Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Empirical Approach”

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.

At least 181 records · Page 10Linked to original sources
PubMed2005

Solution behavior of IFN-beta-1a: an empirical phase diagram based approach.

An empirical phase diagram approach has been developed as a practical tool to aid macromolecular preformulation/formulation studies. This method employs an eigenvector based procedure to visualize and interpret complex data sets. Human Inteferon-beta-1a, an important therapeutic protein, was used to further develop the method and test its utility. The protein was characterized in solution as a function of pH (2-8), temperature (10 degrees C-85 degrees C) and ionic strength (I = 0.1 and 1.0) using intrinsic and ANS fluorescence, Far-UV circular dichroism (Far-UV CD), Fourier Transform Infrared spectroscopy (FTIR) and derivative UV absorbance spectroscopies, as well as differential scanning calorimetry (DSC) to supplement spectroscopic thermal stability studies. Derivative UV absorbance data were initially used to construct a pH-temperature phase diagram at each ionic strength. Three distinctive phases at I = 0.1 and two major phases at I = 1.0 were identified corresponding to different conformation/aggregation states of the protein. For the first time, heterogeneous data sets (i.e., data from different techniques) including Far-UV CD, fluorescence and UV absorbance results were used to generate empirical phase diagrams. Results from different data sets are compared; precautions in applying the method and its overall utility are discussed.

Calorimetry, Differential Scanning↗
PubMed1995

An empirical Bayes approach to smoothing in backcalculation of HIV infection rates.

Backcalculation is a methodology to reconstruct the past human immunodeficiency virus (HIV) infection rates from the AIDS incidence data and incubation distribution by deconvolution. Smoothing has proved important in backcalculation, and a key question is how to choose the amount of smoothing. This paper proposes an empirical Bayes approach in which the smoothing parameter is estimated from the data. We introduce a family of priors that reflect the notion of closeness of neighboring infection rates. The variance parameter in the prior family plays the role of the smoothing parameter and is estimated by a method similar to the residual maximum likelihood in linear random effects model through an efficient EM (expectation/maximization) algorithm. A number of penalized likelihood functions that have been used in backcalculation have an empirical Bayes formulation. A bootstrap confidence interval for the infection rates is proposed. The methodology is illustrated with United States AIDS incidence data.

Acquired Immunodeficiency Syndrome↗
PubMed2006

How reliable are empirical genomic scans for selective sweeps?

The beneficial substitution of an allele shapes patterns of genetic variation at linked sites. Thus, in principle, adaptations can be mapped by looking for the signature of directional selection in polymorphism data. In practice, such efforts are hampered by the need for an accurate characterization of the demographic history of the species and of the effects of positive selection. In an attempt to circumvent these difficulties, researchers are increasingly taking a purely empirical approach, in which a large number of genomic regions are ordered by summaries of the polymorphism data, and loci with extreme values are considered to be likely targets of positive selection. We evaluated the reliability of the "empirical" approach, focusing on applications to human data and to maize. To do so, we considered a coalescent model of directional selection in a sensible demographic setting, allowing for selection on standing variation as well as on a new mutation. Our simulations suggest that while empirical approaches will identify several interesting candidates, they will also miss many--in some cases, most--loci of interest. The extent of the trade-off depends on the mode of positive selection and the demographic history of the population. Specifically, the false-discovery rate is higher when directional selection involves a recessive rather than a co-dominant allele, when it acts on a previously neutral rather than a new allele, and when the population has experienced a population bottleneck rather than maintained a constant size. One implication of these results is that, insofar as attributes of the beneficial mutation (e.g., the dominance coefficient) affect the power to detect targets of selection, genomic scans will yield an unrepresentative subset of loci that contribute to adaptations.

Africa South of the Sahara↗
PubMed1989

Empirical treatment without bronchoscopy for Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome.

An empirical approach to treating Pneumocystis carinii pneumonia was adopted in a prospective study of 73 men with antibodies to human immunodeficiency virus 1 (HIV-1) presenting with respiratory problems. At presentation 49 patients (group 1) were thought to have a history, findings at clinical examination, chest radiograph, and arterial blood gas tensions typical of pneumocystis pneumonia, and empirical treatment was begun immediately. Twenty four patients (group 2) were thought to have features not typical of pneumocystis pneumonia. All patients were subsequently referred for bronchoscopy to determine the diagnosis. In group 1 four patients were excluded from the analysis because bronchoscopy was not possible. Of the remaining 45, 42 had pneumocystis pneumonia, which was diagnosed at bronchoscopy in 40, and on the basis of the clinical response to co-trimoxazole in two who had negative results from investigations. Of the three patients without pneumocystis pneumonia, one patient with lymphoid interstitial pneumonitis and Branhamella catarrhalis infection would have failed to respond to empirical treatment. The other two had multiple bacterial pathogens at bronchoscopy; one already had Kaposi's sarcoma and the other would have been misdiagnosed as having AIDS. In group 2 a specific diagnosis was made at bronchoscopy in 21 cases, including pneumocystis pneumonia in seven (all had atypical chest radiographs). In three cases no diagnosis was made and spontaneous recovery occurred. Adopting an empirical approach to treatment for typical pneumocystis pneumonia (group 1) led to the correct treatment in 43 of 45 cases (95%) and would have saved 44 of the 45 of bronchoscopies in this group. Adopting an empirical approach would have caused one patient to be misdiagnosed as having AIDS. Overall, 44 out of 69 bronchoscopies (64%) would have been saved; the specificity for the diagnosis of pneumocystis pneumonia was 85% and the sensitivity was 85%. Adopting an "empirical" treatment policy for typical pneumocystis pneumonia will cause a large reduction in the number of "high risk" bronchoscopies performed.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Management of pneumococcal meningitis.

During the past decade antibiotic resistance among Streptococcus pneumoniae isolates has complicated the empiric approach to and treatment of pneumococcal meningitis. Standard empiric therapy for suspected bacterial meningitis for infants and children older than 1 month of age is the combination of cefotaxime or ceftriaxone and vancomycin. Treatment is modified after antimicrobial susceptibilities are available. The optimal treatment of pneumococcal meningitis caused by strains with a cefotaxime/ceftriaxone MIC >2 microg/ml is unknown, although the addition of rifampin to the initial combination is generally recommended. The role of newer agents including quinolones is under investigation. Dexamethasone remains the only adjunctive antiinflammatory therapy to consider. The empiric approach to the child with suspected bacterial meningitis who has received the pneumococcal conjugate vaccine currently remains unchanged.

Adult↗
PubMed1994

An approach to empiric therapy of nosocomial pneumonia.

Because many studies show that antibiotic therapy is effective for nosocomial pneumonia, it is necessary to have an approach to antibiotic selection to reduce mortality. Empiric therapy can be chosen, based on an assessment of patient risk factors for specific organisms and on an evaluation of the severity of illness present. Empiric regimens must be selected from a knowledge of antibiotic pharmacodynamics, as well as from an appreciation of the antimicrobial spectrum of the various antibacterials. When using such an approach, it is necessary to realize the limitations of effective therapy and to evaluate a number of relevant issues if the patient is not improving during treatment.

Anti-Infective Agents↗
PubMed1986

Philosophy of science and DSM-III. Philosophical, idea-historical and sociological perspectives on diagnoses.

The validity of a classification system is primarily a question of philosophical premise. DSM-III is from this point of view a theoretical classification system based on hypotheses currently considered reliable and interesting and which--as presupposed--could not be rejected by empirical methods. The relevance or validity of this empirical approach depends on the aim of the DSM-III. An empirical approach may facilitate communication but can only have limited success as a help for planning treatment of psychiatric disorders where motives and meaning are important factors. The choice of hypotheses and the empirically derived concepts used to construct the classification system neglects other important ways of comprehension. Although aspects of rational philosophy may be found in the DSM-III system too, important ways of comprehension like the metaphysical approach is lacking. It is showed how this fact reflects a philosophical trend in the Western world following the Renaissance. By considering the Myth of Faust it is demonstrated how a metaphysical comprehension of life would lead to a different understanding of states of mind currently assumed to be a reflection of individual psychopathology according to empirical or rational comprehension. Thus in the end the validity of a classification system depends on the basic philosophical assumptions chosen. A choice which may be determined more by irrational and cultural forces than conscious contemplation. The content of DSM-III or ICD is also influenced by professional interests; the needs of the society and international political factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1982

[Current status of drug therapy in male fertility disorders].

Recent advances in the medical treatment of male fertility disturbances by specific and empirical approaches are discussed. Specific approaches follow a pathophysiological concept and require critical patient selection. In contrast, empirical approaches do not allow patient selection, and a predictability of the success is not possible. Therefore, the response of the patients towards one of the available medical compounds has to be checked on an individual basis. Specific treatment includes replacement therapy of hormone-deficient men by human gonadotropins, inhibition of hyperprolactinemia by bromocriptine, antibiotic-antiinflammatory therapy of male genital tract infections and immunosuppressive treatment in cases of autoantibodies against spermatozoa. In addition, special medical approaches are available for disturbances of sperm transport and the retrograde ejaculation using sympathicomimetic or anticholinergic agents. Empirical treatment comprises the use of antiestrogens, human gonadotropins, androgens, kininogenases, and methylxanthines. As supporting therapy psychopharmacological compounds and spasmolytic agents should be mentioned here. The overall result of treatment is moderate. However, considering all possibilities of treatment conception rates between 30% and 50% will be obtained which differ from the spontaneous conception rates of between 10% and 20%.

Androgens↗
PubMed2006

Comparison of Bayesian and empirical ranking approaches to visual perception.

Much current vision research is predicated on the idea--and a rapidly growing body of evidence--that visual percepts are generated according to the empirical significance of light stimuli rather than their physical characteristics. As a result, an increasing number of investigators have asked how visual perception can be rationalized in these terms. Here, we compare two different theoretical frameworks for predicting what observers actually see in response to visual stimuli: Bayesian decision theory and empirical ranking theory. Deciding which of these approaches has greater merit is likely to determine how the statistical operations that apparently underlie visual perception are eventually understood.

Bayes Theorem↗
PubMed2005

Warrants for prescription: analytically and empirically based approaches to improving decision making.

Efforts to improve decision making must appeal to some source of warrant - that is, specific criteria or models for guiding and evaluating decision-making performance. We examine and compare the warrants for two approaches to decision aids, decision training, and consulting: analytically based prescription, which obtains warrant from formal models, and empirically based prescription, which obtains warrant from descriptive models of successful performance. We argue that empirically based warrants can provide a meaningful and valid basis for prescriptive intervention without committing the naturalistic fallacy (i.e., confusing what is with what ought to be) and without the use of formal deduction from first principles. We describe points of divergence as well as convergence in the types of warrant appealed to by naturalistic decision making and decision analysis, letting each approach shed light on the other, and explore the application of empirically based prescription to cognitive engineering. Actual or potential applications of this research include the development of training programs to improve various aspects of naturalistic decision making.

Awareness↗
PubMed1993

Estimating physician costliness. An empirical Bayes approach.

Outpatient data obtained from the general medicine practice of an urban, health care facility are used to provide an application of empirical Bayes techniques in the estimation of physician "costliness." The results illustrate that application of the simplest empirical Bayes estimation procedure can provide more reasonable estimates of physician's utilization of resources than a standard estimation procedure. Empirical Bayes estimates are shown to adjust for potential instability in standard estimates that may arise from either a physician treating a small number of patients or an inappropriate case-mix adjustment. Using simulation, it is demonstrated that the empirical Bayes procedure can provide overall better estimates using fewer data than the standard procedure. This application, although somewhat limited in scope, should provide impetus for increased utilization of the numerous Bayesian and empirical Bayes techniques that currently exist in the statistical literature and pertain to small area estimation techniques.

Ambulatory Care↗
PubMed1983

[The psychosomatic phenomenon--or the phenomenon of psychosomatic research].

In the present article the methods of empirical research are put up for discussion. As a methodological problem the reduction of the subject of research by the empirical approach is pointed out. From lack of consideration of this--inevitably--reductory effect an interpretation of the empirically obtainable data in the sense of a self-fulfilling prophecy may occur. The implication of the interdependence of research methods and results is demonstrated by an empirical study of the author's, wherein it is shown that the finding "alexithymia" as a component of the "psychosomatic phenomenon" is dependent upon the empirical approach.

Affective Symptoms↗
PubMed2004

Empirically informed approaches to topics in suicide risk assessment.

The purpose of this article is to approach topics in suicide risk assessment from a scientifically informed standpoint. We summarize and elaborate a general framework for an empirically supported best practice recommendation in evaluating suicide potential and minimizing risk. This risk assessment framework provides a concise heuristic for assessment of suicidal symptoms, points the way to relatively routinized clinical decision-making and activity, and is compatible with best practices relevant to the legalities of suicide risk assessment. Having established a general and scientifically based framework for risk assessment, we go on to address the other questions noted above, with reference to the framework and to our ongoing scientific work. We conclude by summarizing all the work and providing clear and concise clinical recommendations based thereon.

Decision Making↗
PubMed2003

DSM-oriented and empirically based approaches to constructing scales from the same item pools.

Separately for ages 11/2 to 5 and 6 to 18, used items for rating behavioral and emotional problems to construct (a). "top-down" DSM-oriented scales from experts' ratings of the items' consistency with Diagnostic and Statistical Manual of Mental Disorders (4th ed. [DSM-IV], American Psychiatric Association, 1994) categories, and (b). "bottom-up" empirically based syndromes from factor analyses of parent, caregiver, teacher, and self ratings (N = 14853). Both kinds of scales are scored from the same assessment instruments and are displayed on profiles normed on the same national samples. Psychometric properties were similar for both kinds of scales. Associations between counterpart scales were medium to strong. Quantified, normed DSM-oriented and empirically based scales scored from the same instruments can facilitate assessment of individuals, statistical analyses for research purposes, and integration of top-down and bottom-up approaches to deriving constructs for psychopathology.

Adolescent↗
PubMed1997

[Emotionality, age and aging--research perspectives, methodological approaches and empirical results].

The topic of emotionality can be regarded as a frame of reference for different perspectives in psycho-gerontological research. In the first chapter five facets of the meaning of emotionality are distinguished: emotionality as a trait, emotionality as an attribute describing actual subjective experiences, emotionality as an attribute describing coping with (stressful) experiences and life events or as a consequence of coping activity, emotionality as a result of self-regulating processes and as an attribute describing feelings of subjective well-being in old age. In a further step methodological approaches for these different facets of meaning are described. In the third chapter empirical results of three research questions are reviewed: How do people perceive old age and how do they perceive the process of aging? Do well developed or regressive coping techniques become more important in old age? Which dimensions of personality are the best predictors of life satisfaction and perceptions of the process of aging? Results of our own research on two specific aspects of emotionality in old age are described in detail in the last part of this contribution: How do sensations of pain and limits of independent living in old age influence life satisfaction and perceptions of the process of aging? How do Jewish extermination camp survivors cope with the increasing reminiscence of holocaust-traumatization?

Activities of Daily Living↗
PubMed2006

An empiric integrative approach to the management of cough: ACCP evidence-based clinical practice guidelines.

OBJECTIVE: Review the literature to provide a comprehensive approach, including algorithms for the clinician to follow in evaluating and treating the patient with acute, subacute, and chronic cough. METHODS: We searched MEDLINE (through May 2004) for studies published in the English language since 1980 on human subjects using the medical subject heading terms "cough," "treatment of cough," and "empiric treatment of cough." We selected case series and prospective descriptive clinical trials. We also obtained any references from these studies that were pertinent to the topic. RESULTS: The relative frequency of the disorders (alone and in combination) that can cause cough as well as the sensitivity and specificity of many but not all diagnostic tests in predicting the cause of cough are known. An effective approach to successfully manage chronic cough is to sequentially evaluate and treat for the common causes of cough using a combination of selected diagnostic tests and empiric therapy. Sequential and additive therapy is often crucial because more than one cause of cough is frequently present. CONCLUSION: Algorithms that provide a "road map" that the clinician can follow are useful and are presented for acute, subacute, and chronic cough.

Algorithms↗
PubMed2005

Treatment of community-acquired pneumonia: a descriptive study in an Apulian department of internal medicine.

BACKGROUND: Infections of the lower airways pose a serious problem for the health service, both because of the burden of the disease and because of the large number of resources that need to be devoted to treating it. MATERIAL/METHODS: The present study describes the use of antibiotics to treat acute bronchopneumonia in the Internal Medicine Department "Cesare Frugoni" of a university hospital in southern Italy. A total of 493 patients were studied during a 4.5-year period. RESULTS: In 98.2% of cases an empirical approach to treatment was adopted, and only in 57 patients was targeted treatment administered. Mean duration of the antibiotic therapy was 11.3 days, with a wide range. Assessment of prognosis in the different groups showed that this did not seem to depend on the type of treatment approach or on the type and/or number of antibiotics used. Instead, targeted therapy was correlated with a shorter duration of treatment. Blood culture was very rarely carried out. The almost invariably empirical approach to treatment of bronchopneumonia infections resulted in longer hospital stay and a greater consumption of antibiotics, often of latest generation. CONCLUSIONS: Therefore, more studies would be useful to investigate the real adherence to the guidelines in the clinical practice. Finally, blood culture should be performed routinely in these patients, although the time required for the test could be a limiting factor.

Adult↗
PubMed2000

The rapid diagnosis of smear-negative pulmonary tuberculosis: a cost-effectiveness analysis.

OBJECTIVE: The prompt diagnosis of smear-negative pulmonary tuberculosis (PTB) is a clinical challenge. It may be achieved by a number of tests which have varying accuracies, costs and degrees of invasiveness. The objective of this study was to compare the cost-effectiveness of clinical judgement (empirical), the Roche Cobas amplicor assay for Mycobacterium tuberculosis (amplicor), acid-fast staining of bronchoalveolar lavage specimens (BAL), nucleic acid amplification tests of bronchoalveloar lavage specimens for M. tuberculosis (BAL + NAA), computed tomography (CT) and amplicor assay followed by BAL. METHODOLOGY: The range of predictive values of the various strategies were derived from published data and a new study of 441 consecutive adult patients with suspected smear-negative PTB prospectively stratified into three pretest risk groups: low, intermediate and high. The cost-effectiveness was evaluated with a decision tree model (DATA software). RESULTS: The incidence of PTB was 5.7% (4% culture positive) for the whole group, 95% in the high-risk group, 0.9% in the low-risk group and 3.4% in the intermediate-risk group. The sensitivity of the empirical approach was 49% and of the amplicor assay was 44%. Patient outcomes were expressed as life expectancy for the base case of a 58-year-old man with a pretest probability of 5.7%. At this low pretest risk the differences in life expectancies between tests was < 0.1 years and the empirical approach incurred the lowest cost. Sensitivity analysis at increasing pretest risks showed better life expectancies (approximately 1 years) for CT scan and test combinations than empirical and amplicor for additional costs of US$243-US$309. Bronchoalveolar lavage had the worst overall cost-effectiveness. CONCLUSIONS: We conclude that the pretest risk of active PTB was a key determinant of test utility; that the AMPLICOR assay was comparable to clinical judgement; that BAL was the least useful test; and that with increasing risks, CT scan and test combinations performed better. Further studies are needed to better define patients with intermediate risk for PTB and to directly compare the cost-effectiveness of more sensitive nucleic acid amplification tests such as the enhanced Gen Probe, CT scan and test combinations/sequences in these patients.

Bacteriological Techniques↗