Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “stratification”

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
PubMed2002

The influence of thermal stratification on the hydraulic behavior of waste stabilization ponds.

Thermal stratification, which is characterized by a high vertical thermal gradient, is usually observed in deep lakes. However, although waste stabilization ponds have small depths, their high turbidity provides favorable conditions for the occurrence of this phenomenon, mainly during summer. During that time of the year, the layers nearest to the surface concentrate a larger amount of thermal energy compared to the deeper layers, which results in a temperature difference between the surface and the bottom of the pond. As a consequence a density profile appears, with the less dense layers located at the surface of the pond and the densest ones close to the bottom. This stratification in the water column induces alterations in the flow pattern and a decrease of the useful volume of the pond. This paper presents a mathematical model developed to forecast the conditions of thermal stratification in waste stabilization ponds and the volume actually used for wastewater treatment. With these values it is possible to correct the average residence time of the liquid in the pond. The theoretical results were compared with experimental observations, and maximum differences of 15% between the calculated and observed temperature profiles were found.

Forecasting↗
PubMed2002

[Stratification of arrhythmia risk in infarction: reflexions in the light of large trials].

The identification of patients at higher risk of life-threatening ventricular arrhythmias after myocardial infarction still represents a clinically relevant problem, particularly after results of recent studies which support the efficacy of implantable cardioverter defibrillator (ICD) in reducing total mortality in patients with a previous myocardial infarction and left ventricular dysfunction, with and without additional risk markers. However, owing to the high cost of ICD therapy, an effective arrhythmic risk stratification may be desirable. The low diagnostic accuracy reported by various studies using single risk stratifiers (either invasive and non invasive) suggested a combined use of multiple parameters in order to improve the predictive power of the risk stratification algorithms. This approach, that takes into account the multifactorial genesis of malignant ventricular arrhythmias, has been demonstrated to be able to identify subgroups of patients at very high arrhythmic risk. In particular, a two-level algorithm based upon the selection of candidates to electrophysiologic study among patients with abnormal non-invasive testing, showed itself as a particularly effective tool for identification of such patients. In this paper the Authors summarize most recent results on the risk stratification protocols and the use of ICDs and provide an operative algorithm that keeps into account either aggressive and moderate approaches to patients surviving a myocardial infarction.

Arrhythmias, Cardiac↗
PubMed2003

Impact of carotid intima-media thickening on risk stratification in elderly hypertensives.

BACKGROUND: It has been shown that aging and arterial hypertension are both associated with an increased prevalence of carotid structural abnormalities, such as intima-media (IM) thickening or plaques, which are a powerful independent predictor of cardiovascular (CV) events. We investigated the impact of carotid IM thickening in profiling the absolute CV risk stratification according the 1999 World Health Organization/International Society of Hypertension (WHO/ISH) guidelines in elderly hypertensive patients. METHODS: Two hundred and thirty untreated elderly patients (>65 years) referred to our outpatient hospital clinic were included in the study. They underwent the following procedures: (i) medical history, physical examination and clinic blood pressure measurement; (ii) routine blood chemistry and urine analysis; (iii) electrocardiogram. The risk was initially stratified according to the routine procedures indicated by WHO/ISH guidelines and subsequently reassessed by adding the results of carotid ultrasonography (IM thickening as diffuse IM thickness >0.9 and <1.3 mm). RESULTS: According to routine classification 56% (=129) were medium-risk patients, 29% (n = 67) high-risk and 15% (n = 34) very-high-risk patients. The overall prevalence of carotid IM thickening was 54% (49% in medium-risk vs 60% in high or very high-risk patients, p < 0.05). A marked change in risk stratification was observed when IM thickening was taken in consideration: medium-risk patients decreased to 29% and high-risk rose to 56% (p < 0.01). CONCLUSIONS: Ultrasound assessment of large artery damage is extremely useful for a more accurate estimate of global CV risk in elderly hypertensives, because stratification based on diagnostic routine procedures can underestimate the overall risk in a large fraction of medium-risk subjects.

Age Factors↗
PubMed2003

Critical race theory speaks to the sociology of mental health: mental health problems produced by racial stratification.

The sociology of mental health focuses on the epidemiology, etiology, correlates, and consequences of mental health (i.e., psychiatric disorder and symptoms, psychological distress, and subjective well-being) in an attempt to describe and explain how social structure influences an individual's psychological health. Critical race theory describes and explains iterative ways in which race is socially constructed across micro- and macro-levels, and how it determines life chances implicating the mundane and extraordinary in the continuance of racial stratification (i.e., racism). This paper invoked critical race theory to inform the sociology of mental health's approach to studying race and mental health by conceptualizing five hypothetical mental health problems that could exist because of racial stratification. These problems were: (1) nihilistic tendencies, (2) anti-self issues, (3) suppressed anger expression, (4) delusional denial tendencies, and (5) extreme racial paranoia. Mental health problems such as these and undocumented others can only be recognized given awareness of the social and personal implications of racial stratification.

Humans↗
PubMed2004

Robustness of case-control studies of genetic factors to population stratification: magnitude of bias and type I error.

Case-control studies of genetic factors are prone to a special form of confounding called population stratification, whenever the existence of one or more subpopulations may lead to a false association, be it positive or negative. We quantify both the bias (in terms of confounding risk ratio) and the probability of false association (type I error) in the most unfavorable situation in which only one high-risk subpopulation is hidden within the studied population, considering different scenarios of population structuring and varying sample sizes. In accord with previous work, we find that the bias is likely to be small in most cases. In addition, we show that the same applies to the associated type I error whenever the subpopulation is small in proportion. For instance, when the hidden subpopulation makes up 5% of the entire population, with an allelic frequency of 0.25 (versus 0.10) and a disease rate that is double, then the estimated bias is 1.07 and the type I error associated with a sample of 500 cases and 500 controls is 8% (instead of 5%). We also show that the type I error is substantially greater for a rare allele (frequency of 0.1) than for a common allele (frequency of 0.5) and analyze the pattern of increase of vulnerability to stratification bias with sample size. Based on our findings, we may therefore conclude that with moderate sample sizes the type I error associated with population stratification remains very limited in most realistic scenarios.

Bias↗
PubMed2004

Improved stratification of perioperative cardiac risk in patients undergoing noncardiac surgery using new indices of dobutamine stress echocardiography.

OBJECTIVES: Prediction of perioperative cardiac events associated with noncardiac surgery remains difficult in patients whose functional capacity cannot be evaluated by exercise testing. Dobutamine stress echocardiography (DSE) has been used in these patients to improve risk stratification, but the results of standard DSE provide only a binary index of risk (positive or negative). Two new semiquantitative indices of DSE (semi-DSE) were retrospectively examined to determine the prediction of perioperative cardiac events compared to standard DSE. METHODS AND RESULTS: Clinical assessment of cardiac risk factors and standard DSE were performed safely in 122 consecutive patients (73 men, 49 women) undergoing noncardiac surgery. Preoperative revascularization was performed in 12 patients. The perioperative cardiac events consisted of 2 deaths, 4 cases of heart failure, and 2 cases of angina pectoris. For the semi-DSE indices, the extent of ischemia was indexed as the number of wall segments (SEG) displaying biphasic or worsening segmental wall-motion score, and the severity of ischemia (SI) was indexed as the sum of the differences in wall-motion scores between peak stress and rest divided by the number of affected segments. The optimal cut-off values of these indices for predicting cardiac events were 4.0 for SEG and 1.0 for SI. The risk stratification was further refined by these indices (high-, moderate-, and low-risk groups). The diagnostic accuracy of the semi-DSE indices, evaluated by the area under the receiver operating characteristic curves, was better than that of standard DSE (p < 0.001). CONCLUSIONS: Semi-DSE may improve cardiac-event risk stratification compared to standard DSE in patients undergoing noncardiac surgery whose functional capacity cannot be evaluated by exercise stress testing.

Aged↗
PubMed1992

[Risk stratification in patients recuperating from acute myocardial infarct. How useful is it?].

The author intended to discuss the individual prognostic value of some best known risk stratification variables after Acute Myocardial Infarction (AMI), whose tests have a low diagnostic accuracy due to high risk individual variations, emphasizing the statistic errors of using one single risk variable on post AMI risk stratification schemes. Some epidemiologic data about AMI survivors are reviewed and the author concludes by emphasizing the importance of using more AMI population characteristics on post AMI risk stratification schemes.

Arrhythmias, Cardiac↗
PubMedDate not supplied

[Risk marker stratification in coronary acute syndromes].

Acute coronary syndromes have a heterogeneous clinical presentation with a broad spectrum for mortality and adverse events. It is mandatory to identify high risk groups for percutaneous coronary intervention and intensive antithrombotic treatment or common risk for standard treatment. In contemporaneous medicine it is important to get adequate risk stratification because the impact of hospitalary costs, antithrombotic and reperfusion treatment on health systems. The current pathophysiology of atherosclerosis is moving from a disease secondary to cholesterol deposit, to an inflammatory disease. In the stratification process, familiar history, chest pain, ST dynamic abnormalities, left ventricular wall motion abnormalities, all have predictive value. The association of indirect endothelial dysfunction, micro or macronecrosis and ventricular dysfunction markers increase this value. In our experience a close relationship among abnormal fibrinolysis, inflammation and anticoagulation proteins with adverse events has been proved in acute coronary syndromes. Other interesting finding--for it accessibility--in acute myocardial infarction under coronary percutaneous intervention is persistent ST elevation, leukocytes and fibrinogen predictive value. In population allelic polymorphisms -455A and -148T and fibrinogen ( >450 mg/dL) were associated with coronary disease. These polymorphisms improve risk stratification of coronary disease to establish a better secondary prevention and treatment.

Acute Disease↗
PubMed2005

The effect of seed source, light during germination, and cold-moist stratification on seed germination in three species of Echinacea for organic production.

Organic production of one of the most popular botanical supplements, Echinacea, continues to expand in the U.S. Echinacea seeds typically show a high degree of dormancy that can be broken by ethephon or gibberelic acid (GA), but these methods are currently disallowed in organic production. In order to determine the efficacy of non-chemical seed treatments, we evaluated the effect of varying seed source and supplying light, with and without cold-moist stratification, on seed germination of the three most important medicinal species of Echinacea, E. angustifolia DC, E. purpurea (L) Moench, and E. pallida (Nutt.) Nutt. Treatments included cold-moist stratification under 24 h light, 24 h dark, and 16/8 h light/dark to break seed dormancy. We found that germination was greater in the E. purpurea and E. pallida seeds from a commercial organic seed source compared to a public germplasm source. When seeds were not cold-moist stratified, 16-24 h light increased germination in E. angustifolia only. Echinacea angustifolia, E. purpurea, and E. pallida seeds that were cold-moist stratified under 16-24 h of light for 4 wk had a significantly greater percentage and rate of germination compared to seeds germinated in the dark. Therefore, cold-moist stratification under light conditions is recommended as a method to break seed dormancy and increase germination rates in organic production of Echinacea.

Journal Article↗
PubMed1991

Disability and social stratification.

This paper suggests that, for a variety of reasons, the sociology of social stratification--and, as a consequence, mainstream sociology more generally--has neglected the topic of disability. Using material drawn from a range of sources, it is argued that disability is related in definite ways to social class. Further, it is also argued that disability must be considered as a factor contributing to the production and reproduction of stratification in its own right, independently of class relations. These arguments are further advanced in the course of a more detailed consideration of research evidence concerned with mental handicap. The paper ends with a consideration of the role of non-class factors--specifically social status and citizenship--in the stratification systems of modern industrial societies.

Persons with Disabilities↗
PubMed1985

Prognostic significance of stratification systems in multiple myeloma. I. Risk categories (good and poor risk).

A group of 193 patients with multiple myeloma (MM) consisting of cases treated only symptomatically or by nonsystematic therapy with Cyclophosphamide or Melphalan (1959-76), and of patients given systematic polychemotherapy with intensive supportive treatment (1976-84) were subjected to prognostic analysis of the importance of MM stratification into two categories, poor and good risk. The evaluation included only hitherto untreated patients with MM of the IgG, IgA, and Bence-Jones' types. All the three evaluated stratification systems (ALGB, NCI-SECSG and CALGB) were found in the present study to show a good, equally significant relation to the prognosis of the disease. The survival median of poor risk patients in terms of the used classification system for the 1959-76 subgroup was 5-6 months, for the 1976-84 subgroup 20-22 months. In the good risk category it was 24-27 months in the 1959-76 subgroup and 47-50 months in the 1976-84 subgroup. Permanent validity of the initial prognosis and in the poor risk category safe coverage of patients with a high risk of early death was proved. Good agreement of the studied stratification systems with the clinical staging system of Durie and Salmon [14] (most of the Stage III patients consisted of poor risk patients) was recorded, which, however, was not the case with the staging system of Merlini, Waldenström and Jayakar [27]. The CALGB system is considered the most suited to the needs of clinical practice.

Adult↗
PubMed1977

A study of the relationships between perceived organizational stratification, and individual job satisfaction and adaptiveness in hospital laboratories.

Most studies of organizational stratification have remained largely at the narrative or inferential level. Few attempts have been made to empirically assess the consequences of a status system. This paper sought to examine the proposition that stratification is inversely related to job satisfaction and adaptiveness. Although not overwhelmingly demonstrated, there is presumptive evidence that stratification does have an impact upon the organization. It was concluded that medical technologists prefer a supportive, well-structured environment that provides an opportunity for them, through participation, to maintain a degree of control over their work setting. Practical implications of the findings and recommendations were made.

Adaptation, Psychological↗
PubMed1995

Risk stratification and prediction of sudden death following myocardial infarction.

Accurate and reliable identification of those survivors of acute myocardial infarction who are at high risk of sudden death remain an important and challenging problem. This review summarises the current state-of-the-art of the risk stratification techniques and lists achievements in this field. The review comments in detail on individual factors used in risk stratification. Residual ischemia may be considered as one of the main triggering factors of post-infarction arrhythmia. Depressed left ventricular ejection fraction indicates deterioration of ventricular function. Electrical instability of the myocardium reflects the potential substrate of arrhythmia. Frequent ventricular ectopic activity provides triggers of ventricular tachycardia and/or fibrillation when acting on a suitable substrate. Impaired autonomic status of the heart may lead to the loss of vagal antiarrhythmic protection. Further, the tests used for risk stratification are discussed. Ventriculography provides estimates of left ventricular ejection fraction. Holter monitoring is used for the assessment of ventricular ectopic activity and heart rate variability. Exercise testing is used to address residual ischemia. Programmed ventricular stimulation and the analysis of signal averaged electrocardiograms estimate electrical instability of the myocardium. Baroreflex sensitivity is a measure of cardiac parasympathetic reflexes. The design and results of different experimental and clinical studies which utilised these tests are also discussed.

Autonomic Nervous System↗
PubMedDate not supplied

Stratification of composite restorations: systematic and durable replication of natural aesthetics.

A thorough knowledge of the internal structure of natural dentition provides invaluable information for increasing the aesthetic potential in dental restorations. To achieve the optimal aesthetic results, this knowledge must be integrated in a systematic therapeutic procedure. The learning objective of this article is to guide the practitioner in clinical case analysis, evaluation, and the application of a personalized technique of stratification for each individual case in direct composite restorations. The article evaluates treatment demarcations, differences in composite stratification between anterior and posterior teeth, color selection, and the "sandwich technique." The treatment protocol section discusses the element of reference, which can be either an adjacent natural tooth or provisional restorations, permitting the diagnostic study of a more extensive case. The structure of the element of reference is analyzed as to the enamel, dentin, and incisal edge, and replicated. Since light penetration is different in the anterior and posterior dentition, the color stratification must differ accordingly. The "worn" tooth must be distinguished from the "unworn" tooth. In color selection, the luminosity and saturation of the teeth are evaluated first; tint is selected from the element of reference.

Composite Resins↗
PubMed1996

[Stratification of patients at risk for sudden cardiac death with special reference to the autonomic nervous system].

The autonomic nervous system plays a decisive role in the genesis of sudden cardiac death. During recent years, two noninvasive tests for quantitative assessment of cardiac autonomic tone have become available: analysis of heart rate variability from 24-h ambulatory recordings and determination of baroreflex-sensitivity by means of the phenylephrine method. Numerous experimental and clinical studies suggest that heart rate variability assesses tonic vagal activity whereas baroreflex-sensitivity is considered to reflect phasic or reflex vagal activity. Both methods, however, are not redundant but rather complimentary. An advantage of assessment of baroreflex-sensitivity is represented by the fact that it can be performed under controlled laboratory conditions which yields a good intra- and interindividual comparability of test results. Some retrospective as well as prospective studies have assessed the value of determination of cardiac autonomic tone with respect to risk stratification after myocardial infarction. In general, these studies indicate that the combined assessment of autonomic tone together with left ventricular function yields an improved prediction particularly of the risk of dying due to arrhythmic events. It appears that baroreflex-sensitivity is particularly useful to predict arrhythmic events whereas heart rate variability seems to be linked more to cardiovascular mortality. Preliminary results of the largest prospective study of this kind, the ATRAMI study, indicate that the combined assessment of LVEF and baroreflex-sensitivity considerably improve risk stratification after myocardial infarction. If the final analysis of this trial confirms this, prospective interventional studies should be initiated to evaluate our ability of reducing the risk of sudden death based on noninvasive risk stratification.

Animals↗
PubMed2026

Artificial Intelligence for Diagnosis, Risk Stratification, and Prognosis of Neuroblastoma - A Systematic Review and Meta-Analysis.

PURPOSE: To synthesizes evidence on artificial intelligence (AI) performance in neuroblastoma (NB) diagnosis, risk stratification, prognosis, and genomic characterization. MATERIALS AND METHODS: A systematic review and meta-analysis was conducted following PRISMA 2020 guidelines (PROSPERO: CRD42024539475) across five databases. Meta-analyses used random-effects models with logit-transformed Area Under the Curve (AUCs) and cluster-robust standard errors. AI models were classified as Machine Learning Models (MLM) or Hybrid Nomograms (HN) based on their construction methodology. RESULTS: Of 3,742 articles identified, 53 were included. MLMs demonstrated higher point estimates than radiologists in differential diagnosis (AUC: 0.87 vs. 0.83), though this difference was not statistically significant and carried substantial uncertainty. HNs achieved stronger performance in risk stratification (AUC: 0.87). AI-derived nomograms (AUC: 0.9) and gene signatures (AUC: 0.8) outperformed conventional prognostic markers descriptively. Chemotherapy response prediction remained below clinical utility thresholds across all model types. Only 33.9% of models reported calibration and 24.5% underwent external validation. CONCLUSIONS: AI demonstrates proof-of-concept across multiple NB clinical domains. However, clinical adoption remains premature given persistent gaps in external validation, calibration, dataset size, and pediatric-specific model development. Future studies should test these models prospectively in multicenter pediatric cohorts, ideally through COG or SIOPEN, using shared definitions for diagnosis, risk group, treatment response, and survival outcomes.

Humans↗
PubMed2026

Genome-wide association, polygenic risk scores, and machine learning for chronic post-surgical pain risk stratification: A UK biobank study.

Chronic post-surgical pain is a prevalent and debilitating complication following surgery, representing a clinical challenge. Despite the established heritability of pain phenotypes, large-scale genetic studies remain limited. This study aimed to identify genetic variants associated with chronic post-surgical pain, develop polygenic risk scores, and integrate these with clinical features for risk prediction. UK Biobank data from 47,836 participants (2490 cases and 45,346 controls) were split into training (80%; n = 38,268) and validation (20%; n = 9568) sets prior to analysis. A genome-wide association study was conducted on the training set only, across 19 million variants, and polygenic risk scores were constructed and integrated with clinical features in a logistic regression framework. Two close, rare, imputed signals crossed the genome-wide significance threshold but lacked local linkage-disequilibrium support, while 220 variants crossed the suggestive threshold. In the held-out validation set, cases had higher mean polygenic risk scores than controls (0.138 vs. -0.021; Cohen's d = 0.16, p < 0.001). A logistic regression model integrating clinical features and polygenic risk scores achieved an area under the curve of 0.639 (95% CI: 0.583-0.693), higher than models using either feature set alone. The polygenic risk score for chronic post-surgical pain was among the most important predictors. Risk stratification revealed the top quartile had 3.84-fold higher odds of chronic post-surgical pain than the bottom quartile (95% CI: 2.00-7.37). These findings suggest a possible modest genetic contribution to chronic post-surgical pain. Polygenic risk scores may complement clinical factors in surgical risk stratification. PERSPECTIVE: Chronic post-surgical pain may have a modest genetic contribution. This UK Biobank study identified over 220 variants at suggestive significance and constructed a polygenic risk score that was significantly elevated in cases. A combined clinical-genomic model achieved a 3.84-fold difference in odds across predicted-risk quartiles.

Chronic post-surgical pain↗
PubMed2026

Circulating IGF2BP3 enables risk stratification and predicts treatment response in Ewing sarcoma.

Ewing sarcoma (EWS), the second most common pediatric bone tumor, presents with a markedly heterogeneous clinical spectrum and optimal risk stratification is therefore crucial for improving treatment outcomes. The RNA-binding protein IGF2BP3 is a critical oncogenic driver of EWS malignancy. This study evaluates the clinical utility of circulating IGF2BP3 as a biomarker to predict treatment response and risk of disease progression in patients with EWS. Plasma samples from 60 patients with EWS diagnosed and treated at the IRCCS Rizzoli Orthopedic Institute (Bologna, Italy) were collected at diagnosis before treatment initiation and/or after induction chemotherapy. For 51 of these patients, blood was collected at diagnosis, prior to any treatments. For 25 patients, blood samples were available at diagnosis and before surgical intervention, allowing longitudinal analysis in the same patient. For 9 patients, blood was collected only after preoperative chemotherapy, before surgical intervention. Circulating IGF2BP3 levels were quantified using a highly specific and sensitive ELISA assay. Plasma samples from healthy donors served as controls. IGF2BP3 plasma levels were correlated with IGF2BP3 tumor tissue expression, established clinical risk factors, and cumulative incidence of relapse using univariable and multivariable analyses. Plasma IGF2BP3 levels were significantly elevated in patients with EWS compared with healthy controls, with a subset of patients (22/51, 43.2%) exhibiting clinically relevant concentrations. Circulating IGF2BP3 levels reflected tumor expression of the molecule and provided additional prognostic information beyond standard clinicopathologic features. The prognostic impact of circulating IGF2BP3 was primarily observed in patients with localized disease, in whom elevated levels were identified as a significant adverse prognostic factor for disease-specific survival (hazard ratio, 10.63; 95% CI, 1.27-88.62; P = 0.029). Longitudinal monitoring demonstrated that persistence of IGF2BP3 in plasma after induction chemotherapy was a strong predictor of poor clinical outcomes. Circulating IGF2BP3 represents a valuable biomarker for early risk stratification in EWS, particularly in patients with localized disease. Although this is single-marker assay, the expression of the molecule may impact on the fate of many mRNAs. We present an accurate, simple, cost-effective and easy clinical applicable tool to support risk-adapted therapeutic interventions. The limited number of employed patients warrants the need of larger cohorts for validation.

Humans↗