SEARCH · Search PubMed

Results for “Accuracy”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed2005

Is the accuracy of blood pressure measuring devices underestimated at increasing blood pressure levels?

BACKGROUND: In validation studies reporting on the accuracy of blood pressure measuring devices (ambulatory and non-ambulatory systems), it is frequently stated that the accuracy of blood pressure devices seems to decrease at increasing blood pressure levels. This has been shown for several ambulatory devices in the past. Whether more recently validated devices are less accurate at increasing blood pressure levels is unknown, however. OBJECTIVES: We therefore retrospectively searched the literature for studies performed between 1993 and 2003, reporting on the accuracy of blood pressure measuring devices over different blood pressure levels. When needed, additional information from the authors was requested. METHODS: In total, 30 studies were selected. Of these, the studies reporting on the accuracy of 14 different ambulatory and nine different non-ambulatory devices were useful. For both ambulatory and non-ambulatory devices, accuracy appeared to decrease at increasing blood pressure levels. This was particularly shown for systolic blood pressure. RESULTS: We speculate whether this finding is due to the oscillometric method of blood pressure measurement. Another explanation may exist, however. Blood pressure variability increases with higher blood pressure. Further, the British Hypertension Society protocol 1993 uses sequential measurements. This may be the reason that, owing to the increased blood pressure variability, the accuracy of most devices tends to decrease at higher blood pressure levels. Consequently, the accuracy of blood pressure measuring devices may be underestimated at higher blood pressure levels. CONCLUSION: Currently used automated blood pressure measurement devices seem to be less accurate at increasing blood pressure levels. It is important to be aware of this phenomenon when treating hypertensive patients. The reported decrease in accuracy, however, may well be explained by the increasing blood pressure variability at increasing blood pressure and the use of sequential measurements. If this is the case, then the accuracy of these devices is perhaps underestimated.

Blood Pressure↗

PubMed2006

Evaluation of the accuracy of three electronic apex locators using glass tubules.

AIM: To evaluate the accuracy of three different electronic apex locators (EALs) using glass tubules. METHODOLOGY: Forty-eight glass tubules with different diameters and an agar model were used to mimic root canals. A size 15 stainless steel K-file was used as the measuring electrode. The Root ZX, Propex and Neosono Ultima EZ were used to measure the tubule length with tubules dry, or filled with 0.9% NaCl, 3% H(2)O(2), 2.5% NaOCl or 17% EDTA. The distance between the real length (RL) and measured length (ML) of the tubules was recorded. The range of RL +/- 0.5 mm and RL +/- 1 mm was used to evaluate the accuracy of the EALs. Results were subject to correlation analysis and Friedman's test. RESULTS: In dry tubules, the accuracy of Root ZX was 75-91.7% for RL +/- 0.5 mm and 100% for RL +/- 1 mm, whilst the measurements of the other two EALs were all within the RL +/- 0.5 mm. No influence from the increase in tubule diameter on the accuracy of all three EALs was observed in dry tubules. In tubules filled with electrolyte, the accuracy of the Root ZX decreased as tubule diameter increased (R(d) > 0, P < 0.05). The RL-ML distance recorded by Propex was inversely related to the tubule diameter (R(d) < 0, P < 0.05). The accuracy of Propex was 75-100% for RL +/- 0.5 mm and 100% for RL +/- 0.5 mm when the tubule diameter was not more than 0.80 mm, but decreased in tubules with diameter over 0.80 mm and filled with 2.5% NaOCl or 17% EDTA. Nearly, all the measurements (except for six tubules) using Neosono Ultima EZ were within 1 mm shorter than RL despite the contents in tubules and the increase of tubule diameter. CONCLUSIONS: The accuracy of the Root ZX decreased as the tubule diameter increased when tubules were filled with electrolytes. The electrolytes in the tubules decreased the accuracy of Propex when the tubule diameter was large. The electrolytes in tubules and tubule diameter had no influence on the accuracy of Neosono Ultima EZ. The Propex and Neosono Ultima EZ were more accurate than the Root ZX under various conditions in this laboratory study.

Chelating Agents↗

PubMed2006

Assessing glucose meter accuracy.

BACKGROUND: Self-monitoring of blood glucose plays an important role in the management of diabetes, particularly in patients treated with insulin. Blood glucose meters must have sufficient accuracy to allow patients and clinicians to monitor glycemic control and then modify treatment accordingly. Although several standards have been proposed, a consensus about how to measure glucose meter accuracy is not available. SCOPE: An informal review of recently published articles dealing with glucose meter accuracy was conducted to provide recommendations for evaluating accuracy relevant to the practicing clinician. FINDINGS: Whether in clinical practice or in accuracy studies, the accuracy of blood glucose meters is typically determined by comparing meter results to those obtained by a clinical laboratory method on samples collected from the same patient at the same time. However, multiple sample-related, analysis-related, and data display-related factors can have an impact on accuracy determination. Clinicians need to recognize these factors and take steps to minimize their impact when assessing the accuracy of glucose meters used by their patients. CONCLUSIONS: Although modern glucose meters show variable results with respect to analytical measures of accuracy, error grid analysis demonstrates that measurements deemed clinically acceptable approach 100%.

Blood Glucose Self-Monitoring↗

PubMed2001

Accuracy of thyroid fine-needle aspiration using receiver operator characteristic curves.

Although many large series demonstrate the effectiveness of thyroid fine-needle aspiration (FNA), measuring its accuracy has been suboptimal owing to inappropriate statistical methods. All thyroid fine-needle aspirates were correlated with corresponding histologic and cytologic follow-up for a 4-year period, and the accuracy was determined using receiver operator characteristic curves, which allow inclusion of nondiagnostic and indeterminate cases. There were 1,085 cases, 291 with follow-up. The overall accuracy was 0.90 +/- 0.02 for a single aspiration session. A nondiagnostic aspirate was associated with a significant risk of malignancy (16%). However, 70% of patients who underwent reaspiration had adequate and negative results, and reaspiration significantly increased overall accuracy. Subcategorizing the nondiagnostic category did not affect accuracy, but did define categories with a significantly different change of a negative diagnosis on repeated aspiration. Although subcategories of papillary carcinoma were associated with significantly different risks of carcinoma (40% vs 81%), they did not significantly improve overall accuracy. Receiver operator characteristic curves can be used to define the accuracy of thyroid FNA. This method demonstrates significantly increased accuracy with repeated aspiration of nondiagnostic cases and demonstrates that subcategorization does not improve the overall accuracy of the test.

Adenocarcinoma↗

PubMed1994

Reference citations in radiology: accuracy and appropriateness of use in two major journals.

OBJECTIVE: Errors in reference citation and use are common in the medical and scientific literature. The prevalence of such errors in the radiology literature has not been reported. We did a study to assess the accuracy and appropriateness of use of references cited in two general radiology journals. MATERIALS AND METHODS: All references cited in the June 1993 issues of the American Journal of Roentgenology and Radiology were numbered consecutively. Fifty references were chosen at random from each journal, and copies of the original publications were obtained from the medical library at our institution or through interlibrary loan. Each reference was studied for accuracy and appropriateness of its citation in the June 1993 journal article (the "index article"). Errors were classified as major or minor in each category. Data were analyzed with the SAS statistical package. RESULTS: Forty-seven (94%) of 50 references were obtained from AJR, and 48 (96%) of 50 from Radiology. Of the 47 from the AJR, one (2%) had a major error and 21 (45%) had a minor error in accuracy. Of the 48 from Radiology, two (4%) had a major error and 11 (23%) had a minor error in accuracy. These values were significantly different for minor errors (p = .0188), but not for major ones (p = 1.000). When we adjusted for index article type, error rates for the two journals were not significantly different (p = .0612). We found four major errors (9%) and two minor errors (4%) in appropriateness of citation in the AJR references we studied. Three references (6%) from Radiology contained major errors in appropriateness of use; we found no minor errors of that type. These values were not significantly different (p = .232 for minor errors; p = .709 for major errors). One error in accuracy prevented location of the original reference. Errors were not related to the number of references cited in an index article (p = .528 for accuracy; p = .092 for appropriateness). CONCLUSION: The rate of minor errors in accuracy of references is fairly high in the two journals studied and is comparable to rates previously reported for other types of journals. The rate of major errors in accuracy of references is slightly lower than rates for other types of journals. The percentage of cited references that could not be located was also smaller than in previous reports. Errors in citation appropriateness were less common as well. Given the small number of errors that prevented references from being located, significant expenditure of time and money by journal staff members in checking references is probably not justified. However, authors should be encouraged to exercise greater care in checking all of their references for both accuracy and appropriateness of use. Differences in error rates between AJR and Radiology may have resulted in part from the random sampling method, which produced different mixtures of index articles for the two journals.

Bibliographies as Topic↗

PubMed1996

Percutaneous core biopsy of the breast: effect of operator experience and number of samples on diagnostic accuracy.

OBJECTIVE: The purpose of our study was to assess the degree of operator experience and the number of core biopsy samples required to achieve an accurate histologic diagnosis for each of five common mammographically defined lesions, using percutaneous core breast biopsy performed on a dedicated prone biopsy table. SUBJECTS AND METHODS: A prospective multisite study was performed that involved nine institutions (academic and private) with experienced breast radiologists and the use of dedicated prone biopsy table units with digital assistance and standardized protocol. Asymptomatic women evaluated during a 2-year study period were assigned a mammographic diagnosis reported in a manner prescribed by the American College of Radiology Breast Imaging Reporting and Data System lexicon. Mammographic lesions evaluated included masses, masses with calcifications, clustered calcifications, focal asymmetries, and architectural distortions. Where histologic diagnosis was indicated, core biopsy was performed with five individual samples obtained and sequentially analyzed. Two hundred thirty patients had immediate excisional biopsy, the results of which provided the basis for a statistical analysis to compare the accuracy of each sequential core biopsy sample with surgical results. Statistical analysis was also done to ascertain the accuracy of core biopsy diagnosis as a function of operator experience. RESULTS: Trends toward increasing accuracy were observed by increasing the number of core biopsies for each of five types of mammographically defined lesions, especially for clustered calcifications. Statistically significant increased accuracy was observed when the number of biopsies was increased beyond one (p = .003). Trends toward increased accuracy with more experience were observed for all lesions, especially for calcifications. Of the 230 lesions studied with immediate surgical validation, more than 80% of all lesions except clustered calcifications (75%) were diagnosed on the basis of two core biopsies; accuracy after five biopsies was 98% for masses, 91% for calcifications, 100% for masses with calcification, 100% for focal asymmetries, and 86% for architectural distortions. CONCLUSIONS: Accuracy of diagnosis based on the results of percutaneous core breast biopsy improved with an increase in the number of core biopsy samples obtained for any given lesion seen on mammograms and with increased experience in performing the procedure. Five samples yielded an overall diagnostic accuracy of 97%. Familiarity with expected accuracy from this procedure for different mammographic lesions and following increased experience may assist physicians in planning patient management.

Analysis of Variance↗

PubMed2005

Design, implementation and accuracy of a prototype for medical augmented reality.

OBJECTIVE: This paper is focused on prototype development and accuracy evaluation of a medical Augmented Reality (AR) system. The accuracy of such a system is of critical importance for medical use, and is hence considered in detail. We analyze the individual error contributions and the system accuracy of the prototype. MATERIALS AND METHODS: A passive articulated arm is used to track a calibrated end-effector-mounted video camera. The live video view is superimposed in real time with the synchronized graphical view of CT-derived segmented object(s) of interest within a phantom skull. The AR accuracy mostly depends on the accuracy of the tracking technology, the registration procedure, the camera calibration, and the image scanning device (e.g., a CT or MRI scanner). RESULTS: The accuracy of the Microscribe arm was measured to be 0.87 mm. After mounting the camera on the tracking device, the AR accuracy was measured to be 2.74 mm on average (standard deviation = 0.81 mm). After using data from a 2-mm-thick CT scan, the AR error remained essentially the same at an average of 2.75 mm (standard deviation = 1.19 mm). CONCLUSIONS: For neurosurgery, the acceptable error is approximately 2-3 mm, and our prototype approaches these accuracy requirements. The accuracy could be increased with a higher-fidelity tracking system and improved calibration and object registration. The design and methods of this prototype device can be extrapolated to current medical robotics (due to the kinematic similarity) and neuronavigation systems.

Humans↗

PubMed2006

[A study on the accuracy of electronic root canal length measurement and its influential factors].

PURPOSE: To study the accuracy of JUSTY-II electronic apex locator and the influential factors on the accuracy of root canal working length measurement. METHODS: 148 teeth, including 71 teeth with pulpitis, 46 with necrotic pulp and 31 with apical periodontitis, were divided into two groups in random. The accuracy of electronic root canal working length measurement group was compared with that of the manual measurement group by Chi(2) test. The influence of clinical types, root canal in dry or moisture conditions and root canal preparation on the accuracy of root canal working length measurement was analyzed. RESULTS: The accuracy of electronic apex locator was 87.84%, while it was 43.24% in manual measurement, the difference was significant (P<0.01). The accuracy in the group of apical periodontitis was significantly lower than that of the other groups (P<0.05). Root canal in dry or moisture conditions had no effect on the accuracy of root canal length measurement, but root canal preparation could decrease the accuracy of measurement (P<0.05). CONCLUSION: Electronic apex locator is an accurate and convenient device in measurement of root canal working length. Apical periodontitis and root canal preparation can decrease the accuracy of measurement.

Bicuspid↗

PubMed2001

Accuracy of primary care and hospital-based physicians' predictions of elderly outpatients' treatment preferences with and without advance directives.

BACKGROUND: Past research has documented that primary care physicians and family members are often inaccurate when making substituted judgments for patients without advance directives (ADs). This study compared the accuracy of substituted judgments made by primary care physicians, hospital-based physicians, and family surrogates on behalf of elderly outpatients and examined the effectiveness of ADs in improving the accuracy of these judgments. PARTICIPANTS AND METHODS: Participants were 24 primary care physicians of 82 elderly outpatients, 17 emergency and critical care physicians who had no prior experience with the patients, and a baseline comparison group of family surrogates. The primary outcome was accuracy of physicians' predictions of patients' preferences for 4 life-sustaining treatments in 9 hypothetical illness scenarios. Physicians made substituted judgments after being provided with no patient AD, patient's value-based AD, or patient's scenario-based AD. RESULTS: Family surrogates' judgments were more accurate than physicians'. Hospital-based physicians making predictions without ADs had the lowest accuracy. Primary care physicians' accuracy was not improved by either AD. Accuracy and confidence in predictions of hospital-based physicians was significantly improved for some scenarios using a scenario-based AD. CONCLUSIONS: Although ADs do not improve the accuracy of substituted judgments for primary care physicians or family surrogates, they increase the accuracy of hospital-based physicians. Primary care physicians are withdrawing from hospital-based care in growing numbers, and emergency medicine and critical care specialists most often are involved in decisions about whether to begin life-sustaining treatments. If ADs can help these physicians better understand patients' preferences, patient autonomy more likely will be preserved when patients become incapacitated.

Adult↗

PubMed2002

Accuracy of reporting endocervical component adequacy--a continuous quality improvement project.

Inaccurate reporting of the absence of an endocervical (EC) component on Pap smears often results in slide rescreens, amended reports, clinician dissatisfaction, and sometimes unnecessary repeat smears. Therefore, the accuracy of reporting EC component adequacy was selected as a quality indicator for the laboratory continuous quality improvement program (CQI). The process consisted of problem identification, analysis of the situation, collection of data, implementation of solutions, and evaluation of results. The objective of the study was to determine if the accuracy of reporting EC component adequacy on Pap smears improved after application of such a program. During the first phase, 150 Pap smears originally reported with the absence of an adequate EC component and 150 smears reported with the presence of an adequate EC component were rescreened to measure the baseline accuracy of EC component adequacy reporting. The improvement process was then implemented. A cause-and-effect diagram was developed and root cause was determined. A presentation was then made to the cytology staff. Criteria for EC component adequacy were reviewed, examples were shown, and standardized marking of EC component was implemented. Following improvement actions, a second audit of 150 Pap smears reported with the absence of an adequate EC component as well as 150 smears reported with the presence of an adequate EC component was undertaken to measure change in performance in assessing EC component adequacy. For the baseline rescreening, before initiation of the CQI program, 98% accuracy was achieved with smears that were reported as adequate for EC component present. However, the accuracy with smears reported as absence of an adequate EC component was only 71%, i.e., an adequate EC component was identified in almost 1/3 of these cases on rescreen. After the implementation of improvement actions, the accuracy with smears reported with the presence of EC component remained high (98%) and the accuracy of reporting the absence of EC component was 90%. The difference of the latter before and after the implementation was statistically significant (P = 0.015, z-test). The accuracy of reporting EC component adequacy increased following the CQI process. Using reporting EC component adequacy as an example, we demonstrate that by treating clinical problems as quality control issues and applying basic quality improvement tools, a positive outcome can be effected.

Cell Biology↗

PubMed2001

The role of accuracy motivation on children's and adults' event recall.

To examine the role of accuracy motivation in event recall, 6-, 7-, and 8-year-old children and adults were shown a short video about a conflict between two groups of children. Three weeks later, participants were asked a set of unbiased specific questions about the video. Following A. Koriat and M. Goldsmith's (1994) distinction of quantity- and quality-oriented memory assessments, and based on their model of strategic regulation of memory accuracy (1996), accuracy motivation was manipulated across three conditions. Participants were (a) forced to provide an answer to each question (low accuracy motivation), (b) initially instructed to withhold uncertain answers by saying "I don't know" (medium accuracy motivation), or (c) rewarded for every single correct answer (high accuracy motivation). When motivation for accuracy was high, children as young as 6 were to withhold uncertain answers to the benefit of accuracy. The expected quality-quantity trade-off emerged only for peripheral items but not for the central items. Participants who were forced to provide an answer gave more correct answers but also high numbers of incorrect answers than participants who had the option to answer "I don't know." The results are discussed in terms of the underlying model as well as in terms of forensic interviewing.

Adolescent↗

PubMed1990

Recognition accuracy with a voice-recognition system designed for anesthesia record keeping.

We tested on three occasions, with anesthetists as subjects, the accuracy of two voice-recognition systems designed for anesthetic record keeping. Initially, a prototype system was tested (10 subjects); several years later the resulting commercial system was tested in a quiet environment (11 subjects) and in noisy operating rooms (10 subjects). For each test an anesthetist first trained the system to recognize his or her voice by reading aloud a list of common anesthetic terms. To determine recognition accuracy, the percentage of words recognized correctly by the computer, each subject repeated the vocabulary words ten times. Although accuracy was similar during the three tests, it was slightly higher with the laboratory test (mean percent of words recognized correctly, 96.5%; range of accuracy for individual anesthetists, 91.6 to 98.8%) than with the prototype test (95.9%; range, 89.1 to 99.6%). Accuracy was lowest with the operating room test (95.3%; range, 87.8 to 98.4%). Twenty-four words caused particular difficulty during the laboratory test and were eliminated from the vocabulary of the subsequent operating room test. Omitting these 24 words from the laboratory vocabulary list allowed a more nearly direct comparison with the results from the operating room list; recognition accuracy improved in the former to 97.5% (range, 92.1 to 98.9%). Two anesthetists--one each from the laboratory and operating room tests--performed poorly, and eliminating their scores changed the respective overall scores to 98.2% (range, 96.7 to 98.9%) and 96.5% (range, 94.3 to 98.4%). Thus, the corrected difference between the laboratory accuracy and the operating room accuracy was 1.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗

PubMed1994

Exposure parameters and their effects on diagnostic accuracy.

A new method for analyzing diagnostic accuracy is introduced. A diagnostic accuracy curve may be obtained by plotting receiver operating characteristic analysis data, P(A), as a function of exposure. By means of diagnostic accuracy curves the effects on diagnostic accuracy of tube potential, exposure, and size of carious lesions was studied. It was found that the effect of the tube potential on the accuracy of caries diagnosis is negligible. About 25% of the variation in diagnostic accuracy depends on the exposure and about 80% on lesion depth. With the lesion depth constant, about 75% of the variance in diagnostic accuracy depended on observer performance. The peak of a diagnostic accuracy curve indicates optimum performance. This is found at an exposure that gives a radiographic density of about 1 in enamel and dentin although the tolerable exposure increases with increased lesion depth.

Absorptiometry, Photon↗

PubMed1988

The analytic and functional accuracy of a video densitometry system.

Applications using radiotracers and quantitative film autoradiography are increasing dramatically in the neurosciences. Microcomputer-based image analyzing systems with video input have been developed to provide rapid quantification of autoradiographic images on relatively inexpensive systems. However, there has been some question as to whether such systems can reliably produce high levels of densitometric accuracy, especially when compared to mechanical scanners which are standard in research requiring extreme fidelity of measurement. We report methods and results from tests done to determine the analytical and functional accuracy of the Drexel Unix-based Microcomputer image Analysis System (DUMAS), which is a video densitometric system designed to provide quantitative data from autoradiograms. Analytical accuracy was determined by measuring photometric uniformity, the optical density transfer function, temporal stability, geometric uniformity, and flare. In addition, data are provided on the resolution of the system at several magnifications. Functional accuracy, the accuracy of the estimates of mean isotope concentrations in diverse neural structures, was determined by comparing the results obtained on the DUMAS system with the results from analyzing the same [14C]2-deoxyglucose images with two different Optronics P1000 systems. Our results show that, provided care is taken in the choice of a camera and a light source, the analytic accuracy of videodensitometry is high. Its functional accuracy is also high in that measurements of radioisotope concentrations in diverse neural structures made on the DUMAS system agree closely with the measurements from a properly adjusted Optronics P1000 system. The rapidity and economy of videodensitometry is not, therefore, obtained at the sacrifice of densitometric accuracy. Given adequately tested hardware and provided that suitable checks on instrument calibration and adjustment are made, the errors in autoradiographic quantification due to the image analyzing system itself are minor in comparison to other sources of error, including, as we show, variations in the user's delineation of the boundaries of neural structures.

Autoradiography↗

PubMed2005

Consumer health information on the Internet about carpal tunnel syndrome: indicators of accuracy.

PURPOSE: To identify indicators of accuracy for consumer health information on the Internet. METHODS: Several popular search engines were used to find websites on carpal tunnel syndrome. The accuracy and completeness of these sites were determined by orthopedic surgeons. It also was noted whether proposed indicators of accuracy were present. The correlation between proposed indicators of accuracy and the actual accuracy of the sites was calculated. RESULTS: A total of 116 websites and 29 candidate indicators were examined. A high Google toolbar rating of the main page of a site, many inlinks to the main page of a site, and an unbiased presentation of information on carpal tunnel syndrome were considered genuine indicators of accuracy. Many proposed indicators taken from published guidelines did not indicate accuracy (e.g., the author or sponsor having medical credentials). CONCLUSION: There are genuine indicators of the accuracy of health information on the Internet. Determining these indicators, and informing providers and consumers of health information about them, would be useful for public health care. Published guidelines have proposed many indicators that are obvious to unaided observation by the consumer. However, indicators that make use of the invisible link structure of the Internet are more reliable guides to accurate information on carpal tunnel syndrome.

Carpal Tunnel Syndrome↗

PubMed2005

The accuracy of maternal anthropometry measurements as predictor for spontaneous preterm birth--a systematic review.

OBJECTIVE: To assess the accuracy with which antenatal maternal anthropometric measurements predict the risk spontaneous preterm birth. STUDY DESIGN: (1) DATA SOURCES: Studies were identified without language restrictions from MEDLINE, EMBASE, PASCAL, BIOSIS, the Cochrane Library, MEDION, National Research Register, SCISEARCH and Conference Papers, and manual searching of bibliographies of known primary and review articles, and contact with authors. (2) STUDY SELECTION AND DATA EXTRACTION: Studies were selected if they used antenatal maternal anthropometric features (pre-pregnancy weight, maternal pregnancy weight gain and maternal height) to predict spontaneous preterm birth. Two reviewers independently selected studies and extracted data on their characteristics, quality and accuracy. Accuracy data were used to form 2 x 2 contingency tables of the maternal anthropometric test results with spontaneous preterm birth as the reference standard. (3) DATA SYNTHESIS: Heterogeneity assessments were carried out to aid the decision regarding pooling of the accuracy results. Likelihood ratios for positive (LR+) and negative (LR-) test results were calculated, and summary estimates were produced in absence of heterogeneity of the accuracy results. RESULTS: There were eight primary accuracy articles that met the selection criteria, which included a total of 122,647 asymptomatic women. There were six studies on pre-pregnancy weight where five measured the body mass index (BMI) and one used an arbitrary measure. There were four studies on the adequacy of pregnancy weight gain and two studies on maternal height as a predictor for the risk of preterm birth. One article contributed three studies, while two articles provided two studies each. The commonest reference standard used was birth before 37 weeks' gestation. None of the studies fulfilled the ideal test accuracy study criteria. There was heterogeneity in the accuracy results of pre-pregnancy BMI but not in the adequacy of weight gain. All three maternal anthropometric features were poor predictors of preterm labour. Pre-pregnancy BMI is a poor predictor of preterm birth before 37 weeks' gestation (LR+ that ranged from 0.96 (95% confidence interval (CI) 0.66-1.40) to 1.75 (95% CI 1.33-2.31)) as are the adequacy of pregnancy weight gain (summary LR+ of 1.81, 95% CI 1.45-2.30) and short maternal height (LR+ of 1.79 (95% CI 1.27-2.52). CONCLUSION: Routine antenatal maternal anthropometric measurements are not useful in predicting the risk of preterm birth before 37 weeks' gestation. Further studies should address their use in combination with other test but need to use a more clinically appropriate reference standard of preterm birth, such as birth before 32-34 weeks' gestation, and improve on the quality of study design.

Anthropometry↗

PubMed2005

Improved mass accuracy for tandem mass spectrometry.

With the emergence of top-down proteomics, the ability to achieve high mass measurement accuracy on tandem MS/MS data will be beneficial for protein identification and characterization. (FT-ICR) Fourier transform ion cyclotron resonance mass spectrometers are the ideal instruments to perform these experiments with their ability to provide high resolution and mass accuracy. A major limitation to mass measurement accuracy in FT-ICR instruments arises from the occurrence of space charge effects. These space charge effects shift the cyclotron frequency of the ions, which compromises the mass measurement accuracy. While several methods have been developed that correct these space charge effects, they have limitations when applied to MS/MS experiments. It has already been shown that additional information inherent in electrospray spectra can be used for improved mass measurement accuracy with the use of a computer algorithm called DeCAL (deconvolution of Coulombic affected linearity). This paper highlights a new application of the strategy for improved mass accuracy in tandem mass analysis. The results show a significant improvement in mass measurement accuracy on complex electron capture dissociation spectra of proteins. We also demonstrate how the improvement in mass accuracy can increase the confidence in protein identification from the fragment masses of proteins acquired in MS/MS experiments.

Algorithms↗

PubMed2004

Factors affecting the accuracy of elastometric impression materials.

OBJECTIVES: The purpose of this study was to evaluate the effects of (1) various impression materials, (2) different storage times and (3) the proportion of inorganic filler on the accuracy and stability of elastometric impression materials. METHODS: The impression materials studied included three alginate impression materials (Algiace Z, CAVEX and Jeltrate), five commercial silicone impression materials (Aquasil, Exaflex regular type, Express, Coltex fine and Rapid liner) and two experimental silicone impression materials designed for this study (KE106A and KE106B). Impressions were made of 10 metal dies that mimicked prepared crowns. After an impression was taken, dental stone was immediately poured into the alginate impressions, while the silicone impressions was poured 30 min later and waited for 1 h for setting. The second and third stone dies were made 1 and 24 h later, respectively. The diameters of the occlusal surfaces of the metal dies and stone casts were determined using photographs of the surfaces taken with a Kodak DC 290 digital camera. The pictures were then measured using a photomicrograph digitized integration system to calculate any discrepancy. Because each impression was used to make three rounds of stone dies, two-factor mixed factorial ANOVA was used to evaluate the effect of materials and storage time on the accuracy of the stone casts. The simple effects analysis, combined with multiple comparisons considering the per family type I error rate, was performed following confirmation that an interaction between the two factors was significant. RESULTS: The results showed that: (1) there was a significant interaction effect between materials and storage times on the accuracy of the impressions. (2) Two addition type silicone materials, Aquasil and Exaflex, had the greatest accuracy and stability. (3) The experimental material KE106A had the least accuracy in the first and second rounds and the alginate impression material CAVEX had the least accuracy in the third round. (4) The stabilities of CAVEX and Jeltrate were the least consistent of the 10 materials and decreased significantly with storage time. (5) When the experimental material had a low proportion of filler (KE106A), there was a significantly greater dimensional discrepancy compared to the same material with a higher proportion of filler (KE106B). CONCLUSIONS: The accuracies varied among the 10 impression materials over three rounds. Of all the materials, the addition type silicone materials, Aquasil and Exaflex, had relatively greater accuracy and stability. The discrepancy of the alginate impression materials increased with storage time. The large loading of filler showed less discrepancy.

Alginates↗