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At least 19 recordsLinked to original sources
PubMed1990

Canadian Farm Operator Study: methodology.

A mortality study of about 326,000 Canadian male farm operators enumerated in the 1971 Census of Agriculture is being conducted by Health and Welfare Canada in collaboration with Statistics Canada. The study examines the mortality patterns of farm operators in relation to farm practices and a variety of socio-demographic variables. The prime concern is the association between pesticide use and certain cancers suggested in previous studies of farmers. This article describes the methodology used to create the study cohort and the analysis files. Highlights of the preliminary results from this study for Saskatchewan are also presented. Results for other regions are forthcoming. Among the Saskatchewan cohort of farm operators, 94% of deaths occurred within the province. The average age at death was 67.9 years and the average length of survival from 1971 was 13.9 years. Although the cohort as a whole had no excess mortality for any specific cause of death--including non-Hodgkin's lymphoma--significant dose-response relationships were noted between risk of non-Hodgkin's lymphoma and acres sprayed with herbicides in 1970, as well as with dollars spent in 1970 on fuel and oil for farm purposes (1).

Adult↗
PubMed1990

Object representations in descriptions of significant others: a methodological study.

The aim of this methodological study was to extend Blatt, Wein, Chevron, and Quinlan's (1979) coding system for assessing levels of mental representations of others. Blatt devised a system for scoring spontaneous descriptions of parental figures on a scale that spanned five levels of object differentiation. A single level score was assigned. In this study a procedure was developed to generate scores for each of five representational levels, for two object descriptions, for each subject. The new procedure was based on the assumption that in each individual, all levels of differentiation are maintained albeit in varying proportions. The new coding method was tested in a contrast study in which the responses of a cohort of borderline patients were compared with those of a cohort of nonpsychiatric subjects. As predicted, all subjects were assigned scores at all five representational levels; however, the borderlines had a higher proportion of content units in the lower, least differentiated levels of object representation, and the nonpsychiatric subjects had higher scores at the more differentiated, conceptually complex levels. Results of the psychometric properties of the coding method are discussed. Work in progress to refine the method is outlined.

Adult↗
PubMed1992

Computer-aided S-phase fraction determination in DNA static cytometry in breast cancer. A preliminary methodologic study on cytologic material.

This methodologic study was performed on a single-cell-cycle breast carcinoma to evaluate the feasibility of computer-aided S-phase fraction determination in DNA static cytometry. The investigation was performed on Feulgen-stained cytologic material in which the total optical density values of 1,000 consecutive, randomly selected nuclei were analyzed (MultiCycle software). A good correlation in the S-phase fraction value with flow cytometry was obtained when the G2/G1 ratio was fixed at 1.95, when the histogram data points were smoothed at least once and the coefficient of variation of the G2 peak was the same as that of G0-G1 or when a first-order S-phase polynomial model was used. The percentages of nuclei in G0-G1 and G2 were somewhat similar to those obtained with flow cytometry. The greatest discrepancy with flow cytometry was observed in the value of the coefficient of variation of the G0-G1 peak of the static cytometric data: it was at least twice as great. It always remained high despite the software options used. As for the influence of the sample size in the S-phase calculation, the software was also run on samples of 600 and 200 nuclei. When the G2/G1 ratio was fixed at 1.95, the data obtained from 600 nuclei did not differ from those obtained with 1,000 nuclei, whereas an analysis on 200 nuclei showed a substantial variation. The software also allowed calculation of the ratio of the G0-G1 peak of the neoplastic population against that of the diploid reference (DNA index), the value of which in flow cytometry was 1.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗
PubMed1991

Intraoral strain gauge measurements on complete dentures: a methodological study.

This paper discusses the advantages and the limitations of strain gauge clinical research in prosthodontics. It also demonstrates the possibility of long term studies by explaining a methodological study that was undertaken on a group of 19 patients on two occasions a year apart. Of this group six were supplied with maxillary and mandibular complete dentures, five had maxillary complete dentures and mandibular osseointegrated fixed 10-12 unit bridges, and eight had maxillary and mandibular complete dentures at the first experimental session and osseointegrated fixed 10-12 unit bridges in the mandible at the second. It was found that during maximum biting the direction of functional strain was comparatively stable at a given point of a denture. It was evident that in experiments 12 months apart no major changes had taken place in the experimental dentures nor the denture bearing tissues. The accuracy of the strain gauges used was maintained and there were no failures due to loss of retention of the gauges. Loss of insulation and short circuiting was an occasional problem but instantly recognized if it occurred.

Aged↗
PubMed1989

National General Practice Study of Epilepsy and Epileptic Seizures: objectives and study methodology of the largest reported prospective cohort study of epilepsy. National General Practice Study of Epilepsy and Epileptic Seizures (NGPSE).

Most available data on the prognosis of epileptic seizures come from hospital-based clinics in which patients with chronic or severe disease are over-represented. The National General Practice Study of Epilepsy and Epileptic Seizures is a large prospective community-based study of people with newly diagnosed seizures which aims to address questions related to the early prognosis of epilepsy. 275 general practitioners throughout the United Kingdom have registered a total of 1,195 patients. In this paper we discuss the background to the study and the methodology used.

Cohort Studies↗
PubMedDate not supplied

The International Cooperative Study of Extracranial/Intracranial Arterial Anastomosis (EC/IC Bypass Study): methodology and entry characteristics. The EC/IC Bypass Study group.

This report summarizes the protocol of a randomized trial of superficial temporal artery-middle cerebral artery (STA-MCA) bypass procedure and presents the entry characteristics of its patients. The trial has been designed to determine whether this EC/IC bypass reduces the rate of subsequent stroke among patients with recent hemispheric or retinal strokes and/or transient ischemic attacks who have angiographically proven atherosclerotic narrowing or occlusion of the ipsilateral internal carotid or middle cerebral artery. Of the 1377 eligible patients entered from the 71 participating centers, 714 (52%) have been assigned to medical treatment alone (daily aspirin and aggressive hypertension control) while 663 (48%) have been assigned to receive STA-MCA bypass in addition to medical therapy. The two treatment groups have been well balanced for important prognostic factors. Bypass patency rates of 95% have been documented. At the end of the study in mid-1985, an average follow-up of five years and a minimum follow-up of 33 months will have been achieved. On both clinical and methodologic grounds, this study will have provided a rigorous test of the STA-MCA bypass procedure.

Cerebral Revascularization↗
PubMed1986

Twin study methodology and variability in xenobiotic placental metabolism.

The present study assesses the contribution of genetic and environmental factors to variability in placental aryl hydrocarbon hydroxylase and glutathione transferase activities using twin study methodology. Twin placentas were collected at the time of delivery. The placenta, except for a single layer of maternal decidua, consists of fetal tissue exhibiting fetal genotype. Microsomal and cytosolic fractions were prepared under stringent protocols to prevent enzyme activity loss. There were two monozygotic-monochorionic pairs, five monozygotic-dichorionic pairs, and 21 dizygotic-dichorionic pairs that showed measurable aryl hydrocarbon hydroxylase activity using the direct fluorometric assay. Most of the mothers were smokers. Aryl hydrocarbon hydroxylase activity was measured with two different substrates, benzo(a)pyrene and 7-ethoxyresorufin. Glutathione transferase activity was measured using glutathione and 1-chloro-2,4-dinitrobenzene as substrates for a spectrophotometric assay that follows the conversion of the aromatic substrate. Twin pair similarity was calculated with intraclass correlation coefficients. There is a high correlation between the activities of the two aryl hydrocarbon hydroxylase substrates (r = .814), but no correlation between aryl hydrocarbon hydroxylase and glutathione transferase activity levels. There is little evidence of genetic variability underlying the variation in the enzyme activities because monozygotic-dichorionic twins are no more similar to each other for the three substrate activities than are the dizygotic twins. To delineate the prenatal environmental influences on placental enzyme variability, dichorionic placentation was subdivided further into contiguous and noncontiguous placental position. Lower intraclass correlation coefficients are obtained for the dizygotic twins whose placentas were noncontiguous compared with dizygotic twins with contiguous placentas. The results suggest that most of the variability seen in these placental enzyme systems is due to environmental differences within uteri, rather than genetic variability in the population. This does not negate the possibility that between-pair, or population, variability may have a genetic component, because even dizygotic twins share a large proportion of their genes. This study points out that a significantly variable environment exists within the human uterus.

Aryl Hydrocarbon Hydroxylases↗
PubMed1989

A methodological study of a nonlinear stochastic model of an AIDS epidemic with recruitment.

A nonlinear stochastic model of an AIDS epidemic with recruitment of infectives, susceptibles, and AIDS cases into a randomly mixing population of male homosexuals was formulated and studied from a methodological point of view through intensive computer experimentation. Probability generating functions were used to formulate a model for the monthly probability that a susceptible individual becomes infected with HIV, under the assumption that the probability of infection per sexual contact varies as a function of the duration of infection. A method for taking into account the use of condoms to prevent infection with HIV was also introduced. Nonlinear difference equations, resembling deterministic epidemic models, were embedded in the stochastic population process by iterating an initial conditional expectation. Examples of Monte Carlo experiments are presented, illustrating that solutions of these nonlinear difference equations are not always good measures of central tendency for variations in the sample functions of the process. Two important substantive conclusions drawn from the Monte Carlo experiments were that efforts should be made to collect quantitative information on the probability of infection per sexual contact as a function of duration of infection and the frequency of condom use within and among risk categories in a population.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Microcalorimetric studies on metabolism of hepatic tissue. I. A methodological study of normal tissue.

In the present study, the heat production of liver biopsies (5-8 mg) was measured by a microcalorimetric technique. Tissue incubated in Leibowitz L-15 medium (L-15) showed a higher metabolic rate compared to tissue incubated in a medium without substrate 2.8 microW/mg and 1.75 microW/mg, respectively. Heat production was found to be related to weight density. No difference in the metabolic rate was found after organ perfusion in comparison to nonperfused liver. Storage in medium L-15 at 4 degrees C caused a lower rate of heat production, but if the tissue was stored in an electrolyte balance solution without substrate, no difference was seen compared to fresh tissue. Recording heat production with the present calorimetric technique is relatively simple and rapid and allows measurement of small samples.

Animals↗
PubMed1992

CBF studies with Xenon-133 in arteriovenous malformations: a methodological study.

A new model for the two dimensional rCBF technique using the inhalation of Xenon 133 was tested in patients with arteriovenous malformations. It was hypothetized that, in contrast to the conventional CBF model, it corrects for the artifactual shunt flow through the AVM and thus yields physiological CBF data. Four regions of interest (AVM, contralateral to AVM, ipsilateral hemisphere, contralateral hemisphere) were defined in 17 patients with AVMs and analyzed for differences in grey matter flow (F1). In contrast to the conventional CBF model, the new model shows a decreased flow over the AVM area, corresponding to the results of Xenon CT and SPECT. Furthermore, the blood pool parameter P4 is very sensitive to the location of the AVM. Thus further investigations of the hemodynamics of AVMs with this model are encouraged.

Adult↗
PubMed1991

Adult day health care evaluation study: methodology and implementation. Adult Day Health Care Evaluation Development Group.

The Adult Day Health Care Evaluation Study was developed in response to a congressional mandate to study the medical efficacy and cost effectiveness of the Adult Day Health Care (ADHC) effort in the Department of Veterans Affairs (VA). Four sites providing ADHC in VA facilities are participating in an ongoing randomized controlled trial. Three years of developmental work prior to the study addressed methodological issues that were problematic in previous studies. This developmental work resulted in the methodological approaches described here: (1) a patient recruitment process that actively recruits and screens all potential candidates using empirically developed admission criteria based on predictors of nursing home placement in VA; (2) the selection and development of measures of medical efficacy that assess a wide range of patient and caregiver outcomes with sufficient sensitivity to detect small but clinically important changes; and (3) methods for detailed, accurate, and efficient measurement of utilization and costs of health care within and outside VA. These approaches may be helpful to other researchers and may advance the methodological sophistication of long-term care program evaluation.

Aged↗
PubMed1978

Panel studies of acute health effects of air pollution. II. A methodologic study of linear regression analysis of asthma panel data.

Panel studies relating illness, such as asthma attacks, cardiopulmonary symptoms, and acute respiratory symptoms, to daily air pollution and weather are important in environmental epidemiology. A study of the practical robustness of multiple linear regression procedures, which have been the preferred statistical models in analyses, is presented. The study is based on data from three asthma panels in Chattanooga, Tennessee, collected in 1972-1973. Linear regression models, commonly used, which incorporate only minimum temperature and an air pollutant were found to be potentially misleading; such models are highly sensitive to reporting trends in the data and do not correct adequately for weather variables. Temporal and spatial control strategies were employed and proved to be useful in detecting problems in the data due to undiscovered intervening variables. True day-to-day relationships estimated by a pair-day analysis were frequently inconsistent with "daily" effects estimated by the usual regression models and suggested that, in fact, the asthma panel data contained no useful information concerning day-to-day relationships.

Adolescent↗
PubMed1978

[Comparative study of carcino-embryonic antigen and beta2-microglobulin. Methodological study and clinical interpretation (author's transl)].

beta2m was determined by radioimmunoassay in 43 serums from healthy blood donors. Serum concentrations varied from 0.67 to 1.9 mg/l with a mean of 1.29 mg/l. Reproductibility and sensitivity of the method were evaluated. 66 patients with advanced neoplasia were studied. Serum beta2m was greater than 2 mg/l in 70% of the cases and carcinoembryonic antigen (CEA) in 54%. In 26 documented cases with tumor progression and 14 with regression, associated variations of CEA were formed more frequent and of greater magnitude than those of beta2m.

Beta-Globulins↗
PubMed1989

Cytomorphometry. A methodologic study of preparation techniques, selection methods and sample sizes.

The influence of methodologic aspects on cytomorphometric features was studied using preparations of hepatoma and/or mastocytoma cells. First, two preparation techniques (smear and oese) were compared. Second, four methods of selecting cells for cytomorphometric analysis (two conventional and two stratified methods) were tested for reproducibility. Third, heterogeneous cell populations were used to estimate the required sample size using the running coefficient of variation (CV), and the results were compared with expected (theoretical) values of the required sample size calculated using the standard error of the mean. The results showed significantly lower CVs for the smear preparation technique. The stratified methods appeared to be superior to the conventional methods for selecting cells for measurement. The experimentally assessed sample sizes were considerably lower than the corresponding theoretical calculations. These findings suggest that morphometric assessments in cytologic smears should utilize a stratified cell selection method. While experimentally assessed sample sizes are relatively small and therefore better routinely applicable, they may yield less reliable results in some cases. The need to test a sample for its reproducibility as well as its discriminatory power is emphasized.

Animals↗
PubMed1990

One year's experience of major trauma outcome study methodology.

OBJECTIVE: To assess the feasibility and the validity of an audit using major trauma outcome study methods in an accident and emergency department. DESIGN: Prospective audit of all cases of trauma in patients admitted to a hospital from an accident and emergency department. SETTING: Accident and emergency department in a teaching hospital. PATIENTS: 1577 Patients admitted with trauma, of whom 695 met the inclusion criteria for the study--that is, were admitted for more than three days, or admitted to intensive care, or died. 17 Patients were excluded because of failure to trace their notes. OUTCOME MEASURES: Review of case notes with TRISS (trauma score, injury severity score) methodology to compare expected and observed survival. RESULTS: Most (421/678) admissions were due to single orthopaedic injury. Serious injury was uncommon with only 43 patients having injury severity scores greater than 15. The calculated probability of survival matched the observed outcome for most of the seriously injured patients, with only two unexpected deaths. However, 36 of the 61 deaths in the 678 patients occurred in elderly patients with a fractured neck of the femur, and all of these patients had a high probability of survival predicted by TRISS methodology. CONCLUSIONS: Application of TRISS methodology seems to be valid for seriously injured patients except for elderly patients with single orthopaedic injuries, in whom there were major differences between observed and expected outcomes. Using outcome norms from the United States may not be applicable for this group. IMPLICATIONS: Audit of management of major injuries should be carried out by every hospital, and the methodology of the major trauma outcome study is an excellent system for carrying out such audit. The study of all patients admitted with trauma requires appreciable extra resources, but most hospitals should be able to monitor the care of seriously injured patients as their numbers are much fewer.

Adolescent↗
PubMed1990

Cancer incidence in young offspring of Jewish immigrants to Israel. A methodological study. I. Nasopharyngeal malignancies and Ewing sarcoma.

Differences in cancer incidence among various immigrant groups in Israel raised the question of persistence in their descendants. The methodological problems of identification of both parents and their origins, the choice of the denominator, and the long period of observation necessary for the rare childhood tumors have been examined. From 22-years data of the Israel Cancer Registry (ICR), three malignancies were chosen as examples: epithelial carcinoma of nasopharynx (31 cases), non-Hodgkin's lymphoma of nasopharynx (14 cases), and Ewing sarcoma (55 cases). The actual number of cases, in spite of the long period of incidence, is small and the computed significance must be accepted with reservation. There are two outstanding findings: the higher incidence in males as well as in females for nasopharynx carcinoma corresponds to that of their African-born parents; an increasing trend in the second 11-years period for Ewing sarcoma. Similar studies on leukemias, lymphomas, and others with a greater number of cases can be expected to have more reliable results. This survey relied on the majority of patients with immigrant parents, mostly of the same origin. In the following years, second and later generations of Israel-born and an increasing part of intermarriages will severely impede similar studies.

Adolescent↗