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At least 631 records · Page 35Linked to original sources
PubMed2004

Simultaneous confidence intervals for ratios with applications to the comparison of several treatments with a control.

OBJECTIVES: In this article, we illustrate and compare exact simultaneous confidence sets with various approximate simultaneous confidence intervals for multiple ratios as applied to many-to-one comparisons. Quite different datasets are analyzed to clarify the points. METHODS: The methods are based on existing probability inequalities (e.g., Bonferroni, Slepian and Sidak), estimation of nuisance parameters and re-sampling techniques. Exact simultaneous confidence sets based on the multivariate t-distribution are constructed and compared with approximate simultaneous confidence intervals. RESULTS: It is found that the coverage probabilities associated with the various methods of constructing simultaneous confidence intervals (for ratios) in manyto-one comparisons depend on the ratios of the coefficient of variation for the mean of the control group to the coefficient of variation for the mean of the treatments. If the ratios of the coefficients of variations are less than one, the Bonferroni corrected Fieller confidence intervals have almost the same coverage probability as the exact simultaneous confidence sets. Otherwise, the use of Bonferroni intervals leads to conservative results. CONCLUSIONS: When the ratio of the coefficient of variation for the mean of the control group to the coefficient of variation for the mean of the treatments are greater than one (e.g., in balanced designs with increasing effects), the Bonferroni simultaneous confidence intervals are too conservative. Therefore, we recommend not using Bonferroni for this kind of data. On the other hand, the plug-in method maintains the intended confidence coefficient quite satisfactorily; therefore, it can serve as the best alternative in any case.

Abdominal Pain↗
PubMed2004

The Global Error Assessment (GEA) model for the selection of differentially expressed genes in microarray data.

MOTIVATION: Microarray technology has become a powerful research tool in many fields of study; however, the cost of microarrays often results in the use of a low number of replicates (k). Under circumstances where k is low, it becomes difficult to perform standard statistical tests to extract the most biologically significant experimental results. Other more advanced statistical tests have been developed; however, their use and interpretation often remain difficult to implement in routine biological research. The present work outlines a method that achieves sufficient statistical power for selecting differentially expressed genes under conditions of low k, while remaining as an intuitive and computationally efficient procedure. RESULTS: The present study describes a Global Error Assessment (GEA) methodology to select differentially expressed genes in microarray datasets, and was developed using an in vitro experiment that compared control and interferon-gamma treated skin cells. In this experiment, up to nine replicates were used to confidently estimate error, thereby enabling methods of different statistical power to be compared. Gene expression results of a similar absolute expression are binned, so as to enable a highly accurate local estimate of the mean squared error within conditions. The model then relates variability of gene expression in each bin to absolute expression levels and uses this in a test derived from the classical ANOVA. The GEA selection method is compared with both the classical and permutational ANOVA tests, and demonstrates an increased stability, robustness and confidence in gene selection. A subset of the selected genes were validated by real-time reverse transcription-polymerase chain reaction (RT-PCR). All these results suggest that GEA methodology is (i) suitable for selection of differentially expressed genes in microarray data, (ii) intuitive and computationally efficient and (iii) especially advantageous under conditions of low k. AVAILABILITY: The GEA code for R software is freely available upon request to authors.

Algorithms↗
PubMedDate not supplied

The possibilities and the realities of home care.

BACKGROUND: An analysis of a provincial home care dataset, comparing home care client, service, and providers in 1991/92 through 2000/01, was undertaken to describe changes over the decade, and permit a more informed discussion of home care in relation to Canadian health policy developments and health system reforms. METHODS: After data were obtained upon request from Alberta's Ministry of Health and Wellness, descriptive and comparative statistical analyses were undertaken using the SPSS computer program. Logistic regression was used to compare multiple client characteristics in the first and last years. RESULTS: Home care clients doubled and the mean hours of care per client increased substantially, although the duration of care provision declined. The mean age of clients also declined. Home care continued to be primarily provided by Home Support Aides, with self-managed care increasing dramatically. Sustained geographical differences in home care were noted. CONCLUSION: Although home care has much potential for enabling early discharge from hospital, and for maintaining or improving health, few population-level studies of home care trends exist. In Alberta, although formal home care hours increased, home care expansion was not uniform across the province. Home Support Aides continued to be the primary care provider. In the face of substantial hospital downsizing, these observations could imply that the provision of home care has been off loaded to families. Moreover, home care increases do not appear to be related to an aging population.

Aged↗
PubMedDate not supplied

Self-care strategies and sources of information for HIV/AIDS symptom management.

BACKGROUND: Self-care is one of the challenges that people with HIV/AIDS face in the long-term symptom management of the disease. OBJECTIVE: To identify the category schemes of self-care strategies and sources of information for symptom management reported by HIV-positive individuals. METHODS: A secondary analysis was conducted in a large dataset of an HIV/AIDS symptom management study. Narrative data of symptom self-care management strategies and sources of information for symptom management were analyzed by a content analysis technique to identify category schemes. The 359 participants in the study reported 776 symptom self-care strategies and 526 sources of information for these strategies. RESULTS: The symptom self-care management strategies were summarized into eight categories: medications (23.45%), self-comforting (15.21%), complementary treatments (14.69%), daily thoughts and activities (12.89%), diet changing (10.95%), help seeking (9.28%), spiritual care (6.83%), and exercise (6.70%). There were four categories of information sources: self (34.41%), healthcare provider (27.95%), personal network (19.20%), and community (18.44%). The category schemes had moderate to high interrater reliability (Cohen's kappa:.49-1.00 for self-care strategy and .70-.87 for source of information). Most of the self-care strategies were perceived as helpful. Except for complementary treatments, self-care strategies were used differently among people with the six most frequently occurring symptoms (chi2 [5, n = 286] = 28.53-79.89). DISCUSSION: The eight categories of self-care strategies identified in this study showed that people with HIV/AIDS not only seek the help of medications, but also follow a wide array of other self-developed or self-taught nonpharmaceutical strategies to allay their symptoms.

Adolescent↗
PubMed2005

Heart disease and prevention: race and age differences in heart disease prevention, treatment, and mortality.

OBJECTIVE: The objective of this study was to analyze race and age differences in the distribution of health promotion and cardiovascular screening tests, and the prevalence of serious heart disease and cardiovascular mortality in the United States. DATA SOURCES/STUDY POPULATION: Data are from 7 federal datasets represented in the first National Healthcare Quality Report and the National Healthcare Disparities Report, and include surveys, administrative and vital statistics data systems. The study analyzes blacks and whites. MEASURES: Counseling on diet and nutrition, exercise, and tobacco during an outpatient visit indicate the availability of health promotion services, and screening for high blood pressure and cholesterol represent preventive services. Hospitalizations for heart-related conditions and use of certain cardiac procedures identify serious heart disease. Deaths from coronary artery disease and stroke are the heart-related mortality measures. PRINCIPAL FINDINGS: Counseling and education services tend to occur more on outpatient visits by individuals aged 45 to 64 years than in younger age groups. Screening rates among individuals aged 45 to 64 years of approximately 90% for hypertension and 80% for high cholesterol suggest progress in early detection of cardiac risk factors. However, blacks aged 45 to 64 years are 5.6 times more likely than their white counterparts to be hospitalized for hypertension, approximately one third less likely to receive a cardiac procedure, and almost twice as likely to die of coronary heart disease. CONCLUSIONS: Although findings indicate few racial differences in health promotion services in ambulatory care or screening for cardiac risk factors, the prevalence of serious cardiovascular disease, use of cardiac procedures, and heart-related mortality suggest continuing racial disparities in heart disease.

Adolescent↗
PubMed2005

Health disparities in lifestyle choices among hypertensive Korean Americans, non-Hispanic Whites, and Blacks.

PURPOSE AND METHODS: To describe medication profile, diet, and exercise/physical activity in hypertensive Korean Americans, a convenience sample of 100 hypertensive Korean Americans (KAs) at two KA health clinics were interviewed by bilingual Korean nurses using questions from the 1988-1994 Third National Health and Nutrition Examination Survey (NHANES III). One hundred age- and gender-matched hypertensive non-Hispanic Whites and 100 Blacks were randomly selected from the NHANES III dataset, and results were compared to describe the health disparities in lifestyle choices among the three groups. RESULTS: The medication profile among the three groups was similar. A majority of members of all three groups had been told by health professionals to exercise for hypertension. KAs made significantly less effort to reduce salt in their diets than did members of the other two groups (p < .05). Fewer KAs than non-Hispanic Whites or Blacks were following their health professionals'advice to control or lose weight for their high blood cholesterol levels. KAs had the lowest body mass index and were older and more educated than members of the other two groups. KAs' primary reasons for using the KA clinic were the respect they received and the use of the Korean language. IMPLICATIONS: KA health professionals need to teach their patients more about the importance of health-promoting lifestyles for hypertension and its contributing factors. More KA hypertensive patients should follow the advice of health professionals on healthy lifestyles. Nurses should continue to treat patients with respect and provide care with sensitivity to language needs of patients.

Adult↗
PubMed2002

Integration of genomic datasets to predict protein complexes in yeast.

The ultimate goal of functional genomics is to define the function of all the genes in the genome of an organism. A large body of information of the biological roles of genes has been accumulated and aggregated in the past decades of research, both from traditional experiments detailing the role of individual genes and proteins, and from newer experimental strategies that aim to characterize gene function on a genomic scale. It is clear that the goal of functional genomics can only be achieved by integrating information and data sources from the variety of these different experiments. Integration of different data is thus an important challenge for bioinformatics. The integration of different data sources often helps to uncover non-obvious relationships between genes, but there are also two further benefits. First, it is likely that whenever information from multiple independent sources agrees, it should be more valid and reliable. Secondly, by looking at the union of multiple sources, one can cover larger parts of the genome. This is obvious for integrating results from multiple single gene or protein experiments, but also necessary for many of the results from genome-wide experiments since they are often confined to certain (although sizable) subsets of the genome. In this paper, we explore an example of such a data integration procedure. We focus on the prediction of membership in protein complexes for individual genes. For this, we recruit six different data sources that include expression profiles, interaction data, essentiality and localization information. Each of these data sources individually contains some weakly predictive information with respect to protein complexes, but we show how this prediction can be improved by combining all of them. Supplementary information is available at http:// bioinfo.mbb.yale.edu/integrate/interactions/.

Cell Cycle↗
PubMed2006

Functional imaging analysis contest (FIAC) analysis according to AFNI and SUMA.

The Functional Imaging Analysis Contest (FIAC) datasets were analyzed with the AFNI software package. Two types of linear regression analyses were carried out: "fixed shape" hemodynamic response, where a preselected incomplete gamma function is used to model each brief activation episode, and "variable shape" analysis, where the temporal shape of the response model in each stimulus block class is allowed to vary separately in each voxel. These time series regressions were carried out both in the volume and on the original data projected to individual standardized cortical surface models. Intersubject analyses were carried out voxel-wise on the regression amplitudes obtained from these time series results, using a multi-way within-subject analysis of variance (ANOVA). Group analysis of the block design demonstrated a significant repetition suppression of the BOLD signal within blocks in the superior and middle temporal gyrus. This effect may represent differences in the response to the first stimulus following a period of silence compared to the remaining sentences in the block. Analyzing the event-related data, Brodmann area 31 showed significant sentence effect and consecutive-sentence repetition effect. However, no significant speaker effect was found; these results may be consistent with the instructions to the subjects that they would be tested on the sentence content. Sentence by speaker interaction effects were found in bilateral middle temporal gyrus, left inferior frontal, and left inferior temporal gyrus.

Brain Mapping↗
PubMed1997

The digital anatomist information system and its use in the generation and delivery of Web-based anatomy atlases.

Advances in network and imaging technology, coupled with the availability of 3-D datasets such as the Visible Human, provide a unique opportunity for developing information systems in anatomy that can deliver relevant knowledge directly to the clinician, researcher or educator. A software framework is described for developing such a system within a distributed architecture that includes spatial and symbolic anatomy information resources, Web and custom servers, and authoring and end-user client programs. The authoring tools have been used to create 3-D atlases of the brain, knee and thorax that are used both locally and throughout the world. For the one and a half year period from June 1995-January 1997, the on-line atlases were accessed by over 33,000 sites from 94 countries, with an average of over 4000 "hits" per day, and 25,000 hits per day during peak exam periods. The atlases have been linked to by over 500 sites, and have received at least six unsolicited awards by outside rating institutions. The flexibility of the software framework has allowed the information system to evolve with advances in technology and representation methods. Possible new features include knowledge-based image retrieval and tutoring, dynamic generation of 3-D scenes, and eventually, real-time virtual reality navigation through the body. Such features, when coupled with other on-line biomedical information resources, should lead to interesting new ways for managing and accessing structural information in medicine.

Anatomy↗
PubMed2006

Exploring predictive and reproducible modeling with the single-subject FIAC dataset.

Predictive modeling of functional magnetic resonance imaging (fMRI) has the potential to expand the amount of information extracted and to enhance our understanding of brain systems by predicting brain states, rather than emphasizing the standard spatial mapping. Based on the block datasets of Functional Imaging Analysis Contest (FIAC) Subject 3, we demonstrate the potential and pitfalls of predictive modeling in fMRI analysis by investigating the performance of five models (linear discriminant analysis, logistic regression, linear support vector machine, Gaussian naive Bayes, and a variant) as a function of preprocessing steps and feature selection methods. We found that: (1) independent of the model, temporal detrending and feature selection assisted in building a more accurate predictive model; (2) the linear support vector machine and logistic regression often performed better than either of the Gaussian naive Bayes models in terms of the optimal prediction accuracy; and (3) the optimal prediction accuracy obtained in a feature space using principal components was typically lower than that obtained in a voxel space, given the same model and same preprocessing. We show that due to the existence of artifacts from different sources, high prediction accuracy alone does not guarantee that a classifier is learning a pattern of brain activity that might be usefully visualized, although cross-validation methods do provide fairly unbiased estimates of true prediction accuracy. The trade-off between the prediction accuracy and the reproducibility of the spatial pattern should be carefully considered in predictive modeling of fMRI. We suggest that unless the experimental goal is brain-state classification of new scans on well-defined spatial features, prediction alone should not be used as an optimization procedure in fMRI data analysis.

Artifacts↗
PubMed2005

Linear analysis of carbon-13 chemical shift differences and its application to the detection and correction of errors in referencing and spin system identifications.

Statistical analysis reveals that the set of differences between the secondary shifts of the alpha- and beta-carbons for residues i of a protein (Deltadelta13C(alpha)i - Deltadelta13C(beta)i) provides the means to detect and correct referencing errors for 1H and 13C nuclei within a given dataset. In a correctly referenced protein dataset, linear regression plots of Deltadelta13C(alpha)i, Deltadelta13C(beta)i, or Deltadelta1H(alpha)i vs. (Deltadelta13C(alpha)i - Deltadelta13C(beta)i) pass through the origin from two directions, the helix-to-coil and strand-to-coil directions. Thus, linear analysis of chemical shifts (LACS) can be used to detect referencing errors and to recalibrate the 1H and 13C chemical shift scales if needed. The analysis requires only that the signals be identified with distinct residue types (intra-residue spin systems). LACS allows errors in calibration to be detected and corrected in advance of sequence-specific assignments and secondary structure determinations. Signals that do not fit the linear model (outliers) deserve scrutiny since they could represent errors in identifying signals with a particular residue, or interesting features such as a cis-peptide bond. LACS provides the basis for the automated detection of such features and for testing reassignment hypotheses. Early detection and correction of errors in referencing and spin system identifications can improve the speed and accuracy of chemical shift assignments and secondary structure determinations. We have used LACS to create a database of offset-corrected chemical shifts corresponding to nearly 1800 BMRB entries: 300 with and 1500 without corresponding three-dimensional (3D) structures. This database can serve as a resource for future analysis of the effects of amino acid sequence and protein secondary and tertiary structure on NMR chemical shifts.

Amino Acid Sequence↗
PubMed2006

Recent results on modelling the spatial and temporal structure of the Earth's gravity field.

The Earth's gravity field plays a central role in sea-level change. In the simplest application a precise gravity field will enable oceanographers to capitalize fully on the altimetric datasets collected over the past decade or more by providing a geoid from which absolute sea-level topography can be recovered. However, the concept of a static gravity field is now redundant as we can observe temporal variability in the geoid due to mass redistribution in or on the total Earth system. Temporal variability, associated with interactions between the land, oceans and atmosphere, can be investigated through mass redistributions with, for example, flow of water from the land being balanced by an increase in ocean mass. Furthermore, as ocean transport is an important contributor to the mass redistribution the time varying gravity field can also be used to validate Global Ocean Circulation models. This paper will review the recent history of static and temporal gravity field recovery, from the 1980s to the present day. In particular, mention will be made of the role of satellite laser ranging and other space tracking techniques, satellite altimetry and in situ gravity which formed the basis of gravity field determination until the last few years. With the launch of Challenging Microsatellite Payload and Gravity and Circulation Experiment (GRACE) our knowledge of the spatial distribution of the Earth's gravity field is taking a leap forward. Furthermore, GRACE is now providing insight into temporal variability through 'monthly' gravity field solutions. Prior to this data we relied on satellite tracking, Global Positioning System and geophysical models to give us insight into the temporal variability. We will consider results from these methodologies and compare them to preliminary results from the GRACE mission.

Earth, Planet↗
PubMedDate not supplied

Relationship of oral antihyperglycemic (sulfonylurea or metformin) medication adherence and hemoglobin A1c goal attainment for HMO patients enrolled in a diabetes disease management program.

BACKGROUND: There is limited information in the primary literature regarding the relationship of medication adherence to attainment of glycosylated hemoglobin A1c (A1c) goals. The 2 oral antihyperglycemic medications, sulfonylurea and/or metformin, were chosen for retrospective analysis because they are the 2 most common oral medications used by patients with diabetes. OBJECTIVE: To describe the relationship between adherence with 1 or both of 2 oral antihyperglycemic medications (sulfonylurea and metformin) and A1c goal attainment for health maintenance organization (HMO) patients enrolled in a diabetes disease management program. METHODS: This was a retrospective, descriptive evaluation of patients enrolled in a managed care diabetes disease management program in a 188,000-member independent practice association model HMO located in the Southeast. The dataset in this analysis contained demographic, enrollment, pharmacy claims, and clinical laboratory data. Continuously enrolled patients were included if there was a documented A1c value obtained at least 90 days after the initial oral antihyperglycemic medication (sulfonylurea or metformin) prescription index date. The medication possession ratio (MPR) was calculated from the pharmacy claim records and correlated with the A1c value. RESULTS: A total of 42% of patients on sulfonylurea therapy and 46% of those on metformin reached an A1c goal of < or = 7.0%. For patients taking a sulfonylurea, the mean MPR for those who reached the predetermined A1c goal (< or = 7.0) was 0.82 (0.29) compared with 0.72 (0.31) for those patients who did not reach the A1c target goal (P < 0.001). For patients taking metformin, the mean MPR for those who reached the predetermined A1c goal was 0.77 (0.3) versus 0.62 (0.3) for those patients who did not reach the A1c target goal (P < 0.001). A Pearson correlation analysis revealed a positive relationship between the MPR and A1c for sulfonylurea (r = -0.295, P < 0.001) and for metformin (r = -0.285, P < 0.001). For those patients taking both sulfonylurea and metformin, the Pearson correlation analysis showed a positive relationship between the 2 MPRs (r = 0.65, P < 0.001). CONCLUSION: Medication adherence as measured by the MPR was higher for patients taking a sulfonylurea or metformin who reached the target A1c goal of d7.0% compared with patients taking these drugs who did not reach the target A1c goal.

Administration, Oral↗
PubMed2006

Incidence and demographics of hand fractures in British Columbia, Canada: a population-based study.

PURPOSE: To identify population-based hand fracture annual incidence rates, demographics, and seasonal and geographic variations from all patients seeking treatment for a hand fracture in British Columbia, Canada from May 1, 1996 to April 20, 2001. METHODS: All Medical Service Plan and Hospital Separation records that included International Classification of Diseases-9 codes for metacarpal (815), phalangeal (816), and multiple (817) fractures were extracted from the British Columbia Linked Health Dataset, along with the individual registry demographic records linked to each hand fracture. RESULTS: A total of 72,481 hand fractures were identified. Fifty percent were phalangeal fractures, 42% were metacarpal fractures, and 8% were multiple fractures. The total population annual incidence rate for a hand fracture was 36 per 10,000. Age-adjusted annual incidence rates ranged from 29 per 10,000 for people older than 20 years to 61 per 10,000 for people age 20 or younger. The most common age for a hand fracture was 14 years for males and 13 years for females. Males had a 2.08 greater relative risk for hand fracture and they maintained most of this increase in risk between the ages of 15 and 40. For females there was an increased relative risk for a hand fracture after the age of 65. Spring had the highest rates for hand fractures. People in the Northern half of the province had a 1.6 greater relative risk for sustaining a hand fracture, compared with people in the more urbanized, less-industrialized, and more-affluent Southwestern region. CONCLUSIONS: Our study provides a robust projection of annual incidence rates for hand fractures because we were able to review all occurrences of a hand fracture within a population base of approximately 4 million people over a 5-year period. Our study also allowed for the examination of how age, gender, season, and geographic location influenced hand fracture incidence rates within a large, diverse population.

Adolescent↗
PubMedDate not supplied

Using the Veterans Health Administration inpatient care database: trends in the use of antireflux surgery.

Context. In the private sector, the use of surgery to treat gastroesophageal reflux disease has increased substantially since the development of minimally invasive laparoscopic techniques. However, trends in the use of antireflux surgery in the Veterans Affairs (VA) health care system have not been explored. Objective. To compare secular trends in the use of antireflux surgery in VA hospitals and the private sector. Data Sources. VA data are from the 1991-1999 medical SAS datasets for inpatient care (commonly known as patient treatment files); private sector data are from the 1991-1997 Nationwide Inpatient Sample and the U.S. census. Calculations. We compared secular trends in the use of antireflux surgery in the VA and private sector with each group's baseline rate in 1991. For the VA, we calculated annual rates of antireflux surgery among active users of the VA health care system by dividing the number of procedures (based on the appropriate procedure codes from the International Classification of Diseases, ninth revision, clinical modification) by the number of veterans who had at least two hospital or clinic visits in a given year. For the private sector, we calculated true population rates by dividing procedure counts by the total U.S. population. Results. From 1991 to 1995, the annual rate of antireflux surgery among active users of VA hospitals increased by 64%, then decreased over the next 4 years to almost baseline rates. In contrast, rates of antireflux surgery in the private sector increased 185% from 1991 to 1995, then appeared to reach a plateau thereafter. Among patients undergoing antireflux surgery, those in the VA were less likely than those in the private sector to undergo laparoscopic surgery (29% vs. 65%, respectively, in 1997). Conclusions. With the development of laparoscopic surgery, rates of antireflux surgery in VA hospitals increased only modestly compared with the private sector and have decreased in recent years. Both patient and provider factors may explain the substantially higher use of this procedure in the private sector.

Age Factors↗
PubMed1998

Mixed effects logistic regression models for longitudinal binary response data with informative drop-out.

A shared parameter model with logistic link is presented for longitudinal binary response data to accommodate informative drop-out. The model consists of observed longitudinal and missing response components that share random effects parameters. To our knowledge, this is the first presentation of such a model for longitudinal binary response data. Comparisons are made to an approximate conditional logit model in terms of a clinical trial dataset and simulations. The naive mixed effects logit model that does not account for informative drop-out is also compared. The simulation-based differences among the models with respect to coverage of confidence intervals, bias, and mean squared error (MSE) depend on at least two factors: whether an effect is a between- or within-subject effect and the amount of between-subject variation as exhibited by variance components of the random effects distributions. When the shared parameter model holds, the approximate conditional model provides confidence intervals with good coverage for within-cluster factors but not for between-cluster factors. The converse is true for the naive model. Under a different drop-out mechanism, when the probability of drop-out is dependent only on the current unobserved observation, all three models behave similarly by providing between-subject confidence intervals with good coverage and comparable MSE and bias but poor within-subject confidence intervals, MSE, and bias. The naive model does more poorly with respect to the within-subject effects than do the shared parameter and approximate conditional models. The data analysis, which entails a comparison of two pain relievers and a placebo with respect to pain relief, conforms to the simulation results based on the shared parameter model but not on the simulation based on the outcome-driven drop-out process. This comparison between the data analysis and simulation results may provide evidence that the shared parameter model holds for the pain data.

Analgesics↗
PubMed2004

Extensive evaluation of the instrumentation laboratory IL test D-Dimer immunoturbidimetric assay on the ACL 9000 determines the D-Dimer cutoff value for reliable exclusion of venous thromboembolism.

The clinical diagnosis of venous thromboembolism (VTE), which includes both deep vein thrombosis (DVT) and pulmonary embolism (PE), is often difficult and requires a number of imaging tests plus clinical assessment. It is now accepted that pretest clinical probability of disease plus a sensitive, quantitative D-Dimer assay can be used to reliably exclude VTE. In design of diagnostic strategies for VTE it is recommended that the D-Dimer assay be evaluated for sensitivity and specificity in well-designed, blinded studies using a cohort of patients for whom the assay will ultimately be used. Therefore we evaluated the IL Test D-Dimer on the ACL 9000 automated coagulation analyzer for its sensitivity and specificity in the diagnosis of VTE. A total of 512 patients admitted to the emergency department of Providence Hospital with suspected VTE were included in the dataset. Our aim was to find the clinically meaningful IL Test D-Dimer cutoff value, which would give us 100% sensitivity and the highest possible specificity for exclusion of VTE. Patients were categorized clinically into low, medium, or high pretest probability and had computed tomographic and/or ventilation-perfusion scans for investigation of PE and ultrasound studies for suspected DVT, with the laboratory blinded to the clinical findings. Of the 511 patients, 28 (5.4%) had confirmed VTE (PE and/or DVT) based on imaging and clinical studies. Applying receiver operating characteristic curve (ROC) analysis, we determined from our study that a cutoff value of 237 ng/mL IL Test D-Dimer gave a 100% sensitivity with a specificity of 38% for detection of VTE. The findings demonstrate that a diagnostic strategy using the IL Test D-Dimer assay as a first-line test in combination with pretest probability is safe and can be used in patients with suspected VTE. In conclusion, patient analysis results indicating low or moderate pretest probability for VTE and a negative IL Test D-Dimer (cutoff value of 237 ng/mL) assay result on the ACL 9000 reliably exclude VTE (both PE and DVT). We expect that inclusion of the rapid IL Test D-Dimer assay for assessment of suspected VTE in the emergency department at Providence will result in improved patient diagnosis and therapy, reduction in unnecessary radiological investigations, and lowering of overall costs associated with investigation of patients suspected of having VTE disease.

Clinical Laboratory Techniques↗
PubMed2003

Shortened PET data acquisition protocol for the quantification of 18F-FDG kinetics.

UNLABELLED: A modified short dynamic protocol was defined and evaluated to predict kinetic parameters of (18)F-FDG metabolism from a dynamic data acquisition. METHODS: The evaluation included 151 datasets obtained from 60 patients examined with (18)F-FDG and a dynamic data acquisition protocol of 60 min. Standardized uptake values (SUVs) were calculated for the individual time frames, and a 2-compartment model was applied to the data. The kinetic parameters and the (18)F-FDG influx, calculated from the model data, served as the reference for the analysis. Correlation was analyzed for the SUVs and the reference data. Subset analysis identified time intervals that can be used to predict the reference parameters based on a second-order polynomial function. RESULTS: Significant correlations were noted for SUVs and (18)F-FDG influx, vascular fraction (VB), and the rate constant k1. The influx was associated mainly with SUVs of late acquisition times, whereas higher correlations were noted for early acquisition intervals and VB, as well as k1. A short dynamic acquisition protocol was defined on the basis of a short dynamic sequence 1-10 min after tracer injection and a static acquisition 56-60 min after tracer application. The correlation coefficients exceeded 0.9 for influx, VB, and k1 when the SUVs of the input area (blood) and the target area were used to predict the kinetic parameters. CONCLUSION: A short dynamic data acquisition protocol can be used to obtain more detailed information about (18)F-FDG kinetics. The results demonstrate that (18)F-FDG influx, VB, and k1 can be estimated with high accuracy from SUVs.

Computer Simulation↗