SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Oxidative stress is implicated in many pathological processes and results from a disruption of the prooxidant/antioxidant balance. This review will focus on noninvasive biomarkers of radical-induced damage in biological fluids and particularly in blood. Special attention will be addressed to new analytical methods for the measurement of radical-mediated alterations in the integrity of lipids, proteins and DNA.
STUDY OBJECTIVE: We analyze the risks and benefits of alternative treatment strategies for non-septic-appearing febrile patients with influenza-like illnesses and possible exposure to anthrax. METHODS: We used a decision analytic model to evaluate 6 testing and treatment strategies in an emergency department. Patients were non-septic-appearing and had influenza-like illnesses but low likelihood of exposure to anthrax. The following interventions were used: (1) no empiric antibiotics; (2) blood culture and treatment only if the result was positive; (3) rapid testing for influenza and, for those who tested negative, treatment with 60 days of ciprofloxacin; (4) a two-test strategy in which all patients were first tested for influenza; those who tested negative had a blood culture test and were treated empirically with ciprofloxacin for 3 days while waiting for blood culture results; (5) culture test for all patients and treatment with ciprofloxacin for up to 3 days while waiting for blood culture results; and (6) treatment of all patients with ciprofloxacin empirically for 60 days. Main outcome measures were deaths, complications from anthrax, adverse events from ciprofloxacin, and ciprofloxacin patient-days. RESULTS: For nonzero probabilities of anthrax, patient mortality was always lowest in the strategies in which all patients were treated empirically for anthrax either for 60 days or for 3 days pending blood culture results. These strategies, however, were associated with more morbidity (more ciprofloxacin patient-days and more antibiotic adverse events) than were strategies without empiric treatment. The numbers of adverse events and antibiotic patient-days were reduced substantially with the two-test strategy, in which patients with influenza were identified early and not treated. In general, for probabilities of anthrax equaling or exceeding 2%, treating all patients empirically for 60 days was best, but for probabilities between 0.1% and 2%, the sensitivity of blood culture for anthrax determined the optimal strategy: when the sensitivity exceeded 95%, a short course of empiric ciprofloxacin until blood culture results became available was best, but for sensitivities below 95%, more aggressive empiric antibiotics use was warranted. The proportion of patients with influenza in the community affected the choice of strategy, so that seasonal variation exists. CONCLUSION: During influenza season, our findings support rapid testing for influenza, followed by empiric treatment for anthrax pending blood culture results for those who test negative for influenza. Our results help to highlight the importance of developing rapid and sensitive tests for anthrax and of developing improved surveillance and methods to calculate the previous probability of attacks.
Considerable effort in instrument development has made possible detection of picosecond fluorescence lifetimes by time-correlated single-photon counting. In particular, efforts have been made to narrow markedly the instrument response function (IRF). Less attention has been paid to analytical methods, especially to problem of discretization of the convolution integral, on which the detection and quantification of short lifetimes critically depends. We show that better discretization methods can yield acceptable results for short lifetimes even with an IRF several times wider than necessary for the standard discretization based on linear approximation (LA). A general approach to discretization, also suitable for nonexponential models, is developed. The zero-time shift is explicitly included. Using simulations, we compared LA, quadratic, and cubic approximations. The latter two proved much better for detection of short lifetimes and, in that respect, they do not differ except when the zero-time shift exceeds two channels, when one can benefit from using the cubic approximation. We showed that for LA in some cases narrowing the IRF beyond FWHM = 150 ps is actually counterproductive. This is not so for quadratic and cubic approximations, which we recommend for general use.
The purpose of this study was to explore the usefulness of applying decision analysis to nursing decisions about a complex, emergent patient problem. A convenience sample of 31 nurses quantified their intuitive ideas into five mutually exclusive decision alternatives. A decision-analytic process and a preference analysis of each decision alternative were conducted. Nurses' intuitive decision alternatives were compared to the decision alternatives prescribed by the decision-analytic process. Eleven nurses (35%) demonstrated agreement between their first-ranked intuitive choice and the choice prescribed by the decision-analytic model. When the relative ranking of the vector of five treatment choices derived intuitively was compared to the relative ranking prescribed by the decision-analytic model, results showed significant disagreement between nurses' intuitive and quantitative choices.
Metaphors offer exciting opportunities to identify and explore tacit knowledge and behavior that are embedded in complex organizations and shape health care practices. In this article, the authors explore the theoretical rationale, background, and advantages of using metaphor as an analytic strategy in qualitative health research. They used an analysis of 18 practices in a comparative case study designed to explore office practice strategies for delivering cancer prevention services for illustrations. During the individual and comparative stages of the analysis process, researchers heeded the metaphors that they used in their descriptive language of practices. The authors explore examples showing how metaphors clarify unwritten assumptions, values, and motivators that shape variations in practice behavior.
A homogeneous model with stress relaxation that is described by a pure viscoelastic component was recently proposed to describe the mechanical behavior of the respiratory system during mechanical ventilation (Bates et al. J. Appl. Physiol. 67: 2276-2285, 1989). With the use of this model, analytic expressions of the pressure in response to typical volume inputs are developed, and the recently published studies relating to the influence of the ventilatory pattern on respiratory mechanics are reviewed and analyzed. The analytic expression of pressure responses to rapid airway occlusion following constant-flow inflation and to sinusoidal volume oscillations allows prediction of most of the reported results. The theoretical analysis suggests that in normal subjects the observed flow and volume dependencies of respiratory mechanics are, in fact, illustrations of the dependence of the viscoelastic resistance on inspiratory time and respiratory frequency. Thus the homogeneous viscoelastic model appears suitable to describe respiratory system mechanical behavior under mechanical ventilation.
A statistical sea surface specular BRDF (bidirectional reflectance distribution function) model is developed that includes mutual shadowing by waves, wave facet hiding, and projection weighting. The integral form of the model is reduced to an analytical form by making minor and justifiable approximations. The new form of the BRDF thus allows one to compute sea reflected radiance more than 100 times faster than the traditional numerical solutions. The repercussions of the approximations used in the model are discussed. Using the analytical form of the BRDF, an analytical approximation is also obtained for the reflected sun radiance that is always good to within 1% of the numerical solution for sun elevations of more than 10 degrees above the horizon. The model is validated against measured sea radiances found in the literature and is shown to be in very good agreement.
Case control studies on the association between sunlight exposure and melanoma risk show considerable differences in design; this could be responsible for the variation in study results. In an attempt to resolve the controversy between study results, the results of 25 publications on case control studies were evaluated using meta-analytical techniques. Comparison of odds ratios between subgroups of studies revealed that the range of odds ratios was far greater for hospital-based studies than for population-based studies. For the latter type of studies, the odds ratios were homogeneous and the pooled odds ratios were 1.57 (95% confidence interval [CI], 1.29-1.91) for intermittent sunlight exposure and 0.73 (95% CI, 0.60-0.89) for chronic exposure. However, among other problems, the lack of standardized measures for sunlight exposure warrants cautious interpretation of these results. It is concluded that evidence to support the intermittent sunlight theory is still far from complete.
The molecular techniques of in situ transcription and antisense RNA amplification (IST/aRNA) have allowed for the monitoring of coordinate changes in the expression of multiple genes simultaneously. However, the analysis of their concurrent behavior during murine embryogenesis has been problematic. Studies involving the investigation of temporal and spatial gene expression during embryogenesis have focused solely on the analysis of isolated, single gene events. Such an approach has failed to provide an integrative picture of genetic control over the varied and complicated cellular processes governing embryogenesis. In order to interpret the enormous amount of gene expression data generated by these procedures, we have attempted to develop an analytical framework by employing the statistical concepts of principal components analysis (PCA). For the current study, we performed IST/aRNA on neural tubes dissected from the highly inbred LM/Bc murine strain collected during four gestational time periods. A subset of these genes, representing a partial signaling pathway in the developing neuroepithelium, was then subjected to PCA. Here, we report that PCA highlighted the transcriptional interplay among the genes p53, wee-1, Tgf beta-2, and bcl-2 such that the combined reciprocal regulation of their gene products is suggestive of a predominant proliferative state for the developing neuroepithelium. The application of PCA to the gene expression data has elucidated previously unknown interrelationships among cell cycle genes, growth, and transcription factors on a transcriptional level during critical stages of neurulation. The information gleaned from this analysis, while not definitive, suggests distinct hypotheses to guide future research.
The construct of 'dignity' is frequently raised in discussions about quality end of life care for terminal cancer patients, and is invoked by parties on both sides of the euthanasia debate. Lacking in this general debate has been an empirical explication of 'dignity' from the viewpoint of cancer patients themselves. The purpose of the present study was to use factor-analytic and regression methods to analyze dignity data gathered from 213 cancer patients having less than 6 months to live. Patients rated their sense of dignity, and completed measures of symptom distress and psychological well-being. The results showed that although the majority of patients had an intact sense of dignity, there were 99 (46%) patients who reported at least some, or occasional loss of dignity, and 16 (7.5%) patients who indicated that loss of dignity was a significant problem. The exploratory factor analysis yielded six primary factors: (1) Pain; (2) Intimate Dependency; (3) Hopelessness/Depression; (4) Informal Support Network; (5) Formal Support Network; and (6) Quality of Life. Subsequent regression analyses of modifiable factors produced a final two-factor (Hopelessness/Depression and Intimate Dependency) model of statistical significance. These results provide empirical support for the dignity model, and suggest that the provision of end of life care should include methods for treating depression, fostering hope, and facilitating functional independence.
Decision analysis is a quantitative method used to assist difficult decisions. Its goal is to add insights when decision makers are faced with uncertainty. Decision analysis entails estimating the likelihood of clinical events, and, in addition, placing values on those events that are considered outcomes of interest. Placing values on clinical outcomes is called utility analysis. This paper introduces the utility analytic techniques used to quantify the worth of health outcomes for patients.
Fractional anisotropy (FA) and relative anisotropy (RA) are the two most commonly used scalar measures of anisotropy in diffusion tensor (DT) MRI. While a few published studies have shown that FA has superior noise immunity relative to RA, no theoretical basis has been proposed to explain this behavior. In the current study, the diffusion tensor invariants were used to derive a simple analytical expression that directly relates RA and FA. An analysis based on that analytical expression demonstrated that the FA images have a higher signal-to-noise ratio (SNR) than RA for any value of tensor anisotropy RA or FA > 0. This theoretical behavior was verified using both Monte Carlo simulations and bootstrap analysis of DT-MRI data acquired in a spherical water phantom and normal human subjects.
Chronic ulcerative colitis is associated with a high risk of colon cancer. The most appropriate management--prophylactic proctocolectomy or medical surveillance--is, at present, unclear. Recent reports suggest that the presence of colonic dysplasia or "precancer" on endoscopic biopsy may be a reliable predictor of concurrent or future colon cancer. To assess the value of colonic dysplasia in managing colitis patients, I applied decision analytic techniques to currently available data regarding the sensitivity and specificity of colonic dysplasia in colitis patients. Such analysis shows that management based on biopsy for colonic dysplasia, rather than prophylactic proctocolectomy for all colitis patients, will maximize 5-year survival. Sensitivity analysis suggests that management is primarily determined by the sensitivity of biopsy-diagnosed dysplasia--elective prophylactic surgery would be preferred only when sensitivity of dysplasia on biopsy is less than or equal to 0.70 at 20 years, or less than or equal to 0.85 at 30 years of colitis, and changing surgical mortality and survival benefit from early diagnosis within a range established by previous studies affects management decisions only when sensitivity of dysplasia is at the lower end of its reported range.
Factor analysis models have played a central role in formulating conceptual models in personality and personality assessment, as well as in empirical examinations of personality measurement instruments. Yet, the use of item-level data presents special problems for factor analysis, applications. In this article, we review recent developments in factor analysis that are appropriate for the type of item-level data often collected in personality. Included in this review are discussions of how these developments have been addressed in the context of two different (but formally related) statistical models item response theory (IRT: Hambleton, Swaminathan, & Rogers, 1991) and structural, equation modeling (Bollen 1989) for item-level data. We also discuss the relevance of item scaling in the context of these models. Using the restandardization data for the Minnesota Multiphasic Personality Inventory-2 Scale (cf. Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989), we show brief examples of the utility of these approaches to address basic questions about responses to personality scale items regarding: (a) scale, dimensionality and general item properties, (b) the "appropriateness" of the observed responses, and (c) differential item functioning across subsamples. implications for analyses of personality item-level data in the IRT and factor analytic traditions are discussed.
The relation between meat consumption and colorectal cancer risk remains controversial. In this report, we quantitatively reviewed the prospective observational studies that have analyzed the relation between meat consumption and colorectal cancer. We conducted electronic searches of MEDLINE, EMBASE, and CANCERLIT databases through to the end of June 1999 and manual searches of references from retrieved articles. We used both fixed and random-effects meta-analytical techniques to estimate the overall association and to investigate possible sources of heterogeneity among studies. Thirteen studies were eligible for inclusion in the meta-analysis. Pooled results indicate that a daily increase of 100 g of all meat or red meat is associated with a significant 12-17% increased risk of colorectal cancer. The marginally significant between-study heterogeneity for all meat and red meat was explained by a number of study-level covariates. A significant 49% increased risk was found for a daily increase of 25 g of processed meat. The individual study estimates for processed meat showed no detectable heterogeneity. On the basis of this quantitative review of prospective studies, the overall association between meat consumption and risk of colorectal cancer appears to be positive, with marginal heterogeneity between studies. The finding for processed meat and data from experimental studies suggests that it may also be an important predictor of colorectal cancer risk. However, because only a few of the studies reviewed here attempted to examine the independent effect of meat intake on colorectal cancer risk, the possibility that the overall association may be confounded or modified by other factors cannot be excluded.
We use soliton perturbation theory and collective coordinate ansatz to investigate the mechanism of soliton ratchets in a driven and damped asymmetric double sine-Gordon equation. We show that, at the second order of the perturbation scheme, the soliton internal vibrations can couple effectively, in presence of damping, to the motion of the center of mass, giving rise to transport. An analytical expression for the mean velocity of the soliton is derived. The results of our analysis confirm the internal mode mechanism of soliton ratchets proposed in [Phys. Rev. E 65, 025602(R) (2002)].
INTRODUCTION: The development of AIDS as a result of HIV transmission and of cirrhosis as a result of chronic non-A, non-B hepatitis are the greatest infectious risks associated with transfusion in the United States. The goal of this study is to provide explicit quantitative guidelines to determine when the risk of death from all causes associated with transfusion exceeds the risk associated with anemia. METHODS: This study uses a decision-analytic model. RESULTS: On the basis of reported transfusion complication rates and an independent worst-case calculation of the risk of AIDS and non-A, non-B hepatitis, transfusion with red blood cells should be recommended as long as each unit received reduces the patient's risk of dying from anemia by at least 1/1100. DISCUSSION: Because of the relative safety of the blood supply as a result of universal screening and donor deferral, the overestimation in practice of fatal infectious complications, and the possible underestimation of the risk of anemia, undertransfusion has the potential to be as serious a problem in the United States as is overtransfusion. Although caution should be exercised not to undertransfuse when a patient has an appreciable risk of anemia-associated death, we must be wary not to overtransfuse for temporary relief of morbidity.
Miniaturization embracing instrumentation, column particle size, and column dimensions is one of the major current trends in separation techniques. This leads to shortening of analysis time and great savings in solvent consumption. Ultra performance liquid chromatography (UPLC) is one of the new developments in liquid chromatography. An ultra-high pressure system allows using of small particle-packed columns with small diameter, which has a positive effect on both system efficiency and analysis time. An analytical method for determination of the active substance diclofenac, the degradation product 1-(2,6-dichlorphenyl)-2-indolinone, and the preservatives methylparaben and propylparaben was used for testing and comparing LC systems. Various octadecylsilica-based analytical columns were examined. Acquity UPLC BEH C18 (2.1 x 50 mm, 1.7 microm) and (2.1 x 100 mm, 1.7 microm) were tested for UPLC. The following analytical columns were used in a test for HPLC: Purospher RP 18e (125 x 4.0 mm, 5 microm), Zorbax Eclipse XDB C18 (75 x 4.6 mm, 3.5 microm), Zorbax Eclipse SB C18 (50 x 4.6 mm, 1.8 microm), as was a monolithic column (Chromolith Performance RP-18e (100 x 4.6 mm). Results of a System Suitability Test (SST) were calculated and compared for each chromatographic peak. System efficiency and analysis duration were compared with regard to solvent consumption and system maintenance