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PubMedDate not supplied

Simplified scoring and psychometrics of the revised 12-item Short-Form Health Survey.

The 12-item Short-Form Health Survey was developed to describe mental and physical health status of adults and to measure the outcomes of healthcare services. Based on testing of the original SF-12 with a group of older adults, a revised scoring system and measurement model of the SF-12 Health Survey was proposed. The purpose of this study was to test the reliability and validity of this revised measurement model and scoring system. Testing was done with a sample of 187 older adults in a continuing care retirement community and a sample of 211 older adults discharged from an acute care setting. There was sufficient evidence for the internal consistency of the revised SF-12 (Cronbach alpha coefficients of 0.72 to 0.89); test retest reliability (r = 0.73-0.86); reliability based on R2 values; and validity based on confirmatory factor analysis, contrasted groups, and hypothesis testing. The revised SF-12 is a valid and reliable measure that can be used with confidence to measure outcomes for older adults.

Aged↗
PubMed1998

Hypotensive response during dobutamine stress echocardiography in coronary patients: a common event of well-functioning left ventricle.

BACKGROUND: Hypotensive response during dobutamine stress echocardiography (DSE) is a common complication, lacking the prognostic significance of hypotension during exercise treadmill test. HYPOTHESIS: The present study aimed to assess the possible mechanisms of hypotensive response during DSE and to compare it with exercise treadmill test. METHODS: In all, 91 patients with known coronary artery disease (CAD) underwent both DSE and exercise treadmill test. Dobutamine-induced hypotension was defined as a systolic blood pressure drop > or = 20 mmHg from baseline or from the previous level of infusion. RESULTS: Twenty-one (23%) patients, 10 of whom also had bradycardia, developed hypotension during dobutamine infusion. Five (5.5%) patients were severely symptomatic and the infusion was stopped prematurely, while in the remaining 16 the addition of atropine allowed the continuation of the test. Patients prone to hypotension were predominantly female (p = 0.0004), had smaller (p = 0.01) and better functioning left ventricles (p = 0.0004), were unlikely to have rest wall motion abnormalities (p = 0.0008) or multivessel CAD (p = 0.02), and had less ischemia (wall motion score difference) (p = 0.03). Hypotension during exercise treadmill test was observed in only one (1%) patient with left main disease. CONCLUSION: Hypotension during DSE is unrelated to the anatomical or functional extent of CAD and is frequent in the setting of a well-functioning left ventricle. We suppose that vigorous contraction of a small chamber during dobutamine infusion results in an excessive stimulation of cardiac mechanoreceptors that mediate reflex hypotension and bradycardia.

Adult↗
PubMed1995

Notes on conditional confidence limits under inverse sampling.

When the number of subjects in a two-by-two table is small or moderate, we may commonly use the exact conditional distribution with all marginals fixed to derive the conditional confidence limits on the underlying parameter. Under inverse sampling, in which we continue to sample subjects until we obtain exactly a pre-determined number of subjects failing into a specific category, this paper notes that derivation of a confidence interval, which has the coverage probability equal to or larger than a nominal 1-alpha confidence level, for relative risk and relative difference in cohort studies is straightforward. This paper further finds that, when the underlying disease is rare, we can similarly apply an inverse sampling to produce an approximate 1-alpha conditional confidence limits on attributable risk in case-control studies as well. When the number of subjects is small and the test statistic derived on the basis of large sample theory is not strictly adequate for use, this paper also presents an exact hypothesis testing procedure for the above parameters in the corresponding study designs.

Case-Control Studies↗
PubMed1998

Levels of sentence constraint and lexical decision in the two hemispheres.

This study used a lexical decision-priming paradigm to investigate the relative sensitivity of the two cerebral hemispheres to linguistic constraint. Level of constraint of syntactically and semantically correct priming sentences was determined by the Cloze procedure and constraint was manipulated by means of these sentences. High-, medium-, and low-constraining as well as neutral incomplete sentences were presented centrally prior to the appearance of a target word or nonword either to the left or to the right visual field of sixteen righthanded subjects. The hypothesis tested was that the left hemisphere benefits more from linguistic constraint than the right hemisphere. Although reaction time data generally supported this hypothesis, the right hemisphere also seemed to benefit from the constraint produced by high-constraint sentences. The relevance of these findings to the manner in which the two hemispheres process different kinds of linguistic material is discussed.

Adult↗
PubMed1983

Left ventricular functional alterations at rest and during submaximal exercise in patients with recent myocardial infarction.

Submaximal exercise testing with radionuclide ventriculography was performed in 117 patients prior to hospital discharge 16.7 +/- 6.7 days (SD) following acute myocardial infarction. The hypothesis tested in this study was that patients with different locations and types of infarction have different functional responses to submaximal exercise prior to discharge. The distribution of the myocardial infarctions were anterior transmural in 33, inferior transmural in 39, anterior nontransmural in 23, inferior nontransmural in 19, and indeterminant in three. Patients with transmural infarction generally had significantly larger resting left ventricular volumes at end-diastole and end-systole and lower ejection fractions and systolic blood pressure/end-systolic volume indexes than patients with nontransmural infarctions (p less than 0.05). During submaximal exercise, the change in end-systolic volume was significantly different in these two groups. When patients were separated further into anterior and inferior transmural subgroups, the patients with anterior transmural infarction had significantly lower left ventricular ejection fractions and higher right ventricular ejection fractions than the group with inferior transmural infarction (p less than 0.05). In response to exercise, the group with anterior transmural infarction had a significant decrease in left ventricular ejection fraction and a blunted systolic blood pressure/left ventricular end-systolic volume index, in comparison to patients with inferior myocardial infarction (p less than 0.05); this was the only group to have a significant increase in end-systolic volume. The group variance for the parameters studied was large, particularly during exercise when the individual responses were frequently directionally opposite from the group means. The group with anterior transmural infarction was the most homogeneous, with 26 of 33 having a directionally abnormal response to submaximal exercise. It was concluded that the group with anterior transmural infarction generally displayed the most abnormal left ventricular function. However, despite significant group differences in resting ventricular function with different infarcts, the intragroup variability at rest and in response to exercise was too great to permit an accurate prediction of the subject's resting ventricular performance or to permit a prediction of exercise response based solely on location of the infarct.

Aged↗
PubMed1992

Commentary on NASCIS-2.

Release of results of a clinical study to the public press prior to dissemination in a professional journal is a substantive issue which must undergo continued scrutiny. This report analyzes the second National Acute Spinal Cord Injury Study (NASCIS-2) and its subsequent reportage. NASCIS-2 was an elaborate protocol consisting of the randomized blinded use of methylprednisolone (MP), naloxone or placebo in 487 patients within 12 hours of spinal cord injury. Analysis of the entire population failed to show a significant clinical difference among treatments although data stratification revealed a significant change in patients with a complete loss of function who received MP within 8 hours of injury. The administration of MP was associated with a 7.1% incidence of wound infection. While these results suggested clinical benefit, incomplete data and statistical descriptions reduced assertions. Discrepancies in the report included lack of radiological data or descriptions of time-dependent surgical manipulations and extent of rehabilitative therapy. Justification for the broad 8-hour stratum and multiple hypothesis testing was unclear; incomplete design details included level of statistical significance, study power, stopping rules, trial duration and odds ratio data. The hypothesis that press release prior to publication in a professional journal would result in rapid therapy remained unproven. Reasons for pre-release, including limited peer review, physician familiarity with drug and dosage, and lack of alternative treatment or treatment complications were either unjustified or problematic. Early disclosure to the press resulted in da ta misinterpretation and oversimplification, failure to recognize exclusion or appropriate legal ramifications,and lack of communication to appropriate physicians.

Clinical Trials as Topic↗
PubMed2004

Comments on: A methodology for evaluation of boundary detection algorithms on medical images.

In this paper we analyze a result previously published about a comparison between two statistical tests used for evaluation of boundary detection algorithms on medical images. We conclude that the statement made by Chalana and Kim (1997) about the performance of the percentage test has a weak theoretical foundation, and according to our results, is not correct. In addition, we propose a one-sided hypothesis test for which the acceptance region can be determined in advance, as opposed to the two-sided confidence intervals proposed in the original paper, which change according to the estimated quantity.

Abdomen↗
PubMed2000

Nonlinear dynamics of heart rate variability during experimental hemorrhage in ketamine-anesthetized rats.

Indexes of heart rate variability (HRV) based on linear stochastic models are independent risk factors for arrhythmic death (AD). An index based on a nonlinear deterministic model, a reduction in the point correlation dimension (PD2i), has been shown in both animal and human studies to have a higher sensitivity and specificity for predicting AD. Dimensional reduction subsequent to transient ischemia was examined previously in a simple model system, the intrinsic nervous system of the isolated rabbit heart. The present study presents a new model system in which the higher cerebral centers are blocked chemically (ketamine inhibition of N-methyl-D-aspartate receptors) and the system is perturbed over a longer 15-min interval by continuous hemorrhage. The hypothesis tested was that dimensional reduction would again be evoked, but in association with a more complex relationship between the system variables. The hypothesis was supported, and we interpret the greater response complexity to result from the larger autonomic superstructure attached to the heart. The complexities observed in the nonlinear heartbeat dynamics constitute a new genre of autonomic response, one clearly distinct from a hardwired reflex or a cerebrally determined defensive reaction.

Anesthesia↗
PubMed2005

Scale and shape issues in focused cluster power for count data.

BACKGROUND: Interest in the development of statistical methods for disease cluster detection has experienced rapid growth in recent years. Evaluations of statistical power provide important information for the selection of an appropriate statistical method in environmentally-related disease cluster investigations. Published power evaluations have not yet addressed the use of models for focused cluster detection and have not fully investigated the issues of disease cluster scale and shape. As meteorological and other factors can impact the dispersion of environmental toxicants, it follows that environmental exposures and associated diseases can be dispersed in a variety of spatial patterns. This study simulates disease clusters in a variety of shapes and scales around a centrally located single pollution source. We evaluate the power of a range of focused cluster tests and generalized linear models to detect these various cluster shapes and scales for count data. RESULTS: In general, the power of hypothesis tests and models to detect focused clusters improved when the test or model included parameters specific to the shape of cluster being examined (i.e. inclusion of a function for direction improved power of models to detect clustering with an angular effect). However, power to detect clusters where the risk peaked and then declined was limited. CONCLUSION: Findings from this investigation show sizeable changes in power according to the scale and shape of the cluster and the test or model applied. These findings demonstrate the importance of selecting a test or model with functions appropriate to detect the spatial pattern of the disease cluster.

Journal Article↗
PubMed1994

A note on the use of confidence intervals in psychiatric research.

The emphasis on hypothesis testing, which characterizes the majority of medical research, is often inappropriate because it focuses on statistical significance (the viability of the nil hypothesis) rather than substantive significance (the magnitude of the treatment effect). An alternative approach, the reporting of a treatment effect with the corresponding confidence interval, may better reflect the researcher's intent since these are the issues that are relevant to an informed clinical decision. Additionally, results reported in this format are less likely to be misinterpreted than results presented as p values since the precision with which the effect size is estimated would be reported separately from the effect size itself.

Psychiatry↗
PubMed1999

Asymptotic power calculations: description, examples, computer code.

This paper describes two asymptotic methods for sample size and power calculation for hypothesis testing. Both methods assume that the distribution of the likelihood ratio is approximately distributed as a central chi(2) distribution under the null hypothesis and as a non-central chi(2) under the alternative hypothesis. The approximation to the non-centrality parameter differs between the methods. It is shown how these methods can be automatically extended from constraints setting parameters to constant values to constraints positing equality of parameters. Two very simple examples are presented; one demonstrates that the information method can produce arbitrarily incorrect results. Four more comprehensive examples are then discussed. In addition to demonstrating the wide range of applicability of these methods, the examples illustrate techniques that may be used in cases in which there is insufficient initial information available to perform a realistic calculation. The availability of a computer implementation of these methods in S-plus is announced, as are routines for computing the cumulative distribution function of the non-central chi(2) and its inverse.

Computer Simulation↗
PubMed2003

Exercise capability and myocardial perfusion in chronic angina patients treated with enhanced external counterpulsation.

BACKGROUND: Enhanced external counterpulsation (EECP) has been shown to improve treadmill times and myocardial perfusion. However, improvement in perfusion defects has been demonstrated only in patients exercised to the same cardiac workload on the post-EECP as the pre-EECP stress test. HYPOTHESIS: This study was to determine the effect of EECP on exercise capacity and myocardial perfusion by comparing results of maximal exercise radionuclide testing pre- and post-EECP treatment. METHODS: This prospective study included 25 patients with angina who had performed maximal symptom-limited exercise tolerance tests (ETT) with Bruce protocol and radionuclide perfusion single-photon emission computed tomography (SPECT) study prior to and at completion of EECP treatment. RESULTS: After 35 h of EECP, 23 patients (93%) improved by at least one functional angina class. There is a significant improvement in their total treadmill times (357 +/- 93 to 449 +/- 97 s, p < 0.001). There was a significant change in their peak double products, from 18,891 +/- 3,939 pre-EECP to 20,464 +/- 4,305 post-EECP ETT (p < 0.03). Pre EECP, 16 patients had ST-segment depression on their initial ETT. After EECP, 13 of these patients (80%) either no longer had ST depression or had a significant increase in their time to ST depression (229 +/- 52 to 315 +/- 60 s, p < 0.001). The radionuclide perfusion scores also showed a significant reduction in ischemic segments (16.36 +/- 10.52 to 14 +/- 10.9, p < 0.05). CONCLUSIONS: Patients treated with EECP demonstrated a reduction in angina symptoms, improvement in exercise capacity, increase in time to ST-segment depression, and decrease in perfusion defects despite performing at a higher workload.

Aged↗
PubMed1984

Segregation analyses of stuttering.

Although stuttering is known to be a familial disorder, no clear evidence regarding precise mode of transmission has arisen from previous research. In this report segregation analysis is applied to data on 386 stuttering probands and their first-degree relatives in an effort to discriminate among possible genetic models for the transmission of stuttering. Two different segregation analysis programs, PAP and POINTER, gave comparable results with respect to both hypothesis testing and parameter estimation. Specifically, the transmission of stuttering observed in these families cannot be adequately explained by a Mendelian major locus. The hypothesis of no polygenic component in the transmission of stuttering can, however, be rejected. Existence in these data of potential heterogeneity and possible violations of assumptions concerning ascertainment are considered in interpreting the results.

Adolescent↗
PubMed1993

Propofol-ketamine technique.

Case reports are presented demonstrating a new, safe, and simple intravenous technique for outpatient anesthesia. Vinnik's technique requires hypnotic doses of diazepam (Valium) to prevent ketamine-induced hallucinations. The initial hypothesis tested in this clinical series was whether hypnotic doses of propofol would prevent hallucinations from ketamine as satisfactorily as diazepam. Once the initial hypothesis was confirmed, consideration was given to moderating the cost of propofol by determining the effect of two levels of midazolam premedication on propofol requirements. Hypnotic doses of propofol do prevent ketamine-induced hallucinations. It is possible to achieve significant propofol savings by premedication with midazolam without compromising patient readiness for discharge by the end of the first postoperative hour.

Adolescent↗
PubMed1997

Felodipine protects human atrial muscle from hypoxia-reoxygenation dysfunction: a force-frequency relationship study in an in vitro model of stunning.

AIMS: We aimed at investigating contractile changes after hypoxia-reoxygenation and dobutamine challenge in superfused human atrial pectinate muscle to see whether high versus low stimulation rate during hypoxia might account for outcome differences compatible with the definition of an in vitro model of myocardial stunning and whether pretreatment with the dihydropyridine Ca2+ entry blocker felodipine might afford protection. METHODS: Human right atrial trabeculae obtained from adult patients were superfused in an organ bath with oxygenated (O2 content 16 ml/l) and modified (NaHCO3 25.7 mmol/l) Tyrode's solution at 37 degrees C. Dobutamine (1 nmol/l to 10 micromol/l) was superfused in 10 oxygenated preparations to select the optimal drug concentration to be used in another 22 which were randomized. Group (A) consisted of time-related controls (Tyrodes's solution for 225 min at cycle length (CL) 1600 ms and no dobutamine). There were two test groups, respectively: (B) low (1600 ms CL) and (C) high (400 ms CL) stimulation rate. After 60 min of stabilization, in groups B and C, hypoxic superfusion (O2 content 5 ml/l) lasted 60 min, then reoxygenation (60 min) and dobutamine challenge (1 micromol/l, 15 min) were performed. Analysis of variance for repeated measures with the Greenhouse-Geisser correction, and a repeated measures model with structured covariance (preparation mass, length, width and time-varying time to peak tension) matrices were used whereby grouping (G), time (T) and G x T interaction were weighted. Force-frequency relationship and post-pausal potentiation were studied after each phase. Electrophysiology, histomorphometry and electron microscopy were carried out (n=6). Felodipine (0.1 micromol/l, n=5) pretreatment (15 min before hypoxia) was given in parallel experiments. RESULTS: Time-related controls showed approximately 10% per hour decrease of developed tension and the Paradise test provided approximately 80% of control values. In test groups (as compared to baseline values) contractility was decreased approximately 65% after hypoxia-reoxygenation and it increased approximately 25% after dobutamine (G, 0.0065<P<0.0155; T, P=0.00005; G x T, P=0.00005). High stimulation rate during hypoxia worsened hypoxia-reoxygenation contractile changes, whereas reversibility after dobutamine was less. In both B and C groups during hypoxia, contractility decreased quite rapidly, although by 10 min or so a plateau (approximately 50%) was reached in group B, whereas in group C contractility decreased to <20%. None of the covariates contributed significantly to predict the dependent variables investigated. Force-frequency relationship and post-pausal potentiation were repeatable, paralleled overall changes due to hypoxia, reoxygenation and dobutamine challenge and were useful to discriminate Ca2+-related diastolic processes thus helping index myocardial contractile reserve. Force-frequency relationship was negative at high stimulation rates, concomitant to an abrupt change of shape and duration of action potential with little time for Ca2+-related Ca2+ release and ensuing systolic processes. Felodipine pretreatment enabled an unblunted response to dobutamine. Histomorphometry showed an unexpected 'fibrotic core'. At electron microscopy, subendocardial and deep part of the same pectinate muscles showed identical degrees of degenerative lesions. Superfused samples showed, unexpectedly, less anoxic lesions than preparations fixed within 15 min from surgical explant, although lesions were higher than in samples fixed immediately after explant. CONCLUSIONS: This might be a relevant model, whereby pharmacological or physical interventions are tested. Native human atrial trabeculae might be used without dissection and/or preservatives. If high stimulation rate during hypoxia is used the power of hypothesis testing is maximized. Future studies with this material will be easier and comparatively smaller series might be investigated. Felo

Adult↗
PubMed2004

A coarse-to-fine strategy for multiclass shape detection.

Multiclass shape detection, in the sense of recognizing and localizing instances from multiple shape classes, is formulated as a two-step process in which local indexing primes global interpretation. During indexing a list of instantiations (shape identities and poses) is compiled, constrained only by no missed detections at the expense of false positives. Global information, such as expected relationships among poses, is incorporated afterward to remove ambiguities. This division is motivated by computational efficiency. In addition, indexing itself is organized as a coarse-to-fine search simultaneously in class and pose. This search can be interpreted as successive approximations to likelihood ratio tests arising from a simple ("naive Bayes") statistical model for the edge maps extracted from the original images. The key to constructing efficient "hypothesis tests" for multiple classes and poses is local ORing; in particular, spread edges provide imprecise but common and locally invariant features. Natural tradeoffs then emerge between discrimination and the pattern of spreading. These are analyzed mathematically within the model-based framework and the whole procedure is illustrated by experiments in reading license plates.

Journal Article↗
PubMedDate not supplied

[Epidemiology of cognitive deterioration in geriatric population of 'Casals d' Avis' in the city of Barcelona].

The aim of the study is to carry out a clinico-epidemiological study of the part of Barcelona's population over the age of 65 that suffers from cognitive deterioration, users of 'Casal d'Avis' (Old-folks centres). 369 users of 'Casals d'Avis' were studied. A specific questionnaire was used to collect the following data: personal details, social and family situation, health profile and a quantification of their degree of cognitive degeneration using Lobo's cognitive test. The quantitative and qualitative variables were studied statistically, and the arithmetical average and standard deviation were found, as well as which bivariant hypothesis tests and multivariant analyses, using the logistic regression method, were carried out. The degree of cognitive deterioration is 8.67%. Age, female sex, being widowed or single, and illiteracy are associated with low scoring in the MEC. It is also associated with subjective loss of memory and hearing difficulties. The multivariant analyses are influenced by length of schooling, age and sex. Early detection of cognitive deterioration and the supply of resources and services oriented towards cognitive stimulation and social integration would, if well-planned, do away with the need for their confinement.

Age Factors↗
PubMedDate not supplied

[Epidemiology of cognitive deterioration in the institutionalized geriatric population of the socio-sanitary centers in the city of Barcelona].

The aim of the study is to carry out a clinico-epidemiological study of the part of Barcelona's in-patients of 'Health-centers/Nursing-homes' elderly people that suffers from cognitive deterioration. 363 in-patients of 'Health-centers/Nursing homes' were studied. A specific questionnaire was used to collect the following data: Personal details, social and family situation, health profile and quantification of their degree of cognitive deterioration using Lobo's cognitive test. The quantitative and qualitative variables were studied statistically, and the arithmetical average and standard deviation were found, as well as which bivariant hypothesis tests and multivariant analyses, using the logistic regression method, were carried out. Adjusted degree of cognitive deterioration was 56%. The age, the fact that the patients were female, illiteracy and working as house-wives all made for low MEC ratings. Variables such as health, subjective memory loss, the presence of cerebral vascular pathology an hypercholesterolemia behaved in a similar fashion. Age, female sex, illiteracy and being a house-wife are associated with low scoring in the cognitive test, as well as subjective loss of memory, cerebral vascular pathology and hypercholesterolemia. The multivariant analyses are affected by: age and length of schooling. Were the in-patient group is concerned, functional remodelling of specific areas is indicated, and who have to be taken into care as a result of the seriousness of deterioration their dependence and their need for assistance.

Age Factors↗