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Biomedical subjects

G A Chase

Publications and source records attributed to G A Chase.

At least 91 records · Page 5Linked to original sources
PubMed1986

Detection of dyslipoproteinemia with the use of plasma total cholesterol and triglyceride as screening tests. The Lipid Research Clinics Program Prevalence Study.

The efficiency of screening for dyslipoproteinemias associated with hyperlipoproteinemia or with hypolipoproteinemia was examined in 8449 white examinees from the Lipid Research Clinics Prevalence Study. A two-stage lipid screening approach was used. A positive screening test for hyperlipidemia was defined as an elevated level of plasma total cholesterol or triglyceride at both visit 1 and visit 2. A positive screening test for hypolipidemia was defined as a reduced plasma total cholesterol level at both visits. The syndromes of dyslipoproteinemia were defined according to the lipoprotein pattern present at visit 2. When hyperlipidemia was used as a screening tool, generally only about one-half or less of the cases of hyperlipoproteinemia were detected (high proportion of false-negative results). Of all the hyperlipidemic participants, more than 80% had hyperlipoproteinemias (type I, IIa, IIb, III, IV, or V), and such lipid screening therefore provided a lower proportion of false-positive than false-negative results. Most of the participants (greater than 98%) without hyperlipoproteinemia were correctly identified (true negatives). The efficiency of screening for hypolipoproteinemia was in general poorer than that found for hyperlipoproteinemia. Our results were found to be related, in part, to the marked regression to the mean of plasma cholesterol and triglycerides at the extremes of the distributions and to the wide variety of dyslipoproteinemias that can be present within a given range of plasma cholesterol or triglyceride values. The results emphasize the importance of measuring plasma lipoproteins in the patient who is being evaluated for dyslipoproteinemia.

Adolescent↗
PubMed1985

Huntington's disease: two families with differing clinical features show linkage to the G8 probe.

To test the hypothesis that interfamily variability in Huntington's Disease (HD) is due to mutation at different loci, linkage analysis was undertaken in two large HD kindreds that differed in ethnicity, age-at-onset, and neurologic and psychiatric features. Both families showed linkage of the HD locus to the G8 probe. Several recombinants were documented in each family, and the best estimate of the recombination fraction for the two families was 6 percent with a 95 percent confidence interval of 0 to 12 percent. Although the data support the existence of a single HD locus, use of the G8 probe for presymptomatic testing in these kindreds would have resulted in a 12 percent error rate in genotype assignment at the HD locus.

Chromosomes, Human, 4-5↗
PubMed1985

Use of robust variance components models to analyse triglyceride data in families.

A robust approach for analysis of variance components models is presented which does not rely on the assumption of multivariate normality for its validity. This approach uses the multivariated normal distribution as a 'working model' but obtains standard errors for the final estimators which do not depend on this underlying distribution. By using the observed variance in the first derivatives of the multivariate normal 'working model' to modify the conventional score test, hypotheses regarding specific components can also be tested without relying directly on the assumption of multivariate normality. A special case is presented where both the modified score test and the likelihood ratio test are equally robust, and simulated data are used to illustrate this situation. Measurements of triglyceride levels in 391 individuals in 60 families randomly selected from the membership of a health maintenance organization are used to illustrate this robust approach to variance components.

Genetic Variation↗
PubMed1985

Clinical judgements of self-dramatisation. A test of the sexist hypothesis.

It has been claimed that the diagnosis of histrionic personality disorder is inherently sexist. To estimate the extent to which psychiatrists are influenced by sexist prejudice in their judgements about self-dramatization (the central trait in the histrionic cluster), we conducted a study in which male and female subjects rated the degree of self-dramatization portrayed in videotaped vignettes. The results did not support the sexist hypothesis that dramatic behaviour would more often be attributed to a woman than to a man, especially by male raters.

Female↗
PubMed1985

Epidemiologic evaluation of screening for risk factors: application to genetic screening.

To assess the usefulness of screening for risk factors, we derived arithmetic relationships between screening parameters (sensitivity, specificity, and positive predictive value PPV) and risk factor frequency, disease frequency and relative risk. We evaluated these relationships in the special case of genetic markers and disease susceptibility. It can be shown that even in the face of very large relative risks, sensitivity and positive predictive value are affected by the relative magnitude of disease and genetic marker frequencies. When the genetic marker is less frequent than the disease, PPV increases with increasing relative risk but sensitivity remains low. When the genetic marker is more frequent than the disease, sensitivity increases with increasing relative risk but PPV remains low. When marker and disease frequencies are equal, both PPV and sensitivity increase with increasing relative risks, but very high relative risks (greater than 100) have to be obtained for rare diseases. Depending on the goals of the screening program, these relationships can be used to predict the relative magnitudes of false positives (low PPV) and false negatives (low sensitivity). This approach can be generalized to evaluate nongenetic risk factors in screening programs as well.

Epidemiologic Methods↗
PubMed1985

What participants understand about a maternal serum alpha-fetoprotein screening program.

We investigated the knowledge of pregnant women participating in a maternal serum alphafetoprotein (MSAFP) screening program for the detection of neural tube defects (NTDs) in the fetus. Women participating in the screening program scored higher on two knowledge tests than a comparison group of pregnant women who were not offered screening. However, there were substantial gaps in the knowledge base of women in the program, as measured by one of the tests. Women did not misinterpret a negative test result to mean that the test had identified a potential problem with the fetus; instead, there is a suggestion that they tended to interpret a negative result too positively, as an assurance that the baby was healthy in all respects.

Adult↗
PubMed1984

The Collaborative Lipid Research Clinics Program Family Study. III. Transformations and covariate adjustments of lipid and lipoprotein levels.

Several methods of transformation and covariate adjustment have been applied to the Collaborative Lipid Research Clinics Program Family Study data to facilitate analysis of lipid levels of examinees of different sex and age groups. After several exploratory analyses, cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol were logarithmically transformed, and triglycerides were transformed by the power -0.25. Two types of covariate adjustment procedures, the regression and Z score methods, were used. A modified regression method was developed and was found to be preferable to both simple cubic regression and the Z score method on theoretical and empirical grounds. Refinements in this method to correct for change in variance with age, and for the effect of socioeconomic status, seasonality, and anthropometric measures were made. Methodological issues connected with the transformation and adjustment procedures are discussed.

Adolescent↗
PubMed1984

The Collaborative Lipid Research Clinics Program Family Study. IV. Familial associations of plasma lipids and lipoproteins.

Familial associations of total cholesterol, low density lipoprotein cholesterol, triglycerides, and very low density lipoprotein cholesterol were examined in a population-based random sample of 858 white and 73 black probands and their 4,027 white and 245 black relatives from nine North American Lipid Research Clinics. Correlations among biologic relatives were highly significant for total cholesterol and low density lipoprotein cholesterol and to a lesser extent for triglycerides and very low density lipoprotein cholesterol in whites. Correlations for spouses, however, were not significant, suggesting a stronger influence of genes than shared environment in the determination of these traits. Homogeneity of familial correlations across age strata, clinics, and racial groups was examined. In general, correlations were homogeneous across age strata and clinics, and there was no asymmetry in parent-offspring correlations by the sex of the parent or offspring. Racial differences in correlations were not significant except in four of 32 comparisons, with blacks showing weaker correlations than whites in those instances.

Adolescent↗
PubMed1984

Structural determinants of hospital closure.

In a retrospective case-control study, structural characteristics of hospitals that closed during the years 1976-1980 were contrasted with three comparison groups: hospitals that were acquired in a merger; hospitals that joined a multihospital system; and hospitals that remained autonomously opened, to investigate these characteristics as predictors of closure. Characteristics investigated included environmental, structural, and process variables. The independent variables were measured 5 years prior to outcome. Findings indicate that closed hospitals resemble hospitals acquired in a merger ("failure"), and likewise autonomous hospitals resemble hospitals that join a multihospital system ("success"). The most important predictors of hospital failure were the physician-to-population ratio, the East North Central and West North Central census regions, the level of diversification, low occupancy rate, location in a standard metropolitan statistical area, the chief executive officer's lack of affiliation in the American College of Hospital Administrators, profit status, bed size of less than 50, and presence in a state with a rate-setting agency. Surprisingly, this study shows the bed-to-population ratio to be unrelated to closure. In addition, the findings strongly support the open-system perspective, which, unlike the closed-system perspective, is concerned with the vulnerability of the organization to the uncontrollable and often unpredictable influences of the environment.

Bed Occupancy↗
PubMed1984

Phenotypic heterogeneity in Huntington disease.

Two Huntington disease (HD) pedigrees are presented which differ according to mean and distribution of the age at onset, the effect of paternal transmission on the age at onset, presence of manic-depressive symptoms, and type of presenting symptoms. Together with previous reports, the data suggest clinical heterogeneity between HD kindreds which may imply some kind of genetic heterogeneity, most likely subsequent mutation at a single HD locus. The possibility of genetic heterogeneity has important consequences, both in research, and in the counseling and care of families and patients with differing manifestations of the disease.

Adult↗
PubMed1983

Assessment of variance components models on pedigrees using cholesterol, low-density, and high-density lipoprotein measurements.

Plasma total cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) measurements on 402 individuals in 62 randomly selected families from the Columbia Medical Plan population were used to select the "best" model among a series of multifactorial models using the maximum likelihood method described by Lange et al [1976]. These models included both genetic and nongenetic components of variance. The most parsimonious model for each trait was selected and examined using a goodness-of-fit statistic designed by Hopper and Mathews [1982] to test the assumptions of this technique. A simple additive genetic model was the most plausible for all three measurements, suggesting a strong role for genetic factors in determining lipid and lipoprotein levels in these data. Goodness-of-fit statistics for these models were examined and showed little evidence of deviation from the assumption of multivariate normality within pedigrees. This approach of selecting the most parsimonious model among a series of competing models and then assessing its goodness-of-fit has many applications in studying familial aggregation of quantitative traits.

Adult↗
PubMed1983

The association of affective disorder with Huntington's disease in a case series and in families.

Major affective disorder clinically similar to the disorder found in conditions other than Huntington's Disease (HD) was found in 41% of patients with HD in a consecutive case series ascertained through multiple sources in a defined geographical area. The association appears to be confined to certain families, and affective disorder may appear as long as 20 years before the onset of chorea and dementia. The association may represent genetic heterogeneity in HD.

Adolescent↗
PubMed1983

Conduct disorder and affective disorder among the offspring of patients with Huntington's disease.

The rate of occurrence of conduct disorder and affective illness was studied for a sample of 112 offspring of 34 Huntington's Disease (HD) patients. Psychiatric disorder in the offspring was assessed as a function of: (1) age of the parent at the onset of symptoms of HD; (2) family disorganization; and (3) psychiatric disorder in either parent. The findings indicated an increased frequency of conduct disorder in disrupted families, most especially in those where the HD parent had an early onset of symptoms and the non-HD parent showed psychiatric disorder. Affective disorder in the offspring was most strongly associated with the presence of similar symptoms in the HD parent. Affective disorder, but not conduct disorder, may be an early manifestation of the HD gene. The implication of these findings for genetic counselling is discussed.

Adolescent↗
PubMed1983

The East Baltimore study: the relationship of lipids and lipoproteins to selected cardiovascular risk factors in an inner city Black adult population.

Low socioeconomic status, inner city Black adults, aged 20 to 49 yr (24 males and 45 females), were randomly selected from East Baltimore, MD to study plasma lipid and lipoprotein levels. Several factors known to affect these levels also were examined: dietary intake, alcohol intake, degree of obesity (measured by body mass index), physical activity level, smoking, and hormone use. Compared to women, the men consumed 9.3 more calories/kg body weight (p less than 0.005), 273 mg more cholesterol/day (p less than 0.005), and 7% fewer calories as sucrose (p less than 0.01). The P/S ratio of both their diets was 0.5. The men also had a lower body mass index than the women (23.9 kg/m2 versus 29.0; p less than 0.001). Mean lipid and lipoprotein levels were similar in the men and women. However, the men's total cholesterol (167 mg/dl) and low density lipoprotein cholesterol (94 mg/dl) levels were lower than those of adult Blacks in other studies, while the levels of the East Baltimore women were similar to those in other studies. For women, body mass index and high density lipoprotein cholesterol were negatively correlated (p less than 0.01); triglycerides and oral contraceptive use were positively correlated (p less than 0.01). None of the factors studied explained the relatively low total cholesterol and low density lipoprotein cholesterol levels in these inner city Black adult men.

Adult↗
PubMed1983

The use of life tables and survival analysis in testing genetic hypotheses, with an application to Alzheimer's disease.

Because of the late onset of some neuropsychiatric disorders suspected to be under genetic influence, such as Alzheimer's disease, standard techniques for testing genetic hypotheses are difficult to apply to clinical data. The statistical aspects of life table methods and survival probability estimators which can be used to test such hypotheses have been neglected in the psychiatric literature. Two techniques of this kind, the Weinberg morbidity table and the Kaplan-Meier product limit estimator, are applied to real and simulated data. As estimators of lifetime incidence these methods yield roughly equivalent results for both types of data, although from a theoretical standpoint the original Weinberg estimator appears to suffer from logical defects. Parametric models may offer more definitive results, particularly when an estimator of segregation ratio is required. The clinical data in this report were gathered by interviewing relatives of Alzheimer's disease patients sampled through a nursing home survey in metropolitan Baltimore, Maryland during 1980.

Actuarial Analysis↗
PubMed1983

The nucleus basalis in Huntington's disease.

The nucleus basalis of Meynert (nbM) provides most of the cholinergic input to the cerebral cortex. The loss of cortical choline acetyltransferase (CAT) activity in Alzheimer's disease (AD) and senile dementia of the Alzheimer's type (SDAT) appears to be related to a severe depopulation of the nbM in this dementia. In Huntington's disease (HD), by contrast, there is no loss of cortical CAT activity. The present quantitative study indicates that (1) there is no significant loss of neurons from the nbM in HD, and (2) that the previously described cytologic changes in the neurons of this nucleus in HD patients do not differ significantly from controls. These findings are consistent with the working hypothesis that the types of dementia associated with reductions of neocortical CAT activity are characterized by dysfunction or death of neurons in the nbM, but dementing disorders with normal neocortical CAT activity manifest no major abnormalities in this cholinergic nucleus of the basal forebrain.

Aged↗