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Results for “External validity”

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At least 649 records · Page 36Linked to original sources
PubMed2004

Reliability and validity of functional neuroimaging techniques for identifying language-critical areas in children and adults.

Advances in neuroimaging technologies over the last 15 years have prompted their relatively widespread use in the study of brain mechanisms supporting language function in children and adults. We reviewed reliability and external validity studies of 3 of the most common functional imaging methods, functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and positron emission tomography (PET). Although reliability and validity reports for fMRI are generally quite favorable, significant variability was found across studies with respect to methodology, preventing in some cases either the assessment of the reliability of individual datasets, or cross-study comparisons. Reliability and validity reports of MEG are strong, yet methodological questions regarding optimal modeling techniques remain. PET investigators report good concordance of language maps with data from more invasive brain mapping techniques, but its use of radioactive tracers and poorer spatial and temporal resolution make it the least optimal of the 3 methods for language mapping. Investigations of the cortical networks supporting language function during development and into adulthood should be viewed in the context of the validity and reliability of the methods used, with careful attention to details regarding the methodologies employed in the acquisition and analysis of statistical maps.

Aging↗
PubMed1991

Dimensional measurement of seasonal variation in mood and behavior.

Recent epidemiologic studies have found that the behaviors that characterize seasonal affective disorder (SAD) show seasonal variation in 92%-95% of the general population, suggesting that seasonal variation in behavior and mood is a continuous, dimensional variable extending throughout the general population, defined at the upper extreme by SAD. Research into population seasonality will require a dimensional measure of seasonal variation in mood and behavior that produces a broad, finely graded distribution of seasonality scores sensitive to individual differences throughout the entire range of scores. Accordingly, the Inventory of Seasonal Variation (ISV) was developed as such a measure. This study demonstrated that the ISV has high internal structural validity and is highly sensitive to individual differences in seasonality across its entire range of scores in the normal population. This latter characteristic is not shared by other existing measures of seasonality. Initial external validity of the ISV was supported in that the mean of ISV scores of a SAD sample was found to lie at the 97th percentile of the normal population of scores. Analysis of ISV scores revealed that a winter pattern of seasonality was reported by over 95% of subjects, a pattern that was more pronounced in women than men, while a summer type of seasonality was reported by only 0.6% of the general population.

Adult↗
PubMed1993

Predictive equations for basal metabolic rates of Indian males.

The article deals with the generation of a prediction equation for basal metabolic rate (BMR) of well-nourished Indian males, from prospective measurements on 121 males, using a single validated technique. The equation related BMR to simple measures such as weight (WT) and age, and was given by: BMR (kJ/d) = 48.7 * WT-14.1 * AGE + 3599. The equation was internally as well as externally validated against other Indian databases and the net differences of < 2% (100 kJ/d), were non-significant. Interestingly, American BMRs were predicted to within 0.5% (28 kJ/d) by this equation, while European BMRs were significantly higher than predicted by 6.3% (433 kJ/d). Similar results were obtained on validating the American and European data against the equations of C. K. J. Henry & D. G. Rees (1991) Eur J. Clin. Nutr. 45, 177-185. Such results suggest that there are no differences in the BMR of age- and weight-matched Asian Indian males, other tropical populations and Americans. This has implications in the estimation of energy expenditure and hence energy requirements for these populations.

Adolescent↗
PubMedDate not supplied

Perceptions of medical errors by internal medicine residents: development and validation of a new scale.

Efforts to identify the underlying structure of 40 survey items dealing with perceptions of medical errors are reported on the basis of responses from 195 medical residents. Factor analysis revealed that the medical errors perceptions were represented by a 10-factor solution. The external validity of these factors was examined relative to perceptions about the cost of medical errors, the cost of errors to health care, and the need for education and interventions to address errors. Results indicated that 13.9% of the variation in the perceived cost of medical errors and 17.1% of the variation in the perceived need for additional physician education was explained by the factor structure.

Adult↗
PubMed1999

Validation of risk adjustment models for in-hospital percutaneous transluminal coronary angioplasty mortality on an independent data set.

OBJECTIVES: We sought to validate recently proposed risk adjustment models for in-hospital percutaneous transluminal coronary angioplasty (PTCA) mortality on an independent data set of high risk patients undergoing PTCA. BACKGROUND: Risk adjustment models for PTCA mortality have recently been reported, but external validation on independent data sets and on high risk patient groups is lacking. METHODS: Between July 1, 1994 and June 1, 1996, 1,476 consecutive procedures were performed on a high risk patient group characterized by a high incidence of cardiogenic shock (3.3%) and acute myocardial infarction (14.3%). Predictors of in-hospital mortality were identified using multivariate logistic regression analysis. Two external models of in-hospital mortality, one developed by the Northern New England Cardiovascular Disease Study Group (model NNE) and the other by the Cleveland Clinic (model CC), were compared using receiver operating characteristic (ROC) curve analysis. RESULTS: In this patient group, an overall in-hospital mortality rate of 3.4% was observed. Multivariate regression analysis identified risk factors for death in the hospital that were similar to the risk factors identified by the two external models. When fitted to the data set, both external models had an area under the ROC curve >0.85, indicating overall excellent model discrimination, and both models were accurate in predicting mortality in different patient subgroups. There was a trend toward a greater ability to predict mortality for model NNE as compared with model CC, but the difference was not significant. CONCLUSIONS: Predictive models for PTCA mortality yield comparable results when applied to patient groups other than the one on which the original model was developed. The accuracy of the two models tested in adjusting for the relatively high mortality rate observed in this patient group supports their application in quality assessment or quality improvement efforts.

Aged↗
PubMed1987

Stages of adolescent cigarette smoking acquisition: measurement and sample profiles.

A stage model of adolescent cigarette smoking acquisition was developed and an instrument to measure the stages was created. Internal validity was obtained based on principal component analysis, item analysis, and coefficient alpha. Three distinct components were labeled precontemplation, decision-making, and maintenance. The scales had reliability coefficients ranging from .86 to .94. External validity was obtained by relating the scale scores to measures of smoking behavior and intent to smoke. A cluster analysis resulted in nine distinct clusters, including profiles representing precontemplation, contemplation, decision-making, action, and maintenance stages. Further validity was obtained for the clusters by comparing groups on the perceived positive and negative consequences of smoking, and the derived pleasure from smoking.

Adolescent↗
PubMed2005

Derivation and validation of a prognostic model for pulmonary embolism.

RATIONALE: An objective and simple prognostic model for patients with pulmonary embolism could be helpful in guiding initial intensity of treatment. OBJECTIVES: To develop a clinical prediction rule that accurately classifies patients with pulmonary embolism into categories of increasing risk of mortality and other adverse medical outcomes. METHODS: We randomly allocated 15,531 inpatient discharges with pulmonary embolism from 186 Pennsylvania hospitals to derivation (67%) and internal validation (33%) samples. We derived our prediction rule using logistic regression with 30-day mortality as the primary outcome, and patient demographic and clinical data routinely available at presentation as potential predictor variables. We externally validated the rule in 221 inpatients with pulmonary embolism from Switzerland and France. MEASUREMENTS: We compared mortality and nonfatal adverse medical outcomes across the derivation and two validation samples. MAIN RESULTS: The prediction rule is based on 11 simple patient characteristics that were independently associated with mortality and stratifies patients with pulmonary embolism into five severity classes, with 30-day mortality rates of 0-1.6% in class I, 1.7-3.5% in class II, 3.2-7.1% in class III, 4.0-11.4% in class IV, and 10.0-24.5% in class V across the derivation and validation samples. Inpatient death and nonfatal complications were <or= 1.1% among patients in class I and <or= 1.9% among patients in class II. CONCLUSIONS: Our rule accurately classifies patients with pulmonary embolism into classes of increasing risk of mortality and other adverse medical outcomes. Further validation of the rule is important before its implementation as a decision aid to guide the initial management of patients with pulmonary embolism.

Acute Disease↗
PubMed2002

[Scales to measure parents and caretakers satisfaction with the food and nutrition component of Child care Centers].

Two Likert-type scales for measuring parents' and caretakers' level of satisfaction with the food and nutrition services offered at childcare multi-centers in a peri-urban community in Caracas, were developed and validated. An intentional sample of 20 parents and caretakers were interviewed within the naturalistic-constructivist perspective, to capture their perceptions of distinct aspects of the food and nutrition components of the program. Categories emerged from the interviews that served to construct the items for two scales that measure level of satisfaction of parents and caretakers with the food and nutrition aspects of the program. To validate the scales, they were applied to 73 parents and 32 caretakers. Factor and multiple components analysis showed that overall, the scales explained 61% and 69% of the variation in level of satisfaction of parents and caretakers respectively. Confiability measured with Alpha Cronbach coefficient was 0.74 and 0.77 for parents' and caretakers' scales respectively. These results reveal scales that have content validity and good reliability. Besides, the scales detect specific aspects of the food and nutrition service that should be reinforced or modified, to make the Child-care Centers program more effective and efficient. External validation of the scales is recommended, since they provide an instrument capable of capturing useful information for monitoring and evaluating the Child-care Centers program nation-wide, from the perspective of program managers and parents of program users.

Child↗
PubMed2001

Residual mass histology in testicular cancer: development and validation of a clinical prediction rule.

After chemotherapy for metastatic non-seminomatous testicular cancer, surgical resection is a generally accepted treatment to remove remnants of the initial metastases, since residual tumour may still be present (mature teratoma or viable cancer cells). In this paper, we review the development and external validation of a logistic regression model to predict the absence of residual tumour. Three sources of information were used. A quantitative review identified six relevant predictors from 19 published studies (996 resections). Second, a development data set included individual data of 544 patients from six centres. This data set was used to assess the predictive relationships of five continuous predictors, which resulted in dichotomization for two, and a log, square root, and linear transformation for three other predictors. The multiple logistic regression coefficients were reduced with a shrinkage factor (0.95) to improve calibration, based on a bootstrapping procedure. Third, a validation data set included 172 more recently treated patients. The model showed adequate calibration and good discrimination in the development and in the validation sample (areas under the ROC curve 0.83 and 0.82). This study illustrates that a careful modelling strategy may result in an adequate predictive model. Further study of model validity may stimulate application in clinical practice.

Biomarkers, Tumor↗
PubMed2001

Measuring qualitative aspects of preschool boys' noncompliance: the Response Style Questionnaire (RSQ).

Child noncompliance is a core maladjustment factor in current clinical models of aggression and antisocial development. However, little is known about the relations among qualitative aspects of child noncompliance and aggressive maladjustment. The authors developed the Response Style Questionnaire, an instrument designed to measure the multidimensional qualities of child noncompliance, and tested its validity and reliability. Tests of internal validity provided a five-factor solution, featuring distinctions in noncompliance quality between and among skilled noncompliance (verbally skilled and emotionally regulated) and unskilled noncompliance (overt/confrontational, covert/sneaky, and emotionally labile). Theory-driven tests of external validity using peer-adjustment variables as criteria provided discriminant prediction (a) among qualitatively distinct aspects of noncompliance and (b) between noncompliance qualities and rate. Discussion focuses on a modified view of the nature and role of noncompliance in aggressive and antisocial development.

Aggression↗
PubMed2026

Proteomic analysis identifies pathways related to immune dysregulation in patients with hematologic malignancies after COVID-19 infection.

Patients with hematologic malignancies (HMs) are particularly vulnerable to coronavirus disease 2019 (COVID-19) because of underlying immune dysfunction and treatment-related immunosuppression. However, proteomic features associated with different clinical trajectories in this population remain insufficiently characterized. We performed serum proteomic analysis in 40 HM patients with COVID-19 and 15 healthy controls. Compared with controls, HM patients showed impaired immune-related responses during the acute phase of COVID-19. Acute-phase proteomic patterns differed across outcome groups; however, because outcome groups were closely intertwined with initial COVID-19 severity, ICU admission, and systemic illness, and because multivariable adjustment was not performed due to the limited sample size, these patterns should be interpreted as severity- and outcome-associated profiles rather than independent trajectory-specific markers. Fatal cases showed evidence of dysregulated immune activation, whereas patients later classified as having long COVID exhibited broader suppression of immune-related pathways. In addition to immune alterations, pathways related to platelet activation and cardiac-related dysfunction were associated with adverse clinical trajectories. Enzyme-linked immunosorbent assay validation supported the association of selected proteins with outcome groups during acute infection. These findings provide a proteomic overview of COVID-19 in HM patients and offer a basis for future mechanistic studies and larger external validation cohorts.IMPORTANCEPatients with hematologic malignancies are highly vulnerable to severe coronavirus disease 2019 (COVID-19), acute death, and long COVID due to preexisting immune dysfunction. However, the proteomic signatures linked to adverse clinical trajectories remain poorly understood. Our serum proteomic study identifies distinct acute-phase immune profiles associated with different outcomes: broad immune suppression characterizes long COVID, while dysregulated immune activation is associated with fatal cases. Platelet activation and cardiac-related pathways are also linked to poor outcomes. These findings provide key molecular insights for this high-risk population, supporting future biomarker development, risk stratification, and targeted clinical management.CLINICAL TRIALSThis study is registered with ClinicalTrials.gov as NCT05683353.

Humans↗
PubMed2002

[An example of psychometric validation of a mental health questionnaire used at a work place].

Most companies utilize original questionnaires developed by the health-care staff to evaluate their workers' mental health status. To build effective strategies, it is crucial to use proper measures validated psychometrically. We demonstrated the process to evaluate the reliability and validity of the original health questionnaire developed by the health-care team of an industrial company. We used the Beck Depression Inventory-II, and the Job Content Questionnaire as the gold standards for external validation. Out of 21 items in the original health questionnaire, 9 items significantly correlated with depression. From the results of a factor analysis, the 9 items composed 2 independent components out of 5 factors. A subscale which consisted of the 9 items from the original questionnaire was proposed as a screening tool to detect depression, but no items of the original questionnaire correlate with the Support subscale nor the Job Control subscales of the JCQ. Just one item correlated with the Job Demand subscale of the JCQ. Additional information should be added to the original questionnaire to evaluate Job Stress based on the Karsek's Job Demand-Control-Support model.

Humans↗
PubMed1986

The assessment of health policy changes using the time-reversed crossover design.

The time-reversed crossover design is a quasi-experimental design which can be applied to evaluate the impact of a change in health policy on a large population. This design makes use of separate sampling and analysis strategies to improve the validity of conclusions drawn from such an evaluation. The properties of the time-reversed crossover design are presented including the use of stratification on outcome in the sampling stage, which is intended to improve external validity. It is demonstrated that, although this feature of the design introduces internal validity threats due to regression toward the mean in extreme-outcome strata, these effects can be measured and eliminated from the test of significance of treatment effects. Methods for within- and across-stratum estimation and hypothesis-testing are presented which are similar to those which have been developed for the traditional two-period crossover design widely used in clinical trials. The procedures are illustrated using data derived from a study conducted by the United Mine Workers of America Health and Retirement Funds to measure the impact of cost-sharing on health care utilization among members of its health plan.

Costs and Cost Analysis↗
PubMed2026

DNA methylation biomarkers for early detection of ovarian cancer.

Ovarian cancer (OC) remains difficult to detect at an early stage, and current screening approaches using CA125 and transvaginal ultrasonography have not demonstrated sufficient benefit for population screening. DNA methylation is a promising biomarker class because epigenetic alterations may arise early in tumourigenesis, can be detected in circulating cell-free DNA (cfDNA), and may provide tissue-of-origin information. This review critically evaluates recent evidence on DNA methylation biomarkers for early OC detection. PubMed/MEDLINE, Web of Science, and Scopus were searched for studies published between January 2020 and September 2025, supplemented by selected earlier studies of biological or methodological relevance. Evidence was synthesised across single-gene biomarkers, multi-locus panels, genome-wide signatures, assay platforms, and machine-learning classifiers, with emphasis on early-stage performance, histological representation, comparator populations, analytical methodology, and validation design. Single-gene markers such as BRCA1, RASSF1A, OPCML, HOXA9, and HIC1 show variable performance, while multi-gene and classifier-based approaches generally provide stronger discrimination. However, many studies remain limited by retrospective case-control designs, small FIGO stage I-II subsets, predominance of serous disease, and insufficient prospective validation. Integration with CA125 may improve sensitivity but can reduce specificity, which is critical in low-prevalence screening. Clinical translation will therefore require minimal and reproducible methylation signatures, standardised low-input cfDNA workflows, rigorous external validation, and prospective longitudinal evaluation in intended-use populations.

Humans↗
PubMedDate not supplied

Dimensional diagnosis of depression: adding the dimension of course to severity, and comparison to the DSM.

It has long been debated whether depression is best classified with a categorical or dimensional diagnostic system. There has been surprisingly little discussion, however, of what the contents of a dimensional classification should include, with most studies employing a single dimension based on symptom severity. The present study explored whether a dimension based on prior course of depression increases the validity of a dimensional model based on symptom severity alone and whether the two dimensions combined improve upon the present categorical system (DSM). The sample consisted of 133 patients with a broad spectrum of depressive diagnoses. External validators included family history of mood disorder, assessed using the family history method, and course over a 6-month prospective follow-up period. Prior course contributed significant incremental validity over and above symptom severity in predicting subsequent course and family history of mood disorder. However, the linear combination of symptom severity and prior course provided only a minimal increase in predictive power over and above the DSM diagnoses of major depressive disorder (MDD) and dysthymia.

Adult↗
PubMed1994

Multidimensional assessment of acute and long-term effects in antidepressant drug trials.

Contrasting the findings from pharmacoepidemiological studies with the status of registration of new compounds and the legal process of reviewing the old compounds indicates a crisis of the preclinical and clinical investigations of "antidepressants". Within the last two decades, the development of more and more formalized guidelines and regulations for the performance of clinical drug trials could be observed. Certainly, this has resulted into an improved internal validity of the findings. On the other hand, there appears to be a broad consensus among practising psychiatrists that published findings of clinical trials often do not concur with the experiences of psychiatric practice indicating unsatisfactory external validity. With regard to the aim of optimizing the antidepressant therapy and to lower the costs for mental health care, it appears to be of particular importance to test the real effectiveness of an "antidepressant" as close as possible to its use in practice. (To avoid misunderstandings: This does not mean to ask for more so-called "naturalistic" study designs!) It is self-evident that also in the future controlled studies, particularly vs. placebo, cannot be dispensed with. However, more promising for a relevant assessment of old and new substances would be the use and development of suitable mathematical procedures, which might imply re-evaluations and re-classifications of already published findings; furthermore, it seems essential also to integrate the existing experiences of psychiatrists in hospitals and in private practice.(ABSTRACT TRUNCATED AT 250 WORDS)

Antidepressive Agents↗
PubMed1989

Iron deficiency and behavior: criteria for testing causality.

The association between iron deficiency and poor behavioral-test performance is well established. The question of causality, however, remains unanswered. This paper presents the essential criteria for a valid test of causality. Internal validity is examined in terms of positive and negative findings. Plausibility of the findings requires analyzing the congruency of the results; for example, those who respond to the iron treatment are also those who respond behaviorally. External validity describes the extent to which inferences may be made about other populations or circumstances.

Behavior↗
PubMed1999

[Evidence-based and science-based medicine].

Routine medical practice is an admixture of scientific knowledge, uncontrasted physiopathological deduction and intuition based on personal experience. Evidence-based medicine is a new approach to medical practice that is based on appropriately contrasted data and includes the following steps: 1) accurately define the problem we are dealing with, 2) investigate the medical literature efficiently, and 3) select the best, relevant studies and apply the corresponding norms to the evidence. In turn, the application of the corresponding norms to the evidence includes the following aspects: 1) determine if the results of the study are valid; i.e., evaluate the scientific quality of the article, 2) determine the magnitude of the results; i.e., establish is they are clinically relevant, and 3) evaluate their application to the point at issue; i.e., test the external validity of the study. The drawbacks of evidence-based medicine include its insufficient concern for basic research, its disregard for physiopathological hypotheses, and the naïve inductivism of epidemiology-based medical practice. Undoubtedly, evidence-based medicine provides advantages for the medical practice and underscores the importance of data and statistical procedures. This new paradigm, however, should not set aside the traditional, hypothetical-deductive approach.

Clinical Medicine↗