Biomedical subjects
Publications and source records attributed to D Thompson.
To enable an image understanding system to provide an automated interpretation of diagnostic imagery it must have access to all of the concepts, procedures and methods used by human experts. The paper describes information elicitation from experts of different domains and the construction of a knowledge file. Uncertainty management is based on Bayesian belief network methods.
From the studies which are reviewed above, it is generally apparent that in terms of the acute phase response, the initial findings in early inflammatory arthritis (particularly rheumatoid arthritis, with which the majority of such studies are concerned) have little predictive value for either the functional outcome or mortality. The wide interindividual variability in these measurements is also likely to limit their clinical usefulness as predictors of disease outcome. The trend in certain acute phase reactants may be more useful in indicating disease activity, although the number of satisfactory studies in this area is very limited.
We describe and illustrate the use of a generalizable model for evaluating the cost-effectiveness of alternative cholesterol-lowering treatments. We combine standard incidence-based techniques for measuring the cost of illness with logistic risk functions from the Framingham Heart Study to project, for persons with known coronary risk characteristics, the likelihood of developing coronary heart disease (CHD) over a lifetime as well as a number of related outcomes, including the expected loss of years of life due to CHD, the expected lifetime direct and indirect costs of CHD, and the changes in these outcomes that would result from cholesterol-lowering treatment.
To better classify minor injuries in the pediatric outpatient population, we empirically developed a scale to predict functional impairment, one week and one month postinjury, based on data available at the time of care. A sample of 857 injured children aged five to 19 years was randomly split into two subsamples. Using logistic regression techniques, predictive models were developed and confirmed on the subsamples and then applied to the full sample. Age, location of injury, and type of injury were predictive of impairment one week post-injury; however, type of injury was the only consistently significant predictor. Type of injury, specifically fracture, dislocation, and sprain, and location of injury (lower extremity) were significant predictors of functional impairment one month postinjury; however, once again, the type of injury was the only variable consistently significant across all models. Other than the type of injury, the variables available at the time of care were too uniform between disabled and nondisabled patients to be useful in developing a severity scale for minor injuries. We conclude that other outcome measurements or scale development techniques should be explored to develop a useful classification scheme for minor injuries.
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This randomised double-blind, placebo-controlled, cross-over study compared the effects of single oral doses of terfenadine 120 mg, cetirizine 10 mg, and loratadine 10 mg on experimentally induced weal and flare reactions. The areas of weal and flare induced by intracutaneous injections of histamine were measured using planimetry, weal thickness by A-scan pulsed ultrasound and erythema index by a device which measures the relative reflectance of red and green light. All three antihistamines suppressed the weal and flare area and weal thickness 3, 6, 12 and 24 h after dosing. At the usual currently recommended doses terfenadine and cetririzine were most effective after 6 h and were more potent than loratadine for the first 6 h of the study.
There is clearly a role for the measurement of acute phase proteins and other indices of the acute phase reaction but it is equally clear that no one laboratory test is suitable for use in all clinical situations. The choice of acute phase protein measurement depends on the diagnostic sensitivity and specificity of the measurement in the particular clinical situation. The choice of measurement must also include a decision on time of sampling and whether single or serial sampling would be more appropriate. In most situations where acute phase measurement is useful CRP is the assay of choice with alpha 1-antichymotrypsin also being useful in inflammatory bowel disease and other situations where a wider time window is required. The ESR or plasma viscosity can be useful to screen for disease. Cytokine and enzyme-inhibitor complex measurements may be important assays in the future.
OBJECTIVE: To determine whether choice of a first- versus third-generation cephalosporin as initial therapy for lower respiratory tract infections in hospitalized adults affects the course and duration of care, both of which may influence antimicrobial treatment cost. DESIGN: Retrospective analysis of discharge abstracts and hospital pharmacy records. SETTING: Forty-eight US acute-care hospitals. PATIENTS: One thousand ninety-two hospitalized adults (aged > 17 y) with principal diagnoses of lower respiratory tract infections (DRGs 79-80, 89-90). INTERVENTIONS: Cefazolin or ceftriaxone, given as sole antimicrobial therapy for at least one day. MAIN OUTCOME MEASURES: (1) The number of patients who received another parenteral antibiotic anytime prior to hospital discharge; (2) the number of days during which patients received any parenteral antibiotic while in the hospital; and (3) the number of days patients remained hospitalized following the start of antibiotic therapy. RESULTS: Patients treated with cefazolin (n = 763) were more likely to receive another parenteral antibiotic while in the hospital (30.3 vs. 20.7 percent; p < 0.001) and received more total days of therapy (7.2 vs. 6.7 d; p < 0.05) than those treated with ceftriaxone (n = 329). Although the time to hospital discharge did not differ in the full sample (9.2 d for both groups), it was greater among those receiving cefazolin (8.6 vs. 8.0 d; p < 0.05) when patients with lengths of stay exceeding 24 days were excluded from both groups. CONCLUSIONS: In addition to acquisition cost, differences in course and duration of care should be considered when determining the most cost-effective choice for antimicrobial therapy.
In this article we review published studies of the cost-effectiveness of drug therapy for hypercholesterolaemia to take stock of the principal findings that have been reported to date. We identified 9 studies that met all criteria for inclusion in our review, including 3 of bile-acid sequestrants (cholestyramine, colestipol), 2 of HMG-CoA reductase inhibitor (lovastatin), and 4 that considered both an HMG-CoA reductase inhibitor (simvastatin) and a bile-acid sequestrant (cholestyramine). While these studies were largely consistent in methodological approach, some differences were noted in the costs attributed to drug therapy. The cost-effectiveness of therapy with bile-acid sequestrants was found to range from $100 000 to $209 000 per year of life saved (1991 $US) for middle-aged men (42 to 55 years of age) with moderately high cholesterol levels (280 to 290 mg/dl) and otherwise average coronary risk characteristics. Corresponding cost-effectiveness ratios that have been reported for lovastatin range from $64 000 to $82 000, while those for simvastatin range from $45 000 to $65 000. Studies to date therefore suggest that therapy with HMG-CoA reductase inhibitors (i.e. lovastatin and simvastatin) is substantially more cost-effective than treatment with bile-acid sequestrants.
Bayesian belief networks have a dynamic range and numeric response characteristics that make them uniquely suitable for descriptive classification schemes. Features showing considerable overlap of tolerance regions may be used, in a cumulative manner, to derive unequivocal classification decisions. The numeric response characteristics of Bayesian belief networks are analyzed, and their application as control modules in automated scene segmentation in histopathology is demonstrated.
A general method is described for the electrophoretic transfer of proteins from stained gels to membranes and subsequent Western detection of specific proteins on the stained membranes. Proteins are separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, and the gels are stained using either of two different methods followed by electrophoretic transfer to nitrocellulose or Immobilon-P membranes. The transferred proteins remain stained during immunodetection, providing a set of background markers for protein location and size determination.
Uncertainty management for the evaluation of evidence based on linguistic and conceptual data is taking advantage of developments in the Dempster-Shafer (DS) theory of evidence, possibility theory and fuzzy logic. The DS theory offers the capability to assess the uncertainty of different subsets of assertions in a domain and the way in which uncertainty is affected by accumulating evidence. The DS theory goes beyond probability theory in its ability to represent ignorance about certain aspects of a situation. However, the theory is very sensitive to the numerical assessments provided by users and can lead to intuitively unexpected and even undesirable results. Certainty factors are widely used in various expert systems. Their definition and updating may follow either a probabilistic model or fuzzy set theoretic concept.
Expert systems deal with data that are categorical and conceptual, that represent elements of fuzzy sets and that often, by themselves, do not allow an unequivocal decision. The management of uncertainty in expert systems thus becomes a crucial issue. It involves defining measures of uncertainty and procedures for combining accumulating evidence in a manner that properly considers the dependence structure of diagnostic clues. Probability theory offers valuable procedures for uncertainty assessment; however, their practical application in the domain of quantitative histopathology and histopathologic diagnosis can be problematic.
In anesthetized, artificially ventilated guinea pigs, intranasal and intravenous administration of albuterol produced the same maximum degree of protection against bronchoconstriction induced by bilateral electrical stimulation of the cervical vagal nerves. Intranasal albuterol showed a slower onset of action than intravenous albuterol and exhibited equivalent cardiovascular side effects for the same level of bronchoprotection. Accordingly, intranasal albuterol may represent an alternative to metered-dose inhalation for prophylaxis and treatment of bronchoconstriction in humans.
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Spermatozoa normally encounter the egg at the fertilization site (in the Fallopian tube) within 24 hr after ovulation. A considerable fraction of the spermatozoa ejaculated into the female reproductive tract of mammals remains motionless in storage sites until ovulation, when the spermatozoa resume maximal motility and reach the fertilization site within minutes. The nature of the signal for sperm movement is not known, but one possible mechanism is attraction of spermatozoa to a factor(s) released from the egg. We have obtained evidence in favor of such a possibility by showing that human spermatozoa accumulate in follicular fluid in vitro. This accumulation into follicular fluid was higher by 30-260% than that observed with buffer alone and was highly significant (P less than 10(-8)). Not all of the follicular fluids caused sperm accumulation; however, there was a remarkably strong correlation (P less than 0.0001) between the ability of follicular fluid from a particular follicle to cause sperm accumulation and the ability of the egg, obtained from the same follicle, to be fertilized. These findings suggest that attraction may be a key event in the fertilization process and may give an insight into the mechanism underlying early egg-sperm communication.