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PubMed2004

Syndromic surveillance: the effects of syndrome grouping on model accuracy and outbreak detection.

STUDY OBJECTIVE: Data used by syndromic surveillance systems must be grouped into syndromes or prodromes. Previous studies have examined the accuracy of different methods of syndromic grouping. We seek to study the effects of different syndrome grouping methods on model accuracy, a key factor in the outbreak-detection performance of syndromic surveillance systems. METHODS: Daily emergency department visit rates were analyzed from 2 urban academic tertiary care hospitals for 1,680 consecutive days. During this period, each hospital census totaled approximately 230,000 patient visits. Three methods were used to group the visits into a respiratory-related syndrome category: 1 relying on chief complaint, 1 on diagnostic codes, and 1 on a combination of the two. The different groupings of the syndromic data resulting from these methods were used to build different historical models that were then tested for forecasting accuracy and for sensitivity to detecting simulated outbreaks. RESULTS: For both hospitals, the data grouped according to chief complaints alone yielded the lowest model accuracy and the lowest detection sensitivity. Using diagnostic codes to group the data yielded better results in accuracy and sensitivity. Combining the 2 grouping methods yielded the best results in accuracy and sensitivity. Temporal smoothing of the data was shown to improve sensitivity in all cases, although to various degrees in the different models. CONCLUSION: The methods used to group input data into syndromic categories can have substantial effects on the overall performance of syndromic surveillance systems. The results suggest that incorporating diagnostic data into these systems can improve the modeling accuracy and its detection sensitivity. Furthermore, the best results may be achieved by using a combination of methods to group visits into syndromic categories.

Bioterrorism↗
PubMed2005

Accuracy of radiographer plain radiograph reporting in clinical practice: a meta-analysis.

AIM: To determine the accuracy of radiographer plain radiograph reporting in clinical practice. MATERIALS AND METHODS: Studies were identified from electronic sources and by hand searching journals, personal communication and checking reference lists. Eligible studies assessed radiographers' plain radiograph reporting in clinical practice compared with a reference standard, and provided accuracy data to construct 2 x 2 contingency tables. Data were extracted on study eligibility and characteristics, quality and accuracy. Summary estimates of sensitivity and specificity and receiver operating characteristic curves were used to pool the accuracy data. RESULTS: Radiographers compared with a reference standard, report plain radiographs in clinical practice at 92.6% (95% CI: 92.0-93.2) and 97.7% (95% CI: 97.5-97.9) sensitivity and specificity, respectively. Studies that compared selectively trained radiographers and radiologists of varying seniority against a reference standard showed no evidence of a difference between radiographer and radiologist reporting accuracy of accident and emergency plain radiographs. Selectively trained radiographers were also found to report such radiographs as accurately as those not solely from accident and emergency, although some variation in reporting accuracy was found for different body areas. Training radiographers improved their accuracy when reporting normal radiographs. CONCLUSION: This study systematically synthesizes the literature to provide an evidence-base showing that radiographers can accurately report plain radiographs in clinical practice.

Clinical Competence↗
PubMed2006

Feasibility and accuracy of TRUS in the pre-treatment staging for rectal carcinoma in general practice.

AIMS: Transrectal ultrasonography (TRUS) is the diagnostic tool of choice for local staging of rectal carcinoma. The accuracy in determining of tumour infiltration depth has been reported to reach 95% (on average, 85%). The aim of the study was to analyse the diagnostic accuracy of the TRUS in the clinical routine. PATIENTS AND METHODS: From 01/01/2000 to 12/31/2003, all patients with rectal carcinoma were enrolled in a prospective multicenter observational study. In case of complete findings of pre-operative TRUS and post-operative histological investigation of the surgical specimen on the tumour infiltration depth, overall accuracy of TRUS was determined. RESULTS: Overall, 13,610 patients with rectal carcinoma were enrolled in the study. Five thousand and fifty-six subjects (37%) underwent TRUS. In 3,501 patients, TRUS finding (uT-stage) could be compared with the result of the definitive histologic investigation (pT-stage). The accuracy of TRUS in all T-stages was 65.8%. The highest sensitivity was achieved in the T3-stage (74.9%), while in T2, T1, and T4, it was 59.6, 59.0 and 31.1%, respectively. In discriminating tumour growth limited to the rectal wall vs that through the rectal wall into the neighboring tissue, TRUS-associated accuracy was 76.5%. There were no differences between various tumour locations above the anocutaneous line. CONCLUSIONS: Diagnostic accuracy of TRUS in determining depth of tumour infiltration within or through the rectum wall in the routinuous diagnostic of rectal carcinoma does not reach the excellent published study results. A considerable improvement of the qualitative outcome in using this specific diagnostic tool appears to be recommendable to utilize its advantages such as high accuracy, efficacy, and practicability in the diagnostic process and deriving consequences for a possible neoadjuvant treatment as well as optimal planning of the surgical approach.

Carcinoma↗
PubMed2003

Plasma amino-terminal pro-brain natriuretic peptide and accuracy of heart-failure diagnosis in primary care: a randomized, controlled trial.

OBJECTIVES: The purpose of this study was to determine the effect of amino-terminal pro-brain natriuretic peptide (N-BNP) on the diagnostic accuracy of heart failure (HF) in primary care. BACKGROUND: The accurate diagnosis of patients with suspected HF presenting in primary care is difficult. Amino-terminal pro-brain natriuretic peptide is present in high levels in cardiac dysfunction and may improve the diagnostic accuracy of HF in primary care. METHODS: The Natriuretic Peptides in the Community Study was a prospective, randomized controlled trial of the effect of N-BNP on the accuracy of HF diagnosis. Patients presenting to their general practitioner (GP) with symptoms of dyspnea and/or peripheral edema were included. The GPs formulated an initial diagnosis based on clinical assessment. All patients underwent a full cardiologic assessment that included echocardiography and N-BNP. Each patient was randomized to the BNP group (GP received the N-BNP result) or the control group (GP did not receive the N-BNP result). Patients were then reviewed by their GP, and their diagnosis was reviewed. The primary end point was the accuracy of the GPs' diagnoses compared with the panel standard. RESULTS: A total of 305 patients were included; mean age was 72 years, 65% were female. Seventy-seven patients met the panel criteria for HF. The diagnostic accuracy improved 21% in the BNP group and 8% in the control group (p = 0.002). The main impact of N-BNP measurement on diagnostic accuracy was the GPs' correctly ruling out HF. The number needed to diagnose by N-BNP measurement was seven patients. CONCLUSION: This study demonstrates that N-BNP measurement significantly improves the diagnostic accuracy of HF by GPs over and above customary clinical review.

Adult↗
PubMed2006

The accuracy of ultrasonic indentation in detecting simulated bone displacement: a comparison of three techniques.

PURPOSE: Palpation is used most commonly to assess tissue stiffness despite its well-known deficiencies. As an improvement, a mechanical technique known as ultrasonic indentation has been proposed. The purpose of this study was to compare the accuracy of 3 ultrasonic indentation techniques in quantifying bone displacement in a specially constructed tissue simulator. METHODS: Three ultrasonic indentation techniques were tested for their accuracy: a rigid, laboratory-based method (rigid), a less rigid system actuated by hand (assisted), and a totally free-hand system (handheld). Each indentation technique was applied on a tissue simulator, which consisted of a deformable phantom overlying a displaceable piston to simulate soft tissue overlying bone. Measures of piston (ie, bone) displacement obtained by each indentation technique were compared with a gold standard of piston displacement to determine the accuracy of each technique. Statistical tests were used to determine if differences between experimental and reference measures of piston displacement were significant. RESULTS: When indented, phantom deformation preceded piston displacement because of unequal stiffness between the two. The rigid and assisted indentation techniques showed the best accuracy for measuring simulated bone displacement. Differences in accuracy between the rigid and assisted techniques were insignificant. The accuracy of the handheld technique was significantly less than the rigid and assisted techniques. CONCLUSIONS: The clinical utility of assisted ultrasonic indentation should be explored given its accuracy and the excessive size, cost, and complexity of the rigid technique. The large error magnitude of the handheld technique may exclude it from clinical use now.

Equipment Design↗
PubMed2006

Marginal accuracy of titanium copings fabricated by casting and CAD/CAM techniques.

STATEMENT OF PROBLEM: Advances in computer-aided design/computer-assisted manufacturing (CAD/CAM) technology purportedly enhance the marginal fit of dental restorations. However, little information is available on the marginal accuracy of restorations manufactured with various CAD/CAM systems. PURPOSE: The purpose of this study was to evaluate and compare the marginal accuracy and refinement time of titanium copings fabricated by 3 different CAD/CAM systems relative to standard casting techniques. MATERIAL AND METHODS: Sixty-four stone die duplicates of a human maxillary central incisor, prepared for a metal-ceramic crown, with a uniform chamfer design, were divided into 4 groups (n=16). The specimens were restored with titanium copings using CAD/CAM systems Pro 50 (PRO), DCS (DCS), and Everest (EVE). A conventional titanium casting technique, Biotan (BIO), served as a control. Vertical and horizontal discrepancies between restoration margins and the preparations were each measured before and after manual refinement. This refinement was completed using a disclosing agent and by removing the internal positive defects of the copings. The marginal discrepancies of the copings were evaluated at 4 standard areas using 10 measurements, for a total of 160 measurements of each margin. Repeated-measures ANOVA was used for analyzing marginal accuracy. The coping refinement time was analyzed with the Kruskal-Wallis and post hoc Wilcoxon rank sum tests (alpha=.05). RESULTS: The marginal discrepancies (microm) ranged from 32.9 to 127.8 before and from 3.4 to 58.4 after the manual refinement of copings. Manual refinement significantly improved the marginal accuracy (P<.0001) when compared with the initial fabrication. The relative (%) gain of marginal accuracy was PRO, 74.1%; DCS, 69.7%; EVE, 68.7%; and the control, BIO, 69.2%. The median duration of manual refinement time in minutes was 6.0 for PRO, 9.5 for DCS, 4.0 for EVE, and 4.0 for BIO (Kruskal-Wallis-test: P<.0001). CONCLUSION: Manual adjustment significantly improves the marginal accuracy of CAD/CAM system-fabricated titanium copings. The highest marginal accuracy was achieved with the DCS system, using a longer refinement time.

Analysis of Variance↗
PubMed2000

Prompting methods affect the accuracy of children's school lunch recalls.

OBJECTIVES: To evaluate the feasibility of implementing 3 specific prompting methods among students in the first and fourth grades (mean age = 7.2 and 10.1 years, respectively), to validate recall accuracy of first- and fourth-grade students against observation, to develop a single measure of inaccuracy that cumulated errors in reporting food items and amounts without allowing underreporting and overreporting to cancel each other, and to establish information regarding the measure of inaccuracy for use in future studies. DESIGN: Children were interviewed the morning after they were observed eating lunch provided by the school. Interviews included free recall, nonsuggestive prompted recall, and specific prompted recall (either preference, food category, or visual). SUBJECTS/SETTING: Ninety-six children (48 students per grade) were studied--32 per the specific prompting method--stratified by grade, sex, and ethnicity (African-American or white). Specific prompting method was randomly assigned to children within strata. STATISTICAL ANALYSIS: Food items were categorized and weighted as: combination entree = 2, condiments = 1/3, and other = 1. To calculate inaccuracy of recall, absolute differences between amounts reported and observed eaten were calculated for each item and then multiplied by each item's weight; these values were then summed across all items for each child. Inaccuracy of recall was determined before specific prompting and after specific prompting and for the difference (inaccuracy after specific prompting minus inaccuracy before specific prompting). RESULTS: Before specific prompting, median inaccuracy was 2.7 servings for the 48 first-grade students and 1.7 servings for the 48 fourth-grade students. The median difference in inaccuracy from before to after specific prompting was 0 for both grades. Specific prompting increased recall accuracy for 9 first-graders and 12 fourth-graders, but decreased recall accuracy for 21 first-graders and 7 fourth-graders, and did not change recall accuracy for 18 first-graders and 29 fourth-graders. Among children whose recall accuracy increased after specific prompting, 5 first-graders and 8 fourth-graders received prompting for food category. APPLICATIONS/CONCLUSIONS: Among first-grade students, specific prompting (either preference, food category, or visual) may hurt more than help recall accuracy. Among fourth-grade students, prompting for food category yields small gains in recall accuracy with minimal losses. Validation studies are needed with larger sample sizes to determine prompting methods that produce more accurate dietary recalls from children of various socioeconomic status groups, other racial/ethnic groups, and at other meals.

Analysis of Variance↗
PubMed2001

Effect of tissue Doppler on the accuracy of novice and expert interpreters of dobutamine echocardiography.

The subjective interpretation of dobutamine echocardiography (DBE) makes the accuracy of this technique dependent on the experience of the observer, and also poses problems of concordance between observers. Myocardial tissue Doppler velocity (MDV) may offer a quantitative technique for identification of coronary artery disease, but it is unclear whether this parameter could improve the results of less expert readers and in segments with low interobserver concordance. The aim of this study was to find whether MDV improved the accuracy of wall motion scoring in novice readers, experienced echocardiographers, and experts in stress echocardiography, and to identify the optimal means of integrating these tissue Doppler data in 77 patients who underwent DBE and angiography. New or worsening abnormalities were identified as ischemia and abnormalities seen at rest as scarring. Segmental MDV was measured independently and previously derived cutoffs were applied to categorize segments as normal or abnormal. Five strategies were used to combine MDV and wall motion score, and the results of each reader using each strategy were compared with quantitative coronary angiography. The accuracy of wall motion scoring by novice (68 +/- 3%) and experienced echocardiographers (71 +/- 3%) was less than experts in stress echocardiography (88 +/- 3%, p <0.001). Various strategies for integration with MDV significantly improved the accuracy of wall motion scoring by novices from 75 +/- 2% to 77 +/- 5% (p <0.01). Among the experienced group, accuracy improved from 74 +/- 2% to 77 +/- 5% (p <0.05), but in the experts, no improvement was seen from their baseline accuracy. Integration with MDV also improved discordance related to the basal segments. Thus, use of MDV in all segments or MDV in all segments with wall motion scoring in the apex offers an improvement in sensitivity and accuracy with minimal compromise in specificity.

Aged↗
PubMed2002

Impact of graphical user interface screen features on computer task accuracy and speed in a cohort of patients with age-related macular degeneration.

PURPOSE: To investigate the impact of graphical user interface screen features on computer task performance in patients with age-related macular degeneration (AMD). DESIGN: Interventional case series. METHODS: Eighteen patients with visual impairment due to AMD were recruited from the Bascom Palmer Eye Institute Low Vision Clinic. Each patient underwent evaluation of visual acuity using the Early Treatment Diabetic Retinopathy Study protocol, contrast sensitivity using a Pelli-Robson chart, binocular simultaneous visual field using the Esterman program on an automated perimeter, and color vision using Farnsworth D-15. Each subject then completed computer icon identification tasks while the following screen features of the graphical user interface were varied: size of icons displayed, icon set size (number of icons displayed), and background color. Each patient performed all 125 computer tasks with each of five icon sizes (9.2 mm, 14.6 mm, 23.2 mm, 36.8 mm, 58.3 mm), each of five icon set sizes (2, 3, 4, 5, 6), and each of five different background colors (black, white, red, green, blue) in a randomly ordered fashion. Relationships between computer task performance (accuracy and speed) and graphical user interface screen features were studied. RESULTS: Icon size and icon set size are significantly associated with computer task accuracy (P <.001), whereas background color is not a significant predictor of task accuracy (P =.63). The impact of icon size on accuracy is nonlinear, with the data indicating that no additional improvement in accuracy is associated with increasing the icon size beyond 23.2 mm. The impact of icon set size on accuracy is linear, with a smaller icon set size significantly associated with greater computer accuracy. A larger icon size is significantly associated with a shorter time to task completion (P =.001); this relationship is largely linearly related to icon size. There was no significant impact of background color (P =.11) or set size (P =.37) on time to task completion. CONCLUSIONS: Modifications of graphical user interface design may permit improved computer task performance among patients with visual impairment due to AMD.

Adult↗
PubMed2004

Assessment of screw displacement axis accuracy and repeatability for joint kinematic description using an electromagnetic tracking device.

Screw displacement axes (SDAs) have been employed to describe joint kinematics in biomechanical studies. Previous reports have investigated the accuracy of SDAs combining various motion analysis techniques and smoothing procedures. To our knowledge, no study has assessed SDA accuracy describing the relative movement between adjacent bodies with an electromagnetic tracking system. This is important, since in relative motion, neither body is fixed and consequently sensitivity to potential measurement errors from both bodies may be significant. Therefore, this study assessed the accuracy of SDAs for describing relative motion between two moving bodies. We analyzed numerical simulated data, and physical experimental data recorded using a precision jig and electromagnetic tracking device. The numerical simulations demonstrated SDA position accuracy (p=0.04) was superior for single compared to relative body motion, whereas orientation accuracy (p=0.2) was similar. Experimental data showed data-filtering (Butterworth filter) improved SDA position and orientation accuracies for rotation magnitudes smaller or equal to 5.0 degrees, with no effect at larger rotation magnitudes (p<0.05). This suggests that in absence of a filter, SDAs should only be calculated at rotations of greater than 5.0 degrees. For rotation magnitudes of 0.5 degrees (5.0 degrees ) about the SDA, SDA position and orientation error measurements determined from filtered experimental data were 3.75+/-0.30 mm (3.31+/-0.21 mm), and 1.10+/-0.04 degrees (1.04+/-0.03 degrees ), respectively. Experimental accuracy values describing the translation along and rotation about the SDA, were 0.06+/-0.00 mm and 0.09+/-0.01 degrees, respectively. These small errors establish the capability of SDAs to detect small translations, and rotations. In conclusion, application of SDAs should be a useful tool for describing relative motion in joint kinematic studies.

Algorithms↗
PubMed1994

Accuracy of the clinical examination in detecting hypoxemia in infants with respiratory illness.

OBJECTIVES: To evaluate the diagnostic accuracy of the clinical examination in detecting hypoxemia in infants with lower respiratory tract illness. DESIGN: Cross-sectional study. SETTING: Three university pediatric outpatient departments and one private pediatric practice. PATIENTS: Healthy infants less than 1 year of age seen between December and March 1989 and 1990, with symptoms suggesting acute lower respiratory tract illness. MAIN OUTCOME MEASURES: The test characteristics of 27 elements of the clinical examination, as well as the accuracy of the overall examination and the components of the examination in detecting oxygen saturation < 95% measured by pulse oximetry. Reliability of clinical examination findings. RESULTS: None of the 27 clinical findings had sensitivities that would make them useful diagnostic tests for hypoxemia. By combining all the clinical findings, however, we found good diagnostic accuracy (area under the receiver operator characteristic curve 0.90). Three groups of clinical findings--social interactiveness, respiratory effort, and physical appearance--accounted for much of the diagnostic accuracy of the examination. Auscultatory findings contributed little. In these three groups, five clinical findings accounted for almost all the accuracy: attentiveness, consolability, respiratory effort, color, and movement. Together, these findings also had good accuracy (area under the receiver operator characteristic curve 0.95). CONCLUSIONS: A small number of clinical observations may be mostly responsible for the diagnostic value of the clinical examination of infants with symptoms of LRI. Concentrating on a limited group of findings appears to enhance the accuracy of the examination in detecting hypoxemia.

Cross-Sectional Studies↗
PubMed2002

Accuracy of family history of cancer as reported by men with prostate cancer.

OBJECTIVES: To report on the accuracy of probands providing information on specific cancer types in their families and the ability of investigators to document these reports. Accurate information on the health status of family members is critical when studying familial patterns of diseases. However, collecting these data require significant resources. METHODS: We identified 143 patients with prostate cancer from the University of Texas M. D. Anderson Cancer Center who had reported at least 1 first-degree relative with cancer. There were 263 first-degree relatives identified, for whom we confirmed diagnoses using medical records, death certificates, and verbal confirmation. The data are reported in summary statistics and compared with chi-square analysis. RESULTS: We documented 78% of the reports, with an accuracy rate of 81.6%. We found that accuracy was highly related to the site reported. Accuracy and documentation levels were not related to the age or income of the proband. The education level was significantly associated with the ability to document cancer, but not with the accuracy of the report. The accuracy and documentation differed by the relationship of the first-degree relative to the proband. CONCLUSIONS: Proband reporting of cancer in first-degree relatives varies widely by site, with common metastatic sites the most inaccurate. No reliable demographic factors were found that would reasonably predict the ability to document the accuracy of the report. We found a significant proportion of proband-reported prostate cancer was, in reality, benign prostatic hyperplasia. We propose a strategy of targeting male relatives and reports of cancer in common metastatic sites for aggressive follow-up.

Death Certificates↗
PubMed1999

Titanium full crown casting: thermal expansion of investments and crown accuracy.

OBJECTIVES: The aim of the present study was to establish a statistical model between thermal expansion values of investments and dimensional accuracy of cast titanium full crowns. METHODS: Thermal expansion (TE) measurements were made on cylindrical specimens (5O x 20 mm) dried to constant mass and full crown wax patterns were prepared from metal dies having the same design. Castings were made using a one-chamber high-pressure casting machine. Dimensional accuracy of the cast crowns was expressed by the discrepancy (micron) between the wax pattern and a casting prepared from the same die. A simple least squares linear regression analysis was made on data accumulated over the last five years. RESULTS: A high correlation coefficient (R = 0.87) was found between dimensional accuracy (Y) and thermal expansion value (X), and the accuracy was predicted by a formula Y = 1040.50X - 1004.45 microns. For zero discrepancy, a thermal expansion of 0.97% was required. SIGNIFICANCE: The dimensional accuracy expressed as the discrepancy between wax pattern and casting is easy to understand and less confusing than the traditional percentage value. The crown accuracy was highly predictable (R = 0.87) from the thermal expansion value of investments determined under controlled laboratory measuring conditions. New investments being released for titanium casting can be under constant modification. For this, regular monitoring of their TE behaviour is essential and use of the same batch is preferable for expansion measurement and crown accuracy assessment.

Analysis of Variance↗
PubMed2003

Effects of temporal and/or spatial instructions on the speed-accuracy trade-off of pointing movements in children.

The present experiment examined in a visuo-manual task the effects of verbal instructions on the speed/accuracy trade-off across children aged 6, 8 and 10 years and adults. Three different verbal instructions (speed, accuracy and speed-accuracy) had to be respected to perform a pointing task. Analysis of reaction time (RT), movement time (MT) and percentage of targets reach showed that: (1) whatever the age, children were able to comply with the verbal instructions to adapt the velocity and/or the precision of their response (initiation and movement execution); (2) the main age-related difference of the speed-accuracy trade-off concerned the temporal (MT) but not the accuracy (targets reach) characteristics of the pointing movements; and (3) in the older children and even more precisely in adults, a temporal deficit was observed when the accuracy of aiming was required. This deficit increased as accuracy increased. These results were discussed within the theoretical frameworks of the developmental speed processing model proposed by Kail [Psychol. Bull., 109(3) (1991) 490-501] for RT data, and the speed-accuracy trade-off model proposed by Pachella [Pachella, R.G., The interpretation of reaction time in information-processing research, in, Kantowitz, B. (ed) Human Information Processing: Tutorial in Performance and Recognition, Erlbaum, (1974) 41-82] for MT and targets reach data.

Acceleration↗
PubMed1984

Comparison of exercise perfusion and ventricular function imaging: an analysis of factors affecting the diagnostic accuracy of each technique.

Exercise thallium-201 perfusion scans and gated equilibrium blood pool scans were performed in 120 catheterized patients with a chest pain syndrome. Eighty-six patients had coronary artery disease and 34 patients did not. The effects of gender, propranolol, exercise level, exercise ischemia, history of typical angina, history of previous myocardial infarction, electrocardiographic Q waves, number of diseases vessels and extent of coronary artery obstruction on diagnostic accuracy were evaluated. The overall sensitivity and specificity of thallium scans were 76 and 68%, respectively, and those of gated blood pool scans 80 and 62% (p = not significant). Propranolol decreased the specificity of thallium scans (propranolol = 42%; no propranolol = 87%, p less than 0.05). Thallium scans and anginal history were less sensitive for detecting coronary disease in women (men: thallium = 79%; angina = 77%; women: 54 and 46%, respectively; p less than 0.05). Exercise level did not significantly affect the diagnostic accuracy of either scan. Thallium and gated scans were both highly sensitive (95%) in detecting disease in 20 patients with a prior myocardial infarction, angina and a positive electrocardiogram. The sensitivity of the thallium scan significantly decreased as the number of diseased vessels decreased. Both thallium and gated scans were less frequently positive in patients with atypical angina or no Q waves, but were not significantly influenced by electrocardiographic ischemia. The sensitivity and specificity of both scans were low in 57 patients with the combination of atypical angina, no history of infarction and equivocal stress electrocardiogram thallium = 61 and 63%, respectively; gated = 61 and 67%). When stress thallium scan evaluation included the electrocardiogram and thallium scan interpretation, the diagnostic accuracy was 81%. When all the information from gated scans (wall motion, ejection fraction, pulmonary blood volume) was combined for final gated scan evaluation, the diagnostic accuracy was 83%. When electrocardiographic data were added to all three gated scan variables, diagnostic accuracy was 77%. In conclusion, thallium perfusion and gated blood pool scans have reasonable diagnostic accuracy for coronary artery disease in a group of patients with a moderately high prevalence of disease. However, combined variables from each test are needed to provide reliable diagnostic accuracy.

Coronary Circulation↗
PubMed1996

A comparison of accuracy between clinical examination and magnetic resonance imaging in the diagnosis of meniscal and anterior cruciate ligament tears.

A prospective and retrospective study was undertaken to compare the accuracy of magnetic resonance imaging (MRI) with clinical examination in diagnosing meniscal and anterior cruciate ligament (ACL) tears. Pathological findings were then confirmed during arthroscopy. One hundred fifty-four patients clinically diagnosed with a meniscal or ACL tear who ultimately had arthroscopic knee surgery were evaluated; 100 patients underwent clinical examination followed by MRI, and 54 underwent clinical examination alone. The presence or absence of meniscal and ACL tears was confirmed during arthroscopy. The accuracies of clinical examination and MRI were compared for the 100 patients who underwent both clinical examination and MRI. The accuracy of MRI was 75% for medial meniscal tears, 69% for lateral meniscal tears and 98% for ACL tears. The accuracy of clinical examination was 82% for medial meniscal tears, 76% for lateral meniscal tears and 99% for complete tears of the ACL. Furthermore, the accuracy of clinical examination for the 54 patients who underwent clinical examination alone was not significantly different from the accuracy of clinical examination in the 100 patients who also underwent MRI. There was no significant difference between the accuracy of clinical examination and MRI in the diagnosis of meniscal and ACL tears and, overall, MRI contributed to treatment in only 16 of 100 cases. Based on these findings, we feel that MRI, except in certain circumstances, is an expensive and unnecessary diagnostic test in patients with suspected meniscal and ACL pathology.

Adult↗
PubMed2000

Partially pre-calculated weights for the backpropagation learning regime and high accuracy function mapping using continuous input RAM-based sigma-pi nets.

In this article we present a methodology that partially pre-calculates the weight updates of the backpropagation learning regime and obtains high accuracy function mapping. The paper shows how to implement neural units in a digital formulation which enables the weights to be quantised to 8-bits and the activations to 9-bits. A novel methodology is introduced to enable the accuracy of sigma-pi units to be increased by expanding their internal state space. We, also, introduce a novel means of implementing bit-streams in ring memories instead of utilising shift registers. The investigation utilises digital "Higher Order" sigma-pi nodes and studies continuous input RAM-based sigma-pi units. The units are trained with the backpropagation learning regime to learn functions to a high accuracy. The neural model is the sigma-pi units which can be implemented in digital microelectronic technology. The ability to perform tasks that require the input of real-valued information, is one of the central requirements of any cognitive system that utilises artificial neural network methodologies. In this article we present recent research which investigates a technique that can be used for mapping accurate real-valued functions to RAM-nets. One of our goals was to achieve accuracies of better than 1% for target output functions in the range Y epsilon [0,1], this is equivalent to an average Mean Square Error (MSE) over all training vectors of 0.0001 or an error modulus of 0.01. We present a development of the sigma-pi node which enables the provision of high accuracy outputs. The sigma-pi neural model was initially developed by Gurney (Learning in nets of structured hypercubes. PhD Thesis, Department of Electrical Engineering, Brunel University, Middlessex, UK, 1989; available as Technical Memo CN/R/144). Gurney's neuron models, the Time Integration Node (TIN), utilises an activation that was derived from a bit-stream. In this article we present a new methodology for storing sigma-pi node's activations as single values which are averages. In the course of the article we state what we define as a real number; how we represent real numbers and input of continuous values in our neural system. We show how to utilise the bounded quantised site-values (weights) of sigma-pi nodes to make training of these neurocomputing systems simple, using pre-calculated look-up tables to train the nets. In order to meet our accuracy goal, we introduce a means of increasing the bandwidth capability of sigma-pi units by expanding their internal state-space. In our implementation we utilise bit-streams when we calculate the real-valued outputs of the net. To simplify the hardware implementation of bit-streams we present a method of mapping them to RAM-based hardware using 'ring memories'. Finally, we study the sigma-pi units' ability to generalise once they are trained to map real-valued, high accuracy, continuous functions. We use sigma-pi units as they have been shown to have shorter training times than their analogue counterparts and can also overcome some of the drawbacks of semi-linear units (Gurney, 1992. Neural Networks, 5, 289-303).

Artificial Intelligence↗
PubMed1999

Aortic regurgitation reduces the accuracy of exercise echocardiography for diagnosis of coronary artery disease.

The association of aortic regurgitation with left ventricular size, hypertrophy, and abnormal coronary flow may influence the accuracy of stress testing techniques for the diagnosis of coronary disease. We examined the diagnostic accuracy of treadmill exercise echocardiography to predict coronary artery disease in 76 patients with moderate to severe aortic regurgitation. Rest and poststress images were interpreted by 2 experienced observers, and accuracy was defined by comparison with stenoses >/=50% diameter at coronary angiography. Results were compared with accuracy in a control group of previously published studies in patients without valvular heart disease. After 6 patients were excluded because of a submaximal heart rate response (<85% age-predicted maximal heart rate), 70 patients were included in the final analysis. Patients with aortic regurgitation were of comparable age to the control group and exercised to similar workload. In 16 (23%) patients with significant coronary artery disease and significant aortic regurgitation, the sensitivity of exercise echocardiography was 56% compared with 83% in the control group (P =.03). The specificity in 54 patients with aortic regurgitation but no significant coronary artery disease was 67% compared with 83% in the control group (P =.02). Accuracy was 64% in aortic regurgitation compared with 83% in the control group (P =.02). In patients with aortic regurgitation, accuracy in the left anterior descending artery territory (76%) marginally exceeded that in the posterior (right + circumflex coronary artery) circulation (70%). Thus the presence of significant aortic regurgitation affects the regional wall motion of the left ventricle during exercise and adversely affects the accuracy of exercise echocardiography for the diagnosis of coronary artery disease.

Aortic Valve Insufficiency↗