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At least 595 records · Page 33Linked to original sources
PubMed2006

Improving the accuracy of protein secondary structure prediction using structural alignment.

BACKGROUND: The accuracy of protein secondary structure prediction has steadily improved over the past 30 years. Now many secondary structure prediction methods routinely achieve an accuracy (Q3) of about 75%. We believe this accuracy could be further improved by including structure (as opposed to sequence) database comparisons as part of the prediction process. Indeed, given the large size of the Protein Data Bank (>35,000 sequences), the probability of a newly identified sequence having a structural homologue is actually quite high. RESULTS: We have developed a method that performs structure-based sequence alignments as part of the secondary structure prediction process. By mapping the structure of a known homologue (sequence ID >25%) onto the query protein's sequence, it is possible to predict at least a portion of that query protein's secondary structure. By integrating this structural alignment approach with conventional (sequence-based) secondary structure methods and then combining it with a "jury-of-experts" system to generate a consensus result, it is possible to attain very high prediction accuracy. Using a sequence-unique test set of 1644 proteins from EVA, this new method achieves an average Q3 score of 81.3%. Extensive testing indicates this is approximately 4-5% better than any other method currently available. Assessments using non sequence-unique test sets (typical of those used in proteome annotation or structural genomics) indicate that this new method can achieve a Q3 score approaching 88%. CONCLUSION: By using both sequence and structure databases and by exploiting the latest techniques in machine learning it is possible to routinely predict protein secondary structure with an accuracy well above 80%. A program and web server, called PROTEUS, that performs these secondary structure predictions is accessible at http://wishart.biology.ualberta.ca/proteus. For high throughput or batch sequence analyses, the PROTEUS programs, databases (and server) can be downloaded and run locally.

Algorithms↗
PubMed2006

Reproducibility of the STARD checklist: an instrument to assess the quality of reporting of diagnostic accuracy studies.

BACKGROUND: In January 2003, STAndards for the Reporting of Diagnostic accuracy studies (STARD) were published in a number of journals, to improve the quality of reporting in diagnostic accuracy studies. We designed a study to investigate the inter-assessment reproducibility, and intra- and inter-observer reproducibility of the items in the STARD statement. METHODS: Thirty-two diagnostic accuracy studies published in 2000 in medical journals with an impact factor of at least 4 were included. Two reviewers independently evaluated the quality of reporting of these studies using the 25 items of the STARD statement. A consensus evaluation was obtained by discussing and resolving disagreements between reviewers. Almost two years later, the same studies were evaluated by the same reviewers. For each item, percentages agreement and Cohen's kappa between first and second consensus assessments (inter-assessment) were calculated. Intraclass Correlation coefficients (ICC) were calculated to evaluate its reliability. RESULTS: The overall inter-assessment agreement for all items of the STARD statement was 85% (Cohen's kappa 0.70) and varied from 63% to 100% for individual items. The largest differences between the two assessments were found for the reporting of the rationale of the reference standard (kappa 0.37), number of included participants that underwent tests (kappa 0.28), distribution of the severity of the disease (kappa 0.23), a cross tabulation of the results of the index test by the results of the reference standard (kappa 0.33) and how indeterminate results, missing data and outliers were handled (kappa 0.25). Within and between reviewers, also large differences were observed for these items. The inter-assessment reliability of the STARD checklist was satisfactory (ICC = 0.79 [95% CI: 0.62 to 0.89]). CONCLUSION: Although the overall reproducibility of the quality of reporting on diagnostic accuracy studies using the STARD statement was found to be good, substantial disagreements were found for specific items. These disagreements were not so much caused by differences in interpretation of the items by the reviewers but rather by difficulties in assessing the reporting of these items due to lack of clarity within the articles. Including a flow diagram in all reports on diagnostic accuracy studies would be very helpful in reducing confusion between readers and among reviewers.

Advisory Committees↗
PubMed2004

Improving the accuracy of malaria-related laboratory tests in Ghana.

BACKGROUND: Inaccurate malaria results can lead to patient mismanagement, misperceptions about malaria resistance patterns and public health misinformation. All laboratories need to be able to demonstrate that their results are accurate. Establishing and maintaining a system for monitoring test accuracy is a complex, expensive and technically demanding process, which very few poor countries have been able to implement. This study described the process and assessed the feasibility of establishing a nation-wide system for improving the accuracy of malaria-related tests in peripheral laboratories in Ghana. PROGRAMME IMPLEMENTATION: A baseline survey of all 693 laboratory staff in 205 sub-regional government and mission health laboratories in Ghana was conducted by a national network of laboratory supervisors. Survey results guided a training programme to improve test accuracy. Outcomes included changes in the quality of laboratory tests and the system was considered to be feasible if >50% of laboratory staff in each region received training and if test accuracy could be documented. PROGRAMME INDICATORS: 74% (mean) of the 693 laboratory staff were assistants with no professional qualifications. There were marked differences between regions in the availability of essential resources for malaria diagnosis (e.g. microscopes). 93% of laboratory staff received training; in six months there were increases of 11% and 7% respectively in the number of laboratories producing haemoglobin and malaria microscopy results of acceptable quality. CONCLUSIONS: It is possible to establish a system for improving and monitoring test accuracy in peripheral laboratories on a country-wide basis in a developing country using a model that could be adapted for use in other countries and for other components of health care provision.

Clinical Laboratory Techniques↗
PubMed2006

Anechoic stripe size influences accuracy of FAST examination interpretation.

OBJECTIVES: Accurate and precise interpretations of Focused Assessment with Sonography for Trauma (FAST) findings are important factors in managing trauma patients. The objectives were to analyze the influence of anechoic stripe (AS) size on interpretation accuracy by emergency physicians (EPs) and to assess the precision of FAST examination interpretation as a function of EP FAST experience. METHODS: A prospective comparison study of FAST examination interpretation by 11 emergency medicine faculty (FAC), nine community attending EPs (ATT), and nine senior emergency medicine residents (RES) was conducted; these physicians were then divided into more experienced and less experienced cohorts to assess precision. Participants interpreted video recordings of the four standard views from five FAST examinations (20 total video clips); each examination contained views with various AS sizes. Accuracy of FAST examination interpretation was calculated for each group stratified by size of AS. Precision (reproducibility) of FAST examination interpretation was assessed by calculating kappa values. RESULTS: With large, moderate, or no AS, no significant differences in accuracy were found between groups. For small AS, significant differences in accuracy were found between the ATT and RES groups and between the combined FAC + ATT group and the RES group. Kappa was good to excellent when the nth and the (n + 1)th experienced physicians in the more experienced cohort were compared. kappa values reflected that the more experienced cohort was more precise than the less experienced cohort. CONCLUSIONS: AS size visible on FAST examinations and EP experience level with FAST examination interpretation exerted a significant influence on the interpretation accuracy of videotaped FAST examinations. In addition, precision was enhanced by increased EP experience with FAST.

Abdominal Injuries↗
PubMed1991

In vivo biological validation and biophysical modeling of the sensitivity and positive accuracy of endocrine peak detection. II. The follicle-stimulating hormone pulse signal.

Despite interest in the in vivo control of gonadotropin release, valid assessment of the physiological regulation of the pulsatile secretion of the gonadotropin FSH has been hampered by the uncertain validity and reliability of available FSH peak detection algorithms. Difficulties in identifying FSH peaks accurately are believed to arise in part because of the slow metabolic clearance of this glycoprotein hormone. Here, we have used two complementary strategies to test the validity of FSH pulse detection. First, by means of a computer-assisted mathematical model for simulating episodic hormone secretion, we evaluated the effects of various putative FSH secretory pulse amplitudes and half-lives on the sensitivity and positive accuracy of peak detection. Secondly, we used an in vivo primate animal model, in which presumptively true FSH pulses were evaluated independently by continuous electrophysiological monitoring of mediobasal hypothalamic multiunit activity. These two approaches allowed us to define optimal pulse analysis parameters that yield maximal sensitivity and positive accuracy for detecting FSH peaks in synthetic and biological time series. We found (as predicted intuitively) that increasing half-times of hormone disappearance decrease both the sensitivity and positive accuracy of peak detection for any given peak detection thresholds and hormone secretory amplitudes. However, adequately sampled episodic FSH time series could be analyzed for FSH pulsatility by an appropriately constrained, objective computerized algorithm with reasonable (less than 10-15%) false negative and false positive errors, such that resultant sensitivity and positive accuracy exceed 85-90%. Of interest, computer simulations and the in vivo animal model exhibited similar discriminative capabilities. We conclude that increasing half-times of hormone (e.g. FSH) removal do impair hormone peak detection sensitivity and positive accuracy. Nevertheless, gonadotropin time series can be analyzed for FSH pulsatility in a valid manner with adequately constrained false negative and false positive error rates.

Animals↗
PubMed2003

Influence of Alzheimer pathology on clinical diagnostic accuracy in dementia with Lewy bodies.

OBJECTIVE: To determine whether AD neurofibrillary pathology influences clinical diagnostic accuracy in dementia with Lewy bodies (DLB). BACKGROUND: Pathologic diagnosis of DLB mandates Lewy bodies but also allows for AD pathology in the form of plaques and tangles. Because clinical diagnostic accuracy of DLB remains low, the authors questioned whether the severity of AD pathology in the form of tangles might affect the clinician's ability to correctly diagnose DLB in life. DESIGN/METHODS: Ninety-eight subjects with autopsy-proven DLB who had been evaluated annually at the University of California San Diego AD Research Center were identified. The clinical diagnosis used was the last diagnosis before death. Pathologic diagnosis of DLB was made according to Consensus guidelines, and Braak staging was used to assess the degree of neurofibrillary AD pathology. The clinical characteristics of subjects with DLB with low vs high Braak stages were compared and the clinical diagnostic accuracy for subjects stratified according to Braak stage was determined. RESULTS: Only 27% of the subjects with DLB demonstrated both visual hallucinations and spontaneous extrapyramidal signs (EPS). The low Braak stage (0 to 2, n = 24) subjects had a higher frequency of visual hallucinations (65%) than did subjects with DLB with higher (3 to 6, n = 66) Braak stages (33%, p = 0.008), and showed a slightly greater but not significant degree of EPS. Although clinical diagnostic accuracy for DLB was relatively low (49%), it was higher for subjects with low (75%) compared to high (39%) Braak stages (p = 0.0039). CONCLUSIONS: The degree of concomitant AD tangle pathology has an important influence on the clinical characteristics and, therefore, the clinical diagnostic accuracy of DLB.

Aged↗
PubMed2006

The quality of diagnostic accuracy studies since the STARD statement: has it improved?

OBJECTIVE: To assess whether the quality of reporting of diagnostic accuracy studies has improved since the publication of the Standards for the Reporting of Diagnostic Accuracy studies (STARD statement). METHODS: The quality of reporting of diagnostic accuracy studies published in 12 medical journals in 2000 (pre-STARD) and 2004 (post-STARD) was evaluated by two reviewers independently. For each article, the number of reported STARD items was counted (range 0 to 25). Differences in completeness of reporting between articles published in 2000 and 2004 were analyzed, using multilevel analyses. RESULTS: We included 124 articles published in 2000 and 141 articles published in 2004. Mean number of reported STARD items was 11.9 (range 3.5 to 19.5) in 2000 and 13.6 (range 4.0 to 21.0) in 2004, an increase of 1.81 items (95% CI: 0.61 to 3.01). Articles published in 2004 reported the following significantly more often: methods for calculating test reproducibility of the index test (16% vs 35%); distribution of the severity of disease and other diagnoses (23% vs 53%); estimates of variability of diagnostic accuracy between subgroups (39% vs 60%); and a flow diagram (2% vs 12%). CONCLUSIONS: The quality of reporting of diagnostic accuracy studies has improved slightly over time, without a more pronounced effect in journals that adopted the STARD statement. As there is still room for improvement, editors should mention the use of the STARD statement as a requirement in their guidelines for authors, and instruct reviewers to check the STARD items. Authors should include a flow diagram in their manuscript.

Diagnostic Techniques and Procedures↗
PubMed1998

Accuracy of an electromagnetic measurement device and application to the measurement and description of knee joint motion.

The aims of this study were to analyse the accuracy and sensitivity to metals of an electromagnetic motion measurement device and to use it to provide a description of motion of the human knee joint. A calibrated grid and sine bar were used to measure translational and rotational accuracy, which were found to be +/- 0.23 per cent of the step size (translation) and +/- 2.0 per cent of the step size (rotation) within an optimal operational zone of minimal positional error for which the receiver to transmitter separation was between 271 and 723 mm. The presence of multiple receivers was found to have a significant effect on the accuracy only when positioned within 30 mm of one another. Mild steel was found to have a significant detrimental effect when within 150 mm of the transmitter or receiver. A stainless steel bone screw had no effect on the accuracy of the device. A mathematical description of knee joint motion is presented which describes the motion in terms of clinical rotations. The device is a useful tool for measuring joint motion in the operating theatre and laboratory, owing to its accuracy and insensitivity to surgical alloys.

Bias↗
PubMed2003

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

BACKGROUND: To improve the accuracy and completeness of reporting of studies of diagnostic accuracy in order to allow readers to assess the potential for bias in a study and to evaluate the generalizability of its results. METHODS: The Standards for Reporting of Diagnostic Accuracy (STARD) steering committee searched the literature to identify publications on the appropriate conduct and reporting of diagnostic studies and extracted potential items into an extensive list. Researchers, editors and members of professional organizations shortened this list during a 2-day consensus meeting with the goal of developing a checklist and a generic flow diagram for studies of diagnostic accuracy. RESULTS: The search for published guidelines regarding diagnostic research yielded 33 previously published checklists, from which we extracted a list of 75 potential items. At the consensus meeting, participants shortened the list to 25 items, using evidence on bias whenever available. A prototypical flow diagram provides information about the method of patient recruitment, the order of test execution and the numbers of patients undergoing the test under evaluation, the reference standard or both. CONCLUSIONS: Evaluation of research depends on complete and accurate reporting. If medical journals adopt the checklist and the flow diagram, the quality of reporting of studies of diagnostic accuracy should improve to the advantage of the clinicians, researchers, reviewers, journals and the public.

Diagnostic Errors↗
PubMed2006

Diagnostic accuracy of two software modalities for detection of caries lesions in digital radiographs from four dental systems.

OBJECTIVE: To compare the caries diagnostic accuracy of two software modalities used in the assessment of digital radiographs obtained with four different dental systems, and to evaluate whether the software used for image assessment influenced the mutual comparison of those four dental systems relating to their caries diagnostic accuracy. METHODS: Under in vitro and standardized conditions 122 teeth (with 228 unrestored approximal and 99 occlusal surfaces) were radiographed in blocks of 3 test teeth and 2 non-test teeth using two storage phosphor plate systems: Digora (Soredex, Helsinki, Finland) and DenOptix (Gendex, Dentsply, Milan, Italy) and two charge coupled device (CCD)-based sensor systems: Dixi (Planmeca, Helsinki, Finland) and Sidexis (Sirona, Bensheim, Germany). The images were displayed and examined in two software modalities: their own dedicated software and a general software. Three observers examined all images for the presence of approximal enamel and dentine and occlusal dentine caries lesions using a 5-point confidence scale. The true presence of caries was validated by ground section histology. The diagnostic accuracy of the software modalities was expressed as ROC curve areas (A(z)) and differences between modalities were tested by paired t-test. Comparison of systems was analysed by post hoc t-test. RESULTS: Results of approximal and occlusal surfaces assessed together revealed nearly identical mean A(z) with the two software modalities on images obtained with the Digora (A(z)=0.71) and DenOptix (A(z)=0.72) systems. On Dixi images the mean A(z) was 0.75 using the system's own software and 0.73 using the general software. On Sidexis images the corresponding mean A(z)s were 0.79 and 0.75. None of those differences were significant. CONCLUSION: No significant difference in caries diagnostic accuracy was found between two software modalities used for examination of digital radiographs obtained with four different digital systems, and the software modality did not influence the mutual rank of the four systems relating to their diagnostic accuracy.

Data Display↗
PubMed2002

Accuracy and precision of the CoaguChek S versus laboratory INRs in a clinic.

BACKGROUND: The CoaguChek S is the next-generation coagulation monitor for measuring the international normalized ratio (INR) that replaces the CoaguChek device. Studies are lacking comparing the CoaguChek S with local laboratory INR assessment to ensure its accuracy and precision for monitoring patients on anticoagulation. OBJECTIVE: To evaluate accuracy, precision, and technical ease-of-use of the CoaguChek S compared with laboratory measurements. METHODS: Accuracy was evaluated in 101 patients by parallel assessment of INRs (CoaguChek S and laboratory); precision was evaluated in 31 patients using duplicate INRs from CoaguChek S and laboratory and from liquid quality controls. Accuracy was determined using orthogonal regression, Bland-Altman plot, and clinical applicability (INRs discrepant in categorization of INR goal and resulting in different therapeutic decisions). Precision was examined by comparing mean difference +/- SD between repeated INRs from CoaguChek S and laboratory, coefficient of variation (CV), and coefficient of repeatability (CR). The influence of low and elevated INRs on accuracy and precision was also examined. To assess ease-of-use of the monitor, the number of technical errors was recorded. RESULTS: The CoaguChek S significantly correlated to laboratory measurement (r = 0.93); 16.7% of INRs resulted in discrepant categorization and 24.5% would have required a different therapeutic plan. The CV and CR compared well between CoaguChek S and laboratory (6% vs. 4.9%; 0.455 vs. 0.346, respectively). When subgroups of INR values <4.0 and <3.0 were evaluated, the precision improved with both methods. Precision, based on liquid quality controls, was good (CV 4.6% = low-level; 3.3% = high-level). The CoaguChek S was found to have an error rate of 1.8%. CONCLUSIONS: The CoaguChek S is an accurate and precise alternative to laboratory assessment of the INR at values <4.0; it is an efficient device with a low likelihood of errors during testing.

Aged↗
PubMed1999

Accuracy of an infrared tympanic thermometer.

BACKGROUND: The use of infrared thermometry to measure temperatures in hospitalized patients is increasing. Although infrared thermometers have been proven to be accurate when they are used by well-trained personnel, no previous studies have examined their accuracy during routine hospital use. OBJECTIVE: To determine the accuracy and observer variability of temperatures measured with an infrared tympanic thermometer (TT). DESIGN: Prospective, observational study. SETTING: ICUs of a 300-bed teaching community hospital. PATIENTS: Fifty-one critically ill patients. MEASUREMENTS: The mean of three tympanic temperatures measured with the infrared TT (tempTTs) was compared to temperatures simultaneously measured with the thermistor of right heart catheters and rectal mercury thermometers for the following three groups of observers who had been certified in the use of the infrared TT: a single critical care nurse (CCN)/educator (Ed); CCNs, and floor nurses (FNs)/clinical care practitioners (CCPs). RESULTS: Two rounds of measurements were given to 51 patients by 153 observers. Temperatures of the pulmonary artery (PA) measured with the thermistor of right heart catheters (tempPAs) ranged from 96.5 to 102.6 degrees F, with a mean (-/+ SD) of 99.3+/-1.1 degrees F. The intraobserver variabilities (correlation coefficients) of the tempTTs ranged from 0.90 for those measured by FNs/CCPs, to 0.92 for those measured by CCNs, to 0.98 for those measured by the CCN/Ed. Accuracy, arbitrarily defined as within a deviation of -/+0.5 degrees F of the tempPA, was 100% for the rectal mercury thermometer and 98.0% for the infrared TT when used by the CCN/Ed. The accuracy of the infrared TT was 80% when measured by CCNs and 61% when measured by FNs/CCPs. Differences between tempPAs and tempTTs measured by the CCN/Ed ranged from 0 to 0.7 degrees F, with a mean of 0.2 degrees F. Similarly, differences between tempPAs and tempTTs measured by CCNs ranged from 0 to 2.4 degrees F, with a mean difference of 0.3 degrees F. However, differences between tempPAs and tempTTs measured by FNs/CCPs ranged from 0 to 3.0 degrees F, with a mean of 0.6 degrees F (greater differences than those obtained by the CCNs; p < 0.01). The accuracy of rectal mercury thermometry was 100%. If a temperature > or = 101.0 degrees F had been considered as the threshold at which a fever is present, and if the mean of three measurements had been used to designate temperature, workups that were either inappropriately performed or omitted would have resulted from 2% of tempTTs measured by the CCN/Ed, 1% of those measured by CCNs, and 4% of those measured by FNs/CCPs. CONCLUSION: When used properly, both tympanic and rectal thermometry are very accurate. However, the infrared TT produced measurements that were both less accurate and less reproducible when used by nurses who routinely used it in clinical practice.

Ear, Middle↗
PubMed1988

Improved accuracy of the exercise electrocardiogram in detection of coronary artery and three-vessel coronary disease.

The study objective was to assess the widespread applicability of ST/HR slope for the modified Bruce exercise test using a computerized electrocardiogram (ECG); compare the usefulness of the ST/HR slope with standard ECG criteria in detection of coronary artery disease (CAD) and identification of three-vessel or left main CAD; and then develop a new, modified ST/HR score (MSHS) for improving the diagnostic accuracy of ST/HR slope. The studies were retrospective and prospective in design, conducted in referral-based cardiology clinics at a national cardiovascular center. A selected sample of 142 patients underwent exercise ECG and coronary angiography, as did a normal control group of 402 patients who were apparently free from CAD. Sixty three other patients who underwent coronary angiography were also studied prospectively. No limitations of medical treatment were exacted for the test except digitalis treatment. Linear regression analysis, from which ST/HR slope was derived, was done with seven measurements of HR and ST displacement at 60 ms from J point in leads a VF and V5 during 6 min before the end of exercise. MSHS was derived from a multiple regression model with peak HR (% maximum HR), ST index (ST depression + ST slope), and ST/HR slope. Although the usual ST criteria (sensitivity = 63 percent, specificity = 73 percent), ST index (71 percent, 80 percent), and ST/HR slope (70 percent, 97 percent) were equally accurate in detection of CAD, MSHS showed significantly improved sensitivity (88 percent) with similar specificity (81 percent). In identification of three-vessel or left main CAD, when compared with other criteria, ST/HR slope and MSHS provided improved diagnostic accuracy: sensitivity (74 and 78 percent, respectively), specificity (88 and 93 percent) and overall test accuracy (85 and 89 percent). The improved accuracy of ST/HR slope and MSHS was prospectively validated in 63 other patients. ST/HR slope was applicable to computerized ECG data for the standard treadmill test, and showed improved accuracy in detection of three-vessel or left main CAD. The new, modified ST/HR score more accurately predicted not only the presence but also the severity of CAD.

Adult↗
PubMed2003

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

OBJECTIVE: To improve the accuracy and completeness of reporting of studies of diagnostic accuracy, to allow readers to assess the potential for bias in the study and to evaluate its generalisability. METHODS: The Standards for Reporting of Diagnostic Accuracy (STARD) steering committee searched the literature to identify publications on the appropriate conduct and reporting of diagnostic studies and extracted potential items into an extensive list. Researchers, editors, and members of professional organisations shortened this list during a two-day consensus meeting with the goal of developing a checklist and a generic flow diagram for studies of diagnostic accuracy. RESULTS: The search for published guidelines regarding diagnostic research yielded 33 previously published checklists, from which we extracted a list of 75 potential items. At the consensus meeting, participants shortened the list to 25 items, using evidence on bias whenever available. A prototypical flow diagram provides information about the method of patient recruitment, the order of test execution and the numbers of patients undergoing the test under evaluation, the reference standard or both. CONCLUSIONS: Evaluation of research depends on complete and accurate reporting. If medical journals adopt the checklist and the flow diagram, the quality of reporting of studies of diagnostic accuracy should improve to the advantage of clinicians, researchers, reviewers, journals, and the public.

Algorithms↗
PubMed2004

MRA versus DSA in the assessment of occlusive disease in the aortic arch vessels: accuracy in detecting the severity, number, and length of stenoses.

PURPOSE: To compare the diagnostic accuracy of contrast-enhanced magnetic resonance angiography (MRA) to that of digital subtraction angiography (DSA) in the detection, grading, and measurement of atherosclerotic stenoses involving the aortic arch arteries. METHODS: The MRA and DSA studies from 28 patients (16 women; mean age 61.6 years, range 24-83) being evaluated for possible aortic arch vessel disease were examined. The aortic arch vasculature was divided into 9 segments; within each segment, the presence and severity of stenotic or occlusive disease was determined based on a 5-point scale. In addition, stenosis length and distance to the branch were measured in 5-mm increments. Image quality was assessed using a 5-point scale. The accuracy, sensitivity, and specificity values, as well as the positive and negative predictive values in MRA's identification of lesions, were evaluated in comparison to DSA. RESULTS: In 28 patients, 189 segments were assessed by both methods. Of these, 173 were correctly rated by MRA, resulting in an accuracy of 91.5%. The accuracy dropped slightly to 86.5% when 11 "not assessable" lesions were included. Sensitivity and specificity for severity measurement were 88.5% and 95.6%, respectively. In 39 of 45 lesions, stenosis length measurements were identical by both methods, but there was a difference of 0.5 cm each in 6 lesions. CONCLUSIONS: MRA as compared to DSA shows high accuracy in the detection and grading of lesions involving the aortic arch vessels. The noninvasive nature of this method recommends its use for screening, treatment planning, and follow-up in known or suspected arterial disease in aortic arch arteries.

Adult↗
PubMed1981

The effects of instructions and calculation procedures on observers' accuracy, agreement, and calculation correctness.

Although the quality of observational data is generally evaluated by observer agreement, measures of both observer agreement and accuracy were available in the present study. Videotapes with a criterion protocol were coded by 16 observers. All observers calculated agreement scores both on their own and their partner's data and on a contrived data set misrepresented as data collected by other observers. Compared with agreement scores calculated by the experimenter, observers erroneously inflated their own agreement scores and deflated the agreement scores on the contrived data. Half of the observers (n = 8) had been given instructions emphasizing the importance of accuracy during observation while the other half had been given instructions emphasizing interobserver agreement. Accuracy exceeded agreement for the former group, whereas agreement exceeded accuracy for the latter group. The implications are that agreement should be calculated by the experimenter and that the accuracy-agreement relationship can be altered by differential observer instructions.

Journal Article↗
PubMed1972

Accuracy of performance on a matching-to-sample procedure under interval schedules.

Correct matches on a matching-to-sample procedure were reinforced under fixed-interval, chained fixed-interval, and fixed-interval schedules with exteroceptive stimulus changes correlated with time since the last reinforcer (an added clock). For all four pigeons, accuracy changed within the fixed-interval and fixed-interval schedules with added clock, decreasing from the beginning of the interval to some point in the middle. The performance then became increasingly more accurate until the end of the interval. Under the chained schedules, accuracy also changed within the components. During the initial component, accuracy decreased from the beginning of the fixed interval to some point in the middle or at the end. During the middle component, the performance usually remained at an intermediate level of accuracy. During the terminal component, the initially inaccurate performance became increasingly more accurate throughout the interval. Systematic relationships between response rate and per cent error showed that all four pigeons performed most accurately at high rates. The accuracy of the performance at low rates was also quite high. These relationships held for all three types of schedules through an eight-fold variation in scheduled interreinforcement time.

Journal Article↗
PubMed2001

On the wrong side of the tracts? Evaluating the accuracy of geocoding in public health research.

OBJECTIVES: This study sought to determine the accuracy of geocoding for public health databases. METHODS: A test file of 70 addresses, 50 of which involved errors, was generated, and the file was geocoded to the census tract and block group levels by 4 commercial geocoding firms. Also, the "real world" accuracy of the best-performing firm was evaluated. RESULTS: Accuracy rates in regard to geocoding of the test file ranged from 44% (95% confidence interval [CI] = 32%, 56%) to 84% (95% CI = 73%, 92%). The geocoding firm identified as having the best accuracy rate correctly geocoded 96% of the addresses obtained from the public health databases. CONCLUSIONS: Public health studies involving geocoded databases should evaluate and report on methods used to verify accuracy.

Abstracting and Indexing↗