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Biomedical subjects

K Uberla

Publications and source records attributed to K Uberla.

At least 73 records · Page 4Linked to original sources
PubMed1990

Risk analysis in cohort studies with heterogeneous strata. A global chi2-test for dose-response relationship, generalizing the Mantel-Haenszel procedure.

In cohort studies the Mantel-Haenszel estimator ORMH is computed from sample data and is used as a point estimator of relative risk. Test-based confidence intervals are estimated with the help of the asymptotic chi-squared distributed MH-statistic chi 2MHS. The Mantel-extension-chi-squared is used as a test statistic for a dose-response relationship. Both test statistics--the Mantel-Haenszel-chi as well as the Mantel-extension-chi--assume homogeneity of risk across strata, which is rarely present. Also an extended nonparametric statistic, proposed by Terpstra, which is based on the Mann-Whitney-statistics assumes homogeneity of risk across strata. We have earlier defined four risk measures RRkj (k = 1,2,...,4) in the population and considered their estimates and the corresponding asymptotic distributions. In order to overcome the homogeneity assumption we use the delta-method to get "test-based" confidence intervals. Because the four risk measures RRkj are presented as functions of four weights gik we give, consequently, the asymptotic variances of these risk estimators also as functions of the weights gik in a closed form. Approximations to these variances are given. For testing a dose-response relationship we propose a new class of chi 2(1)-distributed global measures Gk and the corresponding global chi 2-test. In contrast to the Mantel-extension-chi homogeneity of risk across strata must not be assumed. These global test statistics are of the Wald type for composite hypotheses.(ABSTRACT TRUNCATED AT 250 WORDS)

Chi-Square Distribution↗
PubMed1989

Developmentally regulated expression of the neural cell adhesion molecule (NCAM) by mouse thymocytes.

The expression of the neural cell adhesion molecule (NCAM) has been investigated during thymus ontogeny. NCAM mRNA was readily detectable at day 19 of gestation, the youngest age studied. Its level declined after birth to become undetectable at 3 weeks of age. Cell surface expression of NCAM protein was detected on 14% of day 15 fetal thymocytes and peaked during the perinatal period, when around 40% of the thymocytes expressed low to medium levels of NCAM. At postnatal day 2, the vast majority of the NCAM+ cells were also CD4+ and CD8+. At embryonic day 15, NCAM appeared also to be expressed by CD4- thymocytes since 14% of the cells were already NCAM+ whereas CD4 was virtually undetectable. In frozen section of the newborn thymus, surface staining for NCAM was present on a subpopulation of cells in the cortex, rare in the medulla and absent from the sub-capsular area. In conjunction with other cell adhesion molecules, NCAM could play a role in cell interactions during thymic development.

Age Factors↗
PubMed1989

A user-oriented protocol for integrating heterogeneous communication systems of medical facilities using ports.

The crucial feature of future communication systems in hospitals will be the heterogeneity between the individual systems. People working in a hospital do not communicate via data objects, but via highly complex functions like preparation of a patient report or diagnosis of patients' symptoms and signs. Essentially such tasks are accomplished by initiating remote functions in various modes of a communication system. The aim of the MEDAS protocol developed by our group is to propose a definition of such a high-level medical protocol and then to implement it. Our user-oriented protocol permits information exchange between heterogeneous systems. Modules and functions are defined. Message passing to and from a processor is realized using ports. The protocol sequence of every communication request is described. The relation of ports to the ISO model is specified. First experiences in a network for a medical school are reported.

Communication↗
PubMed1987

Lung cancer from passive smoking: hypothesis or convincing evidence?

The epidemiological literature on passive smoking and lung cancer is reviewed and the well-known criteria for establishing a causal relationship are applied in order to determine what level of causal evidence currently exists. Three cohort studies and 12 case control studies are analysed. Of the prospective cohort studies, one contributes very little to our knowledge, one shows no risk increase and one results in a moderate risk increase of 1.74 for women married to heavy smokers. The last is the only study which has to be taken seriously, even when other considerations show that its results might be caused by chance, bias or confounding. None of the six case control studies yielding a positive relationship was conducted according to the state of art of epidemiological research, giving reasonable and sound evidence which cannot be explained by chance, bias, confounding or misclassification. Two studies contribute nothing to the evidence. None of the four case control studies yielding no risk change or a risk decrease can exclude the possibility that a causal relation exists. The epidemiological and toxicological evidence is discussed in the light of recent findings. The volume of accumulated data is conflicting and inconclusive. The observations on nonsmokers that have been made so far are compatible with either an increased risk from passive smoking or an absence of risk. Applying the criteria proposed by IARC there is a state of inadequate evidence. The available studies, while showing some evidence of association, do not exclude chance, bias or confounding. They provide, however, a serious hypothesis. Further studies are needed, if one wants to come to an adequate and scientifically sound conclusion concerning the question as to whether passive smoking causes lung cancer in man.

Humans↗
PubMed1987

Measuring problems in estimating the exposure to passive smoking using the excretion of cotinine.

Quality control studies on cotinine measurements following low level environmental tobacco smoke (ETS) exposure are rare. The exposure to ETS was controlled and systematically changed in a series of experiments in a climatic chamber. Healthy nonsmoking volunteers were exposed to ETS simultaneously. The duration and level of exposure varied using high (8, 17 and 25 ppm CO), and low (2 and 5 ppm CO) exposure levels. The variation between radioimmunoassay (RIA) and gas chromatography (GC) was high as was the variation between the results of RIA laboratories. There was also a high within-laboratory-variation. A 1:10 dilution seems to be preferable over a 1:3 dilution. Freezing the urine samples immediately after collection led to the detection of higher cotinine values than freezing the samples 24 h after collection. Highly reliable data for cotinine were obtained when the urine samples were kept frozen immediately after collection and fractionated sampling over 48-72 h was used. Our data show that estimating low-level ETS exposure by measuring urinary cotinine is highly susceptible to uncontrolled variation and errors. Sufficiently reliable estimates of low-level ETS exposure can be made only when fractionated sampling over 48-72 h is used and when the urine samples are kept frozen just after collection.

Chromatography, Gas↗
PubMed1986

Haemostasiological parameters as risk factor for new arterial occlusions in diabetics.

PARD is a prospective study sponsored by the German Research Council with the aim to establish if spontaneously enhanced platelet aggregation or changes of other hemostatic variables are risk factors for new vascular occlusions in diabetic patients. 363 diabetics (aged 45-65, 232 men, 131 women) have been observed for at least 5 years. Of the 232 men, 53 were on diet, 104 on oral antidiabetic agents and 75 on insulin. Of 131 women 16 were on diet, 46 on oral antidiabetic drugs and 69 on insulin. At entry a medical history was obtained and clinical examinations and laboratory tests were performed. Hemostatic tests and clinical examinations were repeated at 3 month's intervals. The life status was followed for all patients with the exception of 2. Until December 31, 1984, 42 patients had died, 23 from cardiovascular disease and 19 from other causes. 13 patients suffered a myocardial infarction, 11 a stroke and 53 a peripheral arterial occlusion. The occurrence of new vascular occlusions was significantly higher in men with enhanced spontaneous platelet aggregation measured by PAT III. This was not the case for women. Other hemostatic parameters with some relation to cardiovascular complications, again only in men, were fibrinogen, von Willebrand factor together with some established risk factors as triglycerides and hypertension.

Aged↗
PubMed1985

PARD: platelet aggregation as a risk factor in diabetics: results of a prospective study.

PARD is a prospective study sponsored by the German research council with the aim to establish whether spontaneously enhanced platelet aggregation or changes of other hemostatic parameters are risk factors for new vascular occlusion in diabetic patients. Hemostatic parameters have been measured in diabetic patients at 3 month-intervals (363 patients aged 45-65 at recruitment). Of the 232 men, 53 were on diet, 104 on oral antidiabetic drugs and 75 on insulin. Of 131 women 16 were on diet, 46 on oral antidiabetic drugs and 69 on insulin. Baseline data and preliminary results obtained between May 1977 and December 31, 1983 are presented. 22 patients have died. 17 diet from cardiovascular disease, 3 from pancreatic cancer and 2 from other causes. 51 patients suffered a myocardial infarction, stroke or peripheral arterial occlusions. The mean levels of spontaneous aggregation (angle alpha-PAT III), F VIIIC, F VIII R:AG, fibrinogen, antithrombin III and plasminogen were higher in men who died or suffered cardiovascular occlusions than in those without these events. In women this difference is less pronounced or absent. In women the mean values of several hemostatic parameters at baseline were higher than in men and the incidence of cardiovascular occlusions was lower. The interim results lead to the hypothesis that spontaneous aggregation, high levels of F VIIIC, F VIII R:AG and to some extent also high levels of fibrinogen, antithrombin III and plasminogen may be indicators of progressive vascular disease and could be useful as predictors of vascular occlusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1980

[Drug monitoring in psychiatry (author's transl)].

The Study Group for Drug Surveillance in Psychiatry (AMUP) has been working since July 1978 as a task force group of the "Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie" (AGNP). A protocol was designed for the initiation of drug monitoring in psychiatric hospitals. With support of the Bundesgesundheitsamt, Berlin, the first part of this project was started as a practicability study in the psychiatric hospitals of the Universities of Berlin, Göttingen, and Munich and in the municipal hospital of Schleswig. The study includes 7650 in-patients. It is based on the following methods: intensive drug monitoring, organized spontaneous monitoring of adverse drug reactions and registration of drug applications. This drug monitoring system in psychiatry will be expanded to other psychiatric hospitals, and eventually to out-patient clinics as well as private practices within the next two years.

Costs and Cost Analysis↗