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PubMed2003

Limits on the accuracy of 3-D thickness measurement in magnetic resonance images--effects of voxel anisotropy.

Measuring the thickness of sheet-like thin anatomical structures, such as articular cartilage and brain cortex, in three-dimensional (3-D) magnetic resonance (MR) images is an important diagnostic procedure. This paper investigates the fundamental limits on the accuracy of thickness determination in MR images. We defined thickness here as the distance between the two sides of boundaries measured at the subvoxel resolution, which are the zero-crossings of the second directional derivatives combined with Gaussian blurring along the normal directions of the sheet surface. Based on MR imaging and computer postprocessing parameters, characteristics for the accuracy of thickness determination were derived by a theoretical simulation. We especially focused on the effects of voxel anisotropy in MR imaging with variable orientation of sheet-like structure. Improved and stable accuracy features were observed when the standard deviation of Gaussian blurring combined with thickness determination processes was around square root of 2/2 times as large as the pixel size. The relation between voxel anisotropy in MR imaging and the range of sheet normal orientation within which acceptable accuracy is attainable was also clarified, based on the dependences of voxel anisotropy and the sheet normal orientation obtained by numerical simulations. Finally, in vitro experiments were conducted using an acrylic plate phantom and a resected femoral head to validate the results of theoretical simulation. The simulated thickness was demonstrated to be well-correlated with the actual in vitro thickness.

Anatomy, Cross-Sectional↗
PubMed2002

High-accuracy standard specimens for the line-focus-beam ultrasonic material characterization system.

We prepared standard specimens for the line-focus-beam ultrasonic material characterization system to obtain absolute values of the propagation characteristics (phase velocity and attenuation) of leaky surface acoustic waves (LSAWs). The characterization system is very useful for evaluating and analyzing specimen surfaces. The calibration accuracy of these acoustic parameters depends on the accuracy of acoustical physical constants (elastic constants, piezoelectric constants, dielectric constants, and density) determined for standard specimens. In this paper, we developed substrates of nonpiezoelectric single crystals (viz., gadolinium gallium garnet [GGG], Si, and Ge) and an isotropic solid (synthetic silica [SiO2] glass) as standard specimens. These specimens can cover the phase velocity range of 2600 to 5100 m/s for Rayleigh-type LSAWs. To determine the elastic constants with high accuracy, we measured velocities by the complex-mode measurement method and corrected diffraction effects. Measurements of bulk acoustic properties (bulk wave velocity and density) were conducted around 23 degrees C, and bulk wave velocities were obtained with an accuracy of within +/-0.004%. We clearly detected differences in acoustic properties by comparing the obtained results with the previously published values; the differences were considered to be due to differences of the specimens used. We also detected differences in acoustic properties among four SiO2 substrates produced by different manufacturers.

Journal Article↗
PubMedDate not supplied

Parenting and adolescents' accuracy in perceiving parental values.

What determines adolescents' accuracy in perceiving parental values? The current study examined potential predictors including parental value communication, family value agreement, and parenting styles. In the study, 547 Israeli adolescents (aged 16 to 18) of diverse socioeconomic backgrounds participated with their parents. Adolescents reported the values they perceive their parents want them to hold. Parents reported their socialization values. Accuracy in perceiving parents' overall value system correlated positively with parents' actual and perceived value agreement and perceived parental warmth and responsiveness, but negatively with perceived value conflict, indifferent parenting, and autocratic parenting in all gender compositions of parent-child dyads. Other associations varied by dyad type. Findings were similar for predicting accuracy in perceiving two specific values: tradition and hedonism. The article discusses implications for the processes that underlie accurate perception, gender differences, and other potential influences on accuracy in value perception.

Adolescent↗
PubMed2005

Diagnostic accuracy of the serum profile of gastric mucosa in relation to histological and morphometric diagnosis of atrophy.

BACKGROUND: Histology is the gold standard for diagnosis of atrophy but is hampered by observer variation. A reliable method to overcome this issue is morphometric analysis of gastric mucosa. Serum pepsinogens and gastrin have been proposed in the diagnostic work-up of gastric atrophy although diagnostic accuracy of these tests is considered unsatisfactory. AIM: To evaluate the diagnostic accuracy of gastric serum profile in relation both to morphological and morphometric diagnosis of gastric atrophy. METHODS: Ninety-four dyspeptic out-patients underwent upper endoscopy and evaluation of serum levels of PGI, PGII and 17-gastrin. Diagnostic accuracy of gastric serum profile was tested by receiver operating characteristic curves and by evaluation of sensitivity and specificity in relation to both histology and morphometric analyses. RESULTS: As far as concern to histological evaluation, only PGI/PGII ratio showed an acceptable diagnostic accuracy in discrimination of gastric atrophy, while, when morphometric analysis was considered as reference, both serum PGI level and PGI/PGII ratio showed an excellent performance. However, both PGI and PGI/PGII ratio showed low sensitivity and high specificity. CONCLUSIONS: Serological gastric profile corresponds better with the morphometric diagnosis of atrophy, even if, because of the low sensitivity, today this could only be used as screening test of chronic atrophic gastritis.

Adult↗
PubMed2006

Measuring diagnostic and predictive accuracy in disease management: an introduction to receiver operating characteristic (ROC) analysis.

Diagnostic or predictive accuracy concerns are common in all phases of a disease management (DM) programme, and ultimately play an influential role in the assessment of programme effectiveness. Areas, such as the identification of diseased patients, predictive modelling of future health status and costs and risk stratification, are just a few of the domains in which assessment of accuracy is beneficial, if not critical. The most commonly used analytical model for this purpose is the standard 2 x 2 table method in which sensitivity and specificity are calculated. However, there are several limitations to this approach, including the reliance on a single defined criterion or cut-off for determining a true-positive result, use of non-standardized measurement instruments and sensitivity to outcome prevalence. This paper introduces the receiver operator characteristic (ROC) analysis as a more appropriate and useful technique for assessing diagnostic and predictive accuracy in DM. Its advantages include; testing accuracy across the entire range of scores and thereby not requiring a predetermined cut-off point, easily examined visual and statistical comparisons across tests or scores, and independence from outcome prevalence. Therefore the implementation of ROC as an evaluation tool should be strongly considered in the various phases of a DM programme.

Data Interpretation, Statistical↗
PubMed2004

In vitro investigation of marginal accuracy of implant-supported screw-retained partial dentures.

Mismatch occurring during the fabrication of implant-supported dentures may induce stress to the peri-implant bone. The purpose of this study was to investigate the influence of two different alloys and the fabrication method on the marginal accuracy of cast partial dentures. Two laboratory implants were bonded into an aluminium block so that the distance between their longitudinal axes was 21 mm. Frameworks designed for screw-retained partial dentures were cast either with pure titanium (rematitan) or with a CoCr-alloy (remanium CD). Two groups of 10 frameworks were cast in a single piece. The first group was made of pure titanium, and the second group of a CoCr-alloy (remanium CD). A third group of 10 was cast in two pieces and then laser-welded onto a soldering model. This latter group was also made of the CoCr-alloy. All the frameworks were screwed to the original model with defined torque. Using light microscopy, marginal accuracy was determined by measuring vertical gaps at eight defined points around each implant. Titanium frameworks cast in a single piece demonstrated mean vertical gaps of 40 microm (s.d. = 11 microm) compared with 72 microm (s.d. = 40 microm) for CoCr-frameworks. These differences were not significant (U-test, P = 0.124) because of a considerable variation of the values for CoCr-frameworks (minimum: 8 microm and maximum: 216 microm). However, frameworks cast in two pieces and mated with a laser showed significantly better accuracy in comparison with the other experimental groups (mean: 17 microm +/- 6; P < 0.01). (i) The fit of implant-supported partial dentures cast with pure titanium in a single piece is preferable to that of those made with the CoCr-alloy and (ii) the highest accuracy can be achieved by using a two-piece casting technique combined with laser welding. Manufacturing the framework pieces separately and then welding them together provides the best marginal fit.

Bone Screws↗
PubMed1992

Standardized (simulated) patients' accuracy in recording clinical performance check-list items.

In large-scale performance-based assessment of medical professionals' clinical competence, simulated patients (standardized patients-SPs) are used not only to simulate case problems but also to record on check-list the examinees' clinical performance during their encounter with the SPs. The purposes of this study were to determine the SPs' overall accuracy in recording check-list items, and whether their accuracy was affected by the various characteristics of the check-list, and by the different times during a day and the different days within the examination when the recordings were obtained. Results showed that the SPs' accuracy in recording check-list items was good to very good and was affected by the length of the check-list, as well as by the type and the clarity of the check-list item. It was further found that the SPs' accuracy was consistent and did not vary over the course of a one-day or a 15-day examination.

Clinical Competence↗
PubMed2005

The accuracy of human population maps for public health application.

OBJECTIVES: Human population totals are used for generating burden of disease estimates at global, continental and national scales to help guide priority setting in international health financing. These exercises should be aware of the accuracy of the demographic information used. METHODS: The analysis presented in this paper tests the accuracy of five large-area, public-domain human population distribution data maps against high spatial resolution population census data enumerated in Kenya in 1999. We illustrate the epidemiological significance, by assessing the impact of using these different human population surfaces in determining populations at risk of various levels of climate suitability for malaria transmission. We also describe how areal weighting, pycnophylactic interpolation and accessibility potential interpolation techniques can be used to generate novel human population distribution surfaces from local census information and evaluate to what accuracy this can be achieved. RESULTS: We demonstrate which human population distribution surface performed best and which population interpolation techniques generated the most accurate bespoke distributions. Despite various levels of modelling complexity, the accuracy achieved by the different surfaces was primarily determined by the spatial resolution of the input population data. The simplest technique of areal weighting performed best. CONCLUSIONS: Differences in estimates of populations at risk of malaria in Kenya of over 1 million persons can be generated by the choice of surface, highlighting the importance of these considerations in deriving per capita health metrics in public health. Despite focussing on Kenya the results of these analyses have general application and are discussed in this wider context.

Climate↗
PubMed2005

Accuracy of ultrasonography and magnetic resonance imaging in the diagnosis of non-palpable testis.

BACKGROUND: Studies were needed to evaluate the accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) for diagnosing non-palpable testis, and to study the clinical usefulness of US and MRI before surgical exploration. METHODS: Fifty-six patients with non-palpable testis aged 1--12 years were examined between 1993 and 2002. Forty-six patients (55 non-palpable testes) underwent US. Forty patients (47 non-palpable testes) were examined using MRI. Both US and MRI were used in 29 patients (34 non-palpable testes). We used Fisher's exact probability test to compare the results of these graphic examinations with the surgical or laparoscopic findings for the non-palpable testis. RESULTS: Ultrasonography had a sensitivity of 76%, a specificity of 100%, and an accuracy of 84% in the diagnosis of non-palpable testis, whereas MRI had a sensitivity of 86%, a specificity of 79%, and an accuracy of 85%. CONCLUSIONS: There were no statistically significant differences in the accuracy rates of US and MRI for diagnosing non-palpable testis. Laparoscopy or inguinal exploration should be performed even if these graphic examinations demonstrate the absence of a testis, because some patients with a non-palpable testis were found to be false negatives. We recommend US as the first step after clinical examination, and MRI could be performed when the US findings are negative preoperatively for a non-palpable testis.

Child↗
PubMed2004

Accuracy of frozen section in the diagnosis of malignant ovarian tumor.

AIM: To evaluate the diagnostic accuracy of frozen section for histopathologic diagnosis of ovarian tumors. METHODS: A total of 147 surgically removed ovarian tumors were studied. Each ovarian tumor sample was evaluated for histopathologic diagnosis using both frozen and paraffin sections. Interpretation was separate and blinded between each technique. Accuracy, diagnostic values and their 95% confidence intervals (CI) were estimated by comparing the results from both techniques, using paraffin section as a gold standard. RESULTS: Overall accuracy of frozen section was 89.8% (95% CI 83.4-94.0). Sensitivity was 90.4% (95% CI 78.2-96.4) for malignant, 33.3% (95% CI 6.0-75.9) for borderline, and 93.3% (95% CI 85.4-97.2) for benign tumors. The predictive value was 100% (95% CI 90.6-100) for malignant, 20% (95% CI 3.5-55.8) for borderline, and 92.2% (95% CI 84.1-96.5) for benign tumors. Most false negatives occurred in mucinous and borderline tumors. No benign tumor was misdiagnosed as malignant by frozen section. Accuracy and negative predictive value were significantly lower in epithelial rather than germ and other cell types. Excellent agreement with regard to histologic cell type was observed (Kappa 0.81). CONCLUSION: Frozen section appears to be an accurate technique for the histopathologic diagnosis of ovarian tumors. Some limitations were observed among borderline and mucinous tumors; this emphasizes the great value of frozen section in the diagnosis of ovarian tumors.

Adult↗
PubMed2006

Institutional variability in the accuracy of urinary cytology for predicting recurrence of transitional cell carcinoma of the bladder.

OBJECTIVE: To assess the contemporary inter-institutional accuracy of urinary cytology in predicting the recurrence of transitional cell carcinoma (TCC) of the bladder, in a large multi-institutional cohort from four continents, as cystoscopy and urinary cytology represent the 'gold standards' for surveillance of TCC recurrences, but the ability of cytology to predict recurrence varies. PATIENTS AND METHODS: Ten institutions contributed 2542 patients with a history of superficial TCC, of whom 898 had TCC recurrence. Age- and gender-adjusted logistic regression models were used to evaluate the association between urine cytology and TCC recurrence. The predictive accuracy derived from the logistic regression model was tested using the area under the receiver operating characteristic curve. The resulting predictive accuracy estimates were internally validated with 200 bootstrap re-samples. RESULTS: The mean (range across institutions) age of the patients was 65 (48-69) years and 75 (67-87)% were men. Cytology was positive in 19 (10-38)% of patients; recurrence was identified in 35 (27-54)% of patients. The sensitivity was 38-65% across institutions. Urinary cytology varied significantly in its ability to predict recurrence of bladder cancer. Institution-specific predictive accuracy adjusted for gender and age was 0.627-0.893. Stratifying by grade and stage only partly attenuated the discrepancies between centres. CONCLUSIONS: The variability of urinary cytology results was very appreciable among the 10 centres and ranged from poor (63%) to excellent (89%).

Aged↗
PubMed1990

An assessment of the accuracy of NovoPen 1 delivery after prolonged use.

Forty-five NovoPen 1 injection devices have been assessed for accuracy of insulin delivery. Twenty-six pen-injectors had been returned either because the device had developed structural faults or the patients had experienced unexpected deterioration in diabetic control. Twelve of these pen-injectors were unusable. The remaining 14 pen-injectors ('faculty pen-injectors') were assessed by measuring the weight of insulin solution delivered in each of 10 depressions of the plunger and compared with similar measurements from 10 unused pen-injectors ('new pen-injectors') and 9 pen-injectors ('used pen-injectors') which had been used uneventfully for greater than 3 years. New pen-injectors delivered insulin solution with an accuracy (median error) of 2.8% and reproducibility (median SD) of 2.0%. Used pen-injectors had an accuracy of 2.3% and reproducibility of 3.5%. The 14 suspect pen-injectors ('faculty pen-injectors') demonstrated an accuracy of 2.8% with reproducibility of 4.0%. The reduction in reproducibility was due to faults in 4 pen-injectors, 2 of which consistently delivered less insulin than expected, while a further two pen-injectors were intermittently inaccurate.

Humans↗
PubMed1994

Prediction accuracy of text recall: ease, effort and familiarity.

Prediction accuracy of text recall was studied in two experiments. Text characteristics (i.e., consistency and distinctiveness) were manipulated in Experiment 1, and familiarity with the reading-task in Experiment 2. The results were also analyzed and discussed in terms of easy processing (Experiment 1), and in terms of increased and more active processing (Experiment 2). Text characteristics did not affect prediction accuracy. However, being familiar with the reading-task led to good and long-lasting prediction accuracy. Thus, subjects reading a school-book text, instructed to learn the contents of it demonstrated reliable memory awareness, both for immediate recall and for delay of one week. It was also suggested that increased processing demands and active reading enhances prediction accuracy.

Achievement↗
PubMed2002

Accuracy of outpatient endometrial biopsy in the diagnosis of endometrial cancer: a systematic quantitative review.

OBJECTIVE: To determine the accuracy of outpatient endometrial biopsy in diagnosing endometrial cancer in women with abnormal uterine bleeding. DESIGN: A systematic quantitative review of published research. METHODS: Studies were selected if accuracy of outpatient endometrial biopsy was estimated compared with a reference standard. Diagnostic accuracy was determined by pooled likelihood ratios for positive and negative test results. There were 1013 subjects in 13 diagnostic evaluations reported in 11 primary studies. RESULTS: A positive test result on outpatient biopsy diagnosed endometrial cancer with a pooled likelihood ratio of 66.48 (95% CI 30.04-147.13) while a negative test result had a pooled likelihood ratio of 0.14 (95% CI 0.08-0.27). The post test probability of endometrial cancer was 81.7% (95% CI 59.7%-92.9%) for a positive test and 0.9% (95% CI 0.4%-2.4%) for a negative test. CONCLUSION: Outpatient endometrial biopsy has a high overall accuracy in diagnosing endometrial cancer when an adequate specimen is obtained. A positive test result is more accurate for ruling in disease than a negative test result is for ruling it out. Therefore, in cases of abnormal uterine bleeding where symptoms persist despite negative biopsy, further evaluation will be warranted.

Ambulatory Care↗
PubMed2006

Accuracy of serum uric acid in predicting complications of pre-eclampsia: a systematic review.

BACKGROUND: Pre-eclampsia is one of the largest causes of maternal and fetal mortality and morbidity. Hyperuricemia is often associated with pre-eclampsia. OBJECTIVE: To determine the accuracy with which serum uric acid predicts maternal and fetal complications in women with pre-eclampsia. STUDY DESIGN: Systematic quantitative review of test accuracy studies. SEARCH STRATEGY: We conducted electronic searches in MEDLINE (1951-2004), EMBASE (1980-2004), the Cochrane Library (2004:4) and the MEDION database to identify relevant articles. A hand-search of selected specialist journals and reference lists of articles obtained was then carried out. There were no language restrictions for any of these searches. SELECTION CRITERIA: Two reviewers independently selected the articles in which the accuracy of serum uric acid was evaluated to predict maternal and fetal complications of pre-eclampsia. DATA COLLECTION AND ANALYSIS: Data were extracted on study characteristics, quality and accuracy to construct 2 x 2 tables with maternal and fetal complications as reference standard. Summary likelihood ratios for positive (LR+) and negative LR(-) test results are generated for various threshold levels of uric acid. MAIN RESULTS: There were 18 primary articles that met the selection criteria, including a total of 3913 women and forty-one 2 x 2 tables. In women with pre-eclampsia, a positive test result of uric acid greater than or equal to a 350-micromol/l threshold predicted eclampsia with a pooled likelihood ratio (LR) of 2.1 (95% CI 1.4-3.5), while a negative test result had a pooled LR of 0.38 (95% CI 0.18-0.81). For severe hypertension as the outcome measure, the LRs were 1.7 (95% CI 1.3-2.2) and 0.49 (95% CI 0.38-0.64) for positive and negative test results, respectively, and for caesarean section the LRs were 2.4 (95% CI 1.3-4.7) and 0.39 (95% CI 0.20-0.76). For stillbirths and neonatal deaths the respective LRs were 1.5 (95% CI 0.91-2.6) and 0.51 (95% CI 0.20-1.3). For the prediction of small-for-gestational-age fetus, the pooled LRs were 1.3 (95% CI 1.1-1.7) and 0.60 (95% CI 0.43-0.83) for positive and negative results, respectively. AUTHOR'S CONCLUSION: Serum uric acid is a poor predictor of maternal and fetal complications in women with pre-eclampsia.

Biomarkers↗
PubMed1997

The accuracy of home glucose meters for the glucose range anticipated in pregnancy.

Home glucose meters are used almost universally for the management of pregnant women with diabetes. However, the degree of accuracy of meters in general and particularly for the lower glucose range, is questionable. Six of the most commonly used meters in Australia were evaluated for analytical accuracy for glucose levels < 8.0 mmol/L--a level below which many important clinical management decisions are made. Two meters, Elite and Precision QID, cannot be recommended. The other 4 meters, Glucometer 3, Reflolux S, Alpha and Advantage produced results with a higher degree of analytical accuracy. Of the meters tested, the Accutrend Alpha had the highest proportion of results within 5% and 10% of a laboratory reference method, the lowest bias with the Altman Bland method of comparison, and is recommended for use in pregnancy. No meter approached the analytical accuracy goal recommended by the American Diabetes Association. Manufacturers should be encouraged to develop or adapt systems for use in pregnancy.

Adult↗
PubMed1995

Accuracy of e-codes assigned to emergency department records.

OBJECTIVE: To determine the accuracy of ICD-9-CM external-cause-of-injury codes (e-codes) assigned to the medical records of injured patients treated in an ED and released. METHODS: A comparison was made of routine coding and expert recoding of medical records generated in the ED for a convenience sample of patients treated for injuries within 24 hours of injury occurrence and subsequently released from the ED. The medical record was handwritten and subsequently coded by three medical records coders (MRCs). The e-coded charts were sent to an external medical record consultant (expert), who was blinded to the codes previously assigned. The expert reading was used as the criterion standard. Accuracy was measured using a kappa statistic, and errors were described. RESULTS: Of 126 available patient charts, 108 (85.7%) were assigned e-codes by MRCs. The expert assigned two codes to (double-coded) 67 patients, while the MRCs double-coded only one patient. The additional code was usually a "place of occurrence code." In 60 cases (55.6%), the expert code exactly matched the MRC code; kappa = 0.462. Of the 48 mismatches (44.4%), 20 (41.7%) were e-coded in the wrong category, 20 (41.7%) were e-coded in the correct category but with incorrect specificity of information, either too specific or not specific enough, and eight (16.6%) had combined coding errors. CONCLUSION: The accuracy of e-codes assigned to ED records was moderate in this single institution analysis. Errors were predominantly related to the specificity of the code, but some e-codes were in the wrong category. There are implications for injury surveillance and research. E-code assignment must be standardized and applied uniformly to obtain accurate codes. Automation of e-coding could improve accuracy and consistency of codes. National and international epidemiologic studies of cause of injury among ED patients will be severely hampered until e-code assignment can be better standardized.

Emergency Service, Hospital↗
PubMed2006

Evaluating the accuracy and precision of cranial morphological traits for sex determination.

Sex determination is a key analysis that forensic anthropologists perform in order to construct a biological profile of human remains. The techniques used in forensic investigations must meet the Mohan or Daubert criteria, for admissibility in a court of law. In this study, the precision and accuracy of 21 morphological characteristics of the skull were tested on a modern sample of 50 adult crania of European White ancestry. The following craniofacial features are identified as high-quality traits, defined by intraobserver error or=80%: mastoid size, supraorbital ridge size, general size and architecture, rugosity of the zygomatic extension, size and shape of the nasal aperture, and gonial angle. Ninety-six percent accuracy and 92% precision were achieved using 20 traits in combination. Fisher's exact probability tests revealed no significant differences (p=0.05) in the levels of precision or accuracy between age categories. Sex-related bias in accuracy was found for the following cranial features: ramus symphysis (p=0.009), zygomatic extension (p=0.0016), and occipital markings (p=0.0013). These traits demonstrated a greater tendency to be scored male than female.

Adult↗