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PubMedDate not supplied

Evidences on weaknesses and strengths from health financing after decentralization: lessons from Latin American countries.

OBJECTIVE: The main objective was to identify trends and evidence on health financing after health care decentralization. STUDY DESIGN: Evaluative research with a before-after design integrating qualitative and quantitative analysis. Taking into account feasibility, political and technical criteria, three Latin American countries were selected as study populations: Mexico, Nicaragua and Peru. DATA SOURCES: The methodology had two main phases. In the first phase, the study referred to secondary sources of data and documents to obtain information about the following variables: type of decentralization implemented, source of finance, funds of financing, providers, final use of resources and mechanisms for resource allocation. In the second phase, the study referred to primary data collected in a survey of key personnel from the health sectors of each country. FINDINGS: The trends and evidence reported in all five financing indicators may identify major weaknesses and strengths in health financing. CONCLUSIONS: Weaknesses: a lack of human resources trained in health economics who can implement changes, a lack of financial resource independence between the local and central levels, the negative behavior of the main macro-economic variables, and the difficulty in developing new financing alternatives. Strengths: the sharing between the central level and local levels of responsibility for financing health services, the implementation of new organizational structures for the follow-up of financial changes at the local level, the development and implementation of new financial allocation mechanisms taking as a basis the efficiency and equity principles, new technique of a per-capita adjustment factor corrected at the local health needs, and the increase of financing contributions from households and local levels of government.

Decision Making, Organizational↗
PubMed2006

Joint learning of gene functions--a Bayesian network model approach.

In this paper, we develop a machine learning system for determining gene functions from heterogeneous data sources using a Weighted Naive Bayesian network (WNB). The knowledge of gene functions is crucial for understanding many fundamental biological mechanisms such as regulatory pathways, cell cycles and diseases. Our major goal is to accurately infer functions of putative genes or Open Reading Frames (ORFs) from existing databases using computational methods. However, this task is intrinsically difficult since the underlying biological processes represent complex interactions of multiple entities. Therefore, many functional links would be missing when only one or two sources of data are used in the prediction. Our hypothesis is that integrating evidence from multiple and complementary sources could significantly improve the prediction accuracy. In this paper, our experimental results not only suggest that the above hypothesis is valid, but also provide guidelines for using the WNB system for data collection, training and predictions. The combined training data sets contain information from gene annotations, gene expressions, clustering outputs, keyword annotations, and sequence homology from public databases. The current system is trained and tested on the genes of budding yeast Saccharomyces cerevisiae. Our WNB model can also be used to analyze the contribution of each source of information toward the prediction performance through the weight training process. The contribution analysis could potentially lead to significant scientific discovery by facilitating the interpretation and understanding of the complex relationships between biological entities.

Artificial Intelligence↗
PubMed2006

springScape: visualisation of microarray and contextual bioinformatic data using spring embedding and an 'information landscape'.

The interpretation of microarray and other high-throughput data is highly dependent on the biological context of experiments. However, standard analysis packages are poor at simultaneously presenting both the array and related bioinformatic data. We have addressed this challenge by developing a system springScape based on 'spring embedding' and an 'information landscape' allowing several related data sources to be dynamically combined while highlighting one particular feature. Each data source is represented as a network of nodes connected by weighted edges. The networks are combined and embedded in the 2-D plane by spring embedding such that nodes with a high similarity are drawn close together. Complex relationships can be discovered by varying the weight of each data source and observing the dynamic response of the spring network. By modifying Procrustes analysis, we find that the visualizations have an acceptable degree of reproducibility. The 'information landscape' highlights one particular data source, displaying it as a smooth surface whose height is proportional to both the information being viewed and the density of nodes. The algorithm is demonstrated using several microarray data sets in combination with protein-protein interaction data and GO annotations. Among the features revealed are the spatio-temporal profile of gene expression and the identification of GO terms correlated with gene expression and protein interactions. The power of this combined display lies in its interactive feedback and exploitation of human visual pattern recognition. Overall, springScape shows promise as a tool for the interpretation of microarray data in the context of relevant bioinformatic information.

Algorithms↗
PubMed2000

Vaccine preventable diseases and vaccination coverage in Australia, 1993-1998.

BACKGROUND: Since the introduction of childhood vaccination for diphtheria in 1932 and the widespread use of vaccines to prevent tetanus, pertussis (whooping cough) and poliomyelitis in the 1950s, deaths in Australia from vaccine preventable diseases (VPDs) have declined by more than 99%. It is important, however, that the downward trend in morbidity and mortality from VPDs is maintained and carefully monitored, and that changes are interpreted in relation to vaccination coverage. AIM: This report aimed to bring together three national sources of routinely collected data on the morbidity and mortality (notifications, hospitalisations and deaths) from VPDs during the period 1993-1998 for the 8 diseases then on the routine childhood vaccination schedule, and for 4 other diseases potentially preventable by childhood vaccination. It also examined vaccination coverage for the same period. METHODS: Data sources included notifications from the National Notifiable Diseases Surveillance System (NNDSS), hospitalisation data from the Australian Institute of Health and Welfare (AIHW) National Hospital Morbidity Database, deaths from the Australian Bureau of Statistics (ABS) Causes of Death Collection and vaccination coverage according to the Australian Childhood Immunisation Register (ACIR). All data sources were expected to have some limitations, the most important being under-reporting for notifications and vaccination encounters, and coding errors in the hospital morbidity data. RESULTS: Notifications for the 8 diseases covered by the routine schedule declined by 42%, from an average of 11,537 cases each year in 1993-1997 to 6700 in 1998, and hospitalisations fell by 12%, from an average of 1745 per year to 1536 in 1997/1998, while deaths remained unchanged at 7 each year over the period of review (Table 1). Tetanus caused 1 or 2 of the deaths each year. However, 6 of the 7 deaths in 1997 were in infants during a major outbreak of pertussis. Pertussis caused most of the notifications, hospitalisations and deaths during the review period. While most of these were in children, 46% of the notifications and 13% of the hospitalisations occurred in persons aged 15 years or more. There were notable declines in the numbers of notifications of invasive Haemophilus influenzae type b (Hib) disease in children under 5 years of age (77%), measles (87%) and rubella (75%), and there were no notifications of diphtheria or poliomyelitis. Vaccination coverage estimated using ACIR data increased during the review period. Coverage for the first 3 doses of diphtheria, tetanus, pertussis and Hib vaccines, assessed at 1 year of age, increased from 75% to 85%, while coverage for measles-mumps-rubella (MMR) vaccine, assessed at 2 years of age, increased from 83% to 86%. It is likely that these data underestimated coverage by 5-10%, and that the increase in coverage partly reflected better reporting to the ACIR by providers.

Adolescent↗
PubMed2000

Indirect modulation of dopamine D2 receptors as potential pharmacotherapy for schizophrenia: II. Glutamate (Ant)agonists.

OBJECTIVE: To summarize the published preclinical and clinical data that suggest the possible use of glutamate receptor agonists or antagonists as novel antipsychotic agents. DATA SOURCES: Primary and review articles were identified by MEDLINE search (from 1966 to December 1999) and through secondary sources. STUDY SELECTION AND DATA EXTRACTION: All of the articles identified from the data sources were evaluated and all information deemed relevant was included. DATA SYNTHESIS: The standard antipsychotic drugs, whose clinical activity correlates with affinity for dopamine D2 receptors, alleviate some of the positive symptoms of schizophrenia, but have limited impact on negative symptoms. Several lines of evidence implicate glutamate-receptor system dysfunction(s) in schizophrenia, either as causative or contributory factors. In addition, several standard antipsychotic drugs modulate glutamate or glutamate receptor activity, suggesting an alternative view of their mechanism of antipsychotic action. Preliminary studies have shown that drugs which modulate glutamate brain concentrations have positive effects in animal models of schizophrenia. CONCLUSIONS: A role for glutamate in the pathogenesis or pharmacotherapy of schizophrenia is suggested from anatomic (interactions between glutamatergic and dopaminergic systems in relevant brain regions), physiologic (implication of glutamate-receptor dysfunction), and pharmacologic (modulation of glutamate or glutamate receptors) evidence. Therefore, compounds that function at glutamate receptors might represent a novel approach to the treatment of the disease or to the amelioration of symptoms, either as monotherapy or as an adjunct to dopamine D2 receptor antagonists.

Animals↗
PubMed2003

Fluoroquinolone AUIC break points and the link to bacterial killing rates. Part 1: In vitro and animal models.

OBJECTIVE: To review in vitro and animal model studies with fluoroquinolones and the pharmacokinetic and pharmacodynamic relationships that are predictive of clinical and microbiologic outcomes and resistance. Data on fluoroquinolones are summarized and examine the premise that a single area under the inhibitory concentration-time curve (AUIC) target >125 may be used for all fluoroquinolones with concentration-dependent killing actions and against all target organisms. DATA SOURCES: Primary articles were identified by MEDLINE search (1966-February 2002) and through secondary sources. STUDY SELECTION AND DATA EXTRACTION: All of the articles identified from the data sources were evaluated, and all information deemed relevant was included. DATA SYNTHESIS: The fluoroquinolones exhibit concentration-dependent killing. This effect clearly depends on concentrations achieved, and outcomes depend on endpoints established by individual investigators. With AUIC values <60, the actions of fluoroquinolones are essentially bacteriostatic; any observed bacterial killing is the combined effect of low concentrations in relation to minimum inhibitory concentration and the action of host factors such as neutrophils and macrophages. AUIC values >100 but <250 yield bacterial killing at a slow rate, but usually by day 7 of treatment. AUICs >250 produce rapid killing, and bacterial eradication occurs within 24 hours. Disagreements regarding target endpoints are the expected consequences of comparing microbial and clinical outcomes across animal models, in vitro experiments, and humans when the endpoints are clearly not equivalent. Careful attention to time-related events, such as speed of bacterial killing, versus global endpoints, such as bacteriologic cure, allows optimal break points to be defined. CONCLUSIONS: Evidence from in vitro and animal models favors the use of AUIC values >250 for rapid bactericidal action, regardless of whether the organism is gram-negative or gram-positive.

Animals↗
PubMed2003

Fluoroquinolone AUIC break points and the link to bacterial killing rates. Part 2: human trials.

OBJECTIVE: To review clinical trials with fluoroquinolones and the pharmacokinetic and pharmacodynamic parameters predictive of clinical and microbiologic outcomes and resistance. Data on fluoroquinolones are summarized and the premise that a single AUIC target >125 may be used for all fluoroquinolones against all target organisms is examined. DATA SOURCES: Primary articles were identified by a MEDLINE search (1966-February 2002) and through secondary sources. STUDY SELECTION AND DATA EXTRACTION: All of the articles identified from the data sources were evaluated and all information deemed relevant was included. DATA SYNTHESIS: The fluoroquinolones exhibit concentration-dependent killing. This effect clearly depends upon concentrations achieved and outcomes depend upon endpoints established by individual investigators. With AUIC values <60, the actions of fluoroquinolones are essentially bacteriostatic; any observed bacterial killing is the combined effect of low concentrations in relation to minimum inhibitory concentration and the action of host factors such as neutrophils and macrophages. AUIC values >100 but <250 yield bacterial killing at a slow rate, but usually by day 7 of treatment. AUICs >250 produce rapid killing, and bacterial eradication occurs within 24 hours. Disagreements regarding target endpoints are the expected consequences of comparing microbial and clinical outcomes across animal models, in vitro experiments (Part 1), and humans when the endpoints are clearly not equivalent. Careful attention to time-related events such as speed of bacterial killing versus global endpoints such as bacteriologic cure allows optimal break points to be defined. CONCLUSIONS: Evidence from human trials favors the use of AUIC values >250 for rapid bactericidal action, regardless of whether the organism is gram-negative or gram-positive.

Animals↗
PubMed2003

Automatic discovery and classification of bioinformatics Web sources.

MOTIVATION: The World Wide Web provides an incredible resource to genomics researchers in the form of query access to distributed data sources--e.g. BLAST sequence homology search interfaces. The number of these autonomous sources and their rate of change outpaces the speed at which they can be manually classified, meaning that the available data is not being utilized to its full potential. Manually maintaining a wrapper library will not scale to accommodate the growth of genomics data sources on the Web, challenging us to produce an automated system that can find, classify and wrap new sources without constant human intervention. Previous research has not addressed the problem of automatically locating, classifying and integrating classes of bioinformatics data sources. RESULTS: This paper presents an overview of a system for finding classes of bioinformatics data sources and integrating them behind a unified interface. We describe our approach for automatic classification of new Web sources into relevance categories that eliminates the human effort required to maintain a current repository of sources. Our approach is based on a meta-data description of classes of interesting sources that describes the important features of an entire class of services without tying that description to any particular Web source. We examine the features of this format in the context of BLAST sources to show how it relates to Web sources that are being described. We then show how a description can be used to determine if an arbitrary Web source is an instance of the described service. To validate the effectiveness of this approach, we have constructed a prototype that correctly classifies approximately two-thirds of the BLAST sources we tested. We conclude with a discussion of these results, the factors that affect correct automatic classification and areas for future study.

Algorithms↗
PubMed2004

Assessment of the reproducibility of postprocessing dynamic CT perfusion data.

BACKGROUND AND PURPOSE: Commercially available software programs for the conversion of dynamic CT perfusion (CTP) source data into cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps require operators to subjectively define parameters that are used in subsequent postprocessing calculations. Our purpose was to define the variability of CBV, CBF, and MTT values derived from CTP maps generated from the same source data postprocessed by three different CT technologists (CTTs). METHODS: Raw data derived from dynamic CTP examinations performed in 20 subjects were postprocessed seven times by three experienced CTTs. Parenchymal regions of interest derived from each map (CBV, CBF, and MTT) were compared. The CBF maps generated by each technologist were also qualitatively assessed. Decisions made by each analyzer during postprocessing were assessed. RESULTS: The intraclass correlation coefficients were 0.73 (95% CI, 0.64-0.81), 0.87 (0.83-0.91) and 0.89 (0.85-0.93), for the CBV, CBF, and MTT parenchymal regions of interest, respectively. All individual correlation coefficients between data sets were significant to a P value <.05. Measurement error, made solely on the basis of different technologists postprocessing the same source data and expressed as the coefficients of variation, were 31%, 30%, and 14% for CBV, CBF, and MTT, respectively. The selection of the arterial input function (AIF) region of interest, venous function region of interest, and preenhancement interval were very reproducible. The technologists differed significantly with respect to the selection of the postenhancement image (PoEI) (P <.01). A retrospective review of the individual CBF maps indicated that variance in the PoEI selection accounted for much of the variation in the qualitative appearance of the CBF maps generated by different technologists. The PoEI was selected to demarcate the baseline of the AIF time-attenuation curve. It is likely that this method of PoEI selection significantly contributed to intra- and interanalyzer variability. CONCLUSION: There is a high degree of correlation between parenchymal regions of interest derived from CBV, CBF, and MTT maps generated from the same dynamic CTP source data postprocessed by different operators. The level of agreement, however, may not be sufficient to incorporate quantitative values into clinical decision making. Quantitative differences between parenchymal regions of interest were not infrequently manifest as significant differences in the qualitative appearance of the CBF maps. It is likely that, with optimization of postprocessing parameter selection, the degree of variability may be substantially reduced.

Arizona↗
PubMed2002

Screening for prostate cancer: an update of the evidence for the U.S. Preventive Services Task Force.

BACKGROUND: In U.S. men, prostate cancer is the most common noncutaneous cancer and the second leading cause of cancer death. Screening for prostate cancer is controversial. PURPOSE: To examine for the U.S. Preventive Services Task Force the evidence of benefits and harms of screening and earlier treatment. DATA SOURCES: MEDLINE and the Cochrane Library, experts, and bibliographies of reviews. STUDY SELECTION: Researchers developed eight questions representing a logical chain between screening and reduced mortality, along with eligibility criteria for admissible evidence for each question. Admissible evidence was obtained by searching the data sources. DATA EXTRACTION: Two reviewers abstracted relevant information using standardized abstraction forms and graded article quality according to Task Force criteria. DATA SYNTHESIS: No conclusive direct evidence shows that screening reduces prostate cancer mortality. Some screening tests can detect prostate cancer at an earlier stage than clinical detection. One study provides good evidence that radical prostatectomy reduces disease-specific mortality for men with localized prostate cancer detected clinically. No study has examined the additional benefit of earlier treatment after detection by screening. Men with a life expectancy of fewer than 10 years are unlikely to benefit from screening even under favorable assumptions. Each treatment is associated with several well-documented potential harms. CONCLUSIONS: Although potential harms of screening for prostate cancer can be established, the presence or magnitude of potential benefits cannot. Therefore, the net benefit of screening cannot be determined.

Cost-Benefit Analysis↗
PubMed2005

Learning yeast gene functions from heterogeneous sources of data using hybrid weighted Bayesian networks.

We developed a machine learning system for determining gene functions from heterogeneous sources of data sets using a Weighted Naive Bayesian Network (WNB). The knowledge of gene functions is crucial for understanding many fundamental biological mechanisms such as regulatory pathways, cell cycles and diseases. Our major goal is to accurately infer functions of putative genes or ORFs (Open Reading Frames) from existing databases using computational methods. However, this task is intrinsically difficult since the underlying biological processes represent complex interactions of multiple entities. Therefore many functional links would be missing when only one or two source of data is used in the prediction. Our hypothesis is that integrating evidence from multiple and complementary sources could significantly improve the prediction accuracy. In this paper, our experimental results not only suggest that the above hypothesis is valid, but also provide guidelines for using the WNB system for data collection, training and predictions. The combined training data sets contain information from gene annotations, gene expressions, clustering outputs, keyword annotations and sequence homology from public databases. The current system is trained and tested on the genes of budding yeast Saccharomyces cerevisiae. Our WNB model can also be used to analyze the contribution of each source of information toward the prediction performance through the weight training process. The contribution analysis could potentially lead to significant scientific discovery by facilitating the interpretation and understanding of the complex relationships between biological entities.

Artificial Intelligence↗
PubMed1994

[Use of microfilters within the scope of infusion therapy].

OBJECTIVE: The aim of our review is to summarize risks and benefits using 0.2-micron in-line filters in intravenous infusion therapy. DATA SOURCES: Own data and the accessible medical literature according to current electronic information sources were exploited. RESULTS: Problems associated with intravenous infusion therapy include contamination of fluids with bacteria, endotoxins, and foreign particles. These factors may be important in the pathogenesis of sepsis, adult respiratory distress syndrome, and multiorgan failure. Elimination of bacteria, endotoxins, and particles can be achieved by 0.2-micron in-line filters. A significant reduction in the rate of phlebitis due to peripheral venous catheters has been demonstrated. However, a reduction in the rate of sepsis by the elimination of bacteria and endotoxins or the prevention of adult respiratory distress syndrome and multiorgan failure by retention of foreign material by these filters has not yet been conclusively proved. The longer intervals between changing of the whole infusion systems with the use of these filters (from 24 h without filter to 96 h with filter) result in cost-effectiveness, waste reduction, and reduction in nursing time. Due to adherence to the filter, small doses of drugs (i.e., < 5 micrograms/ml or < 5 mg/24 h) should not be given through filters. The size of the filter pores (0.2 micron) does not allow for the application of blood products or emulsions. Retention of foreign material results in increasing resistance, so that measurements of central venous pressure may be affected. Filters are constructed so that a potential increase in pressure and a following break would not result in a leakage. CONCLUSION: 0.2-micron in-line filters are useful for the elimination of the bacterial and endotoxic load to the patient and for the removal of foreign material. Thus, they represent a useful and cost-effective adjunct, but not a prerequisite in modern intravenous therapy.

Colony Count, Microbial↗
PubMed2003

Screening for dementia in primary care: a summary of the evidence for the U.S. Preventive Services Task Force.

BACKGROUND: Dementia is a large and growing problem but is often not diagnosed in its earlier stages. Screening and earlier treatment could reduce the burden of suffering of this syndrome. PURPOSE: To review the evidence of benefits and harms of screening for and earlier treatment of dementia. DATA SOURCES: MEDLINE, PsycINFO, EMBASE, the Cochrane Library, experts, and bibliographies of reviews. STUDY SELECTION: The authors developed eight key questions representing a logical chain between screening and improved health outcomes, along with eligibility criteria for admissible evidence for each question. Admissible evidence was obtained by searching the data sources. DATA EXTRACTION: Two reviewers abstracted relevant information using standardized abstraction forms and graded article quality according to U.S. Preventive Services Task Force criteria. DATA SYNTHESIS: No randomized, controlled trial of screening for dementia has been completed. Brief screening tools can detect some persons with early dementia (positive predictive value < or =50%). Six to 12 months of treatment with cholinesterase inhibitors modestly slows the decline of cognitive and global clinical change scores in some patients with mild to moderate Alzheimer disease. Function is minimally affected, and fewer than 20% of patients stop taking cholinesterase inhibitors because of side effects. Only limited evidence indicates that any other pharmacologic or nonpharmacologic intervention slows decline in persons with early dementia. Although intensive multicomponent caregiver interventions may delay nursing home placement of patients who have caregivers, the relevance of this finding for persons who do not yet have caregivers is uncertain. Other potential benefits and harms of screening have not been studied. CONCLUSIONS: Screening tests can detect undiagnosed dementia. In persons with mild to moderate clinically detected Alzheimer disease, cholinesterase inhibitors are somewhat effective in slowing cognitive decline. The effect of cholinesterase inhibitors or other treatments on persons with dementia detected by screening is uncertain.

Aged↗
PubMed1990

Incidence of IDDM during 1984-1986 in population aged less than 30 yr. Residents of Turin, Italy.

The goal of this study was to measure the incidence of insulin-dependent diabetes mellitus (IDDM) during 1984-1986 in residents of Turin, Italy, aged less than 30 yr. The primary data source was the list of all subjects diagnosed with IDDM who attended diabetes clinics in Turin. Other data sources were the general register of death certificates, the list of hospital discharges, and the computerized data base of insulin prescriptions. Eighty incident cases of IDDM were identified during the study in 1,130,284 person-yr for those less than 30 yr of age. Age-adjusted (world standard) incidence rates were 8.05, 8.10, and 6.96/100,000 in the age-groups 0-14, 0-19, and 0-29 yr, respectively. Estimated completeness of the primary data source compared with all other data sources was 91%, whereas the estimated completeness of ascertainment of the registry was 99%. Incidence rates of IDDM in northern Italy compare with those of European countries with low-medium incidence. A population-based register is being established for the province of Turin (951,445 inhabitants aged 0-29 yr) for the collection of incident cases since 1984.

Adolescent↗
PubMed1994

An evaluation of vital registers as sources of data for infant mortality rates in Cameroon.

BACKGROUND: Infant mortality rates have been widely used as indicators of health status and the availability, utilization and effectiveness of health services. Two principal sources of data for infant mortality rates are vital registers and censuses. This study was designed to evaluate the accuracy of vital registers as sources of data for infant mortality rates in Cameroon. METHODS: A household census of births and infant deaths that occurred in Buea Subdivision between 1 November 1991 and 31 October 1992 was conducted to determine the proportion that were registered and the reasons why the remainder were not registered. RESULTS: The registration coverage was found to be 62% for births and 4% for infant deaths. The most frequently reported reasons for not registering births were lack of money, lack of time and a complicated registration procedure. For infant deaths the reasons were lack of knowledge and no perceived benefits. CONCLUSIONS: Vital registers of birth and death are not an accurate source of data for infant mortality rates in Cameroon. Motivation for birth and death registration appear to be dependent on the perceived benefits. A mechanism of registration that uses medical institutions may substantially increase registration coverage for births and infant deaths.

Birth Certificates↗
PubMed2005

Discovering transcriptional modules from motif, chip-chip and microarray data.

We present a method for inference of transcriptional modules from heterogeneous data sources. It allows identifying the responsible set of regulators in combination with their corresponding DNA recognition sites (motifs) and target genes. Our approach distinguishes itself from previous work in literature because it fully exploits the knowledge of three independently acquired data sources: ChIP-chip data; motif information as obtained by phylogenetic shadowing; and gene expression profiles obtained using microarray experiments. Moreover, these three data sources are dealt with in a new and fully integrated manner. By avoiding approaches that take the different data sources into account sequentially or iteratively, the transparency of the method and the interpretability of the results are ensured. Using our method on biological data demonstrated the biological relevance of the inference.

Algorithms↗
PubMed2003

A resampling method for estimating the signal subspace of spatio-temporal EEG/MEG data.

Source localization using spatio-temporal electroencephalography (EEG) and magnetoencephalography (MEG) data is usually performed by means of signal subspace methods. The first step of these methods is the estimation of a set of vectors that spans a subspace containing as well as possible the signal of interest. This estimation is usually performed by means of a singular value decomposition (SVD) of the data matrix: The rank of the signal subspace (denoted by r) is estimated from a plot in which the singular values are plotted against their rank order, and the signal subspace itself is estimated by the first r singular vectors. The main problem with this method is that it is strongly affected by spatial covariance in the noise. Therefore, two methods are proposed that are much less affected by this spatial covariance, and old and a new method. The old method involves prewhitening of the data matrix, making use of an estimate of the spatial noise covariance matrix. The new method is based on the matrix product of two average data matrices, resulting from a random partition of a set of stochastically independent replications of the spatio-temporal data matrix. The estimated signal subspace is obtained by first filtering out the asymmetric and negative definite components of this matrix product and then retaining the eigenvectors that correspond to the r largest eigenvalues of this filtered data matrix. The main advantages of the partition-based eigen decomposition over prewhited SVD is that 1) it does not require an estimate of the spatial noise covariance matrix and 2b) that it allows one to make use of a resampling distribution (the so-called partitioning distribution) as a natural quantification of the uncertainty in the estimated rank. The performance of three methods (SVD with and without prewhitening, and the partition-based method) is compared in a simulation study. From this study, it could be concluded that prewhited SVD and the partition-based eigen decomposition perform equally well when the amplitude time series are constant, but that the partition-based method performs better when the amplitude time series are variable.

Algorithms↗
PubMed2001

Practice guidelines for lipid-based amphotericin B in stem cell transplant recipients.

OBJECTIVE: To provide clinicians who practice in the stem cell transplantation (SCT) setting with practical guidelines for the use of lipid-based amphotericin B (AmB) formulations in SCT patients who have documented or probable invasive fungal infections, are experiencing neutropenic fever, or require secondary prophylaxis for fungal infections. DATA SOURCES: Recommendations are based on the results of a two-day consensus meeting that convened clinicians versed in the management of infectious complications in patients undergoing SCT. This meeting, which was held October 21-23, 1998, in Orlando, Florida, was sponsored by an educational grant from The Liposome Company. In addition, primary articles were identified by MEDLINE search (1980-December 1999) and through secondary sources. STUDY SELECTION AND DATA EXTRACTION: All of the articles identified from the data sources were evaluated, and all information deemed relevant was included in this review. DATA SYNTHESIS: Immunocompromised patients, particularly patients undergoing high-dose chemotherapy with SCT, experience a high degree of morbidity and mortality from invasive fungal infections. Historically, treatment for such infections with conventional AmB had been limited primarily by its associated nephrotoxicity. Lipid-based formulations of AmB have helped to advance the management of invasive fungal infections in the SCT population by offering a treatment alternative that allows for administration of adequate amounts of active drug to produce clinical and mycologic responses, compared with conventional AmB, in a delivery system that is less nephrotoxic. Unfortunately, these agents are relatively expensive. Therefore, patients who are candidates for lipid-based products must be selected carefully. CONCLUSIONS: Practical guidelines are provided for the use of lipid-based AmB formulations in SCT patients who have documented or probable invasive fungal infections, are experiencing neutropenic fever, or require secondary prophylaxis for fungal infections.

Humans↗