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PubMed2002

Effects of efforts to increase response rates on a workplace chronic condition screening survey.

OBJECTIVE: Expanded health risk appraisal (HRA) surveys can help employers target chronic conditions for outreach or disease management interventions by providing data on the prevalences of conditions and their effects on work performance. However, concerns exist about the accuracy of this data because most HRAs have low response rates. We evaluated these concerns by examining the prevalences and work impairments associated with chronic conditions across four HRA subsamples that differed in intensity of recruitment effort. METHODS: Two thousand five hundred thirty-nine working people were invited to complete an expanded HRA survey that included questions about chronic conditions, work impairments, and demographics. Condition prevalences and associations between conditions and work impairment were compared across subsamples who responded after a single mailing, after two mailings, and in a telephone interview after the mailings either with or without a 20 dollars incentive. RESULTS: Consistent with previous research, response rates varied dramatically across the four subsamples (from 20.1% with only one mailing to 67.7% with telephone administration and a financial incentive). However, the estimated prevalences of chronic conditions, levels of work impairment, and effects of chronic conditions on work impairment did not differ with intensity of recruitment effort. CONCLUSIONS: Expanded HRAs can provide useful data on the prevalences and work impairments associated with chronic conditions even if response rates are low. Confirmation of these results is required, however, in new samples. Additional research is also needed on innovative and cost-effective strategies to improve HRA response rates.

Absenteeism↗
PubMed2006

Can Medicare billing claims data be used to assess mammography utilization among women ages 65 and older?

BACKGROUND: Medicare data may be a useful source for determining the utilization of mammography among elderly women, but the accuracy of these data has not been established. OBJECTIVE: We determined whether Medicare physician billing claims are an accurate reflection of mammography utilization among women ages 65 and older and whether they can be used to assess the use of screening as compared with diagnostic mammography. DATA SOURCES: Mammography use was assessed using Medicare billing claims and radiology reports from 2 mammography registries; the San Francisco Mammography Registry and the New Mexico Mammography Registry. METHODS: Completeness of the Medicare data was assessed by comparing mammography use based on Medicare, with radiology reports from the mammography registries, which served as the referent standard. Capture rates for Medicare claims for individual mammograms were examined, and women were characterized as having undergone at least 1 mammogram within each 2-year period based on the Medicare data, and these rates were compared with the referent standard. To determine whether Medicare data can distinguish between screening and diagnostic mammography, we performed a classification analysis using the mammography registries screening/diagnostic designation as the referent standard (dependent variable) and Medicare claim information as the independent/predictor variable. On the basis of the mammogram level classification analysis, women were categorized as having been frequently screened (at least 2 screening mammograms spaced by 12 to 36 months), screened (at least 1 screening mammogram), or not screened. SUBJECTS: Women ages 65 and older, diagnosed with breast cancer between 1992-1999, who had at least 1 mammogram between 1992-1999 were examined. RESULTS: A total of 3340 mammograms were obtained in 1371 women between 1992 and 1999. Overall, 83% of mammograms obtained by these women had a corresponding billing claim in Medicare. This increased from 65% in 1992 to 90% in 1999. Of women who underwent at least 1 mammogram during each 2-year period per the referent standard, 94% of women were accurately classified by Medicare claims as also having undergone mammography during the same 2-year period. In multivariable analysis, a mammogram was more likely to be associated with a billing claim over time, for women 80 years or older, and for white and Asian as compared with Hispanic women. Neither socioeconomic status nor screening/diagnostic designation affected the likelihood that a mammogram would be associated with a billing claim. The Medicare data accurately categorized a given mammogram as screening or diagnostic for 87.5% of mammograms. Lastly, there was moderate to substantial agreement in the categorization of women as frequently screened, screened or not screened between the 2 data sets (weighted kappa 0.74, 95% confidence interval 0.70-0.78). CONCLUSION: Medicare administrative claims are reliable for assessment of mammography utilization and have become more accurate over time. Medicare claims data also provide a mechanism for designating mammography as screening or diagnostic, which subsequently may allow accurate description of a woman's screening history.

Age Distribution↗
PubMed2004

Validation of the Taiwan Birth Registry using obstetric records.

BACKGROUND AND PURPOSE: Birth certificates are a major source of population-based data often used in maternal and child health research, but their value depends upon the level of accuracy of the data. The purpose of this study was to assess the validity of the birth registry data in Taiwan. METHODS: Obstetric records of a total of 2779 infants born at a municipal hospital in Taipei between 1995 and 1997 were abstracted and linked to the Taiwan Birth Registry (TBR). Concordance was presented by agreement percentages for various birth characteristics including gender, birth order, birth weight, and gestational age. Concordance was further assessed using Cohen's k and sensitivity/specificity for both birth weight and gestational age, with both variables categorized according to their customary definitions. RESULTS: Missing data for specific items in the TBR ranged from 0% (gender) to 1.6% (birth order). The birth registry accurately reported all 4 selected items, with the highest and lowest concordance percentage noted for gender (99.0%) and gestational age (88.3%), respectively. The level of agreement indicated by the Cohen's k statistic ranged from 0.92 to 0.96 for birth weight and gestational age when both variables were treated as categorical variables. CONCLUSIONS: The TBR showed a low rate of missing information and high levels of validity for the elements frequently used in maternal and child health research in Taiwan.

Birth Certificates↗
PubMed1994

Protein secondary structure prediction using two-level case-based reasoning.

We have developed a two-level case-based reasoning architecture for predicting protein secondary structure. The central idea is to break the problem into two levels: (i) reasoning at the object (protein) level and using the global information from this level to focus on a more restricted problem space; (ii) decomposing objects into pieces (segments) and reasoning at the level of internal structures. As a last step to the procedure, inferences from the parts of the internal structure are synthesized into predictions about global structure. The architecture has been developed and tested on a commonly used data set with 69.5% predictive accuracy. It was then tested on a new data set with 68.2% accuracy. With additional tuning, over 70% accuracy was achieved. In addition, a series of experiments were conducted to test various aspects of the method and the results are informative.

Amino Acid Sequence↗
PubMed2003

Geometric accuracy in robot-assisted total hip replacement surgery.

OBJECTIVE: Robot-Assisted Surgery in Total Hip Replacement (RAS-THR) has become a fairly widespread procedure for hip replacement surgery in Europe. However, data on the geometric accuracy of the overall process have so far been unavailable. The equipment manufacturers have only published data on the accuracy of certain elements of the procedure (e.g., the accuracy of the robot system). This study aimed to investigate the overall geometric accuracy of the complete process of RAS-THR, as well as the influence of some of the individual component steps. MATERIALS AND METHODS: An anthropomorphic phantom has been developed representing the hip and upper leg region of a human body. The entire RAS-THR procedure can be carried out using this phantom. Studies were conducted to investigate the overall accuracy of the process, as well as the influence of some individual steps in the procedure, using both the ROBODOC and CASPAR systems. RESULTS: Overall geometric accuracy of the RAS-THR process was found to be within a standard deviation of 0.5 mm and 0.3 degrees in the critical directions. Most individual steps in the process make similar contributions to the overall variation. The two robot systems examined offer comparable accuracy. CONCLUSION: Initial results seem to indicate that the RAS-THR process is acceptably accurate. However, acceptance criteria for the necessary geometric accuracy have not yet been defined.

Arthroplasty, Replacement, Hip↗
PubMed2006

Function approximation and documentation of sampling data using artificial neural networks.

Biodiversity studies in ecology often begin with the fitting and documentation of sampling data. This study is conducted to make function approximation on sampling data and to document the sampling information using artificial neural network algorithms, based on the invertebrate data sampled in the irrigated rice field. Three types of sampling data, i.e., the curve species richness vs. the sample size, the curve rarefaction, and the curve mean abundance of newly sampled species vs.the sample size, are fitted and documented using BP (Backpropagation) network and RBF (Radial Basis Function) network. As the comparisons, The Arrhenius model, and rarefaction model, and power function are tested for their ability to fit these data. The results show that the BP network and RBF network fit the data better than these models with smaller errors. BP network and RBF network can fit non-linear functions (sampling data) with specified accuracy and don't require mathematical assumptions. In addition to the interpolation, BP network is used to extrapolate the functions and the asymptote of the sampling data can be drawn. BP network cost a longer time to train the network and the results are always less stable compared to the RBF network. RBF network require more neurons to fit functions and generally it may not be used to extrapolate the functions. The mathematical function for sampling data can be exactly fitted using artificial neural network algorithms by adjusting the desired accuracy and maximum iterations. The total numbers of functional species of invertebrates in the tropical irrigated rice field are extrapolated as 140 to 149 using trained BP network, which are similar to the observed richness.

Algorithms↗
PubMed2006

Indicators of breast cancer severity and appropriateness of surgery based on hospital administrative data in the Lazio Region, Italy.

BACKGROUND: Administrative data can serve as an easily available source for epidemiological and evaluation studies. The aim of this study is to evaluate the use of hospital administrative data to determine breast cancer severity and the appropriateness of surgical treatment. METHODS: the study population consisted of 398 patients randomly selected from a cohort of women hospitalized for first-time breast cancer surgery in the Lazio Region, Italy. Tumor severity was defined in three different ways: 1) tumor size; 2) clinical stage (TNM); 3) severity indicator based on HIS data (SI). Sensitivity, specificity, and positive predictive value (PPV) of the severity indicator in evaluating appropriateness of surgery were calculated. The accuracy of HIS data was measured using Kappa statistic. RESULTS: Most of 387 cases were classified as T1 and T2 (tumor size), more than 70% were in stage I or II and the SI classified 60% of cases in medium-low category. Variation from guidelines indications identified under and over treatments. The accuracy of the SI to predict under-treatment was relatively good (58% of all procedures classified as under-treatment using pT where also classified as such using SI), and even greater predicting over-treatment (88.2% of all procedures classified as over treatment using pT where also classified as such using SI). Agreement between clinical chart and hospital discharge reports was K = 0.35. CONCLUSION: Our findings suggest that administrative data need to be used with caution when evaluating surgical appropriateness, mainly because of the limited ability of SI to predict tumor size and the questionable quality of HIS data as observed in other studies.

Adult↗
PubMed1998

Comparison of repeat videokeratography: repeatability and accuracy.

PURPOSE: We compared the repeatability and accuracy of four commercially available videokeratography instruments and a manual keratometer. METHODS: Ten optometry students and two university employees who had no history of rigid contact lens wear and no soft contact lens wear within 6 months of the study were measured. Two independent measurements were taken on the right eyes only using the Alcon EyeMap EH-290 topography system (both manual and automatic focus), the EyeSys System 2000 corneal topography system, the Humphrey Mastervue topography system, the Humphrey Atlas topography system, and a Marco manual keratometer. A three-factor repeated measures analysis of variance with all factors repeated was performed using SAS and BMDP statistical software. Separate analyses were conducted for paracentral and peripheral data. To test accuracy, measurements were taken with the Alcon EyeMap automatic focus system, the EyeSys System 2000, the Humphrey Atlas system, and the Humphrey Mastervue system using four calibration spheres. RESULTS: There were no statistically significant differences in the repeatability of the instruments. The EyeSys corneal topography system had the most narrow 95% limits of agreement around the mean difference. The two Humphrey instruments performed similarly to the EyeSys. Although the Alcon EyeMap EH-290 had the widest 95% limits of agreement around the mean difference, it showed better repeatability when the manual focus was used compared with the automatic focus. The instruments varied in their level of accuracy, but the highest percentage of data points within +/- 0.37 D of the known values of the calibration spheres was found with the Humphrey Atlas. CONCLUSIONS: Although there were no statistically significant differences in repeatability, the EyeSys System 2000 had the highest repeatability, which may have clinical relevance. The accuracy measured in this study varied tremendously; however, the Humphrey Atlas was found to be the most accurate of the instruments tested.

Cornea↗
PubMed1992

Virtual real-time digital processing of hemodynamic data.

At present, the majority of cardiac catheterization laboratories acquire and store hemodynamic data in analog form. To examine the possibility of performing complex analysis of digital data during the catheterization procedure, we examined whether virtual real-time digital (fast Fourier) analysis improves the accuracy of clinical data. We compared digital filtering of fluid manometry during the right heart catheterization with 10-Hz and 250-Hz analog filters. Using the simultaneously acquired micromanometry as the "gold standard," we found that analog filtering is associated with a greater error and time delay than digital filtering. This study demonstrates that digital hemodynamic data analysis performed during cardiac catheterization can improve the quality of data obtained during right heart catheterization, with the results available within seconds. More extensive use of computers in the cardiac catheterization laboratory may be useful for both clinical and research purposes.

Atrial Function, Right↗
PubMed1995

Establishing baseline data in cancer registration in northern England: implications for Health of the Nation targets.

OBJECTIVE: To assess the completeness and accuracy of cancer surveillance data relevant to Health of the Nation targets. DESIGN: A comparison of locally ascertained data on cancer with recorded cancer registry sources in selected diagnoses. SETTING: The district of South West Durham within the Northern Regional Health Authority. PATIENTS: All patients with lung, skin, and malignant cervical cancer who were resident and diagnosed in the district or identified in the Northern Region Cancer Registry during the calendar period 1989-91. MAIN RESULTS: Of 544 cases of cancer identified from all available sources, 448 (95.8%) were registered, ranging from 93.9% for malignant cervical cancer to 96.7% for skin cancer. In 448 cases which were both identified locally and registered, 53 (11.8%) showed disagreements between local sources and register data, involving classification of site and timing of registration. Twenty three cases were identified locally but were not registered, 22 registered but not identified locally, and 51 registered with the casenotes missing locally. CONCLUSIONS: Any real achievement of Health of the Nation targets may be masked by changes over time in the accuracy and completeness of information systems. In assessing the achievement or otherwise of targets, it is important to be aware of any differences in the completeness and accuracy of the baseline data compared to future measurements.

England↗
PubMed2005

The effect of long-range interactions on the secondary structure formation of proteins.

The influence of long-range residue interactions on defining secondary structure in a protein has long been discussed and is often cited as the current limitation to accurate secondary structure prediction. There are several experimental examples where a local sequence alone is not sufficient to determine its secondary structure, but a comprehensive survey on a large data set has not yet been done. Interestingly, some earlier studies denied the negative effect of long-range interactions on secondary structure prediction accuracy. Here, we have introduced the residue contact order (RCO), which directly indicates the separation of contacting residues in terms of the position in the sequence, and examined the relationship between the RCO and the prediction accuracy. A large data set of 2777 nonhomologous proteins was used in our analysis. Unlike previous studies, we do find that prediction accuracy drops as residues have contacts with more distant residues. Moreover, this negative correlation between the RCO and the prediction accuracy was found not only for beta-strands, but also for alpha-helices. The prediction accuracy of beta-strands is lower if residues have a high RCO or a low RCO, which corresponds to the situation that a beta-sheet is formed by beta-strands from different chains in a protein complex. The reason why the current study draws the opposite conclusion from the previous studies is examined. The implication for protein folding is also discussed.

Amino Acids↗
PubMed1998

Can we trust the quality of routine hospital outpatient information in the UK? Validating outpatient data from the patient administration system (PAS).

BACKGROUND: A validation study of routine hospital outpatient data was carried out as part of a broader project focusing on outpatient re-attendance. The aim was to compare two patient administration system (PAS) data items with the same information collected directly from hospital clinicians. METHODS: A total of 140 cases from four specialties at four National Health Service hospitals was randomly selected for comparison. The specific data items compared were the grade of doctor seen and the management decision taken following an outpatient appointment. The proportion of cases in which there was agreement was calculated, together with kappa values and relevant statistics indicating the accuracy of the PAS data when compared with information compiled immediately after the consultation by the relevant clinician. RESULTS: There was agreement between the clinician's data and the PAS data in 118/140 (84.3%) cases for grade of doctor seen and in 105/139 (76.7%) cases for the management decision. There was complete agreement for both items in 88/139 (62.6%) cases. Kappa values indicated good agreement between the two data sources. However, 'sensitivity' statistics suggested that the likely accuracy of each data item varied. CONCLUSION: Although there was good agreement within individual categories between the two sources, 37% of patient computerised records held at least one inconsistency in this small study focusing on only two data items. Further systematic evaluation is needed to test the extent to which other items are similarly discrepant.

Data Collection↗
PubMed2004

Quality specifications for biochemical markers of myocardial injury.

BACKGROUND: The current approach to the diagnosis and monitoring of myocardial damage, recognizes to biochemical markers, and in particular to troponins, a key role being well demonstrated that all elevated values were associated with a worsened prognosis. In 2001, the IFCC Committee on Standardization of Markers of Cardiac Damage published guidelines addressing the quality specifications for troponin assays in order to guarantee an analytical performance satisfying medical requirements and to standardize the quality of commercial methods. We describe how the application of quality specifications may be useful in daily practice, in order to provide advice to clinicians in the investigations of complex clinical cases of patients suffering from myocardial damage. MATERIALS AND METHODS: The samples from three patients (cases 1-3) admitted to the hospital with symptoms suggestive of cardiac disease, showing high troponin I (cTnI) values not correlated with clinical condition, were investigated in order to verify the accuracy of the laboratory data. The standard of quality specifications related to assay specificity, imprecision and interferences were evaluated using different platforms for cTnI assays, carrying out imprecision profile and specific studies on more common interferents in immunoassays. RESULTS: The obtained results allow us to demonstrate two cases of false-positive cTnI values attributable to a macrocomplex between a modified "in vivo" cTnI and immunoglobulin G (case 1) and to a presence of heterophilic antibodies affecting the RxL Dimension procedure (case 3). Instead, the accuracy of data obtained in case 2 was evidenced by the imprecision profile obtained in our laboratory and by the comparison of results between different laboratories using same platform. CONCLUSIONS: The lack of standardization as well as the wide differences in the development of each assay give rise to major concerns regarding cTnI determinations. The laboratory must therefore check the compliance between the analytical characteristics of the method utilised against recommended quality specifications for a reliable understanding of the frequency of false-positive results as well as other serious analytical errors.

Adult↗
PubMed2003

[Hospital infection surveillance and multiresistance monitoring: role of an external quality control].

The "Relais Régional d'Hygiène Hospitalière du Centre" (RHC) promotes the hospital infection prevention at a regional level in France, including 80 healthcare institutions. The accuracy of antimicrobial susceptibility data submitted by laboratories to surveillance is essential. Since 2001, RHC imposed an external quality control to validate the accuracy of the data submitted by the laboratories that are involved in survey programs. Most laboratories are able to detect homogenous methicillin resistance in S. aureus, and high-level vancomycin resistance in E. faecalis. Nevertheless, the ability of laboratories to detect organisms with emerging antimicrobial resistance patterns is not optimal for (i) detection of heterogeneous methicillin resistance, (ii) reduced susceptibility to teicoplanin in a non-multiresistant S. aureus and (iii) detection of resistance to extended-spectrum cephalosporins. Educational program to optimize the testing methods has been programmed and perennially of quality control testing prior to accepting data from laboratory participating in surveillance system is decided.

Cross Infection↗
PubMed1997

Conversion of a head-mounted microphone signal into calibrated SPL units.

A method is reviewed for conversion of a microphone signal into calibrated Sound Pressure Level (SPL) units. The method follows American National Standards Institute (ANSI) standard for S1.4 SPL meters and requires an accurate SPL meter and an accurate calibration sound source for conversion. Accuracy and validation data from test signals and human phonation are provided. The results indicate that under typical speech conditions, an absolute accuracy of plus or minus 1.6 dB (type 1 SPL meter) can be obtained with a miniature head-mounted microphone.

Amplifiers, Electronic↗
PubMedDate not supplied

An empirical equation for screen MTFs.

An empirical equation is described which accurately fits intensifying-screen MFT data within the accuracy of the MTF measurements. The equation is S (u) = 0.5 erfc[alpha1n(u/u0)]. The equation was fitted to data for 27 intensifying screens. Graphical and numerical results are presented. The maximum standard error was 0.02 and typical standard error was 0.01. Comparisons between results for three experimenters are also presented.

Radiographic Image Enhancement↗
PubMed1998

Target localization and treatment verification for intensity modulated conformal radiation therapy of the head and neck region. The AZ-VUB experience. Akademisch Ziekenhuis-Vrije Universiteit Brussel.

PURPOSE: Based on a previous evaluation of a conventional, non-invasive fixation technique in combination with a commercially available system for conformal radiation therapy by means of intensity modulation of the treatment beam some modifications have been proposed with respect to target localization and treatment verification. This paper reports on an on-going study of which some preliminary results are presented and discussed with respect to reproducibility of the treatment set-up and verification of the dose. METHODS AND MATERIALS: A slice-by-slice arc-rotation approach was used to deliver a conformal dose to the target and patient fixation was performed by means of a thermoplastic cast. In a previous study a procedure for target localization and verification of patient positioning suitable for this particular treatment technique had been developed and verified dosimetrically with an anthropomorphic phantom: both absolute dose measurements (alanine and thermoluminescent detectors) and relative dose distribution measurements (film dosimetry) have been applied. Two issues needed special attention, being: a) increased accuracy in patient set-up and b) deviations between measured and predicted dose values to organs at risk (OAR) in extreme situations. In a 2nd phase, fiducial markers fixed to customized ear moulds and a bite block have been introduced for target localization and verification of patient set-up on a day-to-day basis. A dosimetric verification by means of TLD and an anthropomorphic phantom has been performed to investigate the possible influence of leakage dose. RESULTS: The dose verification with the anthropomorphic phantom yielded a ratio between measured and predicted dose values of 1.0 for typical cases. However, large deviations (i.e. measured/calculated = 2.9) have been observed in cases with extreme dose constraints to the OAR due to a leakage dose of approximately 0.5%. Dosimetric verification showed good agreement with the dose calculation once the limitations of the system (10% of the target dose to the OAR) had been taken into consideration. Day-to-day variations in patient set-up of 0.3 cm (translations) and 2.0 degrees (rotations) were considered acceptable for this particular patient population in an initial phase, whereas variations of less than 0.1 cm can be achieved with the introduction of ear moulds and daily monitoring in a second phase. Preliminary results show a reproducibility of 0.08 cm in positioning of the fiducial landmarks with respect to anatomical landmarks. CONCLUSIONS: The non-invasive fixation technique in combination with fiducial markers fixed to individualized ear moulds and a bite block proved to be acceptable for IMRT of the head and neck region and allow for daily monitoring of patient set-up. The latter becomes mandatory if an accuracy of 0.1 cm and 1.0 degree is required. A clinical trial has been initiated recently to generate substantial data on the accuracy of the presented procedure for treatment set-up. Dose measurements confirmed the predicted dose values to the target and OAR, however, a physical limitation is represented by the 0.5% leakage through the leaves in that dose constraints to the OAR should be limited to 10% of the target dose.

Algorithms↗
PubMed1989

Evaluation of myocardial thallium tomography in patients with chest pain.

Thirty-seven patients with chest pain have been studied by exercise thallium tomography and coronary arteriography to assess the accuracy of thallium tomography in the identification of patients with coronary artery disease and to evaluate whether knowledge of clinical data improves this accuracy. Thallium tomography was also used to identify which coronary arteries were stenosed. Thallium tomography when compared with coronary arteriography has a sensitivity of 97%, a specificity of 75%, and an overall accuracy of 92% for the detection of coronary artery disease. When clinical information was made available, these results improved to a sensitivity of 100%, a specificity of 75%, and an overall accuracy of 95%. In the identification of which coronary arteries were stenosed, thallium tomography had a sensitivity of 85%, a specificity of 89%, and an overall accuracy of 86%. These results show that exercise thallium tomography can be an accurate non-invasive screening test in patients with chest pain thought to be angina.

Angina Pectoris↗