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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed1993

Classifying perinatal death: experience from a regional survey.

OBJECTIVE: To examine problems encountered in classifying perinatal death using the systems proposed by Hey et al. (1986) and Cole et al. (1986). SUBJECTS: 451 deaths from a regional perinatal mortality survey of which 293 had a post mortem examination. METHODS: Documents from each death were reviewed by four assessors, one from each discipline, selected randomly from a pool of obstetricians, paediatricians, general practitioners and midwives. Each assessor classified the cause of death blind to the others. The degree of agreement between assessors was calculated for the full and shortened obstetric and fetal-neonatal classifications using the kappa statistic for inter-rater agreement. RESULTS: The kappa statistic, which is a measure of the proportion of agreement above chance, gave a value of 0.55 for the full obstetric classification and 0.58 for the full fetal and neonatal classification when all four assessors made an assignment. An assignment was omitted in 6.2%, but the kappa value of zero for these omissions suggested that this was a nonsystematic result due to random protocol violations. The grouped (shortened) classifications generated a higher kappa value of 0.62 for the nine point obstetric system and 0.67 for the six point fetal and neonatal (New Wigglesworth) system. Post mortem had little effect on agreement. The best agreement levels observed were for congenital anomaly. CONCLUSION: This survey highlighted the complexity of the 22 and 24 point classifications, the uneven distribution of deaths within their categories, and the variable levels of agreement between professionals classifying deaths, thus questioning the validity of individual maternity units of health districts generating local data in this degree of detail for comparative purposes in regional and national statistics. Grouping the original categories led to greater agreement particularly for the New Wigglesworth classification. The role of post mortems in clarifying the cause of fetal and neonatal death needs further investigation.

Cause of Death↗

PubMed1996

Empirical error-confidence curves for neural network and Gaussian classifiers.

"Error-Confidence" measures the probability that the proportion of errors made by a classifier will be within epsilon of EB, the optimal (Bayes) error. Probably Almost Bayes (PAB) theory attempts to quantify how this confidence increases with the number of training samples. We investigate the relationship empirically by comparing average error versus number of training patterns (m) for linear and neural network classifiers. On Gaussian problems, the resulting EC curves demonstrate that the PAB bounds are extremely conservative. Asymptotic statistics predicts a linear relationship between the logarithms of the average error and the number of training patterns. For low Bayes error rates we found excellent agreement between the prediction and the linear discriminant performance. At higher Bayes error rates we still found a linear relationship, but with a shallower slope than the predicted-1. When the underlying true model is a three-layer network, the EC curves show a greater dependence on classifier capacity, and the linear predictions no longer seem to hold.

Bayes Theorem↗

PubMed1991

Attempts to physiologically classify human thenar motor units.

1. This study was designed to determine whether human thenar motor units can be classified into types by the same physiological criteria used for other mammalian limb motor units and to consider whether such classification is functionally relevant. 2. Contractile responses of 25 human thenar single motor units were examined when their motor axons were stimulated intraneurally at rates from 1 to 100 Hz and intermittently at 40 Hz in a conventional 2-min fatigue test. Twitch and tetanic forces were measured together with various indexes of contractile rate. 3. Twitch contraction times and subtetanic to maximum tetanic force ratios were both distributed continuously. "Sag" in tension was not evident in unfused force profiles. Thus these units could not be divided into fast and slow types by the use of traditional contractile rate criteria. 4. Most units were fatigue resistant, with force fatigue indexes (FI) ranging from 0.33 to 1.14. None could be classified as fatiguable (FI less than 0.25). Seven units (28%) fell into the fatigue-intermediate (FI = 0.25-0.75) category, whereas 18 units (72%) had FI greater than 0.75, i.e., they were fatigue-resistant units. However, these units could not be classified by conventional FI and contractile rate criteria, because fatigue-resistant and fatigue-intermediate units had similar contractile rates. 5. Additional FI were calculated to describe changes in contractile rate. During the fatigue test, units behaved in one of three ways, showing 1) little change in either force or rate; 2) contractile slowing during the contraction and relaxation phases, with little or no force loss; or 3) both force and rate reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Exploration of the precision of classifying sudden cardiac death. Implications for the interpretation of clinical trials.

BACKGROUND: As cardiovascular clinical trials improve in sophistication and therapies target specific cardiac mechanisms of death, a more objective and precise system to identify specific cause of death is needed. Ideally, sudden cardiac death would describe patients dying of ventricular tachycardia and ventricular fibrillation. In this context, we explored the precision of current sudden death classification and implications for clinical trials. METHODS AND RESULTS: Deaths were analyzed in 834 patients who received an automatic implantable cardioverter-defibrillator (ICD). Three arrhythmia experts used a standard prospective classification system to classify deaths into accepted categories: sudden cardiac, nonsudden cardiac, and noncardiac. New aspects to this study included analysis of autopsy results and ICD interrogation for arrhythmias at the time of death. All of the patients receiving the ICD previously had documented sustained ventricular tachycardia/fibrillation or cardiac arrest. Of the 109 subsequent deaths in the 834-patient database, 17 (16%) were classified as sudden cardiac. Compared with the nonsudden cardiac and noncardiac categories, sudden cardiac death was more often identified in outpatients (59% versus 10%) and witnessed less often (41% versus 86%; both P < .001). The autopsy information contradicted and changed the clinical perception of a "sudden cardiac death" in 7 cases (myocardial infarction [n = 1], pulmonary embolism [n = 2], cerebral infarction [n = 1], ruptured thoracic [n = 1], and abdominal aortic aneurysms [n = 2]). Interpretable ICD interrogation was available in 53% of the deaths (47% unavailable: buried, programmed off, or other technical reasons). When evaluated, only 7 of 17 "sudden deaths" were associated with ICD discharges near the time of death. CONCLUSIONS: Even in a group of patients with an ICD, deaths classified as sudden cardiac frequently were not associated with ventricular tachycardia or ventricular fibrillation and were often noncardiac. It is possible to create a wide range of sudden cardiac death rates (more than fourfold) using the identical clinical database despite objective, prespecified criteria. Autopsy results frequently reveal noncardiac causes of clinical events simulating sudden cardiac death. ICD interrogation revealed that ICD discharges were often related to terminal arrhythmias incidental to the primary pathophysiological process leading to death.

Cause of Death↗

PubMed1989

The use of sputum cultures in the evaluation of immigrants classified as tuberculosis suspects.

Because of possible deficiencies in the evaluation, based on symptoms and chest roentgenogram review, of new immigrants classified during the visa application process as tuberculosis suspects, a prospective (cohort) and a retrospective (case control) study were done to test the usefulness of routinely obtaining sputum specimens for culture in that setting. In the prospective study, 249 consecutive classified immigrants who were considered on the basis of clinical and roentgenographic findings to have nonprogressive tuberculosis submitted at least two sputums for culture: 13 (5.2%) had at least one culture positive for M. tuberculosis. Immigrants younger than 50 yr of age and refugees from Kampuchea and Laos had a fivefold to tenfold elevated risk of having a positive sputum culture. The cost per case detected of obtaining and processing sputum cultures was estimated to be +1,996 to +2,994. In the case-control study, 37 classified immigrants evaluated from 1981 through 1986 who had sputum cultures positive for M. tuberculosis even though they fulfilled clinical and roentgenographic criteria for nonprogressive tuberculosis served as control subjects. Several demographic, clinical, and roentgenographic factors were associated with an increased risk of being culture-positive: age younger than 50 yr, a positive tuberculin test, report of a cough, and a cavitary lesion on chest roentgenogram. The history of prior receipt of antituberculosis drugs was associated with having a negative culture, including a marked dose-response effect.

Asia, Southeastern↗

PubMed1991

A comparison of taxonomic systems for classifying homeless men.

The present study compared the relative merits of two taxonomic systems for classifying homeless men. One system classified homeless men based on their past history of psychiatric disability. The other system classified individuals on the basis of their current psychiatric impairment. Both classification systems displayed significant discriminating power using a set of predictor variables that included demographic variables, childhood happiness, current life satisfaction, social support, stressful life events, and history of homelessness. Based on the percentage of correct classifications the system based on current impairment was superior to the system based on past history.

Demography↗

PubMed2026

A cfDNA fragmentomics classifier for noninvasive differentiation of benign and malignant renal masses.

Noninvasive differentiation of malignant and benign renal masses remains a major clinical challenge, particularly for radiologically indeterminate lesions. Here, we developed and validated a plasma cell-free DNA (cfDNA) fragmentomics-based machine learning classifier for renal mass characterization. The model was trained on 331 participants (171 cancer, 160 benign) and independently validated on 144 participants (73 cancer, 71 benign). Three cfDNA fragmentation features, including copy number variation (CNV), fragmentation-based methylation (FRAGMA), and nucleosome footprint (NF), derived from low-pass whole-genome sequencing, were integrated into an ensemble framework. The model achieved strong discriminative performance, with area under the curve (AUC) values of 0.956 in the training cohort and 0.946 in the validation cohort, outperforming individual feature-based models. At a predefined operating threshold corresponding to 90% sensitivity, specificity reached 0.90 and 0.87, respectively. Notably, most cancer samples exhibited low tumor fraction (TF < 3%), yet the model maintained robust performance in low-TF samples (AUCs: 0.952 and 0.941, respectively). Performance remained consistent across tumor stage, grade, and histological subtypes. The classifier also demonstrated potential clinical utility in diagnostically challenging settings, including lipid-poor angiomyolipoma and oncocytoma, with 12 of 13 oncocytoma samples correctly classified in an independent cohort. In addition, the model correctly identified 85.3% of benign masses > 4 cm, for which surgical intervention is more commonly considered, and 84.6% of malignant tumors ≤ 4 cm, for which management can be challenging. Collectively, these findings support cfDNA fragmentomics as a promising noninvasive liquid biopsy approach for renal mass evaluation and clinical decision-making.

Humans↗

PubMed1992

A neural network chromosome classifier.

We present a chromosome classifier for automated karyotyping of banded chromosomes which uses a multi-layer perception neural network. Two network configurations have been investigated. The resulting classifiers have been trained and tested on data from three different data sets covering a range of data quality. Classification results compare very favourably with those obtained using a highly optimised parametric classifier.

Chromosomes↗

PubMed1986

Within- and between-person variation in dietary surveys: number of days needed to classify individuals.

The variation from day to day, between individuals and within individuals, in the consumption of energy and a variety of nutrients is presented for two groups of executive grade civil servants aged 40-49, numbering 83 and 68 and working in London in 1970-1971, and for 98 drivers and 83 conductors aged 30-67 of London's double decker buses in 1958-1967, a total of 332 men. Each man weighed and recorded his food for at least a week. The reliability with which these men could be classified into extreme thirds of the distribution of individual consumption of the various 'nutrients' or foods on the basis of a single day's or of several days' measurement was calculated. The number of days of measurement required to achieve a given reliability of classification into extreme thirds of the distribution was also estimated. The key is the ratio of the 'between-person' to the 'within-person' variance for the particular nutrient. A diagram is presented of how this ratio is related to the number of days of survey required for a given reliability. Nutrients fall into three main groups--those consumed in relatively large amounts each day (eg protein, fat), those found in moderate amounts in many or most foods but in very large quantities in a few foods (eg dietary cholesterol, calcium), and those which may not be consumed at all by some people but are taken in large quantities by others (eg alcohol). The number of days of survey required for 80 per cent reliable classification of individuals varies from 2 or 3 days for some nutrients like sugar or total carbohydrates to 2 or 3 weeks for others like dietary cholesterol or the ratio of polyunsaturated fatty acids to saturated fatty acids. One day's survey classified no nutrients with 80 per cent reliability in our data, whereas one week's survey classified most nutrients with this reliability or better, although for a few the figure is lower. The precision of a week's survey is also shown in absolute quantities such as grams as distinct from thirds of the distribution. The relevance of these observations to the use of the results of 24-hour surveys in population surveys and correlation and regression analysis is discussed.

Adult↗

PubMed1984

Stabilized binary hierarchic classifier in cytopathologic diagnosis.

A binary tree classifier (BTC) algorithm for computer-assisted cell image analysis has been developed that overcomes the problem of overtraining due to inadequate sample size/dimensionality ratio at the higher-order nodes of a hierarchic decision structure. Provisions have been introduced that ensure that decision rules created at each node are based on samples representative of the subpopulation routed to the node. These provisions eliminate problems caused by truncation effects resulting from the application of decision rules at preceding decision nodes. The BTC performs better than do single-stage classifiers in situations where the categories' mean vectors are not well separated and no equality of covariance matrices exists. In applications in which noticeable deterioration of classifier performance on test-set data is common, the classification success rate of the BTC algorithm is not statistically significantly different between the training-set and test-set data.

Cells↗

PubMedDate not supplied

Single step immunophenotyping of acute leukemias not classifiable by standard morphology and cytochemistry: a practical approach.

BACKGROUND: Immunophenotyping is at present a useful aid and often an essential step for correct diagnosis of acute leukemia and for this purpose some investigators have proposed several immunomarker panels. This approach is particularly important in the differential diagnosis of acute leukemias not classifiable by standard morphology and cytochemistry. METHODS: We have tested peripheral blood and/or bone marrow samples from 125 patients not classifiable by FAB criteria. In all the cases, the reactivities of the same panel of 17 monoclonal antibodies were analyzed by flow cytometry, using both single and double fluorescent labeling. RESULTS: Of the 125 patients investigated, 75 (60%) were classifiable as ALL, 58 as B-lineage ALL and 17 as T-lineage ALL; 33 (26.4%) as AML, of which 2 M7; 6 (4.8%) as biphenotypic and 11 (8.8%) as immunophenotypically undifferentiated. CONCLUSIONS: From a critical analysis of our cases and a review of the literature, we suggest that a panel of 9 monoclonal antibodies (CD2, CD5, CD7, CD10, CD19, CD20, CD13, CD33, CD41), is sufficient for reliable, rapid and reasonably low cost typing of acute leukemia, useful for an immediate therapeutic decision.

Acute Disease↗

PubMed1995

Sagittal plane correction in "King-classified" idiopathic scoliosis patients treated with Cotrel-Dubousset instrumentation.

INTRODUCTION AND AIM OF THE STUDY: Whereas Harrington instrumentation (HI) has demonstrated satisfactory frontal plane correction, sagittal plane realignment is difficult. Sagittal plane control is reported to be easier with Cotrel-Dubousset instrumentation (CDI). This study was undertaken to determine if in our series sagittal realignment was achieved with CDI in idiopathic curves classified according to King. MATERIAL AND METHODS: Ninety-seven patients with idiopathic scoliosis classified according to King and treated with CDI underwent coronal and sagittal plane analysis by an unbiased observer. The sagittal curves were measured with the Cobb method from T4-T12 (normals: +25 to +40 degrees) and L1-L5 (normals: -40 to -55 degrees). The thoracolumbar junction (TJ) was divided into an upper TJ (T10-T12) and a lower TJ (T12-L2) with normals between 0 and +10 degrees for the former and 0 and -10 degrees for the latter. RESULTS: In all types of scoliosis with associated thoracic hypokyphosis a significant realignment could be achieved, ranging from 8 degrees in King 1 and 3 curves to 19 degrees in King 4 curves. In normokyphotic curves no significant changes of the thoracic spine were measured postoperatively. Concerning the upper TJ, pathological lordosis was corrected by 7 degrees on the average, whereas correction of kyphosis ranged from 8 to 18 degrees Cobb. Pathologic kyphosis and hyperlordosis of the lower TJ showed a mean correction of 7 degrees and 11 degrees, respectively. There was no significant direct influence of CDI on the sagittal plane of the lumbar spine. CONCLUSION: The data from this study suggest that correction in the sagittal plane can be achieved with CDI in King-classified scoliotic deformities.

Follow-Up Studies↗

PubMed1979

Newer experimental methods for classifying depression. A report from the NIMH collaborative pilot study.

A total of 83 patients receiving diagnoses of major depressive disorder in the pilot phase of the National Institute of Mental Health Collaborative Study of the Psychobiology of Depression were used to evaluate two newer methods of classifying depressive disorders on the basis of family history or course. A third subtype based on family history, nonfamilial depression, was compared with the two subtypes originally proposed by Winokur and colleagues, pure depression and depression spectrum diseases. The system for classifying depressions on the basis of course and antecedent disorder, primary vs secondary depression, was also compared. These data from the pilot study indicate that two newer systems for classification have some predictive, construct, and content validity, but both are in need of further investigation before they become accepted methods for the classification of depressive disorders.

Depression↗

PubMed1996

Classifying visual field data.

We develop a prediction model for classifying an eye according to glaucoma status based on its visual field. We develop measures of both diffuse and localized defects in the visual field as potential predictors of glaucoma. To identify predictors of abnormal fields, we must describe the variability in the fields of normal eyes, hence we first model the mean, variance and correlation structures of normal fields with use of generalized estimating equations. The best measures of diffuse loss include a field's mean level, contrasts of the upper and lower halves, and contrasts of the nasal and temporal halves. Local loss is measured by the depth, area, volume and location of the field's largest defect. We develop logistic regression models to classify eyes as having glaucoma or not. We present ROC curves of the results that are highly competitive with current clinical methods of classification.

Adult↗

PubMed1981

The look-up table: a classifier for cell sorters.

Currently used classifiers for flow cell sorters are described and the look-up table is introduced as such. An experimental setup of a look-up table classifier added to a commercially available cell sorter, under control of a microcomputer is described. The contents of the look-up table are obtained from contours of regions of interest. These regions are defined by the user who designates the areas on a video color display of the bivariate flow data. Since most cell clusters form elliptic or ovoid shapes in a multi-dimensional feature space this method enables a better matching of window shapes to cluster outlines, compared to conventional sort decision circuitry.

Cell Separation↗

PubMed1981

The effect of abnormal cell proportion on specimen classifier performance.

In two previous papers we developed formulas relating the performance (error rates) of a two-class specimen classifier to the performance of a preceding two-class classifier and the number of cells examined (K. R. Castleman and B. S. White, Analytical and Quantitative Cytology 2:117, 1980 and K. R. Castleman and B. S. White, Cytometry 1:156, 1980.). This analysis assumed a certain proportion (p) of abnormal cells on an abnormal specimen. In this paper we examine what happens when a system designed assuming one value of p is presented with a positive specimen having a different abnormal cell proportion. We show that the specimen false negative error rate increases dramatically as p decreases below the design value, and conversely. This suggests that the specimen classification performance of a particular system should be quoted only with reference to the abnormal cell proportion of the specimens used for testing.

Cell Separation↗

PubMed1987

Improved model for specimen classification based on single-cell classifiers.

We consider probabilistic models for specimen classification procedures based on systems which classify individual cells as normal or abnormal. The models which we consider generalize those discussed previously by Castleman and White (Anal. Quant. Cytol. 2:117-122, 1980; Cytometry 2:155-158, 1981) and by Timmers and Gelsema (Cytometry 6:22-25, 1985). In particular, they include the biologically plausible possibility that the specimen contains cells which are intermediate between the extremes of normal and abnormal. We find that if these additional cells occur differentially in normal and abnormal specimens, then specimen classification can become substantially more efficient when the cell classifier has different error rates for these cells.

Cervix Uteri↗

PubMed1996

The use of amino acid patterns of classified helices and strands in secondary structure prediction.

Elements of secondary structure from known protein three-dimensional structures have been classified with respect to their environments in tertiary structures. The size of the solvent-inaccessible face of an alpha-helix and the accessibility patterns on the two sides of a beta-strand have been used to classify the secondary structures. For each class, we have derived a sequence template, giving the amino acid propensity at each position. A prediction is made by calculating the compatibility of segments of polypeptide sequence against templates for each type of secondary structure. This method predicts not only position of a secondary structure in a protein sequence but also the orientation of the secondary structure with respect to the core of the protein tertiary structure. A jack-knife test is applied to 78 proteins of known structure solved at better than 2 A resolution. It shows that this method predicts between 13% and 17% better than the methods of Lim, GOR and Chou and Fasman at the level of secondary structure. The orientations of inaccessible faces are predicted within 50 degrees of correct value for about two-thirds of alpha-helices.

Adenylate Kinase↗