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PubMed1991

Radionuclide esophageal transit studies in progressive systemic sclerosis: an analysis of longitudinal data.

Nineteen patients with progressive systemic sclerosis (PSS) were studied by radionuclide esophageal transit (ET) and followed longitudinally for 3 to 5 years. Results were expressed as percent retention at 20 s and 10 min. There was gradual deterioration of ET at both 20 s and 10 min. When results were grouped into quartiles, deterioration occurred in 58.5% of followup studies in patients who initially had potential to deteriorate regarding 20 s retention and in 48% of similar patients regarding 10 min retention.

Adult↗
PubMed1978

[Tensibility measurements on the rat's aorta III. Analysis of longitudinal and transversal extension as related to age (authors transl)].

Stress-strain diagrams of standardizised longitudinal and transversal stripes of the thoracic aorta of 125 male Sprague-Dawley rats aged 9, 15, 24 and 30 months were recorded by an electromechanical instrument. The stripes were subjected to three successive extension-relaxation cycles. The relaxation curves of the third cycle were approximated to the functions y = a + bx and y = cxd (longitudinal stripes) and y = mxf and y = gxh (transversal stripes) respectively. The parameters could be interpreted as measures for structural and functional properties of elastic and collagenous fibers. The age changes of the curve parameters led to the following conclusions concerning age-dependent functional alterations of the aorta: The emphasis can be placed upon the increasing resistance counteracting the extension occuring with great stroke volumes. This may lead to the reduction of the capacity of the air chamber with great stroke volumes. These phenomena seem to be mainly caused by an increase of the pitch of the spiral of the collagenic fiber and the increase of the amount and/or the stability of the collagen. Age-related alterations of the elastin and of the net structure formed by the fibers influence also the distensibility at smaller extensions but seem to be less important. Therefore, the structural alterations of the aorta with age will affect the function in the first place at large stroke volumes and not be very obvious at a basic heart performance.

Age Factors↗
PubMed1997

Analysis of longitudinal arch supports in stabilizing the arch of the foot.

Two orthotic devices commonly prescribed as arch supports were studied to evaluate their efficacy in stabilizing the foot. Fourteen cadaveric feet were mounted in a loading frame, and an axial load of 222, 445, or 667 N was applied while three-dimensional positions of the talus, calcaneus, navicular, and first metatarsal were monitored with a magnetic tracking system. Feet were tested with and without the use of two commonly prescribed arch supports. The two indices used to assess arch stabilization were arch height and joint rotation. Joint rotations consistently increased on load application. Significant differences were observed with Inserts 1 and 2 in metatarsal talar abduction, dorsiflexion and eversion, calcaneal talar eversion, and talar tibial dorsiflexion. Arch height significantly increased with both inserts. Contrary to previously published results, the arch supports that were studied provided measurable improvement in arch stability in a simulated standing at ease position.

Biomechanical Phenomena↗
PubMed2003

Real-time PCR assay compared to nested PCR and antigenemia assays for detecting cytomegalovirus reactivation in adult T-cell leukemia-lymphoma patients.

We analyzed the efficiency of the quantitative real-time PCR assay for cytomegalovirus (CMV) reactivation in adult T-cell leukemia-lymphoma (ATL) patients and compared the results with those obtained with qualitative nested PCR and antigenemia assays. The viral load obtained by the real-time PCR assay closely paralleled the number of antigen-positive cells obtained with the antigenemia assay. Real-time PCR revealed that a large number of DNA copies could be present even in samples assessed as negative or low in antigen-positive cells (0 to 10 antigen-positive cells/50,000 cells) by antigenemia assay. CMV copy numbers did not differ between the negative and low-antigen-positive groups. When the input concentration for real-time PCR assay was 2,500 to 5,000 copies/ml, the positivity rate for the nested PCR assay was 47.3%, while the positivity rate was more than 90% at an input concentration of >/=50,000 copies/ml. Real-time PCR is more sensitive than the antigenemia and nested PCR assays. Moreover, real-time PCR was able to detect CMV reactivation earlier than the antigenemia and nested PCR assays through the use of longitudinal analysis in four ATL patients with CMV pneumonia. In longitudinal assessments, analysis of the results suggested that a cutoff level of 5,000 copies/ml might be used to initiate treatment. Real-time PCR is more suitable for monitoring CMV reactivation in ATL patients than the antigenemia and nested PCR assays. CMV viral loads of 5,000 copies/ml are proposed as the cutoff for initiating antiviral therapy in ATL patients.

Adult↗
PubMed2006

Gaussian estimation and joint modeling of dispersions and correlations in longitudinal data.

Analysis of longitudinal, spatial and epidemiological data often requires modelling dispersions and dependence among the measurements. Moreover, data involving counts or proportions usually exhibit greater variation than would be predicted by the Poisson and binomial models. We propose a strategy for the joint modelling of mean, dispersion and correlation matrix of nonnormal multivariate correlated data. The parameter estimation for dispersions and correlations is based on the Whittle's [P. Whittle, Gaussian estimation in stationary time series, Bull Inst. Statist. Inst. 39 (1962) 105-129.] Gaussian likelihood of the partially standardized data which eliminates the mean parameters. The model formulation for the dispersions and correlations relies on a recent unconstrained parameterization of covariance matrices and a graphical method [M. Pourahmadi, Joint mean-covariance models with applications to longitudinal data: unconstrained parameterization, Biometrika 86 (1999) 677-690] similar to the correlogram in time series analysis. We show that the estimating equations for the regression and dependence parameters derived from a modified Gaussian likelihood (involving two distinct covariance matrices) are broad enough to include generalized estimating equations and its many recent extensions and improvements. The results are illustrated using two datasets.

Likelihood Functions↗
PubMed1986

[Attitude to the disease model and self-help groups as predictors of participation in after care and of therapeutic outcome in alcoholic patients].

The study was conducted to determine the predictive value of attitudes towards the goals derived from the disease model of alcoholism (life-long acceptance of alcoholic status and endorsement of abstinence) as well as towards self-help groups. The criteria to be predicted were the intention to participate and actual participation in self-help groups as well as four indicators of therapeutic success. Only in cross-sectional analysis were significant correlations found. Longitudinally, there were no relevant relationships between the attitudes expressed by the patients at the end of inpatient treatment (t1) and subsequent participation in self-help groups or indicators of therapeutic success (t2: follow-up, 9 month after discharge). The discrepancy between cross-sectional and longitudinal analysis can be attributed to the fact that attitudes become increasingly less stable with time. This indicates that it is only possible to a limited extent to predict from the attitudes expressed during inpatient treatment how patients will actually behave in daily life outside the clinic. The consequences of these findings for therapy are discussed.

Adult↗
PubMed2001

Application of robust estimating equations to the analysis of quantitative longitudinal data.

A model fit by general estimating equations (GEE) has been used extensively for the analysis of longitudinal data in medical studies. To some extent, GEE tries to minimize a quadratic form of the residuals, and therefore is not robust in the sense that it, like least squares estimates, is sensitive to heavy-tailed distributions, contaminated distributions and extreme values. This paper describes the family of truncated robust estimating equations and its properties for the analysis of quantitative longitudinal data. Like GEE, the robust estimating equations aim to assess the covariate effects in the generalized linear model in the complete population of observations, but in a manner that is more robust to the influence of aberrant observations. A simulation study has been conducted to compare the finite-sample performance of GEE and the robust estimating equations under a variety of error distributions and data structures. It shows that the parameter estimates based on GEE and the robust estimating equations are approximately unbiased and the type I errors of Wald tests do not tend to be inflated. GEE is slightly more efficient with pure normal data, but the efficiency of GEE declines much more quickly than the robust estimating equations when the data become contaminated or have heavy tails, which makes the robust estimating equations advantageous with non-normal data. Both GEE and the robust estimating equations are applied to a longitudinal analysis of renal function in the Diabetes Control and Complications Trial (DCCT). For this application, GEE seems to be sensitive to the working correlation specification in that different working correlation structures may lead to different conclusions about the effect of intensive diabetes treatment. On the other hand, the robust estimating equations consistently conclude that the treatment effect is highly significant no matter which working correlation structure is used. The DCCT Research Group also demonstrated a significant effect using a mixed-effects longitudinal model.

Albuminuria↗
PubMed2002

A prospective study of the factors influencing entry to alcohol and drug treatment.

Much is known about factors related to entering alcohol and drug treatment, but most research comprises cross-sectional "snapshots" in time. It is not known whether the reasons for entering treatment endure when problem drinkers are studied over time. This study contracts characteristics predicting treatment entry in a cross-sectional analysis at baseline with a longitudinal perspective at 1- and 3-year follow-up interviews. Sociodemographic characteristics were less important in the longitudinal analysis. In contrast to the social consequences important at the baseline interview, physiologic symptoms of alcohol dependence and interventions by medical professionals were prominent at later interview points. The findings have implications for interventions by health professionals, both for the development of early interventions targeting individuals to treatment and for a continuing care service model.

Adult↗
PubMed2003

Detection of pulmonary nodules by multislice computed tomography: improved detection rate with reduced slice thickness.

The purpose of this study was to find out if the use of 1.25-mm collimated thin-slice technique helps to detect more small pulmonary lung nodules than the use of 5 mm. A total of 100 patient examinations that allowed a reconstruction of 1.25-mm slice thickness in addition to the standard of 5-mm slices were included in a prospective study. Acquisition technique included four rows of 1-mm slices. Two sets of contiguous images were reconstructed and compared with 1.25- and 5-mm slice thickness, respectively. Two radiologists performed a film-based analysis of the images. The size and the confidence of the seen nodules were reported. We did not perform a histological verification, according to the normal clinical procedure, although it would be optimal regarding research. Statistical analysis was performed by using longitudinal analysis described by Brunner and Langer. In addition, sensitivity, specificity, negative predictive value and positive predictive value were calculated for each reader using the 1.25-mm sections as the gold standard. As an index for concordance the kappa value was used. A value of p<0.05 was regarded as significant. In 37 patients pulmonary nodules were detected. Twenty-four patients showed more than one nodule; among these, 7 patients had disseminated disease and were excluded from the study. Pulmonary nodules larger than 10 mm in size were equally well depicted with both modalities, whereas lesions smaller than 5 mm in size were significantly better depicted with 1.25 mm (p<0.05). Using 1.25 mm as the gold standard, sensitivity for 5-mm reconstruction interval was 88 and 86% for observers A and B, respectively. No false-positive results were reported for 5-mm sections. Interobserver agreement for nodule detection determined for 1.25-mm reconstruction intervals showed a k value of 0.753, indicating a good agreement, and 0.562 for 5-mm reconstruction intervals, indicating a moderate agreement. Brunner and Langer analysis showed significant differences for slice thickness and no significant difference between the observers. Reduced slice thickness demonstrated an improvement of small nodule detection, confidence levels, and interobserver agreement. Application of thin-slice multidetector-row CT may raise the sensitivity for lung nodule detection, although the higher detection rate of smaller nodules has to be evaluated from a clinical perspective and remains problematic about how the detection of small nodules will effect patient outcome.

Adult↗
PubMed2004

A longitudinal population-based study of treated and untreated major depression.

BACKGROUND: Few studies have investigated the factors associated with different outcomes in individuals with major depressive episode (MDE) in relation to mental health service utilization. OBJECTIVES: This study was to, in depressed individuals who used and did not use mental health services, 1) compare the demographic, psychosocial, and clinical characteristics; 2) estimate the risk of MDE in a 6-year follow-up period; and 3) identify the factors associated with the persistence/recurrence of MDE. DESIGN: This was a population- based longitudinal analysis. SUBJECTS: Participants included the longitudinal cohort of the Canadian National Population Health Survey who reported MDE at the baseline survey (n = 609). MEASURES: MDE was measured by the Composite International Diagnostic Interview-Short Form for Major Depression. RESULTS: In the 6-year follow-up period, 49.8% of participants with treated depression developed subsequent MDE; 28.7% of those with untreated depression reported MDE. Multivariate analyses showed that, among those who reported the use of mental health services, childhood and adulthood traumatic events and functional impairment were related to the recurrence of MDE. Among those who did not use mental health services, reported negative life events and the severity of depressive symptoms were predictive of recurrent MDE. CONCLUSIONS: The risk of the recurrence of MDE and associated factors differ in mental health service users and nonusers. Future studies need to confirm these results and to identify service barriers for those who do not use the services and who are at a high risk of MDE.

Adolescent↗
PubMed2006

Zonisamide in the treatment of binge eating disorder with obesity: a randomized controlled trial.

OBJECTIVE: Binge eating disorder (BED) is associated with obesity. Zonisamide is a novel antiepileptic drug associated with weight loss. The purpose of this study was to evaluate zonisa-mide in the treatment of BED associated with obesity. METHOD: In this 16-week, single-center, randomized, double-blind, placebo-controlled, flexible-dose (100-600 mg/day) trial, 60 outpatients with DSM-IV-TR BED received zonisamide (N = 30) or placebo (N = 30). The primary outcome measure was weekly frequency of binge eating episodes. The primary analysis of efficacy was a longitudinal analysis of the intent-to-treat sample, with treatment-by-time interaction as the effect measure. Patients were enrolled from September 5, 2003, through October 1, 2004. RESULTS: Compared with placebo, zonisamide was associated with a significantly greater rate of reduction in binge eating episode frequency (p = .021), body weight (p < .001), BMI (p = .001), and scores on the Clinical Global Impressions-Severity scale (p < .001), Yale-Brown Obsessive Compulsive Scale Modified for Binge Eating (p < .001), and Three Factor Eating Questionnaire disinhibition scales (p < .001). Plasma ghrelin concentrations increased with zonisamide but decreased with placebo (p = .001). The mean (SD) zonisamide daily dose at endpoint evaluation was 436 (159) mg/day. Twelve patients (N = 8 receiving zonisamide, N = 4 receiving placebo) discontinued because of adverse events. The most common reasons for discontinuing zonisamide were accidental injury with bone fracture (N = 2), psychological complaints (N = 2), and cognitive complaints (N = 2). CONCLUSION: Zonisamide was efficacious, but not well tolerated, in the short-term treatment of BED associated with obesity. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov identifier NCT00221442.

Adult↗