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E Hansert

Publications and source records attributed to E Hansert.

13 recordsLinked to original sources
PubMed1996

Detection of short-term fluctuations in measurement systems by determination of extreme values and range.

In the new draft, in preparation, of the guidelines of the German Medical Council (Richtlinien der Bundesärztekammer, RiLiBAK) for quality management of clinical laboratory measurement systems, particular emphasis is placed on the establishment of a lower and upper limit for each control value in a control cycle. In the present study, an attempt is made to show that this approach alone does not detect even relatively large short-term changes in a measurement system. A substantial improvement is possible with modest outlay, by also examining the difference between the largest and smallest individual control values, i.e. by determining the current range. Appropriate practical limits for this procedure are derived from the theoretical behaviour of extreme values, based initially on the usual assumption of a normal distribution. Furthermore, it is shown that these limits are also meaningful for other assumed appropriate distributions.

Guidelines as Topic↗
PubMed1984

The structure of wakefulness and its relationship to daytime sleep in narcoleptic patients.

Seven patients with narcolepsy-cataplexy were continuously monitored during the day using polygraphy and videotape recording. The patients were free to do whatever they wanted while confined to a sitting-at-a-table situation. Daytime activity was evaluated by distinguishing between two polygraphically defined states, namely active wakefulness and quiet wakefulness. The data from the patients were compared with those from 7 normal subjects who were studied under the same experimental conditions. While all patients had recurrent daytime sleep episodes, none of the controls napped during the recording period. The narcoleptic patients showed an altered structure of wakefulness: they spent more of their time awake in the state of active wakefulness and less in quiet wakefulness than the control subjects. Moreover, the patients remained in the quiet state for shorter periods. Daytime sleep selectively diminished the state of quiet wakefulness, whereas it did not affect the amount of time spent in active wakefulness. In addition, in 3 patients there was a clear-cut alternation of periods of sustained wakefulness and transitional phases with a mixture of sleep and wakefulness which occurred rather regularly, suggesting an ultradian cycle of sleepiness.

Adult↗
PubMed1984

Persistence of nerve sprouting with features of synapse remodelling in soleus muscles of adult mice.

An increase in the number of nerve branches of the unmyelinated axon terminals with increasing age was observed in normal adult mouse motor endplates. In addition, ultrastructural investigation revealed signs of nerve retraction. A combined light and electron microscopic investigation was performed on zinc-iodine-osmium stained endplates in soleus muscles. The number of branch points in a synapse, endplate length and muscle fiber diameter were evaluated in "young adult" (3 months) and adult (6 and 11 months) mice. For all 3 parameters, 3-month-old animals had the lowest values. Eleven-month-old animals had more branch points and larger endplate lengths than 6-month-old animals while there was no significant difference in fiber diameters. Branch point numbers and endplate length were correlated in each muscle while fiber diameters did not correlate with any of the other parameters. The ultrastructure of 15 thin nerve branches--likely candidates for new branches--was investigated in serial section and in 14 of them synaptic contacts were found. Near such contacts, empty gutters, possibly abandoned former synaptic sites, were present in several cases. It is concluded that there is continual nerve sprouting in synapses of adult mice and that sprouts form synaptic contacts. The possible signs of nerve retraction observed indicate that, as in the frog, synaptic contacts in mouse muscles undergo some continual remodeling.

Aging↗
PubMed1984

Detection and exclusion of alcoholism in men on the basis of clinical laboratory findings.

Alcoholism is a common disease; it is found in 10% to 15% of all patients admitted to general hospitals. There is no single characteristic finding, but on the other hand, changes as compared with normal values have been reported in the literature for more than 30 frequently assayed clinical chemical and haematological parameters. In the project reported here all 24 clinical chemical parameters and all 8 haematological parameters frequently assayed were studied in each of 82 hospitalized men with a confirmed diagnosis of alcoholism. The diagnosis of alcoholism was made on the basis of the Munich Alcoholism Test (MALT) together with the following standardized assessments and examinations: past history, an alcohol questionnaire, general physical examination and neurological examination. All forms were filled in completely. All steps in the clinical laboratory investigations were standardized, and all were subject to ongoing reliability control. The clinical problem is usually not to differentiate alcohol abusers or alcoholics from healthy persons but rather to identify the alcoholics among a population of patients with a variety of illnesses. For this reason 70 patients from two hospitals who were clearly neither alcohol abusers nor alcoholics were studied in exactly the same manner as the alcoholics. In this combined group of 152 hospitalized patients significant differences were found in the distribution of the values for the alcoholics and the non-alcoholics for the following clinical chemical and haematological parameters: at the 0.1% level gamma-glutamyltransferase, aspartate aminotransferase, urea, creatinine and mean corpuscular volume (MCV), and at the 1% level glutamate dehydrogenase, alanine aminotransferase and alkaline phosphatase. From these eight parameters those combinations of between two and six parameters were selected that discriminated best between the alcoholics and the non-alcoholics. Using conventional decision limits the following was found: For the alcoholics two or more of the results for the following five parameters were outside the decision limits given in parentheses: gamma-glutamyltransferase (greater than or equal to 28 U/l), aspartate aminotransferase (greater than or equal to 18 U/l), alanine aminotransferase (greater than or equal to 22 U/l), MCV (greater than or equal to 96 fl), creatinine (less than or equal to 66.3 mumol/l). The diagnostic sensitivity (alcoholics) is 85%, the diagnostic specificity (non-alcoholics) is 64%.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1984

A new procedure for discriminating between two patient populations using multivariate decision limits: application in the detection and exclusion of alcoholism based on clinical laboratory findings.

A simple, nonparametric discrimination procedure was developed and tested for use in discriminating between two populations, especially in those cases where the properties of the distributions lead to unsatisfactory results by classical discrimination procedures. The procedure is based on transferring the conventional concept of a decision limit from one to several variables, with combinations (in set theory terms: unions and intersections) of multidimensional intervals serving as the discriminant regions (referred to here as simple discriminant regions). The procedure was applied to two groups of patients, alcoholics and non-alcoholics. A level of efficiency 20% higher than that attainable with conventional procedures was obtained using only six clinical chemical parameters. In addition, the procedure is more flexible than conventional procedures. It enables the solution of optimization problems for each of the three common discrimination criteria (sensitivity, specificity and efficiency) with no fundamental difficulties, and it is still possible to select at will the range(s) for the decision point and for the order of the discriminant regions. For all of the clinical chemical parameters studied the distributions of the results for the two patient samples overlapped very markedly. If, for example, a sensitivity of 100% was specified, the best specificity attainable using the six parameters that discriminated best was only about 53%, and if a specificity of 100% was required, the best sensitivity was about 56%. The analogy between the discrimination principle and the principle of a statistical test (the relationship between detection and exclusion of alcoholism) is also discussed.

Alcoholism↗
PubMed1984

Excessive consumption of alcohol in men as a biological influence factor in clinical laboratory investigations.

It is known that excessive alcohol consumption leads to changes in clinical chemical and haematological parameters that are reversed to a greater or lesser degree after alcohol consumption ceases. Such factors that lead to changes in vivo in the parameters studied are termed biological influence factors. In the study reported here the biological influence factor "excessive alcohol consumption" was assessed in its most severe form, namely alcoholism. To this end 24 clinical chemical parameters and 8 haematological parameters were studied in 82 male alcoholics. The diagnoses of alcohol abuse and alcoholism were made on the basis of the Munich Alcoholism Test (MALT) and the information obtained in the following standardized interviews and examinations: past history, an alcohol questionnaire, general physical examination and neurological examination. All forms were filled in completely. All steps in the clinical laboratory investigations were standardized, and all were subject to ongoing reliability control. In the comparison of the analytical results for the alcoholics with reference intervals for healthy persons (normal ranges) the following alterations were found, the percentage of the alcoholics being given in parentheses. (Table: see text) Furthermore, the result was below the location parameter of the reference sample group for: Urea (80%) Thus excessive alcohol consumption is clearly a biological influence factor that must be taken into consideration in the medical assessment of analytical results for numerous clinical chemical and haematological parameters. In determining reference values and reference intervals for the transverse assessment of analytical results for these parameters it is therefore absolutely essential that subjects with excessive alcohol consumption be excluded from the reference sample group. According to the present data, alcoholism can be neither detected nor excluded by evaluating a single parameter, i.e. on the basis of only one clinical chemical finding.

Adult↗
PubMed1980

Determination of assigned values in control specimens for internal accuracy control and for interlaboratory surveys. Evaluation of 200 different lots with identical experimental design: experiences and conclusions.

In the Federal Republic of Germany there are guidelines for a basic program for internal and external quality control of quantitative clinical chemical analyses prepared by the German medical society in connection with the Calibration Act. These guidelines specify that for internal accuracy control and for interlaboratory surveys, control specimens are to be used with assigned values and assigned intervals that have been determined by particularly well-qualified, independent laboratories serving as reference laboratories. The assigned values are often different from the best estimate (by measurement) of the "true value." They are influenced by the matrix of the specimen and by the method used, and they must be determined under routine conditions. The protocol for obtaining the analytical results under carefully defined conditions is described in detail. The statistical treatment of the analytical results and the authors' observations on the structure of the data and the properties of the dispersion and location parameters for the individual laboratories are discussed. These observations led to the development of a procedure for selecting assigned intervals and assigned values in which no special assumptions are made about how the data are distributed. This procedure is described in detail. The importance of the authors' observations for the evaluation of analytical results in the clinical laboratory and for the statistical treatment of such data is discussed. Comparative studies were carried out using the same control specimens with other designs for assigned value determination (e.g. consensus value principle). The advantages of the design presented here are discussed.

Bilirubin↗