identify patients earlier in their course of acute lung injury. However, these definitions have never been compared with any of the older and potentially stricter definitions of ARDS to determine if similar patients are eventually identified. We compared new definitions of ARDS--as represented by the Lung Injury Score, a modified Lung Injury Score, and the American-European Consensus Conference definition--against a stricter definition of ARDS to determine their accuracy. DESIGN: Prospective. SETTING: Intensive care unit (ICU) patients in a tertiary, university-affiliated city hospital. PATIENTS: ICU patients with clearly defined at-risk diagnoses for ARDS (group 1, n = 111) and general medical ICU patients without clearly defined at-risk diagnoses for ARDS (group 2, n = 125). MEASUREMENTS AND MAIN RESULTS: Measurements of hypoxemia, static respiratory system compliance, positive end-expiratory pressure, radiographic changes, and general demographic information were collected. The sensitivity, specificity, positive-predictive value, negative-predictive value, and accuracy of all three new definitions were determined. Accuracy was defined as the true-positive plus the true-negative results divided by the total number of patients. When compared with a stricter definition of ARDS, all three definitions maintained a high degree of accuracy in those patients with a clearly defined at-risk diagnosis (group 1): Lung Injury Score 90.0% (95% confidence interval 84-96); modified Lung Injury Score 97.3% (95% confidence interval 94-100), and the American-European Consensus Conference definition 97.3% (95% confidence interval 94-100). For these at-risk patients, the accuracy of the modified Lung Injury Score and the American-European Consensus Conference definition was significantly better than the Lung Injury Score when compared with the strict definition (p = .027 for both comparisons). Although all three definitions maintained an accuracy of > 90% for general medical ICU patients (group 2), the low frequency of ARDS in these patients (3.4%) produced a low positive-predictive value for all three definitions. CONCLUSIONS: We conclude that the Lung Injury Score, the modified Lung Injury Score, and the American-European Consensus Conference definition identify similar patients, provided that these methods are applied to patients with clearly defined at-risk diagnoses for ARDS.

Adult↗
PubMedDate not supplied

Preoperative staging accuracy of multidetector row computed tomography for extrahepatic bile duct carcinoma.

PURPOSE: This study sought to evaluate the accuracy of multidetector computed tomography (MDCT) for preoperative staging of extrahepatic bile duct (EHD) carcinoma and to assess the value of coronal reformations from isotropic voxels. MATERIALS AND METHODS: Thirty patients with surgically proven EHD cancer underwent dynamic MDCT with coronal reformation. Two experienced radiologists independently evaluated contrast-enhanced dynamic transverse CT images (axial approach) and combined transverse and coronal images (combined approach). The radial extent (TNM staging) and the vertical extent of tumors were assessed and correlated with pathological findings of surgical specimen. RESULTS: All of primary tumors were detected by axial and combined CT imaging (100%). Overall accuracy of the T staging was 73% (22/30) with axial and 77% (23/30) with combined CT imaging (P>0.05). The accuracy of N staging was 57% (17/30) with axial and 63% (19/30) with combined CT imaging (P>0.05). The accuracy of M staging was 97% (29/30) with both axial and combined CT imaging. Upper margin accuracy was 97% (29/30) for axial and 100% for combined CT imaging (P>0.05), whereas that of the lower margin was 90% (27/30) for axial and 93% (28/30) for combined CT imaging (P>0.05). CONCLUSIONS: Multidetector computed tomography was sufficiently accurate for evaluating the vertical extents, but radial extents of EHD cancer. The addition of coronal reformatted images did not improve the accuracy for staging of EHD cancer.

Adult↗
PubMed2001

Comparison of frameless stereotactic systems: accuracy, precision, and applications.

OBJECTIVE: Frameless stereotactic systems have become an integral part of neurosurgical practice. At our center, we recently introduced for clinical use a small, portable, frameless stereotactic system, namely the Cygnus PFS system (Compass International, Rochester, MN). The purpose of this study was to compare the accuracy of the Cygnus PFS system with that of two larger systems that are also currently in use at our institution, i.e., the SMN system (Zeiss, Oberkochen, Germany) and the ISG viewing wand (ISG Technologies, Toronto, Canada). These systems represent three kinds of frameless stereotactic technologies that are commercially available. Each system uses a different method of spatial localization, i.e., mechanical linkage (ISG system), magnetic field digitization (Cygnus system), or optical technology (SMN system). METHODS: Using a stereotactic "phantom," we measured the accuracies of all three systems with identical data sets. The errors in localization in three-dimensional space for nine targets were calculated by using 10 magnetic resonance imaging data sets. The precision of each system was also calculated. RESULTS: With this experimental protocol, the Cygnus system attained a mean accuracy of 1.90 +/- 0.7 mm, the ISG viewing wand system a mean accuracy of 1.67 +/-0.43 mm, and the SMN microscope a mean accuracy of 2.61 +/- 0.99 mm. The precision values were not significantly different among the systems. CONCLUSION: We observed only small differences in accuracy and precision among these three systems. We briefly review the advantages and disadvantages of each system and note that other factors, such as portability, ease of use, and microscope integration, should influence the selection of a frameless stereotactic system.

Humans↗
PubMed1986

The accuracy of functional parameters extracted from ventricular time-activity curves by Fourier curve fitting: a simulation study.

The accuracy of functional parameters derived from multiple harmonic Fourier curve fitting of left ventricular time-activity curves (TACs) was assessed in simulated curves of exactly known characteristics. Curves were generated to represent TACs of equilibrium gated radionuclide ventriculography (ERNV) sampling at 16 frames cycle-1. Curves of varying shape and noise characteristics were studied. The number of harmonics used in the fitting process was variable, the number being determined by an automated 'goodness of fit' test based on the chi-squared test. The accuracy of measured peak ejection rate (PER) and peak filling rate (PFR) was independent of the shape of the curve, but the accuracy of the time to these slopes (TPER, TPFR) was dependent on the steepness of the slope. The accuracy of the measured parameters improved as the influence of noise decreased allowing more harmonics to be added. The values of PER and PFR in control subjects varied between individuals, and with heart rate. There was less variation in the ratio (PER/PFR) of the slopes between individuals, and the accuracy of the ratio was better than that of the individual values of PER and PFR. Functional parameters of predictable accuracy may be determined by Fourier curve fitting at the statistical quality of global or regional ventricular TACs derived from ERNV sampling at 16 frames cycle-1.

Fourier Analysis↗
PubMed1996

Accuracy and precision of the Tomey ViVA infrared photorefractor.

PURPOSE: The Fortune Optical (Tomey ViVA) VRB-100 video refractor was tested to determine its accuracy and precision in measuring manifest refractions of human eyes with and without cycloplegia. The specific issues addressed included its accuracy in measuring spherical and cylindrical refractive errors and its precision in refracting near emmetropia. METHODS: To determine its ability to measure moderate to high (> 4.00 D) myopia, we compared the VIVA's refractions to those taken by a Canon Autorefractor R1 and a retinoscopist. A spherical lens series from -7.00 to + 7.00 D at 1.00 D intervals, or -5.00 to + 5.00 at 0.50 D intervals, was placed over a subject's eye, which was then covered by an infrared (IR) filter, refracted, and analyzed to determine the VIVA's ability to measure spheres. Subjects with refractive errors of -2.00 to + 2.00 DS (diopters sphere) and 0 to 1.00 DC (diopters cylinder) were refracted 7 to 15 times during 1 sitting to determine the VIVA's precision. The instrument's accuracy in measuring cylinders was tested by placing + 3.00 to -3.00 D cylinders (at 0.50 D intervals) over the eyes of subjects at 0 degree, 45 degrees, 60 degrees, 75 degrees, 90 degrees, 105 degrees, 120 degrees, and 135 degrees. RESULTS: The VIVA measured spheres of +/- 3.00 D with a root mean squared (rms) error of 0.5 +/- 0.1 D. Beyond this power, its accuracy progressively worsened. In some subjects, irregular intensity profiles compromised the VIVA's accuracy even with low spherical refractive errors. The VIVA was very precise in measuring spheres from + 2.00 to -2.00 D and cylinders from 0 to 1.00 D. Although the ViVA adequately measured all cylinder powers at 0 degree and 90 degrees, the accuracy of cylindrical power measurement decreased with obliquity; only cylinders < or = 1.00 D magnitude were accurately measured at 45 degrees and 135 degrees. CONCLUSIONS: We conclude that, although the ViVA offers many attractive features for vision screening, it is seriously limited by its inability to property detect and measure oblique astigmatic errors.

Humans↗
PubMed1998

Evaluation of the EyeSys model II computerized videokeratoscope. Part II: The repeatability and accuracy in measuring convex aspheric surfaces.

PURPOSE: To evaluate the precision and repeatability of a Placido disc-based computerized videokeratoscope, using convex surfaces of varying eccentricities and apical radii designed to simulate the range of topographical variations of the human cornea, rather than the purely spherical surfaces used in most previous studies. METHODS: Form Talysurf analysis was used to verify the exact form of 12 Perspex convex surfaces. The EyeSys model II videokeratoscope was used to measure the sagittal radii of curvature twice at known points on each surface. The raw data tables were analyzed to assess the repeatability and accuracy for both central and peripheral points on each surface. The relationship between these factors and the eccentricity was investigated. RESULTS: For central radii the instrument showed high correlation (r = 0.996) between actual and measured values. There was a small instrumental bias of +0.042 mm and the 95% limits of agreement were narrow (+0.121 to -0.037 mm), indicating clinically acceptable accuracy. The accuracy decreased slightly as the p-value decreased (greater peripheral flattening). For peripheral radii, the overall accuracy compared well to central radii, with an average bias of +0.022 mm and maximum error in 95% of cases 0.083 mm (bias +1.96 x SD). However, for surfaces where p = 0.50, the bias was +0.049 and maximum error in 95% of cases 0.110 mm. Repeatability for the aspheric surfaces was shown to be high (SD +/- 0.01 mm in all quadrants). CONCLUSIONS: The accuracy of the EyeSys corneal analysis system (CAS) in measuring central and peripheral radius of curvature was shown to be dependent on the shape of the surface to be measured. For more rapidly flattening surfaces, a decrease in accuracy was found for both central and peripheral radius of curvature, which in clinical terms is thought acceptable.

Cornea↗
PubMed1999

Accuracy of the tomey topographic modeling system in measuring surface elevations of asymmetric objects.

BACKGROUND: Most studies have assessed the accuracy of videokeratographic systems using spheres, ellipsoids, or toric surfaces. Most human corneas are asymmetric to some degree and many pathological corneas are markedly asymmetric. To date, little work has been done to ascertain the accuracy of videokeratographic systems for measuring the shape of asymmetric objects. PURPOSE: The purpose of this study is to determine the accuracy with which the Tomey Topographic Modeling System can evaluate the topography of asymmetric surfaces. METHODS: Calibrated ellipsoidal test objects were tilted with respect to the videokeratometric axis to create asymmetric test surfaces with known characteristics. RESULTS: Root mean squared error of all the measured surface elevations varied from 0.7 microm to 11.3 microm. Although there was a trend for greater error with the more asymmetric surfaces, the trend was not statistically significant. Accuracy was not dependent on apical radius. Measurement error increased toward the periphery. CONCLUSIONS: For the Tomey Topographic Modeling System, the accuracy in measurement of smooth, asymmetric surfaces is comparable the accuracy in measurement of symmetric surfaces.

Cornea↗
PubMedDate not supplied

Triage accuracy at a multiple casualty incident disaster drill: the Emergency Medical Service, Fire Department of New York City experience.

We sought to evaluate the accuracy and speed for the triage of multiple patients during a disaster drill by Emergency Medical Service (EMS) personnel. During a disaster drill (train collision with blast injury and chemical release), the accuracy and speed of triage of 130 patient-actors by the Fire Department of New York City (FDNY) EMS personnel was evaluated using the Simple Triage and Rapid Treatment (START) triage system. All EMS personnel had been previously trained in START, but refresher training was not administered before the drill. Overall triage accuracy was 78%. In patients that had additional changes in their status during the triage process (injects), 62% were retriaged appropriately. Because of security and decontamination procedures, triage at the triage/treatment area began 40 minutes after the drill commenced. It took 2 hours and 38 minutes to completely clear the scene of all patients. On average, the time from the start of triage to transport was 1 hour and 2 minutes. Despite the fact that triage is a skill practiced by every EMS system in the country on a daily basis, few studies regarding triage accuracy are available. Limited data suggest that the triage accuracy rates using different triage strategy algorithms are approximately 45% to 55%. During this drill, FDNY-EMS triage accuracy using the START system exceeded these expectations. This study provides insight as to the triage experience of a large urban EMS system operating at a disaster drill.

Algorithms↗
PubMed2003

The accuracy of computed tomography in assessing cervical pedicle screw placement.

STUDY DESIGN: A blinded, prospective comparison of computed tomography scan accuracy for determining the location of cervical pedicle screw position in human cadavers. OBJECTIVES: To establish recommended computed tomography technique guidelines for assessing location of cervical pedicle screws. SUMMARY OF BACKGROUND DATA: A small number of studies have described the accuracy of roentgenography regarding the assessment of pedicle screw position. However, a few studies have investigated the accuracy of computed tomography in this respect. Ebraheim et al evaluated the relation of lateral mass screws to the nerve roots within the intervertebral foramen on oblique radiographs. No study has been undertaken, to our knowledge, to specifically define the reliability and validity of computed tomography scans in the case of cervical pedicle screw placement. METHODS: As a pilot study, 10 cadaveric cervical spines from another study with bilateral 3.5 mm titanium pedicle screws were scanned with 1.0 mm axial slices. After the scans were interpreted by three blinded readers, each panel member was "trained" with regard to individual accuracy. Ten more cadaveric cervical spines were instrumented with 3.5 mm titanium screws in each pedicle (C2-C7). The specimens were then scanned with a variety of computed tomography techniques, including spiral acquisitions at 1.0 mm, 1.0 mm + reconstruction, 2.5 mm, 5.0 mm slices, and the three-dimensional Stealth Station recipes. The specimens were dissected, and malpositioned screws were recorded and photographed by independent raters. The same three readers from the pilot study then read each new scan in random order. RESULTS: Reader accuracies in the pretraining pilot study were 74%, 68%, and 52%, with kappa coefficients of 0.49, 0.37, and 0.07, respectively, and significant intrarater variances (P = 0.014). After training, the accuracy rate improved significantly to 89%, 88%, and 85% in posttraining study, and the kappa coefficients were 0.81, 0.78, and 0.73, respectively. Kappa statistical analysis showed negligible interreader variance on the entire pivotal study except by the three-dimensional Stealth Station format. The overall mean kappa coefficients were 0.77, 0.75, and 0.73. Assessment of pedicle screw position was statistically inferior with 5.0 mm axial slices, in contrast to slices <3.0 mm. CONCLUSIONS: We demonstrated that reliance on computed tomography scan data in determining the misplacement of a pedicle screw is usually accurate given proper scan acquisition, presentation windows, and adequate reader training, but a clinically significant error rate remains. A conventional computed tomography scan should not be treated as a gold standard, particularly without regard to the readers' training.

Bone Screws↗
PubMed2004

Assessment of pedicle screw placement utilizing conventional radiography and computed tomography: a proposed systematic approach to improve accuracy of interpretation.

STUDY DESIGN: This was a human cadaver study to determine the accuracy of conventional radiography and computed radiography in the evaluation of pedicle screw placement and to identify methodology for more precise reading of these examinations. OBJECTIVES: To determine the accuracy of conventional radiography and computed tomography in the evaluation of pedicle screw placement within lumbar vertebral pedicles and to develop methods to improve imaging interpretation. SUMMARY OF BACKGROUND DATA: Conventional radiography and computed tomography have been used in research and clinical settings to evaluate pedicle screw placement. This study evaluates the interpretative accuracy of readers blinded to the true position of screw placement using both imaging examinations. Furthermore, methodology was developed to improve accuracy of interpretation of these examinations. METHODS: Three cadaver lumbar spines were instrumented bilaterally with pedicle screws from L1 to L5. Thirty pedicles had 6.0 mm AO pedicle screws inserted using standard surgical technique. Seven directions of deliberate misplacement as well as correct placement of screws were performed at random levels for a total of eight possible screw positions. Conventional radiographs and computed tomography scans were obtained. A senior musculoskeletal radiologist and senior spine surgeon interpreted the images while blinded to screw placement. Examiners initially assessed the screws as in or out, followed by assessment of the eight possible types of screw position. Consensus interpretation was obtained regarding the placement of individual screws. The spines were then dissected to visualize the screws and their position related to the pedicle. After determining the true position of the screws, a systematic method was designed and applied to the interpretation of the imaging methods to identify screw positions. RESULTS: Using conventional radiographs, 63% of the screw placements were correctly identified as in or out of the pedicle. Computed tomography improved accuracy to 87%. Identifying the true directional component of screw position led to a decrease in accuracy (conventional radiographs 37% and computed tomography 47%). Using asystematic method to analyze imaging studies enabled detection of screw positions. CONCLUSION: Evaluation of pedicle screw placement is difficult even in experienced hands. A systematic approach to image interpretation should allow for an accurate assessment of pedicle screw placement.

Aged↗
PubMed2005

Accuracy of an automated method to measure rotations of vertebrae from computerized tomography data.

STUDY DESIGN: In this phantom study, rotations of a vertebral body calculated from computerized tomography (CT) were compared to the actual rotations provided by a specially designed device incorporating a reduction gear. OBJECTIVE: The objective was to measure the accuracy of the CT and an automated software program to calculate rotations of lumbar vertebral bodies. BACKGROUND: Rotations of individual vertebrae secondary to a change in position or load can be measured in select patients by roentgen stereophotogrammetry or by using CT and a specially constructed table that creates the rotation of the torso. The purpose of this study was to measure the precision and accuracy of rotation measurements made with a CT scanner and an automated program to calculate rotation. METHODS: We constructed a phantom with a lumbar vertebra that can be rotated within a CT scanner. CT of the vertebra were obtained at angular positions of 0, 0.360 degrees , 1.080 degrees , 2.520 degrees , 5.400 degrees , 11.160 degrees , 29.160 degrees , 29.340 degrees , 29.520 degrees , 29.610 degrees , 29.700 degrees , 29.790 degrees , 29.880 degrees , and 29.889 degrees . With an automated program based on a pixel-shift algorithm, we calculated rotations of the vertebra between pairs of images. Accuracy was calculated as mean difference between the actual and the calculated rotation, and precision was calculated as the standard deviation of the differences. RESULTS: Differences between actual and calculated rotations varied from -0.083 degrees to 0.132 degrees . For rotations less than 15 degrees , mean error (accuracy) was -0.039 degrees , and the standard deviation (precision) was 0.029 degrees . For rotations greater than 15 degrees , the accuracy was 0.086 degrees , and the precision was 0.023 degrees . CONCLUSIONS: This study shows that rotations of lumbar vertebrae may be measured with CT, and an automated program to an accuracy and precision better than 0.1 degrees , comparable to that of roentgen stereophotogrammetry.

Humans↗
PubMed2000

An assessment of gene prediction accuracy in large DNA sequences.

One of the first useful products from the human genome will be a set of predicted genes. Besides its intrinsic scientific interest, the accuracy and completeness of this data set is of considerable importance for human health and medicine. Though progress has been made on computational gene identification in terms of both methods and accuracy evaluation measures, most of the sequence sets in which the programs are tested are short genomic sequences, and there is concern that these accuracy measures may not extrapolate well to larger, more challenging data sets. Given the absence of experimentally verified large genomic data sets, we constructed a semiartificial test set comprising a number of short single-gene genomic sequences with randomly generated intergenic regions. This test set, which should still present an easier problem than real human genomic sequence, mimics the approximately 200kb long BACs being sequenced. In our experiments with these longer genomic sequences, the accuracy of GENSCAN, one of the most accurate ab initio gene prediction programs, dropped significantly, although its sensitivity remained high. Conversely, the accuracy of similarity-based programs, such as GENEWISE, PROCRUSTES, and BLASTX was not affected significantly by the presence of random intergenic sequence, but depended on the strength of the similarity to the protein homolog. As expected, the accuracy dropped if the models were built using more distant homologs, and we were able to quantitatively estimate this decline. However, the specificities of these techniques are still rather good even when the similarity is weak, which is a desirable characteristic for driving expensive follow-up experiments. Our experiments suggest that though gene prediction will improve with every new protein that is discovered and through improvements in the current set of tools, we still have a long way to go before we can decipher the precise exonic structure of every gene in the human genome using purely computational methodology.

Base Composition↗
PubMed1997

Accuracy of determination of position and width of molecular groups in biological and lipid membranes via neutron diffraction.

Neutron diffraction combined with the deuterium-labelled molecular groups of biological and model membrane components allows one to detect with high accuracy the structure of these objects. Experiments of this kind are only possible at unique high-flux neutron sources, and the planning of neutron-diffraction experiments must take into account some special requirements primarily related to the duration of the experiment and the accuracy of estimation of membrane structure parameters as a result of finite time of the measurements. This paper deals with the question of statistical accuracy of the position x(0) and width v of the distribution of deuterium labels in membranes along the normal of their plane, which are determined in a neutron diffraction experiment. It is shown that the accuracy of x(0) and v estimation does not depend on membrane constitution. It is dependent only on the scattering amplitude of the deuterium label, the label position x(0) and the distribution width v. Analytic calculations show that the statistical errors Deltax(0) and Deltav are inversely proportional to the scattering amplitude of the label and, as usual, to the square root of measurement time. The question of Deltax0 and Deltav dependence on the number of structure factors used in the calculations of x(0) and v is also studied. It is shown that, the accuracy of x(0) estimation is approximately constant with down to four structure factors used, and, with the number of the factors below four, it deteriorates drastically. Analogous is the behaviour of Deltav(h(max)) relation with one exception: abrupt deterioration of the accuracy occurs beginning with five structure factors used. One does not have to measure the highest diffraction reflections which takes a much longer time compared with the first ones. It is an important result. All the problems mentioned above have also been considered for the case of two different deuterium labels in membranes.

Journal Article↗
PubMed1998

Visual assessment of the accuracy of retrospective registration of MR and CT images of the brain.

In a previous study we demonstrated that automatic retrospective registration algorithms can frequently register magnetic resonance (MR) and computed tomography (CT) images of the brain with an accuracy of better than 2 mm, but in that same study we found that such algorithms sometimes fail, leading to errors of 6 mm or more. Before these algorithms can be used routinely in the clinic, methods must be provided for distinguishing between registration solutions that are clinically satisfactory and those that are not. One approach is to rely on a human observer to inspect the registration results and reject images that have been registered with insufficient accuracy. In this paper, we present a methodology for evaluating the efficacy of the visual assessment of registration accuracy. Since the clinical requirements for level of registration accuracy are likely to be application dependent, we have evaluated the accuracy of the observer's estimate relative to six thresholds: 1-6 mm. The performance of the observers was evaluated relative to the registration solution obtained using external fiducial markers that are screwed into the patient's skull and that are visible in both MR and CT images. This fiducial marker system provides the gold standard for our study. Its accuracy is shown to be approximately 0.5 mm. Two experienced, blinded observers viewed five pairs of clinical MR and CT brain images, each of which had each been misregistered with respect to the gold standard solution. Fourteen misregistrations were assessed for each image pair with misregistration errors distributed between 0 and 10 mm with approximate uniformity. For each misregistered image pair each observer estimated the registration error (in millimeters) at each of five locations distributed around the head using each of three assessment methods. These estimated errors were compared with the errors as measured by the gold standard to determine agreement relative to each of the six thresholds, where agreement means that the two errors lie on the same side of the threshold. The effect of error in the gold standard itself is taken into account in the analysis of the assessment methods. The results were analyzed by means of the Kappa statistic, the agreement rate, and the area of receiver-operating-characteristic (ROC) curves. No assessment performed well at 1 mm, but all methods performed well at 2 mm and higher. For these five thresholds, two methods agreed with the standard at least 80% of the time and exhibited mean ROC areas greater than 0.84. One of these same methods exhibited Kappa statistics that indicated good agreement relative to chance (Kappa > 0.6) between the pooled observers and the standard for these same five thresholds. Further analysis demonstrates that the results depend strongly on the choice of the distribution of misregistration errors presented to the observers.

Algorithms↗
PubMedDate not supplied

Accuracy of frozen section in diagnosis of ovarian mass.

To determine the accuracy of frozen section according to the status of malignancy and the histologic cell type, we reviewed the frozen and permanent pathologic reports of 212 resected ovarian masses in our hospital. The accuracy, sensitivity, specificity, positive, and negative predictive value of frozen section were studied. The overall accuracy to determine the status of malignancy was 90.9%. Sensitivity of the test was highest in the benign groups at 99.1% and lowest in the borderline groups at 50%. All inaccurate diagnoses were in the common epithelial groups. Problems in diagnosis of mucinous tumors and borderline tumors were striking. The accuracy of the test for histologic diagnosis was 91.9%. Most cases of the incorrect diagnosis (81.3%) were common epithelial tumors. In conclusion, the accuracy of frozen section in the diagnosis of ovarian mass was generally high with a few exceptions in large tumors, mucinous, or borderline tumors that yielded lower accuracy, sensitivity, specificity, and positive predictive value. We encourage both the surgeons and the pathologists to be cautious of these limitations. Additional number of frozen section taken for a mass larger than 10 cm may minimize the error in large tumors to some extent.

Adenocarcinoma, Mucinous↗
PubMed2006

Age changes the diagnostic accuracy of mean profile and nadir growth hormone levels after oral glucose in postoperative patients with acromegaly.

BACKGROUND: This analytical, retrospective study was designed to select cut-off thresholds of mean GH levels during a diurnal profile and nadir GH levels after oral glucose tolerance test (OGTT) according to age to diagnose surgical remission of acromegaly. METHODS: One hundred forty-one patients (76 women, aged 44 +/- 15 years and 65 men, aged 43 +/- 13 years) were included in this study. For the purpose of this study, remission was based on insulin-like growth factor-I (IGF-I) levels in the normal range for age. Diagnostic accuracy was analysed by receiving-operator characteristics (ROC) curves in the entire series, and in young (20-40 years), middle-aged (41-60 years) and older patients (> 60 years), separately. RESULTS: Sixty patients (42.6%) had normal IGF-I levels after surgery. In the entire series, in young and in middle-aged patients, the ROC analysis showed that optimum cut-off for mean GH levels was 2.3 microg/l (diagnostic accuracy range, 94-97%) whereas that for nadir GH after OGTT were, respectively, 0.85, 0.9 and 0.8 microg/l (diagnostic accuracy range, 90-95%). In the older patients, the optimum cut-off selected for mean GH levels was 1.4 microg/l and that for nadir GH after OGTT was 0.5 microg/l (diagnostic accuracy, 100% for both). The comparative analysis of the ROC curves did not show any significant difference between mean GH and nadir GH after OGTT (P = 0.21). CONCLUSIONS: The criteria currently accepted for diagnosing post-surgical remission of acromegaly have high diagnostic accuracy only in the patients aged below 60 years. In older patients, lower cut-offs (i.e. = 1.4 microg/l for fasting GH and = 0.5 microg/l for nadir GH after OGTT) predict normal IGF-I levels. Mean GH levels during a diurnal profile have similar diagnostic accuracy of nadir GH levels after OGTT. This suggests that OGTT is not necessary to establish surgical cure.

Acromegaly↗
PubMed1991

The accuracy of standardized patient presentation.

The accuracy of standardized patient clinical problem presentation was evaluated by videotape rating of a random sample of 839 student-patient encounters, representing 88 patients, 27 cases and two university test sites. Patient-student encounters were sampled from a collaborative inter-university final-year clinical examination of fourth-year medical students which was conducted at the University of Manitoba and Southern Illinois University in 1987 and 1988. The accuracy, replicability and portability of standardized patient cases were evaluated. The average accuracy of patient presentation was 90.2% in 1987 and 93.4% in 1988. Perfect accuracy scores were obtained by 15 patients; however, 11 patients had average scores below 80% with the accuracy of presentation in some encounters being as low as 30%. There were significant differences in the accuracy score achieved by patients trained together for the same case in 6 of 35 possible comparisons. There was also a systematic trend for patients trained at Southern Illinois to be more accurate in their presentation than patients trained at the University of Manitoba. These differences were significant in 5 of the 15 cases used in the examination.

Clinical Clerkship↗