Search PubMed⌕ Search

Biomedical subjects

J L Weissfeld

Publications and source records attributed to J L Weissfeld.

35 records · Page 2Linked to original sources
PubMed1996

Model of the impact of HIV infection on the size of future hemophilia and carrier birth cohorts.

The introduction of human immunodeficiency virus (HIV) infection in almost half of the U.S. hemophilia population during the late 1970s and early to mid-1980s has resulted in significant mortality and morbidity. The predict the quantitative impact of HIV infection through HIV-contaminated clotting factor on the size of future hemophilia and hemophilia carrier populations in the United States, a demographic model was developed for hemophilia and hemophilia carrier birth cohorts for the 200 years between 1980 and 2180. Mortality and fertility rates were estimated from databases of the Hemophilia Malignancy Study (HMS), NHLBI Blood Resources Studies, and Centers for Disease Control (CDC) Minimal Data Set. According to the model, the HIV epidemic will produce small reductions in the expected numbers of hemophilic (1.79%) and carrier (2.63%) births in the next 2 centuries. More substantial reductions in the numbers of hemophilic and carrier births required extreme assumptions regarding the fertility of hemophilic men, the extent of HIV infection among hemophilic men, and the proportion of hemophilic births that arise from spontaneous mutation.

Age Factors↗
PubMed1996

Does visceral adipose tissue differ from subcutaneous adipose tissue in fatty acid content?

OBJECTIVE: To determine whether intra-abdominal adipose tissue differs from subcutaneous adipose tissue in fatty acid content. DESIGN: Cross-sectional study of patients undergoing exploratory laparotomy, with adipose tissue sampling from subcutaneous, omental, mesenteric and retroperitoneal sites. SUBJECTS: Nineteen subjects, 8 men and 11 women, with a mean age of 64 (range 39-80), mean weight 78.9 kg (range 51-157) and mean body mass index of 27.5 (range 19.2-51.4). Fourteen of the 19 were undergoing surgery for colorectal cancer. MEASUREMENTS: Fatty acid content was assessed by gas chromatography and was compared between sites and between patients using general linear modeling. Spearman correlation coefficients were used to assess the association between subcutaneous and visceral adipose tissue. RESULTS: For each of 17 fatty acids analyzed, there was a statistically significant difference in mean fatty acid values across individuals (p < 0.001). For seven of the fatty acids, there was a borderline or significant difference in mean fatty acid values across site, but there was no consistent pattern for one site differing from the others. Subcutaneous adipose tissue fatty acid content was highly correlated to visceral adipose tissue for saturated, unsaturated and trans fatty acids (p < 0.05 for 13 of 17 fatty acids). Variability across individuals was much greater than across site. The total explained variability (R2) for each fatty acid ranged between 49 and 93%, with the vast majority contributed by differences between individuals. CONCLUSION. Fatty acid content of subcutaneous abdominal adipose tissue is a good approximation of visceral adipose tissue. Because variability in fatty acid content is much larger between individuals than within a single individual across sites, subcutaneous abdominal adipose tissue fatty acid content can be used as a distinguishing characteristic among human populations.

Adipose Tissue↗
PubMed1995

Sigmoidoscopy use among primary care physicians.

BACKGROUND: Despite endorsement by a variety of professional societies, screening sigmoidoscopy is performed on a small minority of patients. We performed a survey of primary care physicians in Allegheny County to examine in detail their current practice and attitude toward screening sigmoidoscopy. METHODS: Physicians were surveyed by mail or telephone. Eligible respondents were required to practice in the county and perform direct patients care. RESULTS: Of 732 adult primary care physicians in Allegheny County, 400 were randomly selected for sampling and 279, or 70%, responded. Over 88% of physicians agreed completely or partly with current American Cancer Society recommendations for screening sigmoidoscopy, but only 34% (95% CI 29-39%) reported they regularly refer or schedule patients for screening. Physicians who screen were more likely to be from internal medicine or family practice (P < 0.001) and to be trained in (P < 0.001) or to personally perform (P < 0.001) sigmoidoscopy. The greater the number of barriers to screening cited by physicians, including cost, patient discomfort, equipment availability, low probability of finding a lesion, time it takes to do sigmoidoscopy, and the risk of the procedure, the lower the screening rate (P = 0.002). CONCLUSION: (a) Although primary care physicians in Allegheny County report that they support screening sigmoidoscopy, only one-third regularly refer or schedule patients, (b) physicians who are trained in or who perform sigmoidoscopy are more likely to screen patients, and (c) further education and training of primary care physicians in sigmoidoscopy will be required to increase screening rates.

Adult↗
PubMed1994

Are women with breast, endometrial, or ovarian cancer at increased risk for colorectal cancer?

OBJECTIVES: Evidence is accumulating supporting the use of screening for colorectal cancer. Patients at higher risk for colorectal cancer are more likely to benefit from screening. Women with breast, endometrial, or ovarian cancer are often classified as at high risk for subsequent colorectal cancer, and are urged to undergo screening, but the basis for this is uncertain. METHODS: We performed a meta-analysis of published data to assess the risk of colorectal cancer after these cancers. RESULTS: Based on 154,270 women and 779,251 person-yr of observation (PYO) after breast cancer, 37,266 women and 229,498 PYO after endometrial cancer, and 41,366 women and 126,688 PYO after ovarian cancer, the age-adjusted relative risk (95% CI) for colorectal cancer after breast cancer was 1.1 (1.07, 1.19), after endometrial cancer 1.4 (1.32, 1.55), and after ovarian cancer 1.6 (1.40, 1.80). CONCLUSIONS: 1) Women with a history of breast, endometrial, or ovarian cancer are at a statistically significant increased risk for subsequent colorectal cancer. 2) Women with a history of endometrial or ovarian cancer are at higher risk than are women with breast cancer, but ascertainment bias from heightened medical surveillance after the diagnosis of a gynecologic malignancy may contribute to this observed increase in risk. 3) The association between these cancers and colorectal cancer suggests common etiologic factors, either environmental or genetic, but the degree of increased risk is small.

Aged↗
PubMed1993

Coming to terms with the era of AIDS: attitudes of physicians in U.S. residency programs.

PURPOSE: To examine factors associated with residents' willingness to provide care to persons with AIDS. PATIENTS AND METHODS: Survey of all senior residents in internal medicine and family medicine in ten geographically representative states in early 1989. RESULTS: Preferring not to care for persons with AIDS was less common in the western United States and more common among those with more conservative politics, men physicians, Asian physicians, and foreign medical graduates. Multivariate analysis revealed scores on six attitudinal scales (homophobia, dislike of intravenous drug users, professional responsibility, fear of AIDS, futility of providing AIDS care, and clinical difficulty of AIDS care) to be strong independent predictors of willingness to care for persons with AIDS (adjusted R2 = 0.42). The authors postulated a model in which these six fundamental attitudes functioned as intervening variables between demographic characteristics and expressed willingness to provide AIDS care. Regression results supported the hypothesis that the associations between demographic characteristics and willingness to provide AIDS care were mediated via these attitudes. However, having had ambulatory experience in AIDS care during residency was associated with future intentions to provide such care, independent of negative attitudes. CONCLUSIONS: Physician willingness to care for persons with AIDS is inversely related to fear of acquiring AIDS, viewing treatment as futile or difficult, dislike of certain risk groups, and a lower sense of professional responsibility. These results identify concerns and stresses that should be addressed by residency programs, and emphasize the need for attention to the ethics and ideals of the profession in medical education.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Precision of blood cholesterol measurement and high blood cholesterol case-finding and treatment.

Imprecise blood cholesterol measurement can be expected to adversely affect large scale efforts to detect and treat high blood cholesterol. Using protocols specified by the National Cholesterol Education Program (NCEP), we used computer simulation techniques to quantify the effects of blood cholesterol measurement variability on misclassification rates, costs, effectiveness, and cost-effectiveness of high blood cholesterol case-finding and treatment. At the time of initial case-finding, increased measurement variability was associated with a moderate decrease in the proportions assigned to a treatment state and in the positive predictive value of such an assignment. After 10 years of continual case-finding and treatment, measurement variability dramatically affected proportions assigned to drug treatment and diminished the percent on drugs with blood cholesterol levels truly above NCEP cutpoints. Extreme variability in blood cholesterol measurement increased per capita costs by 14-18% and diminished cost-effectiveness by at least 11-12%. The adverse effects of measurement variability on cost-effectiveness were much more pronounced if adjustments to life-expectancy were made to recognize the lower quality of life associated with drug treatment. Misclassification rates can be decreased and cost-effectiveness improved by performing repeated measurements of blood cholesterol before increasing intensity of treatment. Improvement in the precision of measurement are especially beneficial for low-risk individuals.

Age Factors↗
PubMed1991

Treatment for cigarette smoking in a Department of Veterans Affairs outpatient clinic.

A randomized clinical trial assessed the effectiveness of control, low-intensity, and high-intensity stop-smoking treatments in a Department of Veterans Affairs outpatient setting. The study actively recruited male cigarette smokers attending outpatient clinics at a university-affiliated Veterans Affairs medical center. Subjects in the control group received an informational leaflet on smoking. Subjects in the low-intensity treatment group received a self-help booklet and a 20- to 30-minute session with a trained counselor. Subjects in the high-intensity group received the low-level treatments and individually tailored follow-up treatments provided in person, over the telephone, and through the mail. At least 6 months after randomization or last treatment, biochemically verified 1-month quit-smoking rates were 1.2% in 173 control subjects, 6.3% in 143 low-intensity treated subjects, and 6.0% in 150 high-intensity treated subjects. When rigorously defined, quit rates in each of the treated groups differed significantly from the control rate, but not from each other. The results demonstrated the effectiveness of moderately intensive stop-smoking treatments in a clinical setting of considerable interest, but not the incremental effectiveness of progressively more intensive treatments.

Adult↗
PubMed1990

Health beliefs in a population: the Michigan blood pressure survey.

In a general population sample, we examined relationships between sociodemographic characteristics and health beliefs. Individual questionnaire measures for components of the health belief model were combined to form six scales. In analyses which adjusted for perceived levels of health, sociodemographic markers of social disadvantage (e.g., black race, or low socioeconomic status) appeared to associate with favorable health beliefs, that is, with health beliefs often associated with health promoting behaviors. Specifically, we found that blacks expressed greater concern about health. Women believed they tended to get sick more often and to suffer more severely from illness. Female and older respondents placed greater value on the kinds of services provided by members of the health professions. Female, black, older, and lower socioeconomic status respondents placed greater value on such healthful personal habits as exercise, alcohol avoidance, and proper diet. These results suggested that the poor health suffered by relatively disadvantaged members of society are not, in some manner, a consequence of fundamental beliefs about health.

Adolescent↗
PubMed1989

Effects of deceptive self-reports of quitting on the results of treatment trials for smoking: a quantitative assessment.

Problems with self-report measures for smoking motivate the use of biochemical tests in treatment trials for smoking. These biochemical tests, unfortunately, are not perfect. In this paper, we present an algebraic model of bias in treatment trials for smoking. Bias is expressed in terms of the deception rate among continued smokers in a control group, the relative deception rate among continued smokers in an experimental group, and the sensitivity and specificity of a biochemical test which may be used either to confirm self-reports of quitting or to replace self-report entirely. For given test specificity and sensitivity, the model defines deception rates for which different biochemical testing strategies are preferred. The model is presented in the context of current knowledge on the phenomenon of deception among adult smokers. The paper concludes that better judgements regarding the role of biochemical tests in treatment trials for smoking require more precise information regarding the magnitude and determinants of deception.

Clinical Trials as Topic↗
PubMed1988

Sex and age interactions in the association between alcohol and blood pressure.

The cross-sectional association between alcohol intake and blood pressure was examined in a probability sample of Michigan adults surveyed in 1983. Despite adjustments for race, sex, age, Quetelet index, and current treatment with antihypertensive medications, heavier alcohol intakes (more than one drink daily) were associated with increased systolic blood pressure, diastolic blood pressure, and prevalence of elevated blood pressure. These associations were somewhat exaggerated in women and in younger persons. Statistically significant differences in blood pressure were demonstrated only among consumers of more than one drink daily. Attributable risk calculations indicated that no more than 8.4 and 8.5% of instances of elevated blood pressure (systolic pressure greater than or equal to 140 mmHg or diastolic pressure greater than or equal to 90 mmHg) in men and women, respectively, could be attributed to alcohol intakes exceeding one drink daily.

Adolescent↗
PubMed1987

Urinary obstruction in azotemic patients: detection by sonography.

Renal sonography is frequently requested in patients with an elevated or rising creatinine, often with the instruction to "rule out obstruction." A prospective study of patients undergoing renal sonography for newly discovered azotemia (creatinine greater than 1.8 mg/dl) or worsening renal failure was undertaken to evaluate the clinical utility of the sonographic examination. Patients with known obstructive uropathy, renal calculi, renal mass, or hematuria were excluded. In 189 patients, 17 (9%) had hydronephrosis: 11 unilateral (one with a solitary kidney) and six bilateral. Obstructive causes were subsequently established in the solitary kidney and in four patients with bilateral dilatation. These five patients (2.6%) with clinically significant hydronephrosis were shown subsequently to have a clinical history that strongly suggested the presence of urinary tract obstruction. Our data suggest that, in patients without a clinical history that suggests obstruction (such as calculi, bladder outlet obstruction, or pelvic mass), the likelihood of finding bilateral hydronephrosis by sonography is small.

Humans↗
PubMed1987

Reliability of health belief indexes: confirmatory factor analysis in sex, race, and age subgroups.

Despite frequent reference to the Health Belief Model (HBM), few studies address the internal consistency (within questionnaires) or the stability across populations of scales used to measure HBM variables. As part of a 1983 Michigan statewide blood pressure survey, trained interviewers administered 32 health belief questionnaire items to 2,802 randomly selected adult Michigan residents. Exploratory common factor analysis was used to examine the structure of these questionnaire items. Six correlated factors, which corresponded closely with theoretical constructs, appeared. Guided by these results, we developed a confirmatory common factor model. The model's fit was examined in random population halves and in univariate sex, race, and age subgroups. Except perhaps in the oldest age group, the model's fit appeared constant. Reliabilities estimated for HBM factor scales formed with these questionnaire items appeared independent of age, race, or sex.

Adolescent↗
PubMed1985

Methodologic evaluation of incidence rates for hypertension: calculated for Pittsburgh's MRFIT usual care men.

Methodologic limitations in the calculation of incidence rates for hypertension and in the assessment of associations between rates of change in attributes and the development of hypertension were examined for Pittsburgh's MRFIT Usual Care population. In a group of normotensive middle-aged men at high risk for the development of coronary heart disease, the incidence of hypertension ranged from 6.2 to 15.5 per 100 man years, depending on the definition of hypertension. A simulation study showed that the magnitude of these incidence rates could be explained by random variation in the measurement of blood pressure. Controlling for these random effects, the development of hypertension was associated with high normal baseline diastolic blood pressure and with a reported past diagnosis of hypertension, but not with age or baseline body mass index. Finally, a method, estimating the relative risk associating weight gain and the development of hypertension, was presented.

Adult↗
PubMedDate not supplied

A mathematical representation of the expert panel's guidelines for high blood cholesterol case-finding and treatment.

The National Cholesterol Education Program (NCEP) for high blood cholesterol case-finding and treatment recommended discrete treatments according to the results of sequential measurements of continuous variables (total and low-density lipoprotein cholesterol [LDL-C]). These measurements are subject to intra- and interindividual variability. The authors describe a computer simulation of the NCEP that acknowledges these complexities. The simulation reduces the NCEP into steps, which are represented in a decision tree. The calculation of probabilities at chance nodes takes into account the conditional nature of sequential measurements of blood cholesterol. The simulation tracks medical resource use and estimates LDL-C reductions within 20 strata, each defining 5% of population distribution for LDL-C. This approach enables a detailed representation of the case-finding process--the sequence of blood cholesterol tests and associated cut-off values that identify individuals needing more intensive evaluation and treatment.

Cholesterol↗
PubMedDate not supplied

Evaluation of oncogene-related proteins in serum.

We hypothesize that the products of cellular oncogenes and antioncogenes are biomarkers of events related to cancer risk. This study uses monoclonal antibody technology to examine serum proteins which are immunologically related to ras oncogene and epidermal growth factor receptor proteins. We measured the prevalence of ras- and epidermal growth factor receptor-related proteins in stored and freshly frozen serum from cancer patients, male heavy smokers, and older healthy subjects. Work emphasized the attainment of inter- and intraobserver agreement between independent readings of immunoblot gels. Although we achieved acceptable levels of agreement, we uncovered evidence for blood collection and storage artifacts. Accounting for these artifacts, we compared 80 cancer patients and 188 middle-aged and older community controls and found a strong relationship (odds ratio = 11.1; 95% confidence interval, 6.0-20.6) between cancer and a M(r) 21,000 serum protein related to the ras oncogene product. These results indicate the need and importance of comprehensive pretesting of putative cancer biomarkers before use in applied or etiological epidemiological research.

Antibodies, Monoclonal↗