Biomedical subjects

R du Berger

Publications and source records attributed to R du Berger.

9 recordsLinked to original sources

PubMed2001

Traditional Framingham risk factors fail to fully account for accelerated atherosclerosis in systemic lupus erythematosus.

OBJECTIVE: The frequency of coronary heart disease (CHD) and stroke are increased in systemic lupus erythematosus (SLE), but the extent of the increase is uncertain. We sought to determine to what extent the increase could not be explained by common risk factors. METHODS: The participants at two SLE registries were assessed retrospectively for the baseline level of the Framingham study risk factors and for the presence of vascular outcomes: nonfatal myocardial infarction (MI), death due to CHD, overall CHD (nonfatal MI, death due to CHD, angina pectoris, and congestive heart failure due to CHD), and stroke. For each patient, the probability of the given outcome was estimated based on the individual's risk profile and the Framingham multiple logistic regression model, corrected for observed followup. Ninety-five percent confidence intervals (95% CIs) were estimated by bootstrap techniques. RESULTS: Of 296 SLE patients, 33 with a vascular event prior to baseline were excluded. Of the 263 remaining patients, 34 had CHD events (17 nonfatal MIs, 12 CHD deaths) and 16 had strokes over a mean followup period of 8.6 years. After controlling for common risk factors at baseline, the increase in relative risk for these outcomes was 10.1 for nonfatal MI (95% CI 5.8-15.6), 17.0 for death due to CHD (95% CI 8.1-29.7), 7.5 for overall CHD (95% CI 5.1-10.4), and 7.9 for stroke (95% CI 4.0-13.6). CONCLUSION: There is a substantial and statistically significant increase in CHD and stroke in SLE that cannot be fully explained by traditional Framingham risk factors alone.

Adolescent↗

PubMed1998

Impact of disease activity and cumulative damage on the health of lupus patients.

To test if lupus activity and damage predict physical function and general health in lupus was the objective of this study. Ninety-six patients with lupus were seen at baseline and monthly for 4 months. Sociodemographic characteristics and lupus damage (SLICC/ACR DI), were collected at baseline while lupus activity (SLAM-R, SLEDAI), health status measures (HAQ, SF-36) and immunological tests were collected at each visit. Associations of lupus activity and damage with general health and physical function were evaluated. Baseline health status measures were greatly impaired and comparable to those of severe medical illnesses. In cross-sectional analyses, baseline activity score measured by SLAM-R, but not by SLEDAI, correlated with most subscales of SF-36. Baseline damage score SLICC/ACR DI correlated only with the HAQ and the physical function subscale of SF-36. Differences in both activity measures (SLAM-R and SLEDAI) over time correlated with change in health status measures while baseline cumulative damage (SLICC/ACR DI) correlated with the average level of physical function only. Lupus activity measures, SLAM-R and SLEDAI, although differing cross-sectionally, both reflected patients' health status performance over time and lupus damage measure, SLICC/ACR DI, performed well in assessing physical function. Lupus patients scores for health are poor and comparable to those found in severe medical illnesses.

Activities of Daily Living↗

PubMed1998

The relationship between disease activity and expert physician's decision to start major treatment in active systemic lupus erythematosus: a decision aid for development of entry criteria for clinical trials.

OBJECTIVE: To explore the relationship between patients' systemic lupus erythematosus (SLE) activity and physicians' decision to treat with steroids or alternative medication. METHODS: Baseline information and clinical status was extracted from case histories of 30 patients with lupus and represented in clinical vignettes. These vignettes were then mailed to 60 physicians (rheumatologists and immunologists with experience in the treatment of lupus), asking them in each case whether they would initiate treatment or not. The relationship between the 38 complete responses and the SLE Activity Measure (SLAM-R) and SLE Disease Activity Index (SLEDAI) lupus activity scores was analyzed using a general additive model. RESULTS: SLE disease activity measured by SLAM-R or SLEDAI is a significant predictor (p < 0.0001) of physicians' decision to initiate treatment for patients with lupus. Variation between physicians was observed but was mostly due to a few outliers. Some other variations remained unexplained by patients' SLE disease activity, damage, or by specific organ involvement. CONCLUSION: We present reference tables and curves for research that may be used as a basis to derive standardized quantitative criteria for entry in clinical trials. More research is needed on how these tools can be used by clinicians to guide them in their decision to treat or not.

Allergy and Immunology↗

PubMed1998

Change-point analysis of neuron spike train data.

In many medical experiments, data are collected across time, over a number of similar trials, or over a number of experimental units. As is the case of neuron spike train studies, these data may be in the form of counts of events per unit of time. These counts may be correlated within each trial. It is often of interest to know if the introduction of an intervention, such as the application of a stimulus, affects the distribution of the counts over the course of the experiment. In such investigations, each trial generates a sequence of data that may or may not contain a change in distribution at some point in time. Each sequence of integer counts can be viewed as arising from a Poisson process and are therefore independently distributed or as an integer-valued time series that allows for correlations between these counts. The main aim of this paper is to show how the ensemble of sample paths may be used to make inference about the distribution of the instantaneous times of change in a given population. This will be accomplished using a Bayesian hierarchical model for these change-points in time. A bonus of these models is they also allow for inference about the probability of a change in each unit and the magnitude of the effects, if any. The use of such change-point models on integer-valued time series is illustrated on neuron spike train data, although the methods can be applied to other situations where integer-valued processes arise.

Action Potentials↗

PubMed1997

Bayesian and mixed Bayesian/likelihood criteria for sample size determination.

Sample size estimation is a major component of the design of virtually every experiment in medicine. Prudent use of the available prior information is a crucial element of experimental planning. Most sample size formulae in current use employ this information only in the form of point estimates, even though it is usually more accurately expressed as a distribution over a range of values. In this paper, we review several Bayesian and mixed Bayesian/likelihood approaches to sample size calculations based on lengths and coverages of posterior credible intervals. We apply these approaches to the design of an experiment to estimate the difference between two binomial proportions, and we compare results to those derived from standard formulae. Consideration of several criteria can contribute to selection of a final sample size.

Bayes Theorem↗

PubMed1997

Flexible modeling of the effects of serum cholesterol on coronary heart disease mortality.

Current understanding of the impact of lipids and other risk factors on coronary heart disease is largely based on the results of parametric multiple regression analyses of large prospective studies. To assess the potential impact of the a priori assumption of linearity of continuous risk factors on the results of parametric analyses, the authors completed a secondary analysis of the Lipid Research Clinics Prevalence and Follow-up Studies (1972-1987) data using an assumption-free nonparametric modeling approach. The effects of total serum cholesterol and the ratio of total serum cholesterol to high density lipoprotein cholesterol, adjusted for common risk factors, were estimated using a smoothing spline method available in the generalized additive model extension of the multiple logistic regression. The data set included 2,512 men in the random sample of the Lipid Research Clinics study who did not take lipid-lowering medications. During the median follow-up of 12.6 years, 94 coronary heart disease deaths occurred. The generalized additive model fits the effects of total serum cholesterol (p < 0.01) and the ratio of total serum cholesterol to high density lipoprotein cholesterol (p < 0.02) significantly better than the parametric logistic regression. Validation studies confirmed that, among new observations arising from the same population, generalized additive model estimates predicted outcomes better than the parametric estimates. Nonlinear effects of both lipid measures were robust and may be clinically important. The authors conclude that the linearity assumption inherent in parametric models may result in biased estimates of the effects of total serum cholesterol on coronary heart disease mortality and recommend that their findings be verified in a nonparametric analysis of data from another large prospective study.

Cholesterol↗

PubMed1991

RECPAM: a computer program for recursive partition and amalgamation for survival data and other situations frequently occurring in biostatistics. III. Classification according to a multivariate construct. Application to data on Haemophilus influenzae type b meningitis.

The methodology of RECursive Partition and AMalgamation (RECPAM) previously presented in Parts I and II (A. Ciampi et al., Computer. Methods Progr. Biomed. 26 (1988) 239-256 and 30 (1989) 283-296) pursues its development with an application to predict long-term effects of a disease given a set of clinical information measured at the time of illness. This paper illustrates how RECPAM deals with a situation typical in Medical Informatics applied to data on Haemophilus influenzae type b meningitis.

Adolescent↗

PubMed1991

The risk of developing disease for siblings of patients with insulin dependent diabetes mellitus.

We analyzed the risk of developing insulin-dependent diabetes mellitus (IDDM) in 411 siblings of patients with IDDM. We found that siblings who had a positive test for antibodies against islet cells (ICA) at the time of diagnosis of the index case had a higher risk of developing IDDM than did those who had negative tests. However, of the ten siblings who developed IDDM, only four were positive at the initial testing. The period of time elapsing from a negative test at screening to a positive test at diagnosis varied but was less than one year in one child. Two of the ten siblings who developed IDDM had negative tests both at screening and at diagnosis. Amongst siblings who were negative at the initial screening, those in whom the index case was diagnosed at a young age had a higher risk of developing IDDM than did those in whom the index case was diagnosed at an older age. The age of the sibling at the time of screening, the sex of the sibling, and a positive family history (one which includes in addition to the index case one or more first-degree relatives with IDDM) did not confer increased risk. Our data suggest that screening for ICA will have to be done often and will have to be continued into adult life in order to identify the 70-80% of diabetics who will be positive at some time in the evolution of their disease.

Adolescent↗

PubMed1990

The sequelae of Haemophilus influenzae meningitis in school-age children.

BACKGROUND: Previous data on the consequences of Haemophilus influenzae type b meningitis for school-age children have been inconsistent, and much of the information on risk factors has been inconclusive. The present study was designed to evaluate the sequelae of this disease with a protocol for the comprehensive assessment of neuropsychological function. METHODS: Ninety-seven school-age children (mean age, 9.6 years), each of whom had a school-age sibling, were recruited from a survey of the medical records of 519 children treated for H. influenzae type b meningitis between 1972 and 1984 (at a mean age of 17 months) at the children's hospitals of Toronto, Ottawa, and Montreal. Of the 97 children, 41 had had an acute neurologic complication. Sequelae were assessed by comparing the index children with their nearest siblings on the basis of standardized measures of cognitive, academic, and behavioral status. RESULTS: Only 14 children (14 percent) had persisting neurologic sequelae: sensorineural hearing loss in 11 (unilateral in 6 and bilateral in 5), seizure disorder in 2, and hemiplegia and mental retardation in 1. Although the total sample of index children scored slightly below the siblings in reading ability, the 56 children without acute-phase neurologic complications (58 percent) were indistinguishable from their siblings on all measures. The differences between the groups were small even for the 41 pairs in which the index child had had an acute neurologic complication (mean full-scale IQ, 102 for the index children vs. 109 for the siblings). Sequelae were also associated with lower socioeconomic status and a lower ratio of glucose in cerebrospinal fluid to that in blood at the time of the meningitis. Behavioral problems were more prominent in index boys than index girls and in those who were older at the time of testing, but sex and age were not related to cognitive or academic sequelae. CONCLUSIONS: We find a favorable prognosis for the majority of children who are treated for meningitis caused by H. influenzae type b.

Adolescent↗