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PubMed2003

Feature-sampling and random-walk models of individual-stimulus recognition.

Traditional process models of old-new recognition have not addressed differences in accuracy and response time between individual stimuli. Two new process models of recognition are presented and applied to response time and accuracy data from 3 old-new recognition experiments. The 1st model is derived from a feature-sampling account of the time course of categorization, whereas the 2nd model is a generalization of a random-walk model of categorization. In the experiments, a new technique was used, which yielded reliable individual-stimulus data through repeated presentation of structurally equivalent items. The results from the experiments showed reliable differences in accuracy and response times between stimuli. The random-walk model provided the better account of the results from the 3 experiments. The implications of the results for process models of recognition are discussed.

Adult↗
PubMed1993

The challenge of documenting managed care cost savings and performance.

It is not too late for managed care to turn this situation around because the debate over health care reform and managing change is ongoing. It remains to be seen whether managed care companies will support independent third parties (i.e., researchers) in analyzing proprietary data and making value judgments about their effectiveness. There is a perception among managed care organizations that potentially negative findings could damage them in the marketplace. Nonetheless, smart organizations use negative findings as new opportunity targets for service improvement and product refinement. To what extent will managed care companies voluntarily release accurate data on performance factors in order for researchers to conduct cross-company analyses? Perhaps competitive markets such as managed care are not consistent with voluntary data sharing. On the other hand, mandatory reporting will not ensure data accuracy either. It is up to the managed care industry itself to develop a cooperative approach to data collection, analysis, and dissemination.

Cost Savings↗
PubMed2000

Laboratory standardization of a large international clinical trial: the DAIS experience. DAIS Project Group. Diabetes Atherosclerosis Intervention Study.

OBJECTIVE: To implement a quality control program for the standardization and harmonization of lipid and lipoprotein analyses as performed at two core laboratories (St. Paul's Hospital, UBC [Vancouver], and NPHI [Helsinki]) for the Diabetes Atherosclerosis Intervention Study (DAIS). DESIGN AND METHODS: A DAISSOFT computer program was designed to minimize the occurrence of data and sample management errors during the course of the study. Fresh human serum was used for the provision of an accuracy based external quality control program that monitored the analytical performance of lipid testing at these two laboratories. A separate program was designed for monitoring hemoglobin A1c (HbA1c). At the outset of the study, allowable total error goals were established for each analyte. Ongoing performance was monitored using bimonthly blinded challenges of fresh human serum. The two EQA programs routinely monitored the analysis of total cholesterol, calculated LDL-cholesterol, HDL-cholesterol, net triglycerides, apoprotein A-1, apoprotein B, and HbA1c. RESULTS: The EQA precision and accuracy data for the measurement of total cholesterol at the two core laboratories over the last 5 years indicated both laboratories operated with good precision, approximately 1% CV over the time period. The accuracy at both laboratories was similar initially. Part way through the study, the accuracy of the cholesterol method at NHPI tended to drift upward with an operating positive bias (+3%) relative to the Abell Kendall reference method. Triglyceride measurements were the most problematic for the study. By EQA cycle 8, the accuracy of the method at UBC had stabilized and was meeting the accuracy goals of the study. NPHI's method was negatively biased relative to the accuracy base of the DAIS study. In spite of recalibrating their method, NPHI found it difficult to maintain consistent accuracy for the measurement of triglycerides during the study. Both laboratories operated their HDL methods with excellent precision. Accuracy at NHPI was well maintained over the course of the study whereas the accuracy of HDL measurements at UBC was more problematic. There was an inconsistent variation in the accuracy of apoprotein A-1 measurements at both laboratories. In most cases, the bias would be corrected by the time of the next EQA challenge. In the case of apo B, one laboratory was standardized to the CDC while the other laboratory was standardized to IFCC/WHO. The discrepancy between these two accuracy bases was >20%. Recalibration to a common accuracy base rectified the problem. Only minor problems were encountered with the precision and accuracy of the DIAMAT assay for hemoglobin A-1c. The two DAIS core laboratories consistently operated within the 9% total error goals of the study for HbA1c. CONCLUSIONS: Through the use of this program, the two DAIS core laboratories were able to maintain their lipid analyses within the limits of allowable total error that had been established for the study.

Apolipoprotein A-I↗
PubMed2005

Quantitative determination of antalarmin, a novel corticotropin-releasing hormone receptor-1 antagonist, in canine plasma by HPLC-MS.

A simple and rapid method was developed for the quantitation of antalarmin from plasma using high performance liquid chromatography coupled with electrospray ionization mass spectrometry (ESI/MS). Separation of antalarmin from interfering compounds was achieved using reversed phase chromatography on a C-8 micro-column with an isocratic mobile phase comprised of 80% acetonitrile, 20% water, and 5 mM triethylamine. Detection by ESI/MS was accomplished in positive ion mode using single ion monitoring of the protonated molecular ions of antalarmin and its 13C2-isotopimer. The area ratio of the integrated peaks of interest in the extracted ion chromatogram was used for quantitation. The lower limit of detection was 1 picogram (pg) and the quantitation showed a linear response up to 4 nanograms loaded on column. To achieve acceptable accuracy at or around the limit of quantitation of 20 pg, a 1/x weighting was applied to the calibration data. Accuracy and precision variation for intra and inter-day validation were below the acceptable limit (15%) for pharmacokinetic studies.

Animals↗
PubMed1983

An accurate and reproducible absorptiometric technique for determining bone mineral content in newborn infants.

At the Bone Mineral Laboratory of the University of Wisconsin a microcomputer-based digital read-out system was designed specifically for determining bone mineral content (BMC) and bone width (BW) in newborn infants with the following features: (1) high accuracy and precision; (2) high reproducibility in vivo; (3) direct read-out of BMC and BW; (4) automatic data calibration; and (5) use of a low activity [125I] source (less than 50 mCi). BMC and BW were determined on the left radius on a series of 114 newborn infants of all gestational ages and a curve for intrauterine bone mineral content extrapolated from the data. Accuracy of the photon absorptiometric system was assessed by measuring BMC on a series of nine small bone sections (29-212 mg/cm) and confirmed by subsequent ashing of these bone sections (r = 0.99). Short-term precision (weekly, coefficient of variation 1.7%) and long-term precision (monthly, coefficient of variation 2.1%) for measuring BMC were determined by multiple determinations on a four-chambered bone phantom calibrated with the bone sections. Immediate reproducibility (without repositioning the arm) for the 4-6 scans performed for each determination of BMC and BW was good with a mean coefficient of variation of 3.9% for BMC and 3.6% for BW. In 84 infants, repositioning error was determined by repeating the measurement of BMC and BW after repositioning the arm. The correlation coefficients between measurements before and after repositioning the arm were 0.97 for BMC and 0.95 for BW. BMC correlated well with gestational age (r = 0.92), birth weight (r = 0.89) and bone width (r = 0.92). BW also correlated with gestational age (r = 0.84) and birth weight (r = 0.85). A multiple linear regression analysis of BMC versus BW, gestational age, and birth weight was done. The correlation coefficient between the predicted BMC from these variables and measured BMC was 0.95. Photon absorptiometry can be used with high accuracy, precision, and reproducibility in vivo in newborn infants. BMC correlates with gestational age, birth weight, and bone width.

Birth Weight↗
PubMed2005

Reproducibility of computer based neuropsychological testing among Norwegian elite football players.

BACKGROUND: Head injuries account for 4-22% of all football injuries. The rate of brain injuries is difficult to assess, due to the problem of defining and grading concussion. Thus computerised testing programs for cognitive function have been developed. OBJECTIVE: To assess the reliability of a computerised neuropsychological test battery (CogSport) among Norwegian professional football players. METHODS: Norwegian professional football league players (90.3% participation) performed two consecutive baseline Cogsport tests before the 2004 season. CogSport consists of seven different subtasks: simple reaction time (SRT), choice reaction time (ChRT), congruent reaction time (CgRT), monitoring (MON), one-back (OBK), matching (Match) and learning (Learn). RESULTS: There was a small but significant improvement from repeated testing for the reaction time measurements of all seven subtasks (SRT: 0.7%, ChRT: 0.4%, CgRT: 1.2%, MON: 1.3%, OBK: 2.7%, Match: 2.0%, Learn: 1.1%). The coefficient of variation (CV) ranged from 1.0% to 2.7%; corresponding intraclass correlation coefficients ranged from 0.45 (0.34 to 0.55) to 0.79 (0.74 to 0.84). The standard deviation data showed higher CVs, ranging from 3.7% (Learn) to 14.2% (SRT). Thus, the variance decreased with increasing complexity of the task. The accuracy data displayed uniformly high CV (10.4-12.2) and corresponding low intraclass correlation coefficient (0.14 (0.01 to 0.26) to 0.31 (0.19 to 0.42)). CONCLUSION: The reproducibility for the mean reaction time measures was excellent, but less good for measures of accuracy and consistency. Consecutive testing revealed a slight learning effect from test 1 to test 2, and double baseline testing is recommended to minimise this effect.

Adolescent↗
PubMed2006

Aging, practice, and perceptual tasks: a diffusion model analysis.

Practice effects were examined in a masked letter discrimination task and a masked brightness discrimination task for college-age and 60- to 75-year-old subjects. The diffusion model (Ratcliff, 1978) was fit to the response time and accuracy data and used to extract estimates of components of processing from the data. Relative to young subjects, the older subjects began the experiments with slower and less accurate performance; however, across sessions their accuracy improved because the quality of the information on which their decisions were based improved, and this, along with reduced decision criteria, led to shorter response times. For the brightness, but not the letter, discrimination task, the older subjects' performance matched that of the younger group by the end of 4 sessions, except that their nondecision components of processing were slightly slower. These analyses illustrate how a well-specified model can provide a unified view of multiple aspects of data that are often interpreted separately.

Adult↗
PubMed2006

Computed tomography assessment of the accuracy of in vivo placement of artificial discs in the lumbar spine including radiographic and clinical consequences.

STUDY DESIGN: Prospective cohort study of 52 patients who had undergone artificial lumbar disc replacement. OBJECTIVES: To evaluate the implantation accuracy of prosthesis positioning, subsequent facet joint changes and prosthesis migration, and the clinical consequences of implant position. SUMMARY OF BACKGROUND DATA: Accuracy of spinal prosthesis implantation has not been evaluated rigorously, especially with a mini-incision approach. It is unknown if the inexact placement of a mobile device in the spine has any biomechanical, radiographic, or clinical repercussions. METHODS: A total of 52 consecutive patients were treated using standard methods of disc implantation with an intervertebral prosthesis. Computed tomography scans were performed within 3 days and again at 6 to 24 months. An independent radiologist analyzed the images for prosthesis position, rotation, migration, and facet changes. Results were compared with clinical outcome, measured by the Visual Analog Scale and Oswestry Disability Index. RESULTS: Deviation of the prosthesis from the center position was under 1.2 mm, and rotation off of midline was under 12 degrees. Follow-up CT scans showed no migration or facet changes. Regression analysis showed no correlation of prosthesis position with clinical outcome. CONCLUSIONS: Current prosthetic disc implantation methods, with minimally invasive access techniques, are relatively accurate. Although there can be deviation of the prosthesis from ideal placement, no repercussions were attributable.

Adult↗
PubMed2002

Comparison of estimates and calculations of risk of coronary heart disease by doctors and nurses using different calculation tools in general practice: cross sectional study.

OBJECTIVE: To assess the effect of using different risk calculation tools on how general practitioners and practice nurses evaluate the risk of coronary heart disease with clinical data routinely available in patients' records. DESIGN: Subjective estimates of the risk of coronary heart disease and results of four different methods of calculation of risk were compared with each other and a reference standard that had been calculated with the Framingham equation; calculations were based on a sample of patients' records, randomly selected from groups at risk of coronary heart disease. SETTING: General practices in central England. PARTICIPANTS: 18 general practitioners and 18 practice nurses. MAIN OUTCOME MEASURES: Agreement of results of risk estimation and risk calculation with reference calculation; agreement of general practitioners with practice nurses; sensitivity and specificity of the different methods of risk calculation to detect patients at high or low risk of coronary heart disease. RESULTS: Only a minority of patients' records contained all of the risk factors required for the formal calculation of the risk of coronary heart disease (concentrations of high density lipoprotein (HDL) cholesterol were present in only 21%). Agreement of risk calculations with the reference standard was moderate (kappa=0.33-0.65 for practice nurses and 0.33 to 0.65 for general practitioners, depending on calculation tool), showing a trend for underestimation of risk. Moderate agreement was seen between the risks calculated by general practitioners and practice nurses for the same patients (kappa=0.47 to 0.58). The British charts gave the most sensitive results for risk of coronary heart disease (practice nurses 79%, general practitioners 80%), and it also gave the most specific results for practice nurses (100%), whereas the Sheffield table was the most specific method for general practitioners (89%). CONCLUSIONS: Routine calculation of the risk of coronary heart disease in primary care is hampered by poor availability of data on risk factors. General practitioners and practice nurses are able to evaluate the risk of coronary heart disease with only moderate accuracy. Data about risk factors need to be collected systematically, to allow the use of the most appropriate calculation tools.

Community Health Nursing↗
PubMed1984

An assessment of occupation and industry data from death certificates and hospital medical records for population-based cancer surveillance.

This study analyzed 30,194 incident cases and 4,301 death certificates for completeness of occupational reporting. Analysis of data accuracy was based upon a comparison of more than 2,000 death certificates with incident abstracts and 352 death certificates with interview data. Death certificates had a higher proportion with occupation (94.3%) and industry (93.4%) reported than did incident abstracts of hospital medical records (39.0% and 63.5%, respectively). Compared with occupational history data obtained by interview, 76.1% of the death certificates were exact matches for usual occupation and industry.

Adult↗
PubMed1997

Comparing exemplar-retrieval and decision-bound models of speeded perceptual classification.

The authors compared the exemplar-based random-walk (EBRW) model of Nosofsky and Palmeri (1997) and the decision-bound model (DBM) of Ashby and Maddox (1994; Maddox & Ashby, 1996) on their ability to predict performance in Garner's (1974) speeded classification tasks. A key question was the extent to which the models could predict facilitation in the correlated task and interference in the filtering task, in situations involving integral-dimension stimuli. To obtain rigorous constraints for model evaluation, the goal was to fit the detailed structure of the response time (RT) distribution data associated with each individual stimulus in each task. Both models yielded reasonably good global quantitative fits to the RT distribution and accuracy data. However, the DBM failed to properly characterize the interference effects in the filtering task. Apparently, a fundamental limitation of the DBM is that it predicts that the fastest RTs in the filtering task should be faster than the fastest RTs in the control task, whereas the opposite pattern was observed in our data.

Decision Making↗
PubMed1979

Mass balance: a quantitative guide to clinical nutritional therapy. I. The predialysis patient with renal disease.

Mass balance principles can be readily applied to the patient with chronic renal failure for the more structured management of his/her nutritional and clinical course. Urine values provide valuable information with respect to rates of protein catabolism and sodium intake; creatinine excretion rates provide a ready check on data accuracy and lean body mass; urea and creatinine clearance can be calculated, if blood levels of these solutes are known. With accurate data on creatinine generation and the ratio of urea to creatinine clearance, creatinine clearance, urea generation, and protein catabolism rates can be estimated from blood levels alone. These techniques then provide quantitative guidance for the nutritional/medical staff in its efforts to control the clinical course of the patient with severly diminished renal function.

Acute Kidney Injury↗
PubMed2001

Measuring antibiotic prescribing practices among ambulatory physicians: accuracy of administrative claims data.

To assess the accuracy of administrative claims data for measuring antibiotic prescribing behavior, we conducted a stratified randomized medical record review of office visits by children with pharyngitis, and adults with acute bronchitis, to primary care physicians in Colorado in 1998. The diagnoses of pharyngitis (n = 422) and acute bronchitis (n = 497) based on administrative data were verified in 83% and 79%, respectively, of medical records. The sensitivity, specificity, and positive predictive value of administrative data in identifying antibiotic treatment for pharyngitis was 68%, 91%, and 90%, respectively, and for bronchitis was 79%, 84% and 98%, respectively. The sensitivity, specificity, and negative predictive value of administrative data in identifying group A streptococcal test ordering for pharyngitis was 71%, 86%, and 30%, respectively. Absence of testing in administrative data (when present in the medical record) was more frequent among visits to physicians associated with a capitated health plan. We conclude that administrative claims data are accurate sources for measuring and profiling antibiotic prescribing practices in ambulatory practice, although they underestimate actual antibiotic treatment decisions by individual physicians. Measuring and profiling antibiotic prescribing behavior in relation to group A streptococcal test utilization may overestimate inappropriate antibiotic treatment by physicians enrolled in capitated contracts.

Acute Disease↗
PubMed1999

Accuracy of administrative data in trauma.

BACKGROUND: Accurate data are needed to evaluate outcomes, therapeutics, and quality of care. This study assesses the accuracy of administrative databases in recording information about trauma patients. METHODS: Patients with thoracic aorta injury were identified with a state trauma registry, and the medical records were reviewed. Data collected were compared to administrative data on patients with thoracic aorta injuries, at the same hospitals in the same time period. RESULTS: Fifteen patients (16.3%) with thoracic aorta injury were not recorded in the administrative database, and 23 patients (18.7%) were misdiagnosed. Ninety-one patients were found in both data sources. The administrative database significantly (P < .05) underrecorded abdominal injuries (50 vs 35), orthopedic injuries (117 vs 75), and chest injuries (77 vs 48). The number of aortograms (78 vs 8), type of operative procedures (use of graft; 70 vs 30), use of bypass (35 vs 16), and complications (77 vs 33) were underreported (P < .05). The Injury Severity Score was underestimated by the administrative database (38.65 +/- 12.41 vs 25.66 +/- 9.53; P < .05). CONCLUSIONS: Administrative data lack accuracy in the recording of associated injury, injury severity, diagnostic, and procedural data. Whether these data should be used to evaluate treatment or quality of care in trauma is questionable.

Adult↗
PubMed2000

Adjuvant chemotherapy for localised resectable soft tissue sarcoma in adults. Sarcoma Meta-analysis Collaboration (SMAC).

BACKGROUND: Individually, randomised trilas have not shown conclusively whether adjuvant chemotherapy benefits adult patients with localised resectable soft-tissue sarcoma. OBJECTIVES: Adjuvant chemotherapy aims to lessen the recurrence of cancer after surgery with or without radiotherapy. The objective of this review was to assess the effects of adjuvant chemotherapy in adults with resectable soft tissue sarcoma after such local treatment. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register, UKCCCR Register of Cancer Trials, Physicians Data Query, EMBASE, MEDLINE and CancerLit. SELECTION CRITERIA: Randomised trials of adjuvant chemotherapy after local treatment in adults with localised resectable soft tissue sarcoma were included. Only trials in which accrual was completed by December 1992 were included. DATA COLLECTION AND ANALYSIS: Individual patient data were obtained. Accuracy of data and quality of randomisation and follow-up of trials was assessed. MAIN RESULTS: Fourteen trials of doxorubicin-based adjuvant chemotherapy involving 1568 patients were included. Median follow-up was 9.4 years. For local recurrence-free interval the hazard ratio with chemotherapy was 0.73 (95% Confidence Interval 0.56-0.94). For distant recurrence-free interval it was 0. 70 (95% CI 0.57-0.85). For overall recurrence-free survival it was 0. 75 (95% CI 0.64-0.87). These correspond to significant absolute benefits of 6-10% at 10 years. For overall survival the hazard ratio of 0.89 (95% CI 0.76-1.03) was not significant but potentially represents an absolute benefit of 4% (95% CI -1 to 9) at 10 years. There was no consistent evidence of a difference in effect according to age, sex, stage, site, grade, histology, extent of resection, tumour size or exposure to radiotherapy. However, the strongest evidence of a beneficial effect on survival was shown in patients with sarcoma of the extremities. REVIEWER'S CONCLUSIONS: Doxorubicin-based adjuvant chemotherapy appears to significantly improve time to local and distant recurrence and overall recurrence-free survival in adults with localised resectable soft tissue sarcoma. There is some evidence of a trend towards improved overall survival.

Adult↗
PubMed1997

An empirical study of economies of scope in home healthcare.

OBJECTIVE: To apply the economic theory of economies of scope to the home healthcare industry. DATA SOURCES: Data on 488 observations obtained from the Cost Report (HCFA Form 1728-86) of all Connecticut state-licensed, Medicare-certified home health agencies. STUDY DESIGN: The Cost Report was the primary source of data for this study. Information on total cost, scope, and other related factors was collected. Logarithmic and nonlinear regression analyses were used to identify factors related to scope and also to test for economies of scope. DATA COLLECTION METHOD: Data collected were both cross-sectional and time series (from 1988-1992). Data accuracy was verified using description of frequencies, measures of central tendency and variation, and a calculation package so that a computer calculation on the data could be compared with the agency's calculation. PRINCIPAL FINDINGS: It was determined that initially as scope increases, costs go down, thus proving economies of scope. For larger values of scope, it was determined that costs go up, proving diseconomies of scope. CONCLUSIONS: Many of the home health agencies included in this study provide more services than is cost effective given the economic theory of economies of scope.

Connecticut↗
PubMed1978

An interlaboratory comparison of serum total protein analyses.

An analysis of the 1976 CAP Comprehensive Chemistry Survey of total serum proteins is presented. More than 2,000 laboratories contributed data in this survey. Estimation of total serum protein concentration by the biuret reaction remains the most widely used technic, followed by refractometry. Precision and accuracy data for a number of analytic systems and methods are presented. Precisions for the entire group are nearly comparable. A negative bias for total protein concentration was shown by the SMAC.

Blood Chemical Analysis↗
PubMed2006

Sharing electronic health records: the patient view.

The introduction of a national electronic health record system to the National Health Service (NHS) has raised concerns about issues of data accuracy, security and confidentiality. The primary aim of this project was to identify the extent to which primary care patients will allow their local electronic record data to be shared on a national database. The secondary aim was to identify the extent of inaccuracies in the existing primary care records, which will be used to populate the new national Spine. Fifty consecutive attenders to one general practitioner were given a paper printout of their full primary care electronic health record. Participants were asked to highlight information which they would not want to be shared on the national electronic database of records, and information which they considered to be incorrect. There was a 62% response rate (31/50). Five of the 31 patients (16%) identified information that they would not want to be shared on the national record system. The items they identified related almost entirely to matters of pregnancy, contraception, sexual health and mental health. Ten respondents (32%) identified incorrect information in their records (some of these turned out to be correct on further investigation). The findings in relation to data sharing fit with the commonly held assumption that matters related to sensitive or embarrassing issues, which may affect how the patient will be treated by other individuals or institutions, are most likely to be censored by patients. Previous work on this has tended to ask hypothetical questions concerning data sharing rather than examine a real situation. A larger study of representative samples of patients in both primary and secondary care settings is needed to further investigate issues of data sharing and consent.

Adult↗