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 955 records · Page 53Linked to original sources
PubMed2005

[Comparison of MDS-AC registration and conventional medical records in Iceland and other Nordic countries. A part of a Nordic study].

OBJECTIVE: Complex functional decline and comorbid state is an important indicator of outcome for hospital care of older adults. In today acute care it is important to quickly be able to target those who might benefit from geriatric assessment. The MDS-AC is an evaluation system for geriatric acute care patients that records functional impairment and co-morbid states. The object of this study was to compare the MDS-AC registration with the traditional nurses and doctors records for chosen variables important to older patient care in Iceland and other Nordic countries. METHODS: This was a randomised prospective Nordic study. The study took place in Reykjavík, Copenhagen, Umeå, Oslo and Helsinki. Participants in each country were chosen from 75 year old and older patients admitted to acute care medical wards, 160 patients from each country. The results presented here show data from selected variables collected with the MDS-AC instrument version 1,1 in the first 24 hours of admission, compared with hospital notes for the first 48 hours. RESULTS: For ADL and IADL impairments the medical record missed between 20 to 96% of items registered with the MDS-AC and between 33 to 100% when there is no impairment detected. This was true for all the participating Nordic countries but the Icelandic medical records were in comparison more often incomplete for the variables chosen. CONCLUSION: The MDS-AC documents better than traditional medical records several important variables relating to function among the elderly. It may be possible to improve documentation with a standardized instrument such as the MDS-AC.

Activities of Daily Living↗
PubMed2006

Instrumentation in anaerobic treatment--research and practice.

High rate anaerobic treatment reactors are able to uncouple solids and liquid retention time, resulting in high biomass concentrations. Principal advantages of anaerobic treatment include: energy efficiency, low biomass yield, low nutrient requirement and high volumetric organic loadings. In order to facilitate small reactors operation with stable and good performance automatic process control systems in combination with on-line instrumentation are proposed. The paper reviews the development and availability of the principal instrumentation for anaerobic treatment processes. First, the most important measuring principles are discussed, followed by a review of the most important process variables with emphasis on the development of their instrumental measurement techniques and application in research. Finally, a summary of actual application of instrumentation in full-scale anaerobic treatment plants is presented.

Automation↗
PubMed2005

A portable, low-resistance puff topography instrument for pulsating, high-flow smoking devices.

A smoking topography instrument appropriate for pulsating high flow rate smoking devices, such as the narghile water pipe, has been developed and tested. Instrument precision and repeatability was determined using a digitally controlled smoking machine, and the added draw resistance due to the topography instrument was measured over the range of expected puff flow rates. The maximum error in any topography variable was found to be less than 5%. The instrument was successfully demonstrated in a pilot field study of 30 volunteer narghile smokers. The pilot study yielded an average smoker puff volume, duration, and interpuff interval of 0.531, 2.47 sec, 16.28 sec, respectively.

Artifacts↗
PubMedDate not supplied

Development of the HIV/AIDS Q-sort instrument to measure physician attitudes.

BACKGROUND: Providers'attitudes about HIV/AIDS are an important dimension in the delivery of quality care to persons with HIV/AIDS. It is believed that education can alter attitudes, but there is a needfor a user-friendly instrument to measure the effect that HIV/AIDS educational programs have on attitudes. METHODS: A pool of HIV/AIDS attitude descriptors was collected through literature review and from individuals working in the HIV/AIDS field. Out of this pool of 90 descriptors, 48 descriptors with the highest face validity were selected through expert consensus ranking to create a preliminary survey instrument. Twenty-six physicians completed a pilot Q-Sort instrument with 48 descriptors. A variance analysis was conducted, and the top 28 descriptors with the most variability were selected for the final Q-Sort instrument, which was then completed by 191 physicians. A factor analysis was conducted to identify a small number of factors that explained the 28 descriptors. A subsample of 22 physicians repeated the test to establish test-retest reliability. RESULTS: Factor analysis revealed three factors: (1) emotionality, (2) ability, and (3) reluctance. The Q-Sort instrument demonstrated good test-retest reliability, with reliability for the three factors of .82, .80, and .88, respectively. CONCLUSIONS: This Q-sort instrument is a reliable method for measuring physician attitudes toward HIV/AIDS patients. Further studies can test its use for evaluating the effect of educational programs on changing provider attitudes.

Acquired Immunodeficiency Syndrome↗
PubMed1997

1997 Volvo Award winner in clinical studies. The effect of pedicle screw instrumentation on functional outcome and fusion rates in posterolateral lumbar spinal fusion: a prospective, randomized clinical study.

STUDY DESIGN: A prospective randomized clinical study. OBJECTIVES: To evaluate supplementary pedicle screw fixation (Cotrel-Dubousset) in posterolateral lumbar spinal fusion. SUMMARY OF BACKGROUND DATA: The rationale behind lumbar fusion is to eliminate pathologic motion to relieve pain. To improve fusion rates and to allow reduction, a rigid transpedicular screw fixation may be beneficial, but the positive effect of this may be counter-balanced by an increase in complications. METHODS: The inclusion criteria were severe, chronic low back pain from spondylolisthesis Grades 1 and 2 or from primary or secondary degenerative segmental instability. One hundred thirty patients were randomly allocated to receive no instrumentation (n = 66) or Cotrel-Dubousset instrumentation (n = 64) in posterolateral lumbar fusion. Variables were registered at the time of surgery and at 1 and 2 years after surgery. RESULTS: Follow-up was achieved in 97.7% of the patients. Fusion rates deduced from plain radiographs were not significantly different between instrumented and noninstrumented groups. The functional outcome assessed by the Dallas Pain Questionnaire improved significantly in both groups, and there were no significant differences in results between the two groups, except for significantly better (P < 0.06) functional outcome in relation to daily activities in the instrumented group when neural decompression had been performed. The global patients' satisfaction was 82% in the instrumented group versus 74% in the noninstrumented group (not significant). Fixation of instrumentation increased operation time, blood loss, and early reoperation rate significantly. Patients experienced only a few minor postoperative complications; none were major. Two infections appeared in the Cotrel-Dubousset group. Significant symptoms from misplacement of pedicle screws were seen in 4.8% of the instrumented patients. CONCLUSIONS: Lumbar posterolateral fusion with pedicle screw fixation increases the operation time, blood loss, and reoperation rate, and leads to a significant risk of nerve injury. The functional outcome improves significantly with high patient satisfaction, with or without instrumentation. No significant differences were observed between the two groups in functional outcome and fusion rate. The only gain in functional outcome from instrumentation was found in the daily activity category in patients with supplementary neural decompression. The results of this study do not justify the general use of pedicle screw fixation alone as an adjunct to posterolateral lumbar fusion.

Adult↗
PubMed2002

Autonomic modulation of the heart in systemic arterial hypertension.

OBJECTIVE: To analyze the heart rate variability in patients with mild to moderate systemic arterial hypertension. METHODS: Thirty-two healthy (group I) and 70 systemic arterial hypertensive (group II) individuals, divided according to age (40 to 59 and 60 to 80 years old, respectively) and with a similar distribution by sex were studied. Thirty-one had left ventricular hypertrophy (LVH), 22 were overweight, and 16 had Type II diabetes mellitus. Smoking, alcohol ingestion, and sedentary habits were the same between groups. Variability in heart rate was analyzed in the time domain, using standard deviations of normal RR intervals (SDNN) and the differences between maximal brady- and tachycardia (D-BTmax) during sustained inspiration. Analysis of the frequency band of the power spectrum between 0.05 and 0.40 Hz at rest and during controlled respiration was chosen for analysis of the frequency domain. RESULTS: In both time and frequency domains, variables were lower in group II than in group I. Within groups, statistically significant variables were only found for individuals in the 40 to 59 year old group. The presence of LVH, overweight, or diabetes mellitus did not influence the variability in heart rate to a significant extent. CONCLUSION: Variability in heart rate was a valuable instrument for analyzing autonomic modulation of the heart in arterial hypertension. The autonomic system undergoes significant losses in cardio-modulatory capacity, more evident in subjects between 40 and 59 years old. In those over 60 years old, reduced variability in heart rate imposed by aging was not significantly influenced by the presence of systemic arterial hypertension.

Adult↗
PubMed2000

[The measurement of health related quality of life].

The measurement of health-related quality of life (HRQOL) plays a very important role in the study of health outcomes, particularly in effectiveness studies. Nevertheless, the nature of these studies implies a series of challenges in the use of HRQOL instruments, due to the type of comparisons made, the heterogeneity of subjects included in terms of both the presence of comorbid conditions and the ability to understand and complete questionnaires, and because there is a need to collect the data in conditions of usual clinical practice. The aim of this paper is to discuss some of these issues, as well as other topics of current interest in the field, such as the use of individualized measures, applications of Item Response Theory, and response shift phenomenon research. With regard to the use of HRQOL measures in effectiveness studies, the main conclusions are that: a) instrument selection probably needs to be even more careful than in controlled clinical trials, and needs to take into account time pressures and variability in patients' ability to respond; b) that instrument selection should centre on the use of disease-specific measures; c) that generic measures may play an important role in capturing the broader effects of co-morbidity, and may be useful in controlling certain types of bias, and d) that more comparisons are required between disease-specific instruments for the same condition, particularly with respect to their discriminative power and their sensitivity to change.

Cost of Illness↗
PubMed1996

Focus on qualitative methods: Using qualitative methods in intervention studies.

Qualitative research commonly is viewed as the antithesis of the clinical trial and far removed from the immediate practical aims of intervention studies and nursing practice. Yet, qualitative methods can be used to enhance the significance and harness the benefits of clinical trials, and to emphasize the distinctive work and outcomes of nursing care. Qualitative methods are especially useful for further describing or explaining subject variation on outcome variables, verifying outcomes obtained from standardized instruments, and clarifying and evaluating interventions in their real-life contexts.

Clinical Trials as Topic↗
PubMed1997

Stability enhancement for peptide analysis by electrospray using the triple quadrupole mass spectrometer.

Electrospray ionization sources, used with triple quadrupole mass spectrometers from PE/Sciex (API III+), Micromass (Quattro II), and Finnigan (TSQ 7000), were modified with a 35-gauge stainless steel needle. The dimensions of the needle were 63 microm i.d. by 145 microm o.d. with variable length, depending on the specific instrument. This modification led to enhanced signal stability, improved signal/noise ratios, and lowered sample consumption for a wide range of peptides. Stable baselines were observed with flow rates in the range of 50 nL/min to 5 microL/min. An alternative design, based on a metal wire housed within a fused silica capillary, led to the most stable signals of all during infusion, but caused excessive peak broadening with capillary chromatography. The Finnigan interface was further modified with an external postcolumn addition tee, used in conjunction with capillary liquid chromatography columns of 30 and 50 microm internal diameter. The best results with the modified Finnigan interface were acquired using the 50-microm column at a flow rate of 150 to 200 nL/min.

Factor VII↗
PubMed1986

A set of double-angled needle holders and long, angled tissue forceps for use in surgery of the abdomen.

A set of double-angled needle holders and long, angled tissue forceps have been designed and presented for use in surgery of the abdomen. The problems of passage and control of curved needles in all directions is well recognized. The marriage of design and presentation addresses the mechanical and anatomic needs of surgeons in the pelvis, subdiaphragmatic area, and in large and obese patients. Multiple variables in use provided by these instruments, particularly when used together, enhance surgical control at problem sites.

Abdomen↗
PubMed2003

Analytical procedures for quantification of peptides in pharmaceutical research by liquid chromatography-mass spectrometry.

Peptide quantification by liquid chromatography-mass spectrometry (LC-MS) combines the high resolving power of reversed-phase (RP) chromatography with the excellent selectivity and sensitivity of mass spectrometric detection. On the basis of comprehensive practical experience in the analysis of small molecules, pharmaceutical research is developing technologies for analysis of a growing number of peptidic drug candidates. This article is a detailed review of procedures based on LC-MS techniques for quantitative determination of peptides. With the focus on pharmaceutical applications several technologies for sample preparation, various aspects of peptide chromatography, important characteristics of ESI-MS, selectivity of MS-detection modes, the large variability of internal standards, and modern instrumentation are discussed. The demand for reliable, robust, sensitive, and accurate methods is discussed using numerous examples from the literature, complemented by experiments and results from our laboratory.

Chromatography, Liquid↗
PubMedDate not supplied

Time after bone marrow transplantation as an important variable for quality of life: results of a cross-sectional investigation using two different instruments for quality-of-life assessment.

Quality of life (QoL) was investigated in 56 BMT recipients. The objective was to compare QoL in terms of physical, emotional, and social functioning between patients within the first year after BMT (n = 15) and patients who were alive more than 1 year after BMT (n=41). The Functional Assessment of Cancer Therapy Scale (FACT-BMT) and the EORTC-Quality of Life Questionnaire (EORTC-QLQ C30) were used to evaluate QoL as perceived by the patients. Results show a significantly reduced general QoL in patients within the first year after BMT. Specific differences were identified on the dimensions of physical and emotional well-being and the symptom scales of appetite loss, fatigue, pain, dyspnea, and nausea and vomiting. QoL improves significantly with time after BMT. We suggest that there should be more integration of QoL expectancy into the pre-BMT information process. Patients should be informed about potential deficits in physical and emotional well-being within the first year after BMT. This could enhance insight and compliance in the critical period early after BMT.

Adult↗
PubMed1990

End-cap for the biomechanical testing of spinal segments.

Precise mechanical loading is essential in the in vitro evaluation of spinal fixation instrumentation, but the control of experimental variables is difficult because of variations in specimen morphology, size and end conditions, and gross specimen flexibility. This paper describes an end-cap which is simple in design, time efficient in its attachment to the spine and which provides precise positioning and rigid control of the end fixation points, resulting in excellent experimental control. It is easily adapted to human or animal specimens and provides a reliable load application unit, which permits specific physiological end conditions to be applied.

Animals↗
PubMed1989

Prevalence of psychopathology among mentally retarded adults.

The prevalence of psychopathological disorders was determined in a random, stratified sample of 165 adults, 110 males and 55 females, with mental retardation using the Psychopathology Instrument for Mentally Retarded Adults. Stratified variables included mental retardation level and living environment (institutional, family, independent). Results showed that 35.9% of the sample had at least one significant psychopathological disorder. Presence of pathology was related to level of retardation, but not to living environment, sex, or age. Difficulties associated with assessing pathology in persons with mental retardation are described.

Adult↗
PubMed2005

Evaluation of upper-limb spasticity after stroke: A clinical and neurophysiologic study.

OBJECTIVES: To assess upper-limb spasticity after stroke by means of clinical and instrumental tools and to identify possible variables influencing the clinical pattern. DESIGN: Descriptive measurement study of a consecutive sample of patients with upper-limb spasticity after stroke. SETTING: Neurorehabilitation hospital. PARTICIPANTS: Sixty-five poststroke hemiplegic patients. INTERVENTIONS: Not applicable. Main outcome measures Upper-limb spasticity, as assessed clinically (Modified Ashworth Scale [MAS], articular goniometry) and neurophysiologically (maximum H-reflex [Hmax], maximum M response [Mmax], Hmax/Mmax ratio). RESULTS: Poorer MAS scores were associated with lower passive range of motion (PROM) values at the wrist ( P =.01) and elbow ( P =.002). The flexor carpi radialis Hmax/Mmax ratio correlated directly with MAS scores at the wrist ( P =.005) and correlated inversely with PROM. The presence of pain in the fingers, wrist, and elbow was significantly associated only with lower PROM values at the wrist. CONCLUSIONS: Upper-limb spasticity is involved in the development of articular PROM limitation after a stroke. Pain appears to be related to PROM reduction as well, but the exact causal relationship between these 2 factors is still unclear. The MAS and the Hmax/Mmax ratio correlated when evaluating poststroke spasticity; they characterize 2 different aspects of spasticity, clinical and neurophysiologic, respectively, and they could be used as an integrated approach to study and follow poststroke patients.

Adolescent↗
PubMed2004

Risk of mother-reported child abuse in the first 3 years of life.

OBJECTIVE: The purpose of this research was to investigate, within an at-risk population, parent and child characteristics associated with a mother's self-reports of severe physical assault and assault on the self-esteem of the child in the first 3 years of life. DESIGN: The study population consisted of a community-based sample of mothers of newborns identified as at-risk for child maltreatment (n=595). Families were assessed annually from the child's birth through age 3 using instruments with established psychometric properties. Independent variables investigated included: family socio-demographics, parity, mother's social support, maternal depression, maternal problem drug or alcohol use, partner violence, child's age, child's sex, low birth weight/small for gestational age (SGA), and mother's perception of child's demand level. Associations with maltreatment were examined using multivariable methods for longitudinal data. RESULTS: Child severe physical assault was significantly associated with parent characteristics (maternal depression and partner violence); and child characteristics (SGA). Assault to the child's self-esteem was significantly associated with maternal depression, maternal illicit drug use, partner violence and mother's perception of child's demand level. Controlling for family sociodemographic characteristics did not change the associations. Likewise, while mother's perception of child demand level had an independent association with self-esteem assault, the associations described above persisted while demand level was held constant. In this high-risk sample, abuse was not associated with mother's age, education, race, parity, or household income level. CONCLUSIONS: While characteristics such as SGA can serve as markers for increased abuse risk, they are not amenable to intervention after the child is born. However, certain other risk factors, such as maternal depression and domestic violence are malleable and should be targeted for intervention with the goal of preventing child maltreatment.

Adult↗
PubMed2004

Single sperm cell isolation by laser microdissection.

In 1996, Van Oorschot and Jones firstly reported in scientific correspondence that short tandem repeat (STR) profiles could be obtained from cells left on different objects. Since then, forensic scientists have focused their efforts in isolating single cells as it can be extremely helpful in solving case works where sexual violence was concerned. Laser microdissection is a micromanipulation procedure allowing to cut off precisely the cells of interest from tissue samples or smears by a laser beam fitted with an optical microscope. We have harvested single sperm cells by laser microdissection using a Leica AS LMD (Leica Microsystems, Germany); laser setting, pulse laser intensity and laser alignment as well as recovery of the specimen have been properly fitted to the samples we were dealing with. Different tissue preservation, fixation, histological staining (Papanicolau, Nuclear Fast Red-Picroindigocarmine) methods and number of harvested cells for each sample have been evaluated as well. Finally, the genotype of sperm cells has been determined by STR typing, evaluating the sensibility of this forensic technique according to instrumental and biological above-mentioned variables.

DNA↗
PubMed1999

Predictors of persistent social impairment among recovered depressed outpatients.

BACKGROUND: Though the social functioning of most depressed outpatients improves with effective treatment, a subgroup may remain impaired after recovering from depression. The purpose of this study was to identify predictors of residual social impairment among patients who recovered from depression. METHODS: These data were obtained from the Treatment of Depression Collaborative Research Program (TDCPR) public access tape. The TDCPR tested the relative efficacy of two psychotehrapies, imipramine, and placebo in major depression. Patients received follow-up assessments after completing the clinical trial. The following assessment instruments were used to assess predictor variables: Social Adjustment Scale II, Personality Assessment Form (PAF), Longitudinal Interval Follow-up Events (LIFE), and the Schedule for Affective Disorders (SADS). RESULTS: Recovered patients who were socially impaired at the end of treatment and six months later, had a higher rate of Intermittent Depression, and reported greater malfunctioning during adolescence than recovered patients whose functioning was unimpaired after treatment and at follow-up. The rates of personality disorders were not significantly different between these groups. LIMITATIONS: These analyses were performed post-hoc and the sample size was small. CONCLUSIONS: A chronic course of depression predicted persistent social maladjustment among patients who recovered from depression for 6 months.

Adolescent↗