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Results for “instrumental variable”

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At least 415 records · Page 23Linked to original sources
PubMed2000

A systematic review of the content and quality of wrist outcome instruments.

OBJECTIVE: To assess the content and quality of published wrist outcome instruments using standardized criteria. DESIGN: An analytical study that examined 32 wrist outcome instruments sourced from textbooks, Medline (1951 to present) and Current Contents. MAIN MEASURES: The content of each instrument was classified into four categories: traditional measures (such as range of movement and strength), measures of the ability to perform daily activities, compensatory mechanisms used, and 'other'. Analysis included the frequency of assessment per category and the method of assessment. In addition, each instrument was graded using 13 quality criteria. Three criteria (scientific justification of the content and scoring system used, demographic utility) were considered to be essential. RESULTS: Eighty-two per cent of instruments reviewed for this paper contained traditional measures, of which most were assessed objectively. The ability to perform specific daily activities was assessed in 31% of the instruments whereas compensatory mechanisms were evaluated in only one instrument. These variables were not assessed in a consistent manner. Using the quality scoring system derived for this study, the quality of the instruments was generally poor. Only one instrument fulfilled all of the essential criteria. Only four instruments completely satisfied more than 50% of the criteria. CONCLUSIONS: Most wrist outcome instruments neglected to assess the impact of the disorder on the individual. Outcome was generally not expressed in functional terms or in terms that were relevant to each individual. The majority of the reviewed articles had poor quality. Thus use of these instruments may preclude sensitive evaluation of the efficacy of any intervention.

Activities of Daily Living↗
PubMed1991

Self-report family assessment instruments: an evaluative review [see comment].

Family medicine is challenged to document the impact of family systems on health and physiologic function. For this research investigators must measure family system variables with instruments that are both valid and reliable. In this context, eight self-report measures of total family functioning are reviewed and assessed according to a standardized approach to instrument design. The instruments evaluated include the Family Assessment Device, the Family Assessment Measure, the Family Adaptability and Cohesion Evaluation Scales, the Family Environment Scale, the Family Functioning Index, the Self-Report Family Inventory, the Family APGAR, and the Family Functioning Questionnaire. The analysis indicates two major problems with these instruments. First, there is disagreement on key concepts and definitions. Second, there is inconsistency in design and attention to detail in empirical analysis and psychometic evaluation. Family assessment techniques need further development and remain a fertile research field for family medicine investigation.

Family↗
PubMed2006

Is the involvement of opinion leaders in the implementation of research findings a feasible strategy?

BACKGROUND: There is only limited empirical evidence about the effectiveness of opinion leaders as health care change agents. AIM: To test the feasibility of identifying, and the characteristics of, opinion leaders using a sociometric instrument and a self-designating instrument in different professional groups within the UK National Health Service. DESIGN: Postal questionnaire survey. SETTING AND PARTICIPANTS: All general practitioners, practice nurses and practice managers in two regions of Scotland. All physicians and surgeons (junior hospital doctors and consultants) and medical and surgical nursing staff in two district general hospitals and one teaching hospital in Scotland, as well as all Scottish obstetric and gynaecology, and oncology consultants. RESULTS: Using the sociometric instrument, the extent of social networks and potential coverage of the study population in primary and secondary care was highly idiosyncratic. In contrast, relatively complex networks with good coverage rates were observed in both national specialty groups. Identified opinion leaders were more likely to have the expected characteristics of opinion leaders identified from diffusion and social influence theories. Moreover, opinion leaders appeared to be condition-specific. The self-designating instrument identified more opinion leaders, but it was not possible to estimate the extent and structure of social networks or likely coverage by opinion leaders. There was poor agreement in the responses to the sociometric and self-designating instruments. CONCLUSION: The feasibility of identifying opinion leaders using an off-the-shelf sociometric instrument is variable across different professional groups and settings within the NHS. Whilst it is possible to identify opinion leaders using a self-designating instrument, the effectiveness of such opinion leaders has not been rigorously tested in health care settings. Opinion leaders appear to be monomorphic (different leaders for different issues). Recruitment of opinion leaders is unlikely to be an effective general strategy across all settings and professional groups; the more specialised the group, the more opinion leaders may be a useful strategy.

Journal Article↗
PubMed1976

Evaluation of the airflowmeter in the assessment of airways obstruction.

The airflowmeter, a new inexpensive instrument measuring severity of airways obstruction in arbitrary units, was found to correlate well with standard respiratory function tests, and to be more sensitive than FEV1 in detecting changes in obstruction. Despite the distortion of maximal expiratory flow-volume relationship induced by the resistance of the meter, and the considerable variability between instruments, the airflowmeter should prove useful for regular monitoring of patients with variable airways obstruction.

Airway Obstruction↗
PubMed1984

Predicting male and female contraceptive behavior: a discriminant analysis of groups high, moderate, and low in contraceptive effectiveness.

An exploratory, multivariate study was carried out to assess (a) whether three contraceptive-effectiveness groups (high, moderate, and low) could be differentiated on the basis of variables that have been theoretically and empirically associated with contraceptive behavior and (b) whether an identified set of discriminating variables could accurately classify sexually active college students into these groups. Three hundred sixty-five sexually active, never-married college students (211 males and 154 females) completed instruments measuring variables related to contraception. Four separate discriminant analyses were performed, one for each sex for both their initial sexual encounter and their current sexual interactions. Discrimination and classification of the three contraceptive groups for both males' and females' initial sexual experience was not very successful. Moderate discrimination was achieved for the female current sexual activity subsample and good discrimination and classification was made for the currently sexually active male subsample. The results are discussed in terms of the implications of the findings for understanding contraceptive behavior of males and females, problems with the dependent variable of contraceptive use, and the mounting evidence that emotional orientation to sexuality influences contraceptive behavior.

Adult↗
PubMed1998

The effect of three different recording materials on the reproducibility of condylar guidance registrations in three semi-adjustable articulators.

Sagittal condylar guide settings of three semi-adjustable articulators: WhipMix, Hanau 158 and Denar Mark II were compared using registrations of base plate wax, copper wax and self-curing acrylic resin in two subjects. Four-way ANOVA showed differences between instruments (P < 0.0001), materials (P < 00001), registrations (P < 0.0001), and no difference between operators. Mean differences between materials were 3 degrees and 6 degrees within the range of registration and articulator variability. Denar Mark II gave the highest values, Hanau 158 the lowest with pantronic values generally lower than articulator settings. Neither acrylic nor copper wax were superior to base plate wax. This and previous studies show low reproducibility and variability between instruments, occlusal records and registration material.

Acrylic Resins↗
PubMedDate not supplied

Comparative study of condylar settings of three semiadjustable articulators.

The reproducibility of arcon semiadjustable Whip Mix, Denar Mark II, and Hanau 158 articulators was tested using multiple protrusive and lateral edge-to-edge wax interarch registrations made with an interocclusal device. Photographic and cephalometric tracings verified an identical angulation between the axis-orbital craniofacial reference plane and the maxillary occlusal plane for the subject and both the Denar Mark II and Hanau 158 articulators. This angle was 2.5 degrees less in the Whip Mix instrument. Three operators made three settings for each of 12 protrusive and 24 lateral interarch registrations for each articulator. Results showed significant differences between instruments. Whip Mix consistently gave the highest.angulations and Hanau 158 the lowest. For protrusive records there was no significant difference between examiners, but for lateral records a significant difference in examiner registration was found. For both protrusive and nonworking registrations, interaction was seen between instrument and operator and between instrument and registration, and a significant difference was seen between records. This study supports previous studies showing that semiadjustable articulators using interarch records have a low level of reproducibility and are subject to variables of instrument, operator, and occlusal records.

Adult↗
PubMed2000

Advances in satellite remote sensing of environmental variables for epidemiological applications.

Earth-observing satellites have provided an unprecedented view of the land surface but have been exploited relatively little for the measurement of environmental variables of particular relevance to epidemiology. Recent advances in techniques to recover continuous fields of air temperature, humidity, and vapour pressure deficit from remotely sensed observations have significant potential for disease vector monitoring and related epidemiological applications. We report on the development of techniques to map environmental variables with relevance to the prediction of the relative abundance of disease vectors and intermediate hosts. Improvements to current methods of obtaining information on vegetation properties, canopy and surface temperature and soil moisture over large areas are also discussed. Algorithms used to measure these variables incorporate visible, near-infrared and thermal infrared radiation observations derived from time series of satellite-based sensors, focused here primarily but not exclusively on the Advanced Very High Resolution Radiometer (AVHRR) instruments. The variables compare favourably with surface measurements over a broad array of conditions at several study sites, and maps of retrieved variables captured patterns of spatial variability comparable to, and locally more accurate than, spatially interpolated meteorological observations. Application of multi-temporal maps of these variables are discussed in relation to current epidemiological research on the distribution and abundance of some common disease vectors.

Animals↗
PubMed1991

Frequency and severity of cyclic flow alternations and platelet aggregation predict the severity of neointimal proliferation following experimental coronary stenosis and endothelial injury.

The role of recurrent platelet aggregation in the development of neointimal proliferation of coronary arteries was explored in this study, and the hypothesis was evaluated that recurrent platelet aggregation and the consequent frequency and severity of cyclic coronary blood flow variations are important pathophysiologic factors in the subsequent development of neointimal proliferation. In 24 chronically instrumented dogs, variable degrees of coronary artery neointimal proliferation were observed 3 weeks after mechanical injury of the arterial endothelium and the placement of an external coronary artery constrictor. The severity of neointimal proliferation at 21 days was closely related to the frequency and severity of cyclic coronary blood flow variations during the initial 7 days after instrumentation of the animals, itself a manifestation of recurrent platelet aggregation and dislodgement. Pharmacological therapy with a dual thromboxane A2 synthetase inhibitor and receptor antagonist and with a serotonin S2 receptor antagonist frequently was successful in abolishing cyclic blood flow variations and in retarding neointimal proliferation.

Animals↗
PubMed1998

Breathing difficulties in wind instrument players.

Performance of a wind instrument requires appreciable lung volume and diaphragmatic mechanical force, skilled breath control, adequate patency and humidity of air passages, and precise coordination of the oropharyngeal cavity. Depending on the instrument class, variable rates of air flow, pressure, and duration are necessary to produce optimal tone quality. Wind players may be seriously impaired by respiratory diseases that, comparatively, might appear trivial to the nonperformer. The workplace environment should be assessed for occupational hazards when managing these patients, and smoking should be particularly discouraged. Controversy exists implicating wind instrument use in the exacerbation of respiratory disease, including bronchial, laryngeal, pharyngeal, and oral anatomic changes--a result of the constant barotrauma of performance. Asthma is the most common chronic pulmonary disorder among wind players, and therapeutic programs that include breath training and physical exercise improve symptoms, endurance, and general well-being.

Air Pressure↗
PubMed1991

Doppler color flow image size: dependence on instrument settings.

Doppler color flow imaging provides important qualitative information about the location and spatial distribution of intracardiac blood flow. However, the effect of instrument-related variables on the size of color Doppler images requires further definition. Flow of a silicone particle solution was established in a tube or cylinder and scanned as color gain, pulse repetition frequency, depth, and transducer frequency were varied. The diameter of Doppler color flow images were measured during constant laminar or disturbed flow parallel to the ultrasound beam and during laminar flow perpendicular to the ultrasound beam. The diameter of color Doppler images of laminar flow perpendicular and parallel to the beam varied directly with color gain. Diameter varied inversely with transducer frequency for laminar flow parallel to the transducer and inversely with pulse repetition frequency for laminar flow perpendicular to the transducer. The diameter of laminar flow parallel to the transducer varied directly with the depth of the flow area below the transducer. The size of the color flow dropout of laminar flow exactly perpendicular to the ultrasound beam varied directly with transducer frequency and inversely with gain. During disturbed flow parallel to the transducer, the diameter of the image varied directly with gain and inversely with transducer frequency and pulse repetition frequency. Instrument settings have a significant impact on the size of color Doppler images. Understanding the effects of changes in these variables is important for reliable diagnostic use of Doppler color flow imaging.

Blood Flow Velocity↗
PubMed2005

A consumer health informatics (CHI) toolbox: challenges and implications.

Consumer health informatics (CHI) is a rapidly evolving sub-discipline of medical informatics. Such developing fields typically share common needs, such as harmonizing terms and building a common foundation of research methods and instruments. The authors describe a pilot study to conceptualize and develop a "CHI toolbox," a repository of existing methods and instruments across relevant established fields. The challenges encountered in attempting to organize concepts in a nascent, interdisciplinary field are discussed. The authors' experiences in creating a comprehensive CHI toolbox suggest that a larger, concerted effort to develop a similar product by members of the relevant research communities could accelerate the development of common terms, operational definitions, variables, and instruments within the CHI field.

Health↗
PubMed1984

Interferometric analysis of intrasection and intersection thickness variability associated with cryostat microtomy.

Mach-Zehnder interferometric measurements were used to assess the extent of section thickness variability (inter- and intrasection) associated with cryostat microtomy of adrenal sections over a typical working range of 10-20 micron. Sections were obtained using a Bright's Cambridge rocking type and a Damon rotary type cryostat microtome to allow comparative analyses. The effective thickness of tissue sections after being mounted onto slides by flash drying was reduced by 90% relative to microtome section thickness setting. A linear relationship between measured thickness and microtome setting was obtained with both instruments. Thickness variability between replicate sections over the range of microtome settings approximated 11% for the rocking microtome and 5% with the rotary microtome. Average intrasection variability was found to be 7% for rocking microtome sections and 4% for sections obtained with the rotary microtome. However, this variability is a negligible source of error in cytophotometric analyses, providing replicate sections are used and an adequate number of measurements are made on mask-delimited individual cells or tissue specimen areas.

Adrenal Glands↗
PubMedDate not supplied

Development of a self-assessment instrument to determine daily intake and variability of dietary vitamin K.

OBJECTIVE: To develop and validate a brief, self-assessment instrument (K-Card) to determine daily variations in dietary vitamin K1 (phylloquinone) intake for use in patients receiving oral warfarin anticoagulant therapy. METHODS: The K-Card was designed to include a checklist of selected common foods and beverages providing > or = 5 microg vitamin K per serving in American diets and items with lower vitamin K content typically consumed in quantities which contribute significantly to total vitamin K intake. The K-Card was validated against records of weighed food intake from thirty-six healthy volunteers, 20 to 40 and 60 to 80 years of age, whose phylloquinone intakes and plasma concentrations had been previously measured by the Metabolic Research Unit, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA USA. Future use of the K-Card by patients was simulated by a single investigator using 108 one-day weighed food records to estimate phylloquinone intakes. Dietary phylloquinone calculated from the K-Card was compared to the values of phylloquinone intake from the diet records collected on the same days, and to fasting plasma phylloquinone concentrations obtained from the same individuals on the following day. RESULTS: The mean dietary phylloquinone intake (+/- SEM) was 138.8 +/- 15.7 microg for the K-Cards compared to 136.0 +/- 15.8 microg for the diet records (p = 0.067). Bland-Altman limits of agreement between quantities of dietary phylloquinone calculated from the K-Card and values obtained from the weighed food records were +/- 38 microg. CONCLUSION: In this simulation, the K-Card provided an accurate estimate of dietary phylloquinone intake and therefore deserves further testing for use by patients receiving coumarin-based anticoagulant therapy to determine whether variability in dietary patterns contributes to disruptions in anticoagulant drug efficacy and safety.

Adult↗
PubMed1975

The non-contact ("air puff") tonometer: variability and corneal staining.

We investigated the possibility of significant corneal trauma (as revealed by slit lamp observation of the fluorescein instilled eye), and massage effects following determination of intraocular pressure with the A. O. Non-Contact tonometer (NCT). Fifteen different, normal human eyes were each applanated 150 successive times with the NCT; leading to the conclusion that only minor, superficial corneal epithelial defects sometimes resulted and that, in line with other studies, the initially higher readings (about 1 mm), obtained with the NCT, were most likely due to patient apprehension, while the subsequently lower readings represented patient acceptance of the process and were not a result of true aqueous massage. As in an earlier study, we found the instrument's variability to be about plus and minus 1 or plus and minus 2 mm and probably due to the subject's own cardiac cycle.

Adolescent↗
PubMed1980

A clear view trephine and lamellar dissector for corneal grafting.

We designed a corneal trephine that permits a full view of the cornea while cutting. The drive mechanism of the trephine enables the surgeon to keep the central cutting axis of the instrument stable while the trephine is rotated. The instrument accepts variable sizes of disposable trephine blades, making it versatile and economical. We also devised a lamellar dissector with two blades to negate the splitting force that occurs during a closed lamellar dissection. It enables the surgeon to perform a closed lamellar dissection with minimal force applied to the globe and minimal risk of perforation.

Cornea↗
PubMed2005

Measurement of psychological factors associated with genetic testing for hereditary breast, ovarian and colon cancers.

Despite numerous individual studies of psychological factors (depression, anxiety, distress) related to genetic testing for inherited cancer syndromes (CGT), there has been no systematic review of the psychological factors are measured among individuals at increased risk for hereditary breast, ovarian, or colon cancer. Our review provides an analysis of psychological factors in studies of CGT and discusses the instruments most commonly used to measure them. We performed a literature search using three major OVID databases from 1993 to January 2003. In the 19 studies that met our inclusion criteria, the most commonly assessed psychological factors were distress, anxiety, and depression. These factors were most often measured by the impact of event scale (IES), the state-trait anxiety inventory (STAI), and the Centers for Epidemiologic Studies and Depression scale (CES-D), respectively. Our results show deficits in the existing body of literature on psychological factors associated with CGT including limited documentation of psychometrics and variability in instrumentation.

Anxiety↗
PubMedDate not supplied

Current knowledge about the health behavior of young children: a conference summary.

Twenty-five researchers involved in work related to the health behavior of young children attended an invitational conference to achieve consensus regarding: (a) the definitions, research methods, instruments, and variables that should guide future research into the health behavior of young children, and (b) the nature of the knowledge deficits that should be addressed by future research. The researchers examined the predisposing, enabling, and reinforcing factors related to health behavior, the important types of health behavior of children, the valid indicators of health behavior, and the conceptual framework within which these things can be viewed effectively. Although the stated goal of the conference was not achieved (i.e., to gain consensus about a set of guidelines in order to focus directions in data collection and thereby to facilitate comparability of results), the conference did obtain interdisciplinary perspectives on the state of the theory, research instruments, and knowledge gaps in the health behavior of children. Innovative research designs, and more rigorous research methods need to be applied to the entire area of health behavior before guidelines can be proposed.

Attitude to Health↗