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PubMedDate not supplied

Accuracy of single-time, multilevel registration in image-guided spinal surgery.

BACKGROUND CONTEXT: Computerized frameless stereotactic image-guidance has been used in recent years to improve the accuracy and safety of pedicle screw placement during spine surgery. Because the possibility of intervertebral motion exists, and because the patient is usually in a different position when preoperative imaging is performed compared with the operative position, it has been suggested that the imaging model of the complete lumbar spine and the surgically exposed lumbar spine may be significantly discordant. Consequently, current protocols suggest registering each spinal level (single-level registration) separately before pedicle screw placement at that level, a time-consuming process. PURPOSE: To assess the accuracy of single-time multilevel registration for multilevel pedicle screw placement during image-guided, computer-assisted spine surgery, in the setting of degenerative disorders of the lumbar spine. STUDY DESIGN/SETTING: This is a prospective clinical and radiological study of 45 patients with degenerative disorders of the lumbar spine who underwent instrumented fusion with the use of single-time multilevel registration computer-assisted, image-guided tomography. The accuracy of the pedicle screws placement was confirmed on the basis of a protocol that included intraoperative spontaneous electromyographic (EMG) recordings, direct pedicle visualization, and computer tomography (CT) scans when clinically indicated during the follow-up period. PATIENT SAMPLE: Forty-five consecutive patients who fulfilled the criteria of computer-assisted, image-guided tomography pedicle screw placement for degenerative lumbar spine disease without overt instability. OUTCOME MEASURES: The principal outcome measure was the accuracy of pedicle screw placement with single-time multilevel registration for multilevel pedicle screw placement during image-guided, computer-assisted spine surgery; postoperative CT performed for clinical indications during the follow-up course was used for the assessment of pedicle screw placement. METHODS: Patients were assessed clinically before and after the operation. Data from 45 consecutive cases of image-guided, computer-assisted lumbar spinal fusion were statistically analyzed to determine the relationship between the number of levels registered during single-time registry and the mean registration error (MRE). Intraoperative spontaneous EMG, direct visualization, and postoperative CT scans were used to assess the accuracy of pedicle screw insertion. RESULTS: None of the patients involved in this study experienced clinical sequelae of improper pedicle screw placement. MREs after surface mapping and after point merge were small (less than 1.00 mm and less than 3.00 mm, respectively). During the intraoperative assessment of the pedicle screws placement, no significant spontaneous EMG activity was recorded and the pedicular walls were found intact in direct visualization. The postoperative CT scans showed in 10 patients accurate placement in 55 of the 57 pedicle screws with expansion of the medial wall in two screws. CONCLUSIONS: Single-time, multilevel registration may decrease operative time relative to repeated, single-level registrations, without compromising the increased accuracy of pedicle screw placement afforded by this technique in the setting of degenerative disorders of the lumbar spine. Despite the advantages in computer-guided image surgery, cautious application in the individual patient is recommended until more comprehensive data can be gathered in specific degenerative pathology with overt instability; thus the knowledge of the anatomy remains crucial.

Adult↗
PubMed2000

Effect of patient obesity on the accuracy of thallium-201 myocardial perfusion imaging.

The effects of patient habitus (e.g., breast attenuation in women and diaphragmatic attenuation in men) have long been recognized as factors that reduce the accuracy of myocardial perfusion imaging. Although it has long been assumed that patient obesity effects accuracy, this has never been formally evaluated. We studied the effects of patient obesity, defined as a body mass index (BMI) > or = 30, on 607 patients who underwent exercise thallium-201 single-photon emission computed tomography (SPECT). Because the effects of obesity are most likely mediated through increased photon attenuation and scatter, we also evaluated the effects of other markers of patient size: body surface area (BSA) and patient weight. Accuracy was determined by performing quantitative analysis and measuring the area under the receiver operating characteristic curve (AUC). Obesity was associated with significantly lower accuracy (AUC 0.86 +/- 0.03 vs 0.92 +/- 0.02, p <0.05) despite similar estimates of maximal coronary blood flow (as estimated by heart rate and rate-pressure product at peak exercise) and severity of coronary disease. There were no significant differences attributable to either patient weight or BSA. Weight and BSA correlated significantly with left ventricular chamber size whereas BMI did not. We conclude that the accuracy of quantitative SPECT thallium-201 is significantly reduced by patient obesity and that although BSA and weight are also associated with increased attenuation, they have no effect on accuracy, which is most likely due to the compensating effects of increased chamber size.

Body Mass Index↗
PubMed1999

Accuracy and complication rate of brush cytology from bile duct versus pancreatic duct.

BACKGROUND: The accuracy and complication rates of brush cytology obtained from pancreaticobiliary strictures have not been fully defined. In this study we compared the accuracy and complications of brush cytology obtained from bile versus pancreatic ducts. METHODS: We identified 148 consecutive patients for whom brush cytology was done during an ERCP from a database with prospectively collected data. We compared cytology results with the final diagnosis as determined by surgical pathologic examination or long-term clinical follow-up. We followed all patients and recorded ERCP-related complications. RESULTS: Forty-two pancreatic brush cytology samples and 101 biliary brush cytology samples were obtained. The accuracy rate of biliary cytology was 65 of 101 (64.3%) and the accuracy rate of pancreatic cytology was 30 of 42 (71.4%). Overall sensitivity was 50% for biliary cytology and 58.3% for pancreatic cytology. Of 67 patients with pancreatic adenocarcinoma, sensitivity for biliary cytology was 50% versus 66% for pancreatic cytology. Concurrent pancreatic and biliary cytology during the same procedure increased the sensitivity in only 1 of 10 (10%) patients. Pancreatitis occurred in 11 (11%) patients (9 mild cases, 2 moderate cases) after biliary cytology and in 9 (21%) patients (6 mild cases, 3 moderate cases) after pancreatic cytology (p = 0.22). In 10 patients who had pancreatic brush cytology, a pancreatic stent was placed. None of these patients developed pancreatitis versus 9 of 32 (28%) patients in whom a stent was not placed (p = 0.08). Pancreatic cytology samples obtained from the head of the pancreas were correct in 13 of 18 (72%) cases, from the genu in 7 of 7 (100%) cases, from the body in 5 of 9 (55%) cases, and from the tail in 4 of 7 (57%) cases. CONCLUSION: The accuracy of biliary brush cytology is similar to the accuracy of pancreatic brush cytology. The yield of the latter for pancreatic adenocarcinoma is similar to that of the former. Complication rates for pancreatic cytology are not significantly higher than the rates for biliary cytology. The placement of a pancreatic stent after pancreatic brushing appears to reduce the risk of postprocedure pancreatitis.

Adenocarcinoma↗
PubMed1998

An accuracy evaluation of four removable die systems.

STATEMENT OF PROBLEM: The advent of implant dentistry has redefined the need for accuracy of working cast models. Die stone expansion and errors introduced by removable die casts may exceed the accuracy required for the passive fit of implant prostheses. PURPOSE: Several removable die systems claim improved accuracy because of their design and/or technical advancements. This study evaluated the 3-dimensional accuracy of 4 removable die systems. All 4 systems tested use either 1 or 2 pins as the repositioning device. MATERIAL AND METHODS: Four removable die systems were evaluated (Belle de St. Claire, Pindex, DVA, and conventional brass dowel system). Master model impressions were made with polyvinyl siloxane material and were later cast with type IV die stone material. Comparative dimensional analysis between the master model and the solid and sectioned casts was made by placing the cast in a standardized position and fabricating an individual custom base for each cast. Landmarks were measured with a traveling microscope, and by mathematically rotating the casts. Discrepancies beyond that of stone expansion or residual stress release at the time of die separation were due to the inability to precisely reposition the removable die of the sectioned cast. Data were analyzed with multivariate analysis of variance and paired t tests at alpha = .05 (n = 10). RESULTS: Significant differences were found among die systems tested (P = .005). When sectioned dies were compared with the master model, the accuracy of all 4 die systems was within 0.055 mm of the master model. Once sectioned, the Pindex system had the least linear expansion in the y dimension, and the brass dowel system demonstrated the least reseating discrepancy in the z (occlusogingival) dimension. CONCLUSIONS: All 4 die systems provided a similar degree of dimensional accuracy, although Pindex showed the least horizontal movement and the brass dowel system produced the least occlusogingival reseating discrepancy.

Analysis of Variance↗
PubMed1999

Precision and accuracy of an electrogoniometer.

BACKGROUND: Spinal range of motion has been studied by use of a variety of different methods. One electrogoniometer has been used as a noninvasive, reliable, and accurate method. The accuracy and precision of this device has not been sufficiently documented. OBJECTIVE: To evaluate the precision and accuracy of an electrogoniometer in comparison with two manual protractors. STUDY DESIGN: This study investigated the precision and accuracy of an electrogoniometer (OSI CA 6000). METHODS: The precision and accuracy of the electrogoniometer were determined by a series of tests against two manual protractors. Six different movement directions were tested and 4 or 5 different angles for a given movement direction were evaluated. RESULTS: The precision of the electrogoniometer was found to be +/- 0.1 degree for 4 different angles (10 degrees, 20 degrees, 40 degrees, and 60 degrees) in 6 different movement directions (flexion, extension, left lateral flexion, right lateral flexion, left rotation, and right rotation). The accuracy was tested by comparing both manual protractors with the electrogoniometer. Substantial disagreement for 27 of 28 datasets was found. In only one dataset was there agreement between the two manual protractors and the electrogoniometer. The mean differences were in the interval 2.0% to 11.5% between the electrogoniometer and the protractors. CONCLUSION: The electrogoniometer evaluated has a very high precision when range of motion measurements are made. However, the accuracy of the device is less than acceptable.

Electrodiagnosis↗
PubMed1997

Lead-induced changes in NMDA receptor complex binding: correlations with learning accuracy and with sensitivity to learning impairments caused by MK-801 and NMDA administration.

This study sought to further evaluate potential mechanistic relationships between Pb-induced alterations in glutamate neurotransmission and behavioral toxicity. It examined correlations between Pb-induced changes in [3H]MK-801 and [3H]CGP-39653 binding sites in 4 different brain regions (frontal cortex, dentate gyrus, CA1 and striatum) and (1) changes in learning accuracy on a multiple repeated acquisition and performance schedule, and (2) sensitivity to the accuracy-impairing effects of MK-801 and NMDA on this learning baseline. All data were obtained from a single population of rats that had been chronically exposed from weaning to 0, 50 or 250 ppm Pb acetate in drinking water and demonstrated selective learning impairments and altered sensitivity to the effects of MK-801 and NMDA on learning accuracy. Pb exposure decreased MK-801 binding and possibly increased CGP-39653 binding, effects statistically significant in some brain regions, but generally exhibiting similar trends across regions. At 0 ppm, higher levels, particularly of MK-801 binding, were associated with higher accuracy levels in the learning paradigm and with greater decrements in learning accuracy following MK-801 or NMDA administration. These linear correlations were negated and in some cases even reversed by 50 and 250 ppm Pb, an effect that might be attributable to an alteration of NMDA receptor complex subunit composition and thus, ligand binding. Of the 4 brain regions examined, striatal MK-801 binding proved to be the best predictor of learning accuracy levels. These data provide additional support for an involvement of the NMDA receptor complex in Pb-induced learning impairments. The fact that these effects were noted most frequently in striatum also raises the possibility that dopamine-glutamatergic interactions contribute to Pb's effects.

2-Amino-5-phosphonovalerate↗
PubMed2001

Determination of the accuracy of implant reconstruction and dose delivery in brachytherapy in The Netherlands and Belgium.

PURPOSE: To gain insight into the accuracy of brachytherapy treatments, the accuracy of implant reconstruction and dose delivery was investigated in 33 radiotherapy institutions in The Netherlands and Belgium. MATERIALS AND METHODS: The accuracy of the implant reconstruction method was determined using a cubic phantom containing 25 spheres at well-known positions. Reconstruction measurements were obtained on 41 brachytherapy localizers, 33 of which were simulators. The reconstructed distances between the spheres were compared with the true distances. The accuracy of the dose delivery was determined for high dose rate (HDR), pulsed dose rate (PDR) and low dose rate (LDR) afterloading systems using a polymethyl methacrylate cylindrical phantom containing a NE 2571 ionization chamber in its centre. The institutions were asked to deliver a prescribed dose at the centre of the phantom. The measured dose was compared with the prescribed dose. RESULTS: The average reconstruction accuracy was -0.07 mm (+/-0.4 mm, 1 SD) for 41 localizers. The average deviation of the measured dose from the prescribed dose was +0.9% (+/-1.3%, 1 SD) for 21 HDR afterloading systems, +1.0% (+/-2.3%, 1 SD) for 12 PDR afterloaders, and +1.8% (+/-2.5%, 1 SD) for 15 LDR afterloaders. CONCLUSIONS: This comparison showed a good accuracy of brachytherapy implant reconstruction and dose delivery in The Netherlands and Belgium.

Belgium↗
PubMed2002

Accuracy of internal mammary lymph node localization using lymphoscintigraphy, sonography and CT.

BACKGROUND AND PURPOSE: An accurate internal mammary (IM) lymph node localization technique is required for proper irradiation of the IM lymph nodes in breast cancer patients. In this study the measurement accuracy of three techniques for direct or indirect localization of the IM nodes was estimated. MATERIALS AND METHODS: In 40 patients the IM lymph node depth and lateral distance from the patient midline were measured with lymphoscintigraphy in intercostal spaces 2, 3 and 4. The corresponding position of an IM vessel was measured with sonography and CT in intercostal spaces 1-4. The sonography and CT vessel measurements in the four intercostal spaces were compared to determine the measurement accuracy of sonography. The node and vessel data in intercostal space 2 were inserted into a mathematical model to determine the measurement accuracy of lymphoscintigraphy and CT for node detection. RESULTS: Vessel depths measured by sonography were systematically too shallow and the lateral vessel position could not be accurately determined. The mathematical model showed that the node depth and lateralization in one intercostal space can be measured directly by lymphoscintigraphy within an accuracy (1 SD) of 5 mm in depth and 6 mm in the lateral direction. The accuracy of CT for indirect node detection was 6 mm in depth and 7 mm in the lateral direction. CONCLUSIONS: Sonography is not a suitable technique for measuring the IM vessel or node position. Lymphoscintigraphy and CT have measurement accuracies for node detection that are acceptable for radiotherapy.

Breast Neoplasms↗
PubMed1997

The accuracy of self-reported Pap smear utilisation.

This study assessed the accuracy of self-reported Pap smear utilisation over four different time frames, examining the magnitude of errors in self-report and sociodemographic predictors of accuracy. Self-report data on women's cervical screening was collected by interview in a random household survey (Hunter Region, NSW, Australia), with pathology laboratory data collected by a search of records within laboratories. The magnitude of error in self-report was assessed by comparing it against longer intervals in pathology laboratory data. Sociodemographic predictors of accuracy were explored using chi square analyses. Low values for specificity and positive predictive value across all four time frames indicate a considerable degree of inaccuracy in women's reporting of those instances where, in truth, screening has not occurred. Of women reporting a smear within the last three years, only 61.2% were verified within pathology laboratory records. Allowing women some "leeway" in their reporting, comparing self-report to longer intervals of pathology laboratory data, did not greatly improve the accuracy of reporting, confirming that the magnitude of inaccuracy involved is of real clinical significance. Demographic variables were not related to the accuracy of self-report and, while a woman's certainty of her response was predictive, this had little impact on the measures of agreement. Self-report of Pap smear histories consistently results in over-reporting of screening. Other means of assessing the prevalence of screening may be preferable to self-report. Where self-report data is collected, techniques to improve accuracy should be employed, and care should be taken in comparing screening rates obtained by different methods.

Adolescent↗
PubMed2004

Transthoracic CT-guided biopsy with multiplanar reconstruction image improves diagnostic accuracy of solitary pulmonary nodules.

OBJECTIVE: To evaluate the utility of multiplanar reconstruction (MPR) image for CT-guided biopsy and determine factors of influencing diagnostic accuracy and the pneumothorax rate. MATERIALS AND METHODS: 390 patients with 396 pulmonary nodules underwent transthoracic CT-guided aspiration biopsy (TNAB) and transthoracic CT-guided cutting needle core biopsy (TCNB) as follows: 250 solitary pulmonary nodules (SPNs) underwent conventional CT-guided biopsy (conventional method), 81 underwent CT-fluoroscopic biopsy (CT-fluoroscopic method) and 65 underwent conventional CT-guided biopsy in combination with MPR image (MPR method). Success rate, overall diagnostic accuracy, pneumothorax rate and total procedure time were compared in each method. Factors affecting diagnostic accuracy and pneumothorax rate of CT-guided biopsy were statistically evaluated. RESULTS: Success rates (TNAB: 100.0%, TCNB: 100.0%) and overall diagnostic accuracies (TNAB: 96.9%, TCNB: 97.0%) of MPR were significantly higher than those using the conventional method (TNAB: 87.6 and 82.4%, TCNB: 86.3 and 81.3%) (P < 0.05). Diagnostic accuracy were influenced by biopsy method, lesion size, and needle path length (P < 0.05). Pneumothorax rate was influenced by pathological diagnostic method, lesion size, number of punctures and FEV1.0% (P < 0.05). CONCLUSION: The use of MPR for CT-guided lung biopsy is useful for improving diagnostic accuracy with no significant increase in pneumothorax rate or total procedure time.

Adolescent↗
PubMed1997

Contrast-enhanced MRI of the breast: accuracy, value, controversies, solutions.

OBJECTIVE: Contrast-enhanced MRI of the breast has been one of the most controversial areas of MRI. Even though most investigators have, in selected indications, been able to improve accuracy by the additional use of contrast-enhanced MRI, its abuse has been feared not only because of increased costs for imaging, but also because of increased biopsy rates caused by false positive calls and because of errors caused by insufficient standardisation. In this article an overview is given of the present knowledge about contrast-enhanced MRI of the breast. Factors that influence the accuracy and reproducibility of contrast-enhanced MRI are analysed. METHOD: Factors that influence accuracy include: (1) technical factors that influence accuracy, e.g. slice thickness (partial volume effect), motion reduction, reduction of (cardiac) artifacts, dosage of contrast agent, choice of pulse sequence and echotime, and choice of the method for elimination of fat signal. (2) Hormonal factors (timing of the examination with reference to the menstrual cycle, hormonal replacement therapy). They influence accuracy and must be taken into account. (3) Interpretation guidelines-their choice influences sensitivity and specificity mostly inversely and the use of information from conventional imaging appears necessary. (4) Patient selection influences accuracy for statistical and for biological reasons. RESULTS: Based on the present literature and on the experiences gathered in six German universities (> 12000 examinations) an excellent sensitivity (> 98%) can be achieved for the combination of mammography and MRI. However, specificity strongly varies with the indications. Recommended indications include examination of breasts with impaired evaluation due to severe scarring, after silicon implants and in the dense breast, exclusion of multicentricity and search for primary tumor. Indications under investigation include high risk patients and strictly selected problem cases. CONCLUSION: If appropriately applied and used for selected indications, contrast-enhanced MRI may allow a significant diagnostic gain. In order to take advantage of the full potentials of contrast-enhanced MRI the development of commercially available biopsy coils is essential.

Artifacts↗
PubMed1984

Accuracy and interobserver variability of coronary cineangiography: a comparison with postmortem evaluation.

The accuracy of interpretation of coronary cineangiography by two independent observers was tested against postmortem findings in 27 patients who died within 6 months of cardiac catheterization. Variations in cineangiographic interpretations between the angiographers were also evaluated. Two patients had normal coronary arteries, while the remaining 25 patients had significant coronary artery disease. Significant stenosis was defined as 75% or greater reduction in luminal diameter. Of 326 coronary segments that could be evaluated postmortem, 15% could not be evaluated cineangiographically. The respective overall accuracy of the two observers was 89 and 88% with an accuracy of 96 and 100% for the left main coronary artery, 91 and 93% for the left anterior descending artery, 84 and 86% for the right coronary artery and 89 and 79% for the left circumflex coronary artery. Cineangiographic assessment of luminal status distal to a significant proximal lesion was possible in more than 70% of major vessels with accuracy levels of 86% for both observers. Of 96 distal vessels inadequately opacified cineangiographically, 49 (52%) were found to be free of significant lesions. Both angiographers agreed in their assessment of 86% of the 340 coronary segments. Interobserver agreement was significantly better for the left main, right and left anterior descending coronary arteries than for the left circumflex coronary artery (p less than 0.05). Accuracy was 93% for 244 segments that were adequately opacified and assessed the same by both angiographers. Cineangiography can thus be used to evaluate coronary anatomy with a high degree of accuracy and minimal interobserver variability.

Autopsy↗
PubMed1997

Demographics, health behaviors, and past drug use as predictors of recall accuracy for previous prescription medication use.

Drug data for pharmacoepidemiologic studies are often ascertained by self-report, but little research has addressed the factors influencing its accuracy. Stratified random sampling was used to select individuals for a study comparing interview data on past prescription drug use with dispensation information from the Group Health Cooperative of Puget Sound pharmacy database. The strata included age, gender, and recency of use. Recall accuracy and its determinants were evaluated for repetitively used non-steroidal anti-inflammatory drugs (NSAIDs), short-term NSAIDs (only a single dispensation), and post-menopausal estrogens. We investigated whether recall accuracy was influenced by education, marital status, race, smoking, alcohol consumption, cumulative drug history, the number of different NSAIDs or estrogens dispensed (both by name and dosage), and the number of dispensations of the drug in question. For repetitively used NSAIDs, recall accuracy was positively associated with the number of NSAID dispensations (the odds of recall were 1.7 [95% confidence interval {CL}: 1.3-2.2] times greater for each additional four dispensations of the NSAID), the total number of drugs dispensed and the number of different NSAIDs dispensed. For estrogen and short-term NSAID use, only higher educational attainment improved recall accuracy: the odds of recall were 4.1 (95% CI: 1.4-11.7) and 2.1 (95% CI: 1.0-4.7) times greater for those with some college compared with those with only a high school degree, respectively. This study demonstrates that predictors of recall accuracy for previous medication use differ by the type of drug and the repetitiveness of its use.

Aged↗
PubMed2003

Toward complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative.

RATIONALE AND OBJECTIVES: To comprehend the results of diagnostic accuracy studies, readers must understand the design, conduct, and analysis of such studies. The authors sought to develop guidelines for improving the accuracy and completeness of reporting of studies of diagnostic accuracy in order to allow readers better to assess the validity and generalizability of study results. MATERIALS AND METHODS: The Standards for Reporting of Diagnostic Accuracy group steering committee searched the literature to identify publications on the appropriate conduct and reporting of diagnostic studies and to extract potential guidelines for authors and editors. An extensive list of items was prepared. Members of the steering committee then met for 2 days with other researchers, editors, methodologists, statisticians, and members of professional organizations to develop a checklist and a prototypical flowchart to guide authors and editors of studies of diagnostic accuracy. RESULTS: The search for published guidelines on diagnostic research yielded 33 previously published checklists, from which the group produced an initial list of 75 items. This list was honed to 25 key items by group consensus and on the basis of published research on bias. A prototypical flowchart was developed as a tool for conveying information about the method of patient recruitment, the order of test execution, and the numbers of patients undergoing the test under evaluation, the reference test, or both. Potential users reviewed the conference version of the checklist and flowchart and provided additional suggestions, which were then incorporated. CONCLUSION: Use of these carefully developed, consensus-based guidelines should enable clearer and more complete reporting of studies of diagnostic accuracy, as well as better reader understanding of the validity and generalizability of study results.

Bias↗
PubMed1998

Duplex scanning and effect of multisegmental arterial disease on its accuracy in lower limb arteries.

AIM: To assess the accuracy of duplex in assessment of peripheral arterial disease and determine the effect of multisegmental disease on the accuracy duplex as opposed to single lesion. PATIENTS AND METHODS: One hundred and seventy-seven lower limbs were examined in 90 patients who presented with lower limb arterial disease, (59 male, 31 female, median age 68 years--81 with intermittent claudication, eight rest pain, one ulceration). Patients were examined with duplex US, and arteriography (IA DSA). Two radiologists and two technologists were involved in this double-blind study. Patients were classified into five groups; groups with single stenotic lesions, single occlusions, multiple stenotic lesions or occlusions, and multiple mixed disease. Duplex accuracy was determined in each group. RESULTS: Duplex was able to differentiate between normal and disease arterial segment with a sensitivity of 92%, specificity 99%, PPV 91%, and NPV 100% and Kappa 0.87. Sixty-six limbs were found to have single lesions, and 68 multisegmental disease. Duplex showed accuracy with a sensitivity of 87%, and specificity of 99%, for single stenotic lesion and 95%, 96% respectively for multisegmental. For single occlusions duplex accuracy showed sensitivity 92% and specificity 100%, and for multisegmental occlusions, sensitivity 97%, and specificity 99%. For mixed multisegmental pathology (stenosis and occlusion), sensitivity 94% and specificity 97%. CONCLUSION: Duplex is an accurate tool in diagnosis of lower limb arterial disease and multisegmental pathology does not adversely effect this accuracy.

Aged↗
PubMed2005

Making broad proteome protein measurements in 1-5 min using high-speed RPLC separations and high-accuracy mass measurements.

The throughput of proteomics measurements that provide broad protein coverage is limited by the quality and speed of both the separations as well as the subsequent mass spectrometric analysis; at present, analysis times can range anywhere from hours (high throughput) to days or longer (low throughput). We have explored the basis for proteomics analyses conducted on the order of minutes using high-speed capillary RPLC combined through on-line electrospray ionization interface with high-accuracy mass spectrometry (MS) measurements. Short 0.8-microm porous C18 particle-packed 50-microm-i.d. capillaries were used to speed the RPLC separations while still providing high-quality separations. Both time-of-flight (TOF) and Fourier transform ion cyclotron resonance (FTICR) MS were applied for identifying peptides using the accurate mass and time (AMT) tag approach. Peptide RPLC relative retention (elution) times that were generated by solvent gradients that differed by at least 25-fold were found to provide relative elution times that agreed to within 5%, which provides the basis for using peptide AMT tags for higher throughput proteomics measurements. For fast MS acquisition speeds (e.g., 0.2 s for TOF and either approximately 0.3 or approximately 0.6 s for FTICR), peptide mass measurement accuracies of better than +/-15 ppm were obtained with the high-speed RPLC separations. The ability to identify peptides and the overall proteome coverage was determined by factors that include the separation peak capacity, the sensitivity of the MS (with fast scanning), and the accuracy of both the mass measurements and the relative RPLC peptide elution times. The experimental RPLC relative elution time accuracies of 5% (using high-speed capillary RPLC) and mass measurement accuracies of better than +/-15 ppm allowed for the confident identification of >2800 peptides and >760 proteins from >13,000 different putative peptides detected from a Shewanellaoneidensis tryptic digest. Initial results for both RPLC-ESI-TOF and RPLC-ESI-FTICR MS were similar, with approximately 2000 different peptides from approximately 600 different proteins identified within 2-3 min. For <120-s proteomic analysis, TOF MS analyses were more effective, while FTICR MS was more effective for the >150-s analysis due to the improved mass accuracies attained using longer spectrum acquisition times.

Animals↗
PubMed1993

Precision, accuracy, and data acceptance criteria in biopharmaceutical analysis.

Accuracy and precision are the most important criteria in the assessment of an analytical method, and monitoring quality control during sample analysis is essential to ensure the validity of reported results. Various approaches to testing accuracy, precision, and quality control were applied to 10 analytes from seven chromatographic bioanalytical methods. These methods include fixed interval bias and significance testing for accuracy; fixed interval percentage relative standard deviation (%RSD) and analysis of variance (ANOVA) approaches for precision; +/- 20% fixed range, 99% confidence interval, multiple rules, and range chart for individuals approaches for quality control acceptance criteria. Quality control approaches were also applied to the entire run and to a bracketed approach whereby results are considered valid only if bracketed by acceptable quality control. Accuracy and precision were assessed for six runs of each analyte at three concentrations established to represent the calibration range of the analytical method. Quality control acceptance criteria were evaluated using all data sets from each of the analytical methods collected during the course of running various numbers of real samples. The data suggest that the fixed interval bias criteria for accuracy was a more liberal method of accuracy assessment because three of the seven methods would have been rejected according to the significance testing criteria whereas all were acceptable by the fixed internal bias criteria. Precision can be effectively assessed for between- and within-run data by criteria set on unconfounded %RSD values or by separation of the sources of variation using an ANOVA approach applied to confounded data.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1995

Empathic accuracy in a clinically relevant setting.

This study addressed 3 questions regarding empathic accuracy in a clinically relevant setting. First, does the empathic accuracy of a perceiver improve with increased exposure to a target individual? Second, can empathic accuracy be enhanced by providing the perceiver with feedback about the target's actual thoughts and feelings? Third, are there stable individual differences in empathic accuracy that generalize across different targets? The results indicated that although absolute performance levels varied from 1 target to another, empathic accuracy generally improved with increased exposure to the target. In addition, feedback concerning the target's actual thoughts and feelings accelerated the rate at which the perceivers' empathic accuracy improved. Finally, cross-target consistency in responding (alpha = .86) revealed stable individual differences in the perceivers' empathic ability. Implications of these findings for clinical training and practice are discussed.

Divorce↗