Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “instrumental variable”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed2000

The CNS's impact on process and outcome of patients with total knee replacement.

This study was designed to determine whether differences exist between patients with total knee replacement on hospital units with or without clinical nurse specialists (CNSs) in terms of selected process and outcome variables. The charts of 128 randomly chosen patients who had undergone total knee replacement were reviewed. Sixty-four patients were from orthopedic units with CNSs and 64 were from orthopedic units without CNSs. This study was based on Donabedian's framework for assessment of quality of care using structure, process, and outcome variables. Structural variables were collected on institutional and unit demographics. Data were gathered on nursing care interventions (process variables) using process instruments designed by the investigator. Length of stay, total length of stay, which included rehabilitation length of stay, and complications were the outcome variables used. Patients on units with CNSs had significantly higher process scores, shorter total length of stay, and fewer complications than patients on units without CNSs. In addition, significant negative correlations were found between process instrument scores and total length of stay. Higher scores on the process instruments (with CNS units) were correlated with shorter total length of stay. The number of complications was also negatively correlated to the process instrument scores.

Aged↗
PubMed2002

Reproductive decisions of parents of children with metabolic disorders.

The Interaction Model of Client Health Behavior (IMCHB) served as a guide for variable selection and instrument development for telephone interviews with 230 parents of children with metabolic disorders. Sociodemographic, psycho-affective and client-professional interaction variables were examined in relation to three outcomes: (1) receptivity to future prenatal diagnosis (56% were receptive); (2) likelihood of terminating an affected pregnancy (10% would); and (3) whether or not the parent had taken measures to prevent another affected pregnancy (41% had). All three outcomes were significantly correlated with higher scores on the Parent Stress Index, lower scores on the Vineland Adaptive Behavior Scales, fewer persons in the parent's social support network, greater worry about the living child's future and greater perceived difficulty meeting the child's extra care needs. A regression model constructed to explain taking measures to prevent a future affected pregnancy illustrated the usefulness of the IMCHB in research that involves multiple interacting variables on health outcomes. Few of the parents (7.4%) reported an interaction with a genetic counsellor, highlighting the need for practitioners from multiple disciplines to be adequately educated in principles of genetics, especially the psychological and affective aspects of counselling.

Abortion, Induced↗
PubMed1995

Reading research critically: assessing the validity and reliability of research instrumentation--Part 2.

Accurate measurement of research variables is necessary so that research consumers can trust that it is the research intervention that affected the change in the outcome variable, not some extraneous error component. Reliability is the accuracy with which the research instruments measure the variable that they are designed to measure. A number of known threats to instrument reliability should be anticipated by the researcher and looked for the consumer. These threats are presented in this article.

Bias↗
PubMed1984

Outcome measurement in osteoarthritis clinical trials: the case for standardisation.

Outcome measures for clinical trials to be valid and reliable should also be responsive to change. There are currently no standardised methods of measuring the outcome in osteoarthritis clinical trials. A review of 63 trials of nonsteroidal anti-inflammatory drugs revealed a large degree of variability in the items, instruments and scales employed. The implications of this variability are discussed and methods proposed for rationalising outcome measurement in this area of clinical research.

Activities of Daily Living↗
PubMed2004

The intra- and inter-instrument reliability of DXA based on ex vivo soft tissue measurements.

OBJECTIVE: Comparison of ex-vivo soft tissue measurements using the GE/Lunar pencil (DPX-L; GE/Lunar Co., Madison, WI) and fan beam (Prodigy dual-energy X-ray absorptiometers (DXA) GE/Lunar Co.). RESEARCH METHODS AND PROCEDURES: Intra-instrument reliability was assessed by repeatedly scanning soft tissue phantoms for lean tissue (water) and fat tissue (methanol) using one DPX-L and two identical Prodigy DXAs at fast, medium, and slow scan modes. For each machine, 10 scans of each phantom were performed at each scan speed. The number of scans per instrument totaled 60. Data were analyzed using ANOVA to ascertain whether scan speed affected the intra-instrument reliability and to test whether soft tissue measurements differed among instruments. Percentage fat (phantom density) was the outcome variable. RESULTS: Intra-instrument reliability, expressed as coefficient of variation, ranged between 0.7% and 5.2% for the DPX-L and 0.4% and 4.5% for the Prodigy, with the lowest coefficients of variation observed when scanning the fat tissue phantom. Scan speed also affected the intra-instrument reliability (p < 0.01). Furthermore, differences in the measurement of percentage body fat for both the lean and fat tissue phantoms were observed among all three absorptiometers (all p < 0.01). After adjusting for scan speed, differences persisted for all three instruments. DISCUSSION: Intra- and inter-instrument reliability of DXA machines, even those from the same manufacturer, remains unpredictable. Thus, when measuring body composition using DXA, it is important to consider that even in the absence of measurement bias, the use of different DXA machines, particularly when using a variety of speed settings, will increase the residual error around the true value.

Absorptiometry, Photon↗
PubMed2002

Patient-assessed health outcome measures for diabetes: a structured review.

AIMS: To identify available disease-specific measures of health-related quality of life (HRQL) for diabetes and to review evidence for the reliability, validity and responsiveness of instruments. METHODS: Systematic searches were used to identify instruments. Instruments were assessed against predefined inclusion and exclusion criteria. Letters were sent to authors requesting details of further instrument evaluation. Information relating to instrument content, patients, reliability, validity and responsiveness to change was extracted from published papers. RESULTS: The search produced 252 references. Nine instruments met the inclusion criteria: Appraisal of Diabetes Scale (ADS), Audit of Diabetes-Dependent Quality of Life (ADDQoL), Diabetes Health Profile (DHP-1, DHP-18), Diabetes Impact Measurement Scales (DIMS), Diabetes Quality of Life Measure (DQOL), Diabetes-Specific Quality of Life Scale (DSQOLS), Questionnaire on Stress in Diabetic Patients-Revised (QSD-R), Diabetes-39 (D-39) and Well-being Enquiry for Diabetics (WED). The shortest instrument (ADS) has seven items and the longest (WED) has 50 items. The ADS and ADDQoL are single-index measures. The seven multidimensional instruments have dimensions covering psychological well-being and social functioning but vary in the remainder of their content. The DHP-1 and DSQOLS are specific to Type 1 diabetes patients. The DHP-18 is specific to Type 2 diabetes patients. The DIMS and DQOL have weaker evidence for reliability and internal construct validity. Patients contributed to the content of the ADDQoL, DHP-1/18, DQOL, DSQOLS, D-39, QSD-R and WED. The authors of the ADDQoL, DHP-1/18, DQOL, DSQOLS gave explicit consideration to content validity. The construct validity of instruments was assessed through comparisons with instruments measuring related constructs and clinical and sociodemographic variables. None of the instruments has been formally assessed for responsiveness to changes in health. CONCLUSIONS: Five of the diabetes-specific instruments have good evidence for reliability and internal and external construct validity: the ADDQoL, DHP-1/18, DSQOLS, D-39 and QSD-R. Instrument content should be assessed for relevance before application. The instruments should be evaluated concurrently for validity and responsiveness to important changes in health.

Diabetes Mellitus↗
PubMedDate not supplied

[Instruments for quantitative methods of nursing research].

Instruments for quantitative nursing research are a mean to objectify and measure a variable or a phenomenon in the scientific research. There are direct instruments to measure concrete variables and indirect instruments to measure abstract concepts (Burns, Grove, 1997). Indirect instruments measure the attributes by which a concept is made of. Furthermore, there are instruments for physiologic variables (e.g. for the weight), observational instruments (Check-lists e Rating Scales), interviews, questionnaires, diaries and the scales (Check-lists, Rating Scales, Likert Scales, Semantic Differential Scales e Visual Anologue Scales). The choice to select an instrument or another one depends on the research question and design. Instruments research are very useful in research both to describe the variables and to see statistical significant relationships. Very carefully should be their use in the clinical practice for diagnostic assessment.

Humans↗
PubMed1996

The relationship of cardiovascular and psychological impairments to the health status of patients enrolled in cardiac rehabilitation programs.

BACKGROUND AND PURPOSE: Understanding the causes of differences in disability among individuals is an important research focus for rehabilitation professionals. The purpose of this study was to examine the relationship between health status and the impairments commonly associated with cardiovascular pathophysiology. SUBJECTS: The subjects were patients (N=789) enrolled in 13 cardiac rehabilitation programs in Massachusetts. METHODS: Data were collected on psychological and physiological impairments, demographic characteristics, and health status. Multivariate analyses were used to determine which measures of impairment and patient characteristics were related to health status. RESULTS: Psychological impairment was related to all scales of the MOS 36-item Short-Form Health Survey (SF-36). Very few measures of physiological impairment and individual characteristics were related to SF-36 scores. The models accounted for 16% to 57% of the variability of the instrument's scales. CONCLUSION AND DISCUSSION: In patients entering cardiac rehabilitation, psychological distress is related to poor health in both the physical and psychological dimensions. Variability in health status is not well explained by traditional measures of impairment or demographic characteristics. Physical therapists working to address their patients' health needs must consider collecting data, setting goals, and devising interventions that address psychological impairment.

Adult↗
PubMed2004

Factors responsible for the variability of saquinavir absorption: studies using an instrumented dog model.

PURPOSE: To study the effect of dose and food on the bioavailability of saquinavir in dogs. METHODS: A Youden Square block design was used for six female mongrel dogs (20-24 kg) who received six saquinavir treatments. The six randomized treatments were 1 mg/kg intravenous infusion over 30 min; 200, 400, 600, and 800 mg of saquinavir in the form of 200-mg capsules given orally with food; and 400 mg of saquinavir given orally after an overnight fast. A 200-mg 14C-saquinavir capsule was used to replace one of the 200-mg unlabeled saquinavir capsules in the 200- and 800-mg oral study. RESULTS: Absorption of saquinavir from the gut was variable. (F(A): 49-95%). The 14C-saquinavir study shows that the total radioactivity absorbed from the gut was insignificantly different from that of unlabeled saquinavir, suggesting first-pass gut metabolism was unimportant. The bioavailability of saquinavir under fasting condition was significantly lower (8.41 +/- 4.7% vs. 20.3 +/- 2.6%, p < 0.05). Saquinavir underwent significant first-pass liver metabolism because hepatic clearance values (22 to 30 ml min(-1) kg(-1)) approached that of liver blood flow. CONCLUSIONS: Incomplete gut absorption and extensive first-pass liver metabolism are the causes for low bioavailability of saquinavir in dogs. Absorption was further reduced under fasted conditions.

Administration, Oral↗
PubMed1999

Validation of the force and frequency characteristics of the activator adjusting instrument: effectiveness as a mechanical impedance measurement tool.

OBJECTIVE: To determine the dynamic force-time and force-frequency characteristics of the Activator Adjusting Instrument and to validate its effectiveness as a mechanical impedance measurement device; in addition, to refine or optimize the force-frequency characteristics of the Activator Adjusting Instrument to provide enhanced dynamic structural measurement reliability and accuracy. METHODS: An idealized test structure consisting of a rectangular steel beam with a static stiffness similar to that of the human thoracolumbar spine was used for validation of a method to determine the dynamic mechanical response of the spine. The Activator Adjusting Instrument equipped with a load cell and accelerometer was used to measure forces and accelerations during mechanical excitation of the steel beam. Driving point and transfer mechanical impedance and resonant frequency of the beam were determined by use of a frequency spectrum analysis for different force settings, stylus masses, and stylus tips. Results were compared with beam theory and transfer impedance measurements obtained by use of a commercial electronic PCB impact hammer. RESULTS: The Activator Adjusting Instrument imparted a very complex dynamic impact comprising an initial high force (116 to 140 N), short duration pulse (<0.1 ms) followed by several lower force (30 to 100 N), longer duration impulses (1 to 5 ms). The force profile was highly reproducible in terms of the peak impulse forces delivered to the beam structure (<8% variance). Spectrum analysis of the Activator Adjusting Instrument impulse indicated that the Activator Adjusting Instrument has a variable force spectrum and delivers its peak energy at a frequency of 20 Hz. Added masses and different durometer stylus tips had very little influence on the Activator Adjusting Instrument force spectrum. The resonant frequency of the beam was accurately predicted by both the Activator Adjusting Instrument and electronic PCB impact hammer, but variations in the magnitude of the driving point impedance at the resonant frequency were high (67%) compared with the transfer impedance measurements obtained with the electronic PCB impact hammer, which had a more uniform force spectrum and was more repeatable (<10% variation). The addition of a preload-control frame to the Activator Adjusting Instrument improved the characteristics of the force frequency spectrum and repeatability of the driving point impedance measurements. CONCLUSION: These findings indicate that the Activator Adjusting Instrument combined with an integral load cell and accelerometer was able to obtain an accurate description of a steel beam with readily identifiable geometric and dynamic mechanical properties. These findings support the rationale for using the device to assess the dynamic mechanical behavior of the vertebral column. Such information would be useful for SMT and may ultimately be used to evaluate the [corrected] biomechanical effectiveness of various manipulative, surgical, and rehabilitative spinal procedures.

Acceleration↗
PubMed1986

Psycho-social and environmental factors in triad model for the management of control programme: focus on leprosy.

The study addresses the question of how the qualitative aspect of the interaction between the people involved in the leprosy control programme affects the process of patients (P), service providers (SP) and satellite informants (SI) composed of community leaders, in the delivery of basic leprosy control services in two high leprosy endemic villages in La Union province, the Philippines. The interaction between P, SP and SI as an independent variable is imagined to be linked in a form of a triad, influenced by psycho-social and environmental variables. Data was gathered by conventional methods as interviews, historical research and use of rating scales as well as non-conventional methods as PUP, a locally developed standardized instrument which measures variables that determine a Filipino's adjustment to social situations, and photographic documentation. Statistical analysis was made on the independent variable and the dependent variable - an improved Leprosy Control Programme. It was observed that the stigmatization of Hansenites had deep historical roots with the policy of colonial administrations to isolate and segregate Hansenites. This stigma remains to the present and was observed to exist even among service providers: Low knowledge levels of patients on the causes of the disease on the one hand, and service providers on the cure, particularly on the use of Multiple Drug Therapy. The reorganization scheme of the Health Ministry also resulted in the slow down of leprosy control activities thereby affecting delivery of services. Individual personality traits and other psycho-social factors of P, SP and SI further contributed to the lag in service delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude of Health Personnel↗
PubMed2004

How adolescents construct their future: the effect of loneliness on future orientation.

This study examined the effect of loneliness, gender, and two dimensions of prospective life domains on adolescent future orientation. Future orientation was studied in four prospective domains: social relations, marriage and family, higher education and work and career. These domains are described in terms of two dimensions: theme (relational vs. instrumental) and distance (near vs. distant future). Data collected from Israeli Jewish adolescents (11th graders) were analysed by repeated measures ANOVAs and ANCOVAs (covariate: depressive experiences) for seven future orientation variables: value, expectance, control (motivational variables), hopes, fears (cognitive representation variables), exploration, commitment (behavioural variables). As predicted, lonely adolescents scored lower than socially embedded adolescents on future orientation variables applied to the relational and near future domains and lonely boys scored lower than lonely girls. However, effects were found only on the three future orientation motivational variables and not on the cognitive representation and behavioural variables. Contrary to prediction controlling for the effect of depressive experiences did not reduce the effect of loneliness on the future orientation variables, but reduced the tendency of adolescents to score higher on all future orientation variables in the instrumental than in the relational prospective domains. The contribution of these findings to the understanding of adolescent loneliness and future orientation was discussed and directions for future research were suggested.

Adolescent↗
PubMed1992

The use of cognitive style mapping as a predictor for academic success of first-semester diploma nursing students.

This study determined the relationship between the components of the cognitive map and the diploma nursing student's successful academic completion of the first semester. This ex post facto study applied the Modified Hill Cognitive Style Model (MHCSM) instrument; the final grade, the dependent variable, was intercorrelated with the instrument's 28 mapping elements. Data analysis indicated three positively correlated predictors: a preference for finding meaning from written words, for independent problem-solving, and for a logical deductive approach in decision-making. Four negatively correlated predictors included a preference for finding meaning from the spoken word, for finding meaning from sight, for problem-solving with peers, and for categorical reasoning. Implications applicable to nursing education are included.

Cognition↗
PubMed1999

Patient centred assessment of quality of life for patients with four common conditions.

OBJECTIVES: To assess the reliability, validity, and responsiveness of a new quality of life measure, the patient generated index (PGI) of quality of life, in patients with four common clinical conditions. DESIGN: Prospective one year follow up study. SETTING: Outpatient departments and four general practices in Grampian, Scotland. SUBJECTS: 1746 patients consulting a general practitioner in one of four practices, or referred to outpatients from all Grampian practices over a four month period, with low back pain, menorrhagia, suspected peptic ulcer, and varicose veins. MAIN OUTCOME MEASURES: Postal questionnaire including the PGI, SF-36 health survey, and clinically derived condition specific measures of disease severity. RESULTS: Test-retest reliability was satisfactory for group comparisons (intraclass correlation coefficient 0.65). Validity was confirmed by the observed association of the PGI with the SF-36, condition specific instruments, and sociodemographic variables. For low back pain, the PGI and the SF-36 pain scale were found to be most responsive to clinical change. For patients with menorrhagia and suspected peptic ulcer, only the condition specific instruments detected larger changes than the PGI. CONCLUSIONS: It is possible to develop a patient generated index of quality of life that not only assesses the extent to which patients' expectations are matched by reality but also satisfies criteria of reliability and responsiveness to change. Further work is required to make the PGI more acceptable and meaningful to patients, but it is believed that it offers an exciting new approach to the evaluation of medical care.

Family Practice↗
PubMed2003

Variability of porcelain color reproduction by commercial laboratories.

STATEMENT OF PROBLEM: Many investigations in the field of metal ceramics have examined materials, manipulative variables, and the relationship of these factors to a restoration's color. However, the effect of the artistic component of restoration fabrication is not known. PURPOSE: The purpose of this study was to determine through instrumental colorimetry the variability in color reproduction for metal ceramic crowns fabricated by commercial dental laboratory technicians. MATERIALS AND METHODS: Fifty metal ceramic crowns were fabricated on standardized metal frameworks to the same shade specifications by 5 commercial dental laboratories (n=10). Laboratory prescriptions requested that the technician match the shade and translucency of a provided Vita Lumin A3.5 shade tab. Technicians used the porcelain and technique of their own selection to match the tab. Color differences were determined by use of a colorimeter between crowns and the prescribed shade tab at middle and incisal sites. Analysis of variance was used to determine whether differences in color reproduction existed among laboratories. Where statistically significant interactions existed, the Tukey honestly significant difference test was used to determine significant differences between laboratories according to sites (alpha=.05). RESULTS: Color reproduction was significantly different (P <.0001) among laboratories for both sites. Mean color difference from shade tabs ranged from 3.5 to 11.1 DeltaE units. All laboratories were better at matching shades in the incisal third of the crown. CONCLUSION: Within the limitations of this study, the ability to reproduce the color of the target shade tab differed among laboratories. Most crowns fabricated by the laboratories in this study, when compared to the prescribed shade tab, were above the clinical threshold for an acceptable shade match under intraoral conditions (DeltaE 3.7).

Analysis of Variance↗
PubMed1989

Analysis of haemorheological variables--methodology and reference values.

Routine methods are proposed for the analysis of haemorheologic variables with only one instrument, a Low Shear 30 rotational couette viscometer. The variables are plasma viscosity, whole blood apparent viscosity, erythrocyte aggregation tendency and erythrocyte fluidity. These variables, in addition to erythrocyte volume fraction, were analysed in a population of 83 healthy hospital staff subjects. The following means and standard deviations were found: Erythrocyte volume fraction, women 42 +/- 3%, men 46 +/- 2%; Plasma viscosity 1.31 +/- 0.07 mPa.s; Whole blood apparent viscosity, women 4.3 +/- 0.4 mPa.s, men 4.8 +/- 0.3 mPa.s; Erythrocyte aggregation tendency 1.00 +/- 0.10; Erythrocyte fluidity 122 +/- 10 Pa-1.s-1.

Blood Chemical Analysis↗
PubMed2002

Factors that are associated with clinically overt postpartum urinary retention after vaginal delivery.

OBJECTIVE: This study was undertaken to determine the incidence of clinically overt postpartum urinary retention after vaginal delivery and to examine what maternal, fetal, and obstetric factors are associated with this problem. STUDY DESIGN: This was a retrospective case-controlled study of women who had overt postpartum urinary retention after vaginal delivery from August 1992 through April 2000. RESULTS: Fifty-one of 11,332 (0.45%) vaginal deliveries were complicated by clinically overt postpartum urinary retention. In most cases (80.4%), the problem had resolved before hospital dismissal. Persons with urinary retention were more likely than control subjects to be primiparous (66.7% vs 40.0%; P <.001), to have had an instrument-assisted delivery (47.1% vs 12.4%; P <.001), to have received regional analgesia (98.0% vs 68.8%; P <.001), and to have had a mediolateral episiotomy (39.2% vs 12.5%; P <.001). On multivariate logistic regression analysis, of these 4 variables, only instrument-assisted delivery and regional analgesia were significant independent risk factors. CONCLUSION: Clinically overt postpartum urinary retention complicates approximately 1 in 200 vaginal deliveries, with most resolving before hospital dismissal. Factors that are independently associated with its occurrence include instrument-assisted delivery and regional analgesia.

Adult↗