Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “classifier”

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 685 records · Page 38Linked to original sources
PubMed2002

Clinical features of third ventriculostomy failures classified by fenestration patency.

BACKGROUND: To evaluate strategies for treating endoscopic third ventriculostomy (ETV) failure, we assessed patients, clinical features at failure, and the outcome of VP shunt placement at re-operation, classifying patients by fenestration patency. METHODS: Thirty-six patients with failed ETV were evaluated retrospectively. All but 4 had cine phase-contrast magnetic resonance (MR) images at re-operation to determine whether the fenestration was patent, and were grouped into "patent" and "no flow" groups. Symptoms at re-operation, the interval to failure, and outcome of re-operation were compared between these groups. RESULTS: Progression of elevated intracranial pressure (ICP) signs was significantly more frequent in the "no flow" group than the "patent" group (p = 0.0025). The median interval to failure was 2.5 months, with no statistical difference between the "patent" group (median 4.0 months) and the "no flow" group (median 1.1 months). Re-operations consisted of 29 shunt placements, 4 redo ETVs, and 3 combinations of both. Kaplan-Meier estimation indicates that 41% of shunts would be expected to fail by 5.2 years. The success rate of shunt placement was somewhat worse in the "no flow" group, although the difference was not statistically significant (p = 0.066). Four patients in the "patent" group treated with shunt placements eventually became shunt-independent with continuously patent fenestration; these were considered delayed successes. CONCLUSION: Patients with signs of elevated ICP and "no flow" findings on MR should be given emergency treatment because they have a high risk of symptom progression. The clinical differences between "patent" and "no flow" fenestration at re-operation after ETV failure are considered to be worthy of further study.

Adolescent↗
PubMed2002

Classification of neural signals by a generalized correlation classifier based on radial basis functions.

A common problem in neuroscience is to identify the features by which a set of measurements can be segregated into different classes, for example into different responses to sensory stimuli. A main difficulty is that the derived distributions are often high-dimensional and complex. Many multivariate analysis techniques, therefore, aim to find a simpler low-dimensional representation. Most of them either involve huge efforts in implementation and data handling or ignore important structures and relationships within the original data. We developed a dimension reduction method by means of radial basis functions (RBF), where only a system of linear equations has to be solved. We show that this approach can be regarded as an extension of a linear correlation-based classifier. The validity and reliability of this technique is demonstrated on artificial data sets. Its practical relevance is further confirmed by discriminating recordings from monkey visual cortex evoked by different stimuli.

Animals↗
PubMed1995

How should P2X purinoceptors be classified pharmacologically?

When ATP is released as a neurotransmitter from central and peripheral nerves it acts at P2X purinoceptors to produce postsynaptic depolarization and excitation. The P2X purinoceptor was originally classified on the basis of the relative agonist potencies of ATP and a number of its structural analogues. However, it is now clear that the potency of some agonists is greatly decreased by breakdown by ectonucleotidase enzymes, leading to an incorrect determination of agonist potency order. In this article, Charles Kennedy and Paul Leff discuss recent results that indicate that the established classification of P2X purinoceptors is no longer valid and needs redefinition.

Adenosine Triphosphate↗
PubMed2002

Classifying toxicity and pathology by gene-expression profile--taking a lead from studies in neoplasia.

Microarray technology has given rise to the ability to classify and predict toxin-induced pathological change using gene-expression profiles. However, to date gene-expression profiling of pathological subtype has been exploited mainly in the pathological classification of neoplasia. Using an example of resistance to doxorubicin in vitro and gene-expression profiling in neoplasia, this article explores the potential and challenges for gene-expression profiling in the delineation and understanding of toxicity and toxin-induced pathological change.

Animals↗
PubMed1996

Hepatitis C virus types 7, 8 and 9 should be classified as type 6 subtypes.

Tokita et al. reported the identification of hepatitis C virus type 7, 8 and 9 in Southeast Asia, based on the unweighed pair-group method with the arithmetic mean, a method that may not be appropriate when the nucleotide substitution rate is not constant over time. To determine more accurately the relationship of these proposed types 7, 8, and 9 with other types, a more appropriate approach, the neighbor-joining method, was applied to re-evaluate the phylogenetic relationship. A total of 660 HCV sequences, including the reported sequences, were collected from DNA databases. For every region, the nucleotide substitution rate was estimated by the 6-parameter method, and phylogenetic trees were constructed using the neighbor-joining method. The results of this analysis indicate that the newly proposed HCV types 7, 8 and 9 should be classified as type 6 subtypes. HCV type 6 appears to be diversified.

Evolution, Chemical↗
PubMed2003

A framework for classifying factors that contribute to error in the emergency department.

The Institute of Medicine report in 1999 spurred a national movement in patient safety and focused attention on medical error as a significant cause of preventable injury and death. Throughout the past decade, the medical community has gradually acknowledged the fallibility of medical science and imperfections of our health care organizations. Before significant progress can be made to improve safety in health care, we must better understand the sources of error. This article is presented as one step in the process of change. A framework for classifying factors that contributed to errors identified in the emergency department (ED) is presented. The framework is, in its most basic form, a comprehensive checklist of all the sources of error uncovered in the course of investigating hundreds of cases referred to Stroger Hospital's emergency medicine quality assurance committee throughout the past decade. It begins with a look at error in the ED and then looks beyond the ED to examine error in the context of the wider health care system. It incorporates ideas found in safety engineering, transportation safety, human factors engineering, and our own experience in an urban, public, teaching hospital ED.

Clinical Competence↗
PubMed1990

A scheme for classifying carcinogens.

We present a scheme for classifying chemical carcinogens according to the weight of the evidence that each substance poses a human cancer hazard. The approach represents a logical extension of and builds upon those previously developed by the International Agency for Research on Cancer, the U.S. Environmental Protection Agency, and the so-called Tripartite Group of industrial scientists. It takes into account new scientific knowledge about chemical carcinogenesis and animal models. Eight categories are presented: known human carcinogen (Category 1), carcinogenic activity in animals, probable human carcinogen (Category 2), possible human carcinogen (Category 3), equivocal evidence for carcinogenic activity (Category 4), evidence inadequate for classification (Category 5), carcinogenic activity in animals; probably not a human cancer hazard (Category 6), carcinogenic activity in animals; considered not a human cancer hazard (Category 7), evidence of noncarcinogenicity (Category 8). Evidence useful for categorization includes human studies, animal bioassays, corroborative evidence from bioassays, and mechanistic studies relevant to determining the predictivity of animal responses for human hazard. Weighing this evidence to derive a conclusion about classification is a process that requires expert judgment; it cannot now be reduced to a simple set of decision rules. However, we identify the kinds of information that can be useful in this process, and indicate how each might most appropriately be used.

Animals↗
PubMed2000

Purification and partial characterisation of tentatively classified acid phosphatase from the earthworm Eisenia veneta.

In order to use leakage of lysosomal acid phosphatase (AP) as a biomarker of stress to earthworms, more information about AP's in earthworms are needed. This paper describes the details about tentatively classified APs in the earthworm Eisenia veneta. Two isoenzymes (enzyme I and II) of acid phosphatase (AP) and one alkaline phosphatase (enzyme III) from the earthworm E. veneta were separated by gel filtration. All three enzymes were further purified and concentrated on a Con A Sepharose 4B column. Enzyme I was inhibited by tartrate, showed an optimal pH range between 4.0 and 5.0 and was assumed to be of lysosomal origin. Enzyme II was the major enzyme showing the highest activity of the three enzymes. It was expected to be a lysosomal AP under physiological conditions. Enzyme II had a molecular mass 113 kDa and was composed of apparently identical polypeptide chains of 36 kDa each. This enzyme was inhibited by tartrate, showed an optimal pH in the range 6.0-7.5 and was slowly degraded at temperatures above 40 degrees C. Enzyme III is not inhibited by tartrate and has a pH-optimum > 9. The subcellular location under physiological conditions was assumed to be the cytosol.

Acid Phosphatase↗
PubMedDate not supplied

[Tele-E.E.G. recordings of three epileptic attacks classified as episodes of PM status (author's transl)].

The authors present the tele-E.E.G. resording of three episodes of PM status, occurring in three known epileptics (ages: 16, 20 and 22 years). One episode was induced by an injection of bemegride and the other two by overbreathing. Their duration was 27, 31 and 44 minutes respectively. The development of abnormalities was progressive in all three cases, whilst they disappeared suddenly in two cases. Study of these three episodes was made in two ways: an electrical study and a clinical study. In addition, a brief retrospective study of the psychological experience of the episodes was carried out. The main finding was that the three episodes recorded and observed represented prolonged attacks and not a succession of attacks. The authors concluded that episodes classified under the name of PM Status may be studied in two ways: either considering them as prolonged attacks which are not status epilepticus, or considering them as repeated attacks, their repetition resulting in the appearance of unusual additional signs and which are status epilepticus.

Adolescent↗
PubMed1998

Neural classifier construction using regularization, pruning and test error estimation.

In this paper we propose a method for construction of feed-forward neural classifiers based on regularization and adaptive architectures. Using a penalized maximum likelihood scheme, we derive a modified form of the entropic error measure and an algebraic estimate of the test error. In conjunction with optimal brain damage pruning, a test error estimate is used to select the network architecture. The scheme is evaluated on four classification problems.

Journal Article↗
PubMed1999

Improving support vector machine classifiers by modifying kernel functions.

We propose a method of modifying a kernel function to improve the performance of a support vector machine classifier. This is based on the structure of the Riemannian geometry induced by the kernel function. The idea is to enlarge the spatial resolution around the separating boundary surface, by a conformal mapping, such that the separability between classes is increased. Examples are given specifically for modifying Gaussian Radial Basis Function kernels. Simulation results for both artificial and real data show remarkable improvement of generalization errors, supporting our idea.

Journal Article↗
PubMed2001

Using biological indices to classify schizophrenia and other psychotic patients.

Although classification of mental disorders using more than clinical description would be desirable, there is scant evidence that available laboratory tests (i.e. biological indices) would provide more valid classifications than current diagnostic systems (e.g. DSM-IV). We used cluster analysis of four biological variables to classify 163 psychotic patients and 83 nonpsychiatric comparison subjects. Analyses revealed a three-cluster solution with the first cluster reflecting electrodermal deviance, the second cluster representing nondeviant biological function, and the third cluster reflecting increased nailfold plexus visibility and ocular motor dysfunction. To assess the construct validity of proband clusters we examined ocular motor performance in 156 first-degree relatives as a function of proband cluster membership. First-degree relatives of third cluster probands exhibited worse ocular motor performance than relatives of other cluster probands. Additionally, better classification sensitivity and specificity were obtained for the relatives when they were grouped by proband cluster than by proband DSM-IV diagnosis. When a single proband characteristic (i.e. eyetracking performance) was used to group relatives, classification sensitivity and specificity failed to significantly increase over grouping by proband DSM-IV diagnosis. Multivariate biologically defined clusters may offer an advantage over DSM-IV classification when examining nosology and etiology of psychotic disorders.

Adolescent↗
PubMed1997

Genotypic relationships among strains classified under the (Pasteurella) haemolytica-complex as indicated by ribotyping and multilocus enzyme electrophoresis.

Two-hundred and one strains classified under the (Pasteurella) haemolytica-complex isolated from cattle, sheep, deer, pigs, hares and rabbits were investigated by ribotyping. Fifty-nine of these strains were selected for further studies using multilocus enzyme electrophoresis (MEE). A correlation between the clusters identified by ribotyping and MEE was demonstrated and the results furthermore indicated that a genetic basis exists for most clusters previously outlined by the use of quantitative evaluation of phenotypic data. The taxonomic relevance of ornithine decarboxylase and fermentation of L-arabinose, D-sorbitol and glucosides for taxonomic delineation within the (P.) haemolytica-complex was supported. A taxonomic importance was further indicated for ONPG, ONPX, ONPF, meso-inositol, D-xylose, maltose, dextrine and NPG in relation to some of the taxa. Within the porcine taxon 15, however, differences in ornithine decarboxylase did not correspond to genetic clusters. Six lineages were revealed by MEE. Lineage A contained electrophoretic types (ETs) representing biogroups 1, 3A-3H, 8A and 9, indicating a genetic relationship between these groups--an observation which was supported by ribotyping. Lineage B included biogroup 8D, 3 strains from biogroup 10 and a single strain from biogroup 1 and taxon 18/biovar 1. Lineage C contained strains allocated to biogroup 6 from ruminants and the porcine taxon 15. The similarity between these two groups was accentuated by ribotyping. Lineage D and the single isolate in lineage E contained strains allocated to biogroups 7, 10, 8B and 8C, in addition to single strains from biogroups 6 and 9. The same strains were found in the heterogenous ribotype cluster 17. Lineage F contained strains representing the leprine taxon 20 and the ruminant (P.) granulomatis. Ribotyping indicated that the ruminant biogroup 3J was affiliated with both taxon 20 and (P.) granulomatis.

Alleles↗
PubMed1997

Relationships among strains classified with the ruminant Pasteurella haemolytica-complex using quantitative evaluation of phenotypic data.

The phenotypic relationships among 246 trehalose-negative strains classified under the [Pasteurella] haemolytica-complex in ruminants were investigated by clustering and multidimensional ordinations based upon 79 phenotypic characters. A quantitative evaluation of phenotypic data using a 5-level scoring system is presented permitting a comprehensive utilization of the recorded phenotypic variation among the strains in the analyses. Clustering and ordination analyses display complementary aspects of data which has been clearly demonstrated in this investigation. The main clusters revealed by the numerical techniques could be related to distinctive phenotypic differences and showed an extensive correlation with the recognized biogroups. This classification was based only upon 4 characters (fermentation of L-arabinose, D-sorbitol, glucosides and ornithine decarboxylase). In contrast, there was no obvious interpretation of the clusters formed by using binary scores. Phenotypic subgroups within the recognized biogroups have been described as well as a new, related group of bacteria, tentatively named Bisgaard taxon 36. Quantitative interpretation of phenotypic data seems to represent a promising method for finding relations among affiliated strains of bacteria and to assist in forming hypotheses for subsequent genotypic investigations.

Animals↗
PubMed2002

Dry powder inhalation of antibiotics in cystic fibrosis therapy, part 1: development of a powder formulation with colistin sulfate for a special test inhaler with an air classifier as de-agglomeration principle.

The aim of this study was to investigate the pulmonary administration of antibiotics as dry powder to patients with cystic fibrosis (CF), as an alternative for nebulization. This part of the study describes the development of a powder formulation with colistin sulfate as model substance. The aim of the new dosage form was to increase pulmonary deposition, therapeutic efficiency and, by that, compliance by the CF patients. A physical powder mixture of colistin and a size fraction of lactose (106-150 microm) was prepared and the mixture was optimized with respect to colistin content (83.3%) for use in a special test inhaler. A laser diffraction apparatus with special inhaler adapter was applied for analysis of the size distribution of the aerosol cloud from the inhaler. The size distributions of the aerosol clouds from the test inhaler at flow rates between 30 and 60 l/min for the optimized formulation showed nearly the same median diameter as that for the primary drug particles. But the X(100)-value was much lower, because of an effective large particle separation from the inspiratory air by an air classifier in the test inhaler. The results suggest that dry powder inhalation might be a suitable and highly efficient alternative for nebulization of antibiotic drugs in CF therapy.

Administration, Inhalation↗
PubMed2000

Can some cases of 'possible' spondyloarthropathy be classified as 'definite' or 'undifferentiated' spondyloarthropathy? Value of criteria for spondyloarthropathies. Spanish Spondyloarthropathy Study Group.

OBJECTIVES: When evaluating patients for spondyloarthropathy, clinicians use the 'possible spondyloarthropathy' category to indicate that they are unsure about the diagnosis. We sought to determine whether Amor's criteria or the European Spondyloarthropathy Study Group (ESSG) criteria could lift thi uncertainty. PATIENTS AND METHODS: During a Spanish study designed to validate criteria for spondyloar thropathies, 102 patients were classified in the 'possible spondyloarthropathy' category. We divided these patients into subgroups based on whether or not they met criteria for spondyloarthropathy. We compare baseline characteristics (N = 102) and five-year outcomes (N = 52) in these subgroups. RESULTS: The following features were significantly more common in the subgroups of patients who met Amor's criteria for spondyloarthropathy: oligoarthritis, heel pain, uveitis, balanitis, family history of spondyloarthropathy, an presence of the HLA B27 antigen. No differences were found for age at symptom onset, disease duration, buttock pain, gender, dactylitis, diarrhea, or psoriasis. Of the 52 patients followed up for five years, 17 me Amor's criteria at baseline and 13 were subsequently found to have definite spondyloarthropathy, whic was undifferentiated in six cases. There were only three cases of spondyloarthropathy among the 2 patients who did not meet Amor's criteria at baseline. Of the 28 patients who met ESSG criteria at baseline, 13 had spondyloarthropathy versus three of the 17 patients who did not meet ESSG criteria at baseline CONCLUSION: Amor's criteria or the ESSG criteria allow early classification of most patients with 'possible spondyloarthropathy' and early identification of undifferentiated spondyloarthropathy corresponding to minimal-symptom or incipient disease. In this study, Amor's criteria performed better than the ESSG criteria.

Adult↗
PubMed1999

Comparison of different systems to classify the neurological level of lesion in patients with myelomeningocele.

In 73 patients with myelomeningocele (mean 17.2 years, range 5 to 40 years) the classification of level of lesion was studied according to six commonly used classification systems and to the ambulation groups of Hoffer. The distribution of the patients into classes of thoracic-level lesions was the same for four classification systems in 10 patients and for two classification systems into categories of level L3 in 14 patients. For the other patients discrepancies occurred between systems for lesions of level L3 and downward. None of the patients was consistently categorized in the functional ambulation groups of Hoffer using all classification systems. The results show that it is not possible to compare neurological lesion levels classified according to the different systems described in this study and consequently that the distribution into the functional ambulation groups of Hoffer varies. To enhance communication and facilitate comparing the results of treatment we suggest using some basic criteria for patient documentation.

Adolescent↗
PubMed2006

Defining and classifying occupational rhinitis.

Three categories of rhinitis may occur in the workplace: occupational rhinitis, work-aggravated rhinitis and rhinitis-like conditions. In the present paper, we propose a new definition and a new classification of occupational rhinitis that takes into account mechanisms of induction as well as clinical presentation. In parallel with occupational asthma, occupational rhinitis is defined as a type of rhinitis characterized by intermittent or sometimes permanent nasal airflow limitation due to causes and conditions attributable to the work environment. Occupational rhinitis is classified according to its mechanism of induction as immunological or irritant-induced (non-immunological) rhinitis. Occupational rhinitis of the immunological type can itself be episodic or persistent, whereas the non-immunological type is subdivided into acute, chronic and corrosive.

Humans↗