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Results for “External validity”

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At least 1,081 records · Page 60Linked to original sources
PubMed1998

Worksite physical activity interventions.

BACKGROUND: National objectives for public health have targeted worksite as important settings for interventions to increase physical activity. However, expert reviews reveal no scientific consensus about the effectiveness of worksite interventions for increasing physical activity or fitness. METHODS: We judged the quantity and quality of existing evidence against scientific standards for the internal and external validity of the research design and the validity of measurements. Meta-analytic methods were used to quantify the size of effects expressed as Pearson correlation coefficients (r). Variation in effect was examined in relation to several features of the studies deemed important for implementing successful worksite interventions. Pre-experimental cohort studies were excluded because they are sensitive to secular trends in physical activity. RESULTS: Twenty-six studies involving nearly 9,000 subjects yielded 45 effects. The mean effect was heterogeneous and small, r = 0.11 (95% CI, -0.20 to 0.40), approximating 1/4 S.D., or an increase in binomial success rate from 50% to 56%. Although effects varied slightly according to some of the study features we examined, effects were heterogeneous within levels of these features. Hence, the moderating variables examined did not explain variation in the effects (P > 0.05). The exception was that effects were smaller in randomized studies compared with studies using quasi-experimental designs (P < 0.05). CONCLUSIONS: Our results indicate that the typical worksite intervention has yet to demonstrate a statistically significant increase in physical activity or fitness. The few studies that have used an exemplary sample, research design, and outcome measure have also yielded small or no effects. The generally poor scientific quality of the literature on this topic precludes the judgment that interventions at worksites cannot increase physical activity or fitness, but such an increase remains to be demonstrated by studies using valid research designs and measures.

Adolescent↗
PubMed2003

Natural history of systemic sclerosis and the assessment of disease activity, severity, functional status, and psychologic well-being.

The natural history of systemic sclerosis (SSc) is best understood by dividing patients into those who have diffuse cutaneous involvement or limited cutaneous involvement; each of these subsets can be further divided into early and late disease. Each of these four stages has characteristic clinical and laboratory features. Findings that are typical of inflammation (eg, tendon friction rubs, carpal tunnel syndrome) appear in early disease, whereas those that represent vascular and other organ structural changes (eg, joint contractures, telangiectasias, calcinosis) occur predominantly in late disease. Preliminary methods to measure SSc activity and damage have been published but require external validation and refinement. Among patient-completed instruments that assess functional status, the disability index of the Health Assessment Questionnaire is the most widely used and has face and construct validity, reliability, and sensitivity to change and is an accurate predictor of survival.

Adaptation, Psychological↗
PubMedDate not supplied

Intravascular ultrasound estimation of arterial stenosis.

The evaluation of the degree of reduction in the cross-sectional area of an artery has important pathophysiologic and therapeutic implications. Currently, no technique can easily provide this information. In this in vitro study we evaluated the potential of a new imaging technique, intravascular high frequency ultrasound angioscopy, in the estimation of percentage of cross-sectional area stenosis of an artery. To do this, we compared intravascular high frequency ultrasound to previously-validated external high frequency ultrasound and to anatomic estimation of arterial stenosis. Using a prototype intraluminal imaging catheter with a 20 MHz ultrasound transducer at its tip, we imaged 20 arterial segments of various size (15 to 90 mm2 lumen area by anatomy) in the control state and after experimental stenosis. These arterial segments were also imaged by external high frequency ultrasound. Lumen areas were measured from calibrated ultrasound images in the control state and after stenosis, and percentage of cross-sectional area stenosis was calculated. These data were compared to the percentage of area stenosis derived from calibrated anatomic photographs of the arteries taken in the control state and after stenosis. Both intravascular ultrasound angioscopy and external high frequency ultrasound yielded high-resolution, two-dimensional, circumferential images of the arteries. Alterations in vessel area and shape were apparent after creation of stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed2001

Problems in determining occurrence rates of multimorbidity.

This article describes methodological decisions that have to be made when studying multiple pathology and presents appropriate analytical techniques. The main question of this article is: how can comorbidity and multimorbidity be operationalized with respect to the number and type of diseases studied, and which analytic approaches are available for the evaluation of multiple pathology? Choices regarding the number and type of diseases studied have great impact on the observed incidence and prevalence rates of comorbidity and multimorbidity. These rates are largely dependent on age, sex, and other determinants. In addition to crude descriptive measures, odds ratios and relative risks can be used to study comorbidity, whereas multimorbidity can be studied using observed/expected ratios. While basic analyses of comorbidity can be performed using standard statistical packages, two additional programs were developed for the analysis of the distribution of multimorbidity and statistically unexpected comorbidity, respectively. As some analyses are addressing multicomparisons, external validity testing is recommended.

Aged↗
PubMed2001

Transitions in functional status among older people in Wuhan, China: socioeconomic differentials.

The vast majority of research on socioeconomic status (SES) and old-age disability is based on data derived from the developed nations. This study evaluates the external validity of current findings by examining old-age disability in China, a developing nation. The direct, indirect, and total effects of SES on disability transitions were ascertained during a 3-year period in a probability sample of 2,943 people aged 60 years or older in Wuhan, China. As SES measures, education and urban residence exert distinct direct and indirect effects on functional transitions with complicated underlying mechanisms. SES has differential effects on functional transitions depending on one's prior functional state. Furthermore, the generally positive effects of SES are partially offset by negative indirect effects

Aged↗
PubMed2001

An algorithm for prospective individual matching in a non-randomized clinical trial.

A method is described to achieve balance across prognostic factors in intervention trials for which randomized allocation to treatment group is not possible. The method involves prospective individual matching of patients that have already been assigned to treatment groups. Data can be analyzed using methods appropriate for prospective matched cohort studies. Successful implementation depends on the number and complexity of factors to be matched, and on the number of available control patients. Simulation studies suggest that, in order to yield satisfactory match rates and to reduce costs associated with screening unmatched controls, no more than three prognostic factors should generally be considered. Baseline prognostic indices, incorporating information from multiple variables, provide effective matching factors. The implementation of the method in a successful clinical trial, the Delirium Prevention Trial, is discussed. In that study, treatment group was determined by hospital admission to either an intervention floor or to one of two usual care hospital floors. The ratio of available control to intervention patients was 1.3, and 95% of the eligible intervention floor patients were successfully matched to control floor patients. Excellent balance was demonstrated for non-matching factors, due in part to the use of a composite baseline risk score as a matching factor. In addition, external validity is enhanced because most eligible intervention patients are enrolled as they present. The methods outlined in this report provide a methodologically rigorous alternative for achieving balance across treatment groups, with respect to important prognostic factors, in non-randomized clinical trials, and will have broad applicability in the numerous situations in which randomization is not possible.

Aged↗
PubMed1993

The development of a questionnaire to assess knowledge of epilepsy: 2--Knowledge of own condition.

In a previous paper, a questionnaire to assess general knowledge of epilepsy (E.K.P.--G) was described (same authors). In the present paper, the development of a complementary questionnaire providing a profile of the individual's knowledge of his or her own condition is described. Results from external validation, item refinement and a clinical trial suggest this measure (the Epilepsy Knowledge Profile--Personal) provides a valid and comprehensive assessment profile which has considerable practical applications.

Adaptation, Psychological↗
PubMed1996

The case for better research standards in peripheral thrombolysis: poor quality of randomized trials during the past decade.

RATIONALE AND OBJECTIVES: We assessed how well published randomized controlled trials (RCTs) of peripheral thrombolysis have been designed and how they adjusted for patient characteristics that may influence responses to therapy. METHODS: RCT studies published between 1984 and 1994 were reviewed to determine whether they included nine crucial elements: sample size calculations, description of unenrolled eligible participants, homogeneous samples, balanced experimental groups, equal potency therapies, equal follow-up of outcomes, appropriate statistical inference, multivariable or subgroup analyses, and anonymous review of subjective endpoints. RESULTS: The nine RCTs complied with a median of three of nine standards (range = 2-6). Each report exhibited serious flaws that may affect generalizability and external validity. None adequately adjusted for sample heterogeneity or sought to identify characteristics that may affect responses to therapy. CONCLUSION: Failure to address prognostic or confounding variables restricts the utility of peripheral thrombolysis RCTs and helps explain why contentious debates about this therapy persist. A model for future thrombolysis trials is proposed.

Arterial Occlusive Diseases↗
PubMed1997

Designing research survey design--Part one.

Surveys are essential for discovering the incidence, distribution, and interrelationship of variables within a population. As such, it is important that we are able to critically read published surveys. This manuscript is the first of two dealing with survey research. Sampling and external validity are covered in this manuscript.

Data Collection↗
PubMed2004

Gonadotrophin treatment in patients with polycystic ovary syndrome.

Gonadotrophin treatment in clomiphene citrate resistant polycystic ovarian syndrome (PCOS) patients, using either low-dose step-up or low-dose step-down protocols, is highly effective to achieve singleton live births. Concomitant use of gonadotrophin releasing hormone analogues (GnRHa), which will block the endogenous feedback for monofollicular development during the low-dose step-up protocol, should not be employed. It is more difficult to induce ovulation in patients with more 'severe' PCOS, characterized by obesity and insulin resistance. There is need for optimization of starting doses for both the low-dose step-up and step-down protocols. Such optimization will prevent hyperstimulation due to a starting dose far above the FSH threshold, as well as minimize the time-consuming low-dose increments by starting with a higher dose in women with augmented FSH threshold. External validation of reported models for prediction of FSH response is warranted for tailoring and optimizing treatment for everyday clinical practice. Although preliminary, the partial cessation of follicular development, along with regression leading to atresia, lends support to the LH ceiling theory, emphasizing the delicate balance and need for both FSH and LH in normal follicular development. Future well-designed randomized controlled trials will reveal whether IVF with or without in-vitro maturation of the oocytes will improve safety and efficacy compared with classical ovulation induction strategies.

Adult↗
PubMed2005

Clustering gene expression data based on predicted differential effects of GV interaction.

Microarray has become a popular biotechnology in biological and medical research. However, systematic and stochastic variabilities in microarray data are expected and unavoidable, resulting in the problem that the raw measurements have inherent "noise" within microarray experiments. Currently, logarithmic ratios are usually analyzed by various clustering methods directly, which may introduce bias interpretation in identifying groups of genes or samples. In this paper, a statistical method based on mixed model approaches was proposed for microarray data cluster analysis. The underlying rationale of this method is to partition the observed total gene expression level into various variations caused by different factors using an ANOVA model, and to predict the differential effects of GV (gene by variety) interaction using the adjusted unbiased prediction (AUP) method. The predicted GV interaction effects can then be used as the inputs of cluster analysis. We illustrated the application of our method with a gene expression dataset and elucidated the utility of our approach using an external validation.

Algorithms↗
PubMed2003

Assessing the impact of pediatric epilepsy and concomitant behavioral, cognitive, and physical/neurologic disability: Impact of Childhood Neurologic Disability Scale.

Epilepsy has a significant impact on a child's life, the extent to which is based on four factors: epilepsy, cognition, behavioral, and physical/neurologic function. This study evaluates the ability of the 44-item Impact of Childhood Neurologic Disability Scale (ICND) to assess each of these four realms. Parents of children (aged 2 to 18 years) with epilepsy rated their child's overall quality of life and completed the ICND. External validation compared the ICND with (1) neurologists' reports of children's behavior, cognitive abilities, physical/neurologic disability, and epilepsy; and (2) parents, teachers, and children's ratings on six 'criterion standard' questionnaires. Families of 68 children with epilepsy only and 29 children with 'epilepsy-plus' (additional cognitive, behavioral, or physical/neurologic disability; 39 males, 58 females; mean age at testing 10 years 3 months [SD 4.5] age range 2 to 17 years) participated. Internal consistency was excellent (Cronbach's alpha=0.92) as was test-retest reliability (intraclass correlation=0.89). Caregivers distinguished the impact of each of the four realms. Scores were negatively related to quality of life (Pearson's r=-0.59). Children with high ICND scores had more difficulties at home and school. Their parents saw them as less rewarding and adaptable and the children saw themselves as less intelligent and less popular with more emotional problems. In addition, children with 'epilepsy-plus' had significantly higher total ICND scores as well as markedly elevated scores within each of the four realms when compared with the epilepsy-only group. It is concluded that the ICND is an accurate, quick measurement tool reflecting the impact of behavior, cognitive learning ability, physical/neurologic disability, and epilepsy on children and their families.

Adolescent↗
PubMed2003

Higher male educational hypergamy: evidence from Portugal.

Studies of human mate choice have been based almost exclusively on stated preferences and personal advertisements, and the external validity of such studies has therefore been questioned. In the present study, real-life matings based on a large representative sample of newly wed couples in 1998 (n=66,598) were analysed according to educational assortative mating. The results demonstrate a strong educational homogamy in this national Portuguese sample. However, men tend to marry women who are slightly more educated than themselves. The results are compared with those of a modern society (US, 1940-87) and a traditional society (Kipsigis, 1952-91). Since educational attainment is strongly associated with social status and intelligence, these results are discussed in an evolutionary perspective.

Educational Status↗
PubMed1988

A study of depressive typologies using grade of membership analysis.

Grade of Membership (GOM) analysis, a multivariate technique for studying disease, was used to explore depressive typology and relationships between depression and anxiety. One hundred and ninety patients with RDC diagnoses of major or minor depression were assessed by the Hamilton and SCL-90 symptom rating scales, the Newcastle diagnostic indices for endogenous depression and for anxiety and depression. Demographic, family and treatment response information were used as external validators. Five pure types provided the most satisfactory solution to these data. One group corresponded to classical melancholia, occurring in older, stable, in-patients, who lacked panic-phobic symptoms. All patients with agoraphobia fell into two distinct in-patient and out-patient groups, which differed from each other in several ways. In one group, a link was found between panic attacks, agitated melancholia and familial pure depression. The second group was less symptomatic and had more atypical vegetative symptoms. Two more groups comprised mildly symptomatic, hypochondriacal, depression, and a highly neurotic, obsessive, anxious, non-phobic depression, which was commonly related to a physical stressor.

Adolescent↗
PubMed2003

The clinical effectiveness of counselling in primary care: a systematic review and meta-analysis.

BACKGROUND: Counselling is frequently used in the management of common mental disorders (such as anxiety and depression) in primary care. However, there are concerns over the clinical effectiveness of counselling, both in comparison with usual general practitioner care, and with other treatments such as alternative psychological therapies and antidepressant treatment. This study used systematic review methodology to assess the current evidence-base. METHOD: A systematic literature review located seven trials of relevance, comparing counselling with usual general practitioner care, cognitive-behaviour therapy and antidepressant medication. Data on internal and external validity were examined using a standardized quality rating scheme. Data concerning the impact of counselling on symptoms of anxiety and depression were pooled using meta-analytical procedures. RESULTS: The main analyses showed significantly greater clinical effectiveness of counselling compared with usual general practitioner care in the short-term (standardized mean difference -0.28, 95% CI -0.43 to -0.13, N=741, six trials) but not the long-term (standardized mean difference -0.07, 95% CI -0.26 to 0.12, N=447, four trials). Sensitivity analyses were undertaken to test the robustness of the results. CONCLUSION: Counselling is associated with modest improvement in short-term outcome compared with usual general practitioner care, and thus may be a useful addition to mental health services in primary care.

Cognitive Behavioral Therapy↗
PubMed2005

Personality subtyping and bulimia nervosa: psychopathological and genetic correlates.

BACKGROUND: There is empirical evidence suggesting that individuals with bulimia nervosa vary considerably in terms of psychiatric co-morbidity and personality functioning. In this study, latent profile analysis was used to attempt to identify clusters of bulimic subjects based on psychiatric co-morbidity and personality. METHOD: A total of 178 women with bulimia nervosa or a subclinical variant of bulimia nervosa completed a series of self-report inventories of co-morbid psychopathology and personality, and also provided a buccal smear sample for genetic analyses. RESULTS: Three clusters of bulimic women were identified: an affective-perfectionistic cluster, an impulsive cluster, and a low co-morbid psychopathology cluster. The clusters showed expected differences on external validation tests with both personality and eating-disorder measures. The impulsive cluster showed the highest elevations on dissocial behavior and the lowest scores on compulsivity, while the affective-perfectionistic cluster showed the highest levels of eating-disorder symptoms. The clusters did not differ on genetic variations of the serotonin transporter gene. CONCLUSIONS: This study corroborates previous findings suggesting that the bulimia nervosa diagnostic category is comprised of three classes of individuals based on co-morbid psychopathology and personality. These differences may have significant etiological and treatment implications.

Adolescent↗
PubMed2005

The clinical effectiveness of guided self-help versus waiting-list control in the management of anxiety and depression: a randomized controlled trial.

BACKGROUND: There are significant barriers to accessing effective psychological therapy in primary care resulting from a lack of suitably trained therapists to meet current demand. More efficient service delivery using minimal interventions (such as bibliotherapy) provided by paraprofessional therapists may be one method of overcoming these problems, and is the subject of attention in the UK and elsewhere. A randomized trial was conducted to test the clinical effectiveness of this model. Assistant psychologists delivered a guided self-help intervention to patients with anxiety and depression who were currently waiting for psychological therapy. METHOD: A total of 114 patients were randomized either to guided self-help or a waiting-list control group. All patients were followed up 3 months later, prior to starting conventional psychological therapy. Measures included self-reported adherence to the intervention, anxiety and depressive symptoms, social functioning and patient satisfaction. RESULTS: Adherence to the guided self-help intervention was acceptable and patients reported satisfaction with the intervention. However, there were no statistically significant differences between groups in anxiety and depression symptoms at 3 months. CONCLUSIONS: The results demonstrate that this model of guided self-help did not provide additional benefit to patients on a waiting list for psychological therapy. The results are considered in the context of possible internal and external validity threats, and compared with previous trials of minimal interventions. The implications of the results for the design of future minimal interventions are considered.

Adult↗
PubMed1997

Family caregiving: measurement of emotional well-being and various aspects of the caregiving role.

BACKGROUND: Past research and instrument development in caregiving have focused on specific aspects of caregiving or specific disability groups. This paper reports the scale characteristics of a new generic instrument developed to assess the experience of caregiving, and the social and emotional well-being of caregivers and a comparison group of 'non-caregivers'. METHODS: Using computer-assisted telephone technology, a random survey of 26000 households was conducted in Victoria, Australia to identify and interview 976 caregivers of people who were aged or had a long-term illness or disability of any kind, and 219 non-caregivers. Both groups were re-interviewed after 15 months. Scales administered on each occasion to caregivers and non-caregivers included life satisfaction, positive and negative affect, social support and overload; and to caregivers, caring role satisfaction, resentment and anger, and, in relation to the care recipient, measures of help provided and needed, severity of disability and behaviour problems. RESULTS: On each occasion and with each sample all scales demonstrated a satisfactory reliability. With a subsample of caregiver-care-recipient dyads (N = 67), caregiver reports of severity of disability, level of helped needed and provided were validated externally by clinician assessments. CONCLUSIONS: A comprehensive instrument to assess the experience of caregiving was developed. It is relevant to a broad range of ages, levels and types of disability and care provided; and, in assessing health and well-being, to both caregivers and non-caregivers. Scales, including both positive and negative dimensions, have demonstrated good internal consistency on two occasions. The instrument is potentially useful in a range of research and practical settings.

Activities of Daily Living↗