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PubMed1994

Microbiological collaborative studies for quality control in food laboratories: reference material and evaluation of analyst's errors.

Working groups of the Federal Health Office in Germany and of the International Dairy Federation (IDF) have developed a quality assurance system to assess the analyst performance for colony count methods. The experiment design consists of several dilution series produced from a homogeneous sample suspension. Each series contains a number of twofold dilution steps with parallel plates on each level. The structure of this design permits a detailed analysis of the total variance and identification of analysts' methodological errors as single effects. A computer-based interpretation aid may classify the laboratory as working in correspondence with good laboratory practice ('acceptable') or, otherwise, furnishing 'to good' or 'unacceptable' results. Some examples are given for deviation depending on individual faults. Both, internal quality assurance and collaborative studies demand suitable reference samples. The reference material used has to meet certain requirements concerning homogeneity, contamination level and microbiological stability during a period of storage and transport. A naturally contaminated sample material was prepared, which has been used successfully in microbiological collaborative studies.

Animals↗
PubMed1985

[Experiences with the Meyer-Probst encephalopathy questionnaire].

The validity of the questionnaire elaborated by Meyer-Probst for recording the typical behaviour of encephalopaths was checked on a sample comprising 254 high-risk and control children aged 6 to 7 years. The results confirm its value as a diagnostic aid in outpatient work and as methodological tool for research.

Attention Deficit Disorder with Hyperactivity↗
PubMed1995

Liquid chromatographic determination of the antibiotic fumagillin in fish meat samples.

A procedure for the determination of fumagillin, an antibiotic of Aspergillus fumigatus in fish meat samples, using reversed-phase high-performance liquid chromatography is described. Liquid chromatography was performed on an octadecylsilane column using acetonitrile-water-phosphoric acid solution as mobile phase, with detection at 350 nm. Two different types of sample preparation were developed, clean-up and enrichment, and the limits of quantification were 100 ng/g and 5 ng/g, respectively, in fish meat. The recovery was 75 +/- 3% in the concentration range 100-500 ng/g. To introduce the methodology and demonstrate its usefulness, a practical experiment was performed. Trouts fed with fumagillin were examined for elimination of fumagillin. After 24 h, the concentration was shown to decrease to below 100 ng/g.

Animals↗
PubMed1984

Gender differences in antidepressant and activating drug effects on self-perceptions.

Gender difference in neuropharmacologic responsivity have received surprisingly little attention in clinical research. In view of well-known gender differences in the prevalence of depression, we wondered whether men and women would respond differently to antidepressants or to an activational drug known to predict antidepressant response. Using clorgyline and D-amphetamine in 2 small samples, we illustrated several methodological approaches for examining possible gender-linked differences in the effects of these drugs on self-perceptions. Gender-linked differences in cognitive-perceptual processes may, in turn, be linked to differences in encoding or consolidating information about our experiences into our self-image for later recall.

Adult↗
PubMed1991

Bringing social structure back into clinical decision making.

Although research in the past twenty years has resulted in an increasingly sophisticated understanding of clinical decision making processes, the dominant approach in this area of inquiry remains limited. Most studies emphasize normative models of how decisions ought to be made, others attempt to describe physicians' thinking, but few take the social context of decision making systematically into account. Research models typically assume that physicians are autonomous professionals practicing in socially insular clinical settings--an approach that is consistent with classic formulations of the social structure of medical practice, but they ignore 30 years of sociological research on research on patient-physician relationships and major historical changes in the structure of medical practice. Eisenberg's still timely advice to students of clinical decision making--that they need to describe decision making in the context of 'sociologic influences' (including patient, physician and practice setting characteristics)--is expanded in the present discussion. Recent studies are reviewed, highlighting important dimensions of social structure impinging on physicians' decision making. Findings indicate that the process of clinical decision making is likely influenced by patients' age, gender, socioeconomic status, and race, physicians' professional training and experience, as well as by larger structural features of organized clinical settings. Our review of these studies on the social context of clinical decision making, however, reveals major methodological limitations including those inherently imposed by secondary data analysis, normative approaches, written case vignettes, small, non-random samples and the inadequate control of confounding influences. We present a feasible, alternative research strategy, built on a factorial experimental design. Illustrative findings indicate how complex social structural influence on clinical decision making may be disentangled in an unconfounded manner.

Age Factors↗
PubMed1984

Pethidine binding in plasma: effects of methodological variables.

Several methodological variables potentially influencing the plasma protein binding of [14C]-pethidine in vitro were investigated using equilibrium dialysis and rigorous pH control. Ionic strength of buffer, pethidine concentration and 21 days of plasma samples frozen to -8 degrees C did not affect the outcome of the binding experiments. Unbound fraction decreased with increasing temperatures between 25 degrees C and 37 degrees C. Unbound fraction decreased with increased pH between pH 7.0 and 8.0; the mean unbound fraction at an equilibrium pH of 7.4 and at 37 degrees C was 0.58 (s.d. 0.03, n = 58). It is likely that previous reports of pethidine unbound fraction as being between 0.2 and 0.4 represent artefacts caused by inadequate pH control during dialysis.

Blood Proteins↗
PubMed1988

How large should my study be so that I can detect an altered sex ratio?

The world literature on manipulations purported to alter the gender of offspring is a quagmire full of reports presenting inadequate data and contradictory conclusions. Many are due to inappropriate statistical design or analysis. The authors present simple, nontechnical reference tables for determination of the minimum sample size necessary to detect a change in sex ratio (1) from a theoretical value, and (2) between two experimental populations. Simple methods for analyzing the results of gender manipulation experiments are described. Technical details are included in a separate section.

Female↗
PubMed1994

A passive ozone sampler based on a reaction with nitrite.

Standard ozone monitoring techniques utilize large, heavy, and expensive instruments that are not easily adapted for personal or microenvironmental monitoring. For large-scale monitoring projects that examine spatial variations of a pollutant and human exposure assessments, passive sampling devices can provide the methodology to meet monitoring and statistical goals. Recently, we developed a coated filter for ozone collection that we used in a commercially available passive sampling device. Successful preliminary results merited further validation tests, which are presented in this report. The passive ozone sampler used in field and laboratory experiments consists of a badge clip supporting a barrel-shaped body that contains two coated glass fiber filters. The principle component of the coating is nitrite ion, which in the presence of ozone is oxidized to nitrate ion on the filter medium (NO2- + O3 produces NO3- + O2). After sample collection, the filters were extracted with ultrapure water and analyzed for nitrate ion by ion chromatography. The results from laboratory and field validation tests indicated excellent agreement between the passive method and standard ozone monitoring techniques. We determined that relative humidity (ranging from 10% to 80%) and temperature (ranging from 0 degrees C to 40 degrees C) at typical ambient ozone levels (40 to 100 parts per billion) do not influence sampler performance. Face velocity and sampler orientation with respect to wind direction were found to affect the sampler's collection rate of ozone. Using a protective cup, which acts as both a wind screen and a rain cover, we were able to obtain a constant collection rate over a wide range of wind speeds.

Environmental Exposure↗
PubMed1991

The influence of depressive symptomatology on alcoholics' locus of control: a methodological note and a correction.

In a previously published experiment from our laboratory, we reported two findings. First, controls showed the expected negative correlation between internal and external LOC dimensions, while alcoholics did not. Second, a difference score between LOC-internal and LOC-external was correlated significantly and positively with alcoholics' abstracting impairment. Data from two new independent samples of alcoholics and controls confirmed the first finding, but not the second; further, a calculation error was discovered in the previously published data that invalidated the second result. However, in all three studies, depressive symptomatology was found to be correlated negatively with the internal-external LOC difference score in both alcoholics and controls. It is suggested that depressive symptomatology be assessed in any study that investigates LOC.

Adult↗
PubMed1986

Mutagenic activity of disinfection by-products.

Data on raw water quality, disinfection treatment practices, and the resulting mutagenic properties of the treated water were compiled from pilot- and full-scale treatment experiments to evaluate that parameter which might produce variability in the results of a mutagenic study. Analysis of the data and comparison of treatment practices indicated that the measured mutagenic activity is strongly related to the characteristics of the organic matter in the raw water, the methodology used to sample and detect mutagens, the scale of the study both in terms of treatment flow and period of study, and the point at which and the conditions under which oxidants are added during treatment. Conclusions regarding disinfection systems in full-scale water treatment plants include the following: When raw water is pretreated and high concentrations of organics are present in the raw water, both ozonation and chlorination increased mutagenic activity. However, no significant difference in mutagenicity was found between the two oxidants. Both in the case of a nitrified groundwater and a clarified surface water, the mutagenic activity of the water after ozonation was related to its mutagenic activity before ozonation. With ozonation, mutagenic activity decreased after granular activated carbon (GAC) filtration. Thus, when GAC filtration follows ozone disinfection, early addition of oxidants may not be deleterious to the finished water quality. When chlorine or chlorine dioxide is added after GAC filtration, chlorine dioxide was found to produce a less mutagenic water than chlorine. Although these conclusions suggest means of controlling mutagenic activity during treatment, it must be stressed that the measurement of mutagenicity is a presumptive index of contamination level.

Carbon↗
PubMed1990

[Event-related desynchronization and the selection of an alpha-frequency band for quantifying cortical pre- and poststimulus activation].

The amount of event-related decrease of increase in alpha-band power is termed "Event-Related Desynchronization" or ERD. In this study, ERD is used as an index of cortical activation, which not only can be applied to monitor poststimulus but prestimulus processes as well. Usually, ERD is analyzed within a fixed range of alpha-frequency, typically within a range of 8-12 Hz. alpha-frequency, however, shows a considerable between subject variation, even in a sample of subjects with comparable age. The purpose of this study, thus is to show as to how the range of alpha-frequency affects the calculation of ERD. Two different methodological approaches were compared. First, ERD was calculated within a fixed range of 8-12 Hz. Second, ERD was calculated within an individual range, which was adjusted to the individually determined alpha-frequency of each subject. A sample of ten right handed subjects participated in an episodic memory experiment, in which target words, shown in a earlier session of the experiment, were to be identified. A time span of 375 ms preceding and following the presentation of a word was defined as the "pre-" and "poststimulus" interval. EEG-signals were recorded unipolarly from 29 leads. The results show a rather localized increase of ERD in the poststimulus interval. In the prestimulus interval on the other hand, the average magnitude of ERD is much lower and the topographical distribution less localized. Most importantly, however, when comparing the two methods of analyzing ERD, those ERD-values calculated within an individually determined alpha-band, are superior in order to differentiate between the pre- and poststimulus interval.

Adult↗
PubMed1988

Case-control studies of the effect of environmental sanitation on diarrhoea morbidity: methodological implications of field studies in Africa and Asia.

The problems and prospects in the use of case-control studies to assess the effects of improvements in environmental sanitation on diarrhoea morbidity are discussed on the basis of two field studies. It is concluded that an adequate design is available for assessing the effects of a single improvement on diarrhoeal disease. The estimates of effect appear to be valid and sufficiently precise. For addressing more complex questions of interactions, sample sizes would have to be increased substantially. The experience with two field studies suggests that there is hope that a simpler protocol may be feasible, in which only limited information is collected, in which few home visits are made, and in which analytical techniques are simple. Until more field studies have been conducted definitive conclusions cannot be reached on the applicability of such a simple, rapid and inexpensive approach.

Child, Preschool↗
PubMed1988

The use of network sampling for locating the seriously ill.

Network sampling, based on the experience of conducting the large-scale 1986 Robert Wood Johnson Foundation National Access to Health Care Survey, was shown to be a viable alternative to more conventional procedures for oversampling persons with a low incidence and prevalence of health conditions. The network sampling approach was a more economical and methodologically less obtrusive means of increasing sample size of persons with desired characteristics than conventional procedures. The approach requires estimating the incidence, prevalence, or both of the required characteristics in the population. As the proportion of persons in the population with the characteristic increases, network sampling may lose its attractiveness. However, this has to be judged both in economic terms and in terms of the methodologic consequences of using other procedures to increase the size of subgroups of interest. As discussed, additional methodologic work is required on the consequences of network sampling for study group representativeness and sampling bias. However, network sampling, in the authors' opinion, is sufficiently promising to warrant methodologic explorations to answer these and other relevant questions about its use.

Adult↗
PubMed1994

Childhood Experience of Care and Abuse (CECA): a retrospective interview measure.

The development of a retrospective, investigator-based interview measure of Childhood Experience of Care and Abuse (CECA) used with two community samples of adults in London is described. The component ratings are shown to have satisfactory inter-rater reliability and also validity as determined by agreement between sisters' independent accounts. The association between the different childhood scales is explored as well as the relationship of childhood experiences to adult depression. Methodological issues concerning investigator-based versus respondent-based measures of childhood are discussed and a case made for use of the former. Advantages of using the CECA, a retrospective, time-based measure of childhood, are outlined.

Adult↗
PubMed1993

Measuring intrasubject variability: use of the jacknife in doubly labeled water experiments.

The doubly labeled water technique measures energy expenditure; however, very little has appeared in the literature regarding estimation of the intrasubject variation. By use of a statistical resampling procedure called the jackknife, the standard deviation of the determination of energy expenditure in each subject is evaluated. Jackknife methods exploit the regression techniques that are already used with the doubly labeled water technique and are very easy to implement. Estimates of sample sizes for future experiments can easily be done with the jackknife. These formulas give the number of determinations of isotopic enrichment of hydrogen and oxygen over time that are needed to achieve a given degree of accuracy in estimating energy expenditure. An example with two human subjects illustrates the methodology of the jackknife.

Body Water↗
PubMed1989

[Coping with disease from the psychosomatic-psychotherapeutic viewpoint exemplified by pancreatectomized patients].

In the past few years psychosomatic medicine, apart from investigating the psychosocial sources of bodily disorders, has begun to focus also on the opposite side of the problem, the question of how people experience illness and cope with it. This "somatopsychic" view can be regarded as a supplement to the so far prevailing psychosomatic perspective and its approach. The present study describes and analyzes various strategies of coping with illness as observed in a group of pancreatectomized patients, a group of patients which has not been investigated before in this field of research. Based upon the experience of long-term psychotherapeutic care, the study differentiates between the more problematic and the more beneficial forms of coping, and empirically verifies their prevalence and adaptivity in a sample of pancreatectomized patients, not selected with regard to the extent of care needed. The findings are discussed from the methodological and the psychosomatic-psychotherapeutic point of view.

Adaptation, Psychological↗
PubMed1979

Menu planning competencies in administrative dietetic practice. II. Practitioners' ratings of competence.

A nationwide sample of administrative and generalist dietitians rated five competencies with sub-competencies and ninety-two descriptors related to menu planning. Each item was rated numerically for importance and frequency of time consideration. Data were grouped according to three levels of practitioner experience. It was concluded that an effective methodology was developed for analyzing competencies for dietetic practice.

Administrative Personnel↗