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Biomedical subjects

K Abt

Publications and source records attributed to K Abt.

At least 19 recordsLinked to original sources
PubMed1992

HLA-associations in Leponex/Clozaril (clozapine)-induced granulocytopenia and agranulocytosis. Statistical viewpoints.

This paper describes a statistical analysis of the simultaneous occurrence of 48 human leucocyte antigens (HLAs) in an attempt to predict whether a patient treated with clozapine will develop granulocytopenia or agranulocytosis. Whereas the numerical results show that use of HLAs does not appear to satisfy the intended purpose, emphasis is placed on the statistical methodology recommended for a problem of this type. Other work in this area is critically discussed.

Agranulocytosis↗
PubMed1991

Planning controlled clinical trials on the basis of descriptive data analysis.

In controlled clinical trials the problem of multiplicity of desired inferential statements finds attention at an increasing rate. In this paper the previously proposed concept of Descriptive Data Analysis (DDA), situated between Confirmatory and Exploratory Data Analysis, is applied to the planning aspects of controlled trials for which the problem of multiplicity exists. The (non-Bayesian) DDA planning concept should provide the investigator with tools to draw final conclusions from data of several variables possibly observed at several time points in possibly several groups of subjects by combining his pre-trial medical experience with descriptive inferential statements (confidence intervals and test results) at nominal significance levels. DDA also provides for confirmatory statements concerning individual null hypotheses and partially global hypotheses.

Clinical Trials as Topic↗
PubMed1990

Statistical aspects of neurophysiologic topography.

The multitude of electrodes and the large number of EEG variables used in neurophysiologic topography call for new inferential statistical concepts in the analysis of data from corresponding studies. These concepts must take into consideration that significance levels and confidence coefficients lose their numerical meaning in situations with many significance tests and/or interval estimates performed on the data from one sample of subjects or patients. The application of one of these concepts. Descriptive Data Analysis (DDA), is discussed, using the data from a real EEG mapping example. Also, the use of DDA is proposed for the judgement of normality of EEG maps.

Brain↗
PubMed1986

Some correlations in geriatric patients between EEG parameters and clinical status as evaluated using the observer-rated SCAG rating scale. A retrospective study.

In a retrospective analysis, correlations were sought between pretreatment electroencephalographic and clinical data obtained in 18 therapeutic studies conducted in elderly patients according to almost identical protocols. Power spectrum analysis was applied to the EEG tracings, while clinical status was observer-rated using the Sandoz clinical assessment - geriatric (SCAG) scale. The study population comprised a total of 286 patients between the ages of 51 and 97 years (median age 70 years), 162 of whom were male (median age 68 years) and 124 female (median age 73 years). A 2-week washout period and several 'adaptation recordings' preceded the pretreatment EEGs used in this analysis. These tracings were recorded under resting conditions between 8 and 10 a.m. and were followed by an assessment of clinical status. Spearman rank correlations with 4 EEG parameters--total slow waves, alpha and beta waves, and dominant alpha frequency--were computed for all 18 SCAG items and for 'overall impression of patient' as well as for 5 SCAG factors. All 96 - (19 + 5) X 4 - correlation coefficients were formally tested for statistical significance at the nominal level of alpha = 0.05. In this analysis, 9 of the 18 items, 'overall impression' and two of the factors ('apathy' and 'somatic dysfunction') showed nominally significant correlations with at least 1 of the 4 EEG variables. As expected, a positive correlation was found between percentage slow-wave activity and degree of clinical impairment. In addition correlations were identified between clinical data and alpha and beta activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Determination of the central effects of the asthma prophylactic ketotifen, the bronchodilator theophylline, and both in combination: an application of quantitative electroencephalography to the study of drug interactions.

Ketotifen (Zaditen) is a new, orally active benzocycloheptathiophene derivative for use in the prophylaxis of asthma. Besides possessing anti-allergic properties, it also has H1-receptor mediated antihistaminic activity. Drugs which block H1-receptors are known to have some sedative properties. On the other hand the bronchodilator theophylline is a CNS stimulant. We investigated whether these side-effects could be reduced by concomitant administration. In a balanced-sequence crossover study, 12 healthy males received placebo, 1 mg ketotifen + 300 mg theophylline, 1 mg ketotifen + 600 mg theophylline, and each drug separately at 1-week intervals. Quantified electroencephalograms, cardiovascular and behavioral measurements, symptom reports, and blood drug assays were used to assess the drug interaction. Results showed EEG and behavioral effects with both ketotifen and theophylline alone which were less evident with the drugs in combination. Blood drug levels were not altered by combined drug administration. These findings suggest a mutual attenuation of the CNS effects of ketotifen and theophylline at therapeutic doses and encourage their combined use in asthma therapy. The combined effect may be optimized by modifying formulations or timing. The applicability of quantitative EEG to such problems is well demonstrated.

Adult↗
PubMed1983

Pharmaco-EEG and Psychometric study of the effect of single doses of temazepam and nitrazepam.

A double-blind, daytime, placebo-controlled study was carried out in 12 healthy volunteers to investigate the effects of single doses of 5, 15 and 30 mg temazepam and of 5 and 10 mg nitrazepam on the EEG, psychomotor performance, subjective mental and emotional status, blood pressure and heart rate. Each subject received all 6 treatments in a random sequence at intervals of 1 week. The EEG tracings were evaluated quantitatively by spectral analysis. Psychomotor performance was assessed by means of the tapping test. Subjective mental and emotional status were assessed using the Bond and Lader analogue self-rating scale. Procedures were carried out before and at 1/2, 1, 2, 4, 6, 7, 8 and 9 h after drug administration, with the exception of the tapping test, which was carried out before and, again, after 2 and 7 h. EEG estimates of equipotency, based on magnitude of peak effect, were as follows: 15 mg temazepam approximately 5 mg nitrazepam; and 30 mg temazepam greater than or equal to 10 mg nitrazepam. At these approximately equipotent doses, temazepam had a somewhat earlier onset of action on the EEG, a clearly shorter duration of EEG action, and lesser impairment of psychomotor performance than nitrazepam. Qualitatively, both drugs had similar effects on the subjective mental and emotional states of the subjects. There were no clinically relevant changes in mean or individual sitting and standing blood pressure values. After temazepam, but not after nitrazepam, heart rate increased (maximal mean change 10 bpm) as part of a normal startle response to arousal. The results suggest that temazepam has less hangover potential than nitrazepam.

Adult↗
PubMed1980

Age-related histochemical and histological changes in the knee-joint cartilage of C57B1 mice and their significance for the pathogenesis of osteoarthrosis. I. Oxidative enzymes.

For a better understanding of the part played by the aging of cartilage in the pathogenesis ofosteoarthrosis, we attempted to detect functional age-related changes in the knee-joint cartilage of C57B1 mice using histochemical methods and to correlate these changes with the concomitant histological changes. A comparison of 57- and 97-week-old mice revealed a statistically significant age-related focal loss of activity for a number of oxidative enzymes of the chondrocytes. There was an associated significant increase in regressive changes of the chondrocytes. A relation probably exists between these two changes, inasmuch as the focal loss of enzyme activity precedes and possibly gives rise to the regressive changes. A comparison with the changes described in the articular cartilage of other species including man suggests that the phenomena observed are inherent age-related changes. The loss of activity of all the enzymes investigated indicates a far-reaching derangement of cellular metabolism, leading to impaired synthesis of proteoglycans. Since these compounds are major determinants of the physical properties of articular cartilage, the changes described might render the cartilage more vulnerable and might thus play a major part in the pathogenesis of osteoarthrosis.

Aging↗
PubMed1979

Statistical problems in the analysis of comparative pharmaco-EEG trials.

Assuming already condensed data from the EEG power spectra, problems arising with the statistical analysis of such data in comparative pharmaco-EEG trials are discussed. Since, in general, there is only a limited number of subjects available in a study to evaluate and compare the effects of a number of drugs by means of the EEG, the experimental design is usually of the cross-over type. With respect to this design, the requirements for the application and for the appropriate analysis are stated. Further, the problems are indicated which arise when the number of subjects is not a multiple of the number of drugs and/or when there are missing values. Finally, the topic of repeated null hypothesis testing and the inflation of the overall significance level is treated. Suggestions are made how to at least partly avoid the indicated problems at the present stage of methodological statistical research.

Analysis of Variance↗
PubMed1979

[The effect of contrast volume on the radiographic demonstration of the gall bladder and bile duct (author's transl)].

No differences could be detected subjectively in the quality of cholangiograms after the use of varying amounts of contrast medium (20 and 30 ml iodoxaminic acid). Pharmacolinetic data which would indicate the use of either quantity are not available. Densitometric measurements carried out by us showed no significant statistical difference between the results of using 20 or 30 ml iodoxaminic acid.

Cholecystography↗
PubMed1979

A double-blind trial of synthetic salmon calcitonin in the treatment of acute pancreatitis.

A multicenter randomized double-blind trial on the use of synthetic salmon calcitonin (SCT) was carried out in 94 patients with acute pancreatitis. In addition to strict standard treatment--without aprotinin, atropine, or antacids--50 patients received daily 3 x 20 micrograms = 300 MRCU SCT intravenously and 44 patients received placebo for 6 days. Mortality rate was not influenced, overall mortality being 5.3%. The number of patients without pain and with normalized serum amylase on a given day was significantly higher in the group treated with SCT. Other parameters such as doses of analgesics, leukocyte count, and normalization of seven defined clinical and laboratory criteria within 6 days showed a positive trend without reaching significance.

Acute Disease↗
PubMed1977

[Quantification and statistical analysis of ordinal scale type data in psychiatry (author's transl)].

Observational data from psychiatric patients are usually of the ordinal scale type. Therefore, in the traditional one-rating-per-symptom-and-patient-situation, the resulting score values can be analysed only by applying nonparametric statistical methods. These methods are rather inefficient when--as is usual--there are only four-point-scales for evaluating the symptoms. Moreover, non-parametric methods are not available as of yet to take into consideration the often complex structure of data from psychiatric studies. This leads to the conclusion that the quantification of ordinal scale type data would be very desirable in order that parametric statistical methods could be applied. Such a method of quantification is proposed on the basis of the audiovisual psychiatric rating technique. It is shown that the data resulting from the many-ratings-per-symptom-and-patient-situation can be subjected to parametric statistical methods. In applying the proposed method, therefore, much better use could be made of and a maximum of information could be extracted from the data in psychiatric studies.

Humans↗
PubMed1976

The effects of the beta-adrenoceptor blocking agent LL 21-945 on renal hypertensive (Grollman) rats.

Prophylactic administration of LL 21-945 [4-(3-tert. butyl-amino-2-pivaloyloxypropoxy)-9-fluorenone] during 15 weeks to Grollman rats depressed the development of hypertension, tachycardia and myocardial pathogical changes. The tachycardia was eliminated and the degree of the myocardial pathological changes and coronary sclerosis was less severe than in the untreated Grollman rats. The survival rate was slightly improved with LL 21-945. With respect to the biochemical parameters studied, only a tendency of LL 21-945 to moderate the rises in blood cholesterol, total glycerides and urea was observed towards the end of the experiment.

Adrenergic beta-Antagonists↗