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Results for “Internal validation”

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PubMed2001

Exercise and the transtheoretical model: a longitudinal test of a population sample.

BACKGROUND: The purpose of this study was to test the ability of the Transtheoretical Model (TTM) to predict exercise stage transition of individuals in a large, untreated-population-based, random sample of Canadian adults (18-65 years of age) over two consecutive time periods. METHODS: Assessments of TTM's stage of exercise behavior change, self-efficacy, pros, cons, experiential processes, and behavioral processes were made at baseline (time 1), 6 months (time 2), and 1 year (time 3). Six hundred eighty-three men and women, identified through random-digit telephone dialing, completed all measures across the three time points. Within each time period (time 1-2; time 2-3) participants were categorized as having regressed (moved back at least on stage), remained (no stage change), or progressed (moved forward at least one stage). Baseline TTM constructs were analyzed for their ability to predict change transition across the two time periods. RESULTS: Of 40 possible predictions (20 for each time period) 18 (45%) were supported. CONCLUSIONS: Overall, the findings demonstrate partial support for the internal validation of TTM in the exercise domain. Implications of the findings are discussed and future directions for researchers, practitioners, and program planners are provided.

Adolescent↗

PubMed1997

Mental disorders and health care seeking in Bandiagara: a community survey in the Dogon Plateau.

A two-level community study was carried out among the Peul and Dogon populations of the Bandiagara plateau (Mali). For the purpose of the study the Questionnaire pour le depistage en santé mentale (QDSM), a 23-item screening questionnaire derived from the Self-Reporting Questionnaire (SRQ), was adapted and validated; internal consistency and accuracy were evaluated. In the first phase of the study, 466 subjects randomly selected on a residential basis were evaluated by means of the QDSM. In the second phase all subjects who were "positive" at the screening, as well as a sample who were "negative", were examined by means of a semistructured interview. When necessary, clinical and laboratory investigations were performed. The estimated prevalence of psychiatric cases was 6.4%. A significant risk was associated with age and education. Somatic diseases frequently associated with psychiatric disorders were genitourinary tract disorders, tuberculosis and disabling cardiopathies. The main factor determining the seeking of medical help either through traditional of conventional health systems was the presence of a somatic disorder. The presence of a true minor psychiatric disorder, however, was often associated with divining practices.

Adolescent↗

PubMed1994

The psychometric properties of the Eating Attitude Test in a non-Western population.

The psychometric features of the Eating Attitude Test Questionnaire (EAT) are described in an Egyptian population of secondary school girls (n = 351). Confirmatory factor analysis, modelled on studies by Garner et al. (1982) and Eisler and Szmukler (1985), was conducted and pointed to the overall coherence of the EAT in this population. The assessment of the internal validity of each factor, however, showed a high level of consistency amongst the items representing the dieting factor, and a much lower level for those representing the bulimia factor. The results could justify the continued use of the EAT as a valid screening instrument for some aspects of eating morbidity, i.e. dieting and concern about weight and shape in non-Western populations. The analysis clearly suggested that another scale is required for bulimic behaviours.

Adolescent↗

PubMed1986

Client variables and the behavioral treatment of recurrent tension headache: a meta-analytic review.

Meta-analysis revealed that in studies evaluating behavioral treatments for tension headaches, the treatment outcome has varied with the client samples (e.g., age, gender, referral source) that have been used but not with the treatment procedures (e.g., type of behavioral intervention, length of treatment, whether or not efforts were made to facilitate transfer of training) or the research designs (e.g., internal validity, explicitness of diagnostic criteria) that have been used. Mean client age proved the best predictor of treatment outcome, accounting for 30% of the outcome variance following behavior therapy. Significantly poorer outcomes have also been reported in recent studies than were reported in early studies. These findings suggest that outcomes obtained with behavioral interventions have been less dependent upon the treatment variables that have been the primary focus of research attention than upon characteristics of client samples and behavioral interventions may be less effective in reducing headache activity than has previously been assumed.

Adult↗

PubMed1987

The prevention of cigarette smoking in children: two- and three-year follow-up comparisons of four prevention strategies.

Recent studies have suggested that a prevention program that addresses the social influences that encourage smoking can be effective in deterring cigarette use by adolescents. This study presents 1-, 2-, and 3-year follow-up results from two studies which evaluated three variations of the social influences curriculum and compared them to a health consequences program and a usual-care comparison group. These results suggest that a peer-led, social influences program can restrain smoking among both baseline nonsmokers and baseline experimental smokers at 2 years postintervention. Analyses of attrition data suggest no evidence to threaten the internal validity of these findings, although their generalizability to baseline smokers may be limited.

Adolescent↗

PubMed1980

Autoshaping of abnormal children.

Three experimentally naive abnormal children were exposed to a terminal operant contingency, i.e., reinforcement was delivered only if the children pressed a panel during intervals when it was lighted. Despite the absence of both successive approximation and manual shaping, it was found that each child began to respond discriminatively within a small number of trials. These data replicated previous animal studies concerned with the phenomena of autoshaping and signal-controlled responding. It was also found, however, that one type of autoshaping, the classical conditioning procedure, had a powerful suppressive effect on the discriminative responding. An experimental analysis that consisted procedure, had a powerful suppressive effect on discriminative responding. An experimental analysis that consisted of intrasubject reversal an multiple baseline designs established the internal validity of the findings. The finding of rapid acquisition of signal-controlled responding obtained with the initial procedure is suggessted to have practical significance. The disruptive effects of the classical form of autoshaping are discussed in terms of negative behavioral contrast.

Adolescent↗

PubMed1980

Changing measurement instrument at follow-up: a potential source of error.

The purpose of this investigation was to determine whether headache activity information collected over the phone can be directly compared with headache activity information collected by systematic self-observation without jeopardizing internal validity because of calibration differences between the two measurement methods. A number of headache studies have relied on phone information for long-term follow-up data, while using systematic self-observation to collect all other data. Twenty-six headache sufferers participating in a tension headache study reported their headache activity over the phone and subsequently charted their headaches. Correlations were computed between the two measures. Results indicated that differences exist in the calibration of the two measurement methods. This seriously limits the conclusions of studies that used phone information to obtain follow-up data. Other recommendations concerning follow-up methodologies are discussed.

Adult↗

PubMed1996

[Prevalence and distribution of stroke and transient ischemic insults: secondary data analysis of a representative sample of insured members of the General Local Insurance Dortmund].

Apoplexia is not only one of the leading causes of death, but also a major contributor to disability in the aged. Population based prevalence rates, though being of basic importance for describing and planning health care structures, are sparse in the Federal Republic of Germany. We estimated the prevalence of apoplexia and transient ischemic attack (TIA). Data were gathered from a 5% representative random sample of insured of the local statuatory health insurance (AOK) in Dortmund, Germany (n = 7447). Cases were identified by the diagnosis on medical certificates, being further validated internally by other patient data. The rough prevalence rate was 0.86% (m 0.79%, f 0.93%) for apoplexia and 0.6% (m 0.4%, f 0.78%) for TIA. Adjusted for age and sex to the whole population of the FRG (excluding the former German Democratic Republic) the prevalence rate was 0.75% (m 0.8%, f 0.7%) for apoplexia and 0.52% (m 0.41%, f 0.63%) for TIA. 65% of the insured with apoplexia were 70 years and older; their average age was 71.7 years. The average age of the insured with TIA was 65.4 years. Prevalence rates for apoplexia increased continuously by age and were higher for men than for women in all age groups. Prevalence rates for TIA also increased with age, but under men only to the age of 70; after that-simultaneous to a steep rise of apoplexia prevalence-no more TIAs were noticed.

Adult↗

PubMed1990

The impact of methodological factors on child psychotherapy outcome research: a meta-analysis for researchers.

Two recent meta-analyses have generated evidence for child and adolescent psychotherapy effects. However, critics note that such meta-analyses often include studies with methodological shortcomings which might invalidate their results. In the present study, we explored whether the results of the most extensive child/adolescent meta-analysis might have been influenced by such methodological variables, focusing on internal validity and external validity factors. Together, these factors accounted for two-thirds as much variance as the substantive factors (e.g., type of therapy, age) in the original meta-analysis. This suggests that relative to these therapy and child-characteristic variables, methodological factors have a substantial, though smaller, impact on meta-analysis results. In general, increased experimental rigor was related to larger effect sizes; this argues against the hypothesis that methodologically weak studies have led to an overestimate of therapy effects. No significant interactive relations were found between validity factors and predictors of outcome; this suggests that the relations noted in previous meta-analyses between outcome and various variables were not distorted by the validity factors tested here.

Adaptation, Psychological↗

PubMed1994

Subtypes of psychosocial adjustment to breast cancer.

By means of cluster analytic techniques, four subtypes of psychosocial adjustment were identified in a sample of 122 breast cancer patients who completed the Psychosocial Adjustment to Illness Scale. Internal consistency and internal validity of the derived typology were suggested by the finding that two different hierarchical agglomerative clustering methods (average linkage between groups, Ward's) produced similar solutions. Three of the derived subtypes reported normal affect levels but different patterns of relative strengths and dysfunctions, while the fourth subtype appeared to be highly distressed and globally maladjusted. External validation was demonstrated by differentiating the subtypes on variables of negative affect, avoidance coping, and fighting spirit. The clinical and heuristic implications of these findings are discussed. The findings highlight the need for comprehensive assessment of psychosocial functioning of cancer patients. They demonstrate that even non-emotionally distressed patients can have very different profiles of adjustment and may benefit from correspondingly individually tailored psychosocial interventions.

Adaptation, Psychological↗

PubMed1996

A new system to record reliable pulse oximetry data from the Nellcor N-200 and its applications in studies of variability in infant oxygenation.

We have developed a simple system for internal validation of oximetry data collected over many hours from the Nellcor N-200 pulse oximeter (Nellcor, Inc., Hayward, CA). This system uses signals from the oximeter alone and a validation algorithm that is based in a computer connected to the oximeter. Unlike other validation systems, this system does not require connections to other monitors. The system was tested on 10 acutely ill newborns in an intensive care nursery over 16 hr of continuous recording for each infant (birthweight, 2.50 +/- 0.73 kg; age, 3.4 +/- 3.2 days). Oximetry data were accepted as valid using the new system if they surpassed a minimum level of quality (empirically derived, and equal to a 60% fractional success in pulse detection). The validated oximetry data were compared to data obtained using a conventional "compared to the electrocardiogram (ECG)" algorithm. For the new and the conventional algorithms, the distributions of validated SpO2 percents were nearly identical, with data rejection rates of 28.9% for the new system and 37.3% for the conventional system. In the newborns, the new system was used to demonstrate that as the mean saturations decreased, there were striking increases in variability about the reported mean saturation (p < 0.001). While variability in infant SpO2 is a well-known phenomenon, the amount seen here was unexpected. For example, the range of true saturations frequently recorded was quite wide at a reported mean SpO2 of 90% (from 81 to 94%; but, the range was only from 92 to 98% at a mean SpO2 of 96%). These findings demonstrate the usefulness of the new system and, if substantiated in more detailed studies, have important implications for the use of pulse oximeters to assess oxygenation in newborns.

Algorithms↗

PubMed2000

Designing a research study.

There are 10 steps to consider in any research study. These steps can be used to perform a critical appraisal of a published paper, or to design your study in the first place. The use of a simple system such as this can ensure that biases in study design are avoided and that an appropriate study is developed. (1) What is the study hypothesis? (2) What is the study type? (3) What are the outcome measures? Is their measurement biased in any way? (4). What is the study factor (the intervention being offered to the children)? Is there bias in this? (5) Is there a possibility of confounding? (6) What are the reference population, source population and study sample? How have the sampling and selection into the study been performed? (7) Study methods that might threaten the internal validity of the study. (8) Statistical considerations. (9) Are the results clinically and socially significant? (10) Will the conclusions of the study be relevant to the kind of patients you see, or communities you work with?

Bias↗

PubMed1994

Some improvements in the quality of NAA procedures and the reliability of the results.

After considering the need for quality control in NAA, the concept of quality in NAA procedures themselves is discussed, and some important factors identified. Two approaches to improve quality are then described in more detail. The first concerns the unique ability of NAA using different isotopic reactions and different modes (INAA/RNAA) to provide independent data sets in the same laboratory, thus allowing internal validation or crosschecking. The second discusses the need for chemical yield measurements in RNAA and the advantages of the radioisotopic tracer technique. Some recent advances and further possibilities for this use of tracers are listed.

Neutron Activation Analysis↗

PubMed1999

[Basic principles of clinical trials--what, how, and why?].

Treatment evaluation is one of the most important tasks in medical research. Detailed standards have been developed during the last decades. The efficacy/effectiveness of treatments can only be assessed in comparison to control groups. To guarantee the internal validity of these comparisons, the groups have to be comparable at the beginning of the study. This can be achieved by randomized allocation of patients to treatment. Furthermore, as far as possible patient and physician should be blinded to treatment in order to avoid subjective influences on treatment results. Groups should still be comparable when analysing the trial, thus an analysis according to the principle of intention-to-treat ("as randomized") should be performed. These indispensable principles for design, conduct and analysis of clinical trials are widely accepted and contribute to reliable and credible results.

Clinical Trials as Topic↗

PubMed1997

[Workplace contamination from sevoflurane. Concentration measurement during bronchosopy in children].

UNLABELLED: General anaesthetic agents are frequently used for paediatric bronchoscopy. A disadvantage of open-system anaesthesia is the contamination of the working environment. The aim of this study was to determine the exposure of the anaesthesiologist and endoscopist during paediatric bronchoscopy under general anaesthesia in different working environments and to compare these measurements to the currently valid international threshold limits. MATERIALS AND METHODS: Twenty-five children (ASA I-III) scheduled for diagnostic bronchoscopy were included in the study. After inhalational induction, all patients were intubated with a nonflexible bronchoscope and manually ventilated through a side-arm of the bronchoscope. Maintenance of anaesthesia was achieved with sevoflurane (2-3 vol.%) in pure oxygen. Trace concentrations were measured every 90 s in the breathing zones of the operating theatre (OT) personnel by means of a highly sensitive direct-reading instrument (Brüel & Kjaer 1302). The lower detection limit was 0.02 ppm. The investigation was done in an OT with and without air-conditioning and a scavenging system. RESULTS: The mean age of the children was 50.3 months (range: 3-109 months). Ventilation and oxygenation were stable throughout the bronchoscopic procedure. Mean exposure to sevoflurane in the OT without air-conditioning and a scavenging system was over 40 ppm for the anaesthetist and 50 ppm for the endoscopist. All international threshold limit values were exceeded. Peak concentrations higher than 100 ppm could be detected during 40% of the anaesthetics. CONCLUSION: The main finding of the present study is that under inhalation anaesthesia with sevoflurane for paediatric bronchoscopy, occupational exposure is higher than all known health regulation guidelines permit. Therefore, the use of total intravenous anaesthesia is advocated even in very small infants.

Anesthesia, Inhalation↗

PubMed2004

[Medical registries. Benefits and limitations].

Traditionally, registers are understood as tools of epidemiological research. Recently, medical registers have encountered new tasks in quality management and research on medical care. When registers are complete and representative for a target population, they complement the epidemiological and clinical studies that usually focus on specific endpoints using selected study populations. In this process, registers can benefit substantially from the established methodology of planned studies, for instance by application of survey sampling techniques. In order to fulfil the steadily rising expectations, registers have to meet increased methodological standards. Organization and data management should be orientated towards the standards that are meanwhile generally accepted for randomized controlled trials. The evaluation has to go beyond simple descriptive statistics towards complex statistical model building in order to cope with the unavoidable problem of internal validity of comparisons within registers. If registers fulfil these requirements, they are valuable sources of information (that cannot be replaced by other tools) on the spread of risk factors and diseases and on the distribution and usefulness of preventive measures and therapies; general proof of their efficacy should be provided by randomized clinical trials.

Biomedical Research↗

PubMed2004

[Quality of life of patients with occupationally-induced hand eczema].

In recent years quality of life has been studied in a growing number of different dermatological diseases. Internationally validated questionnaires such the RAND-36 (identical to the SF-36) do not contain enough questions which are relevant for skin diseases. There is no publication on quality of life issues in occupational skin diseases, and only one short report gives data on quality of life in hand eczema. The widely used skin specific instrument DLQI has only 2 questions that indirectly refer to employment issues. A quality of life questionnaire on occupational skin diseases (mostly hand eczema) should ideally include questions on work-related impairment of both physical functioning and interaction with colleagues.

Activities of Daily Living↗

PubMed2004

A model to estimate the lifetime health outcomes of patients with type 2 diabetes: the United Kingdom Prospective Diabetes Study (UKPDS) Outcomes Model (UKPDS no. 68).

AIMS/HYPOTHESIS: The aim of this study was to develop a simulation model for type 2 diabetes that can be used to estimate the likely occurrence of major diabetes-related complications over a lifetime, in order to calculate health economic outcomes such as quality-adjusted life expectancy. METHODS: Equations for forecasting the occurrence of seven diabetes-related complications and death were estimated using data on 3642 patients from the United Kingdom Prospective Diabetes Study (UKPDS). After examining the internal validity, the UKPDS Outcomes Model was used to simulate the mean difference in expected quality-adjusted life years between the UKPDS regimens of intensive and conventional blood glucose control. RESULTS: The model's forecasts fell within the 95% confidence interval for the occurrence of observed events during the UKPDS follow-up period. When the model was used to simulate event history over patients' lifetimes, those treated with a regimen of conventional glucose control could expect 16.35 undiscounted quality-adjusted life years, and those receiving treatment with intensive glucose control could expect 16.62 quality-adjusted life years, a difference of 0.27 (95% CI: -0.48 to 1.03). CONCLUSIONS/INTERPRETATIONS: The UKPDS Outcomes Model is able to simulate event histories that closely match observed outcomes in the UKPDS and that can be extrapolated over patients' lifetimes. Its validity in estimating outcomes in other groups of patients, however, remains to be evaluated. The model allows simulation of a range of long-term outcomes, which should assist in informing future economic evaluations of interventions in type 2 diabetes.

Amputation, Surgical↗