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W D Flanders

Publications and source records attributed to W D Flanders.

At least 37 records · Page 2Linked to original sources
PubMed1999

Can dialysis therapy be improved? A report from the ESRD Core Indicators Project.

We assessed the association between quality improvement interventions conducted during the End-Stage Renal Disease (ESRD) Core Indicators Project and changes in the adequacy of hemodialysis between 1993 and 1996. Improvement of hemodialysis adequacy was measured by baseline and annual urea reduction ratios (URRs) in representative samples of ESRD Network patients. Random samples of in-center hemodialysis patients aged 18 years and older who had received hemodialysis during the fourth quarters of 1993, 1994, 1995, and 1996 were used to calculate Network-specific outcomes. A mean URR was calculated for each patient using the first pretreatment and posttreatment blood urea nitrogen for October, November, and December of each study year. Both national and Network-specific interventions were used to provide feedback reports and technical assistance to treatment centers to foster improvement in hemodialysis adequacy. All Networks distributed reports on the patterns of treatment center URR levels and physician and patient educational materials to each center in the Network. Each Network selected an annual 10% sample of treatment centers in 1994 and 1995 and conducted quality improvement activities to assist the selected centers to improve dialysis adequacy. We defined Network-specific interventions by a survey of the 18 Networks conducted during 1995 to determine the characteristics of Network-specific activities used to improve adequacy of hemodialysis. The outcome of interest was the change over time in Network-specific URR value. Sustained improvement in the URR occurred within all 18 Networks between 1993 and 1996. The mean national URR increased from 62.7% in 1993 to 66. 8% in 1996. The proportion of patients with URR >/= 65% increased from 43% in 1993 to 68% in 1996. Networks reported implementing a variety of intervention strategies that included educational activities, continuous quality improvement workshops, on-site assistance, and supervision of selected treatment facilities until care improved. Network-specific interventions independently associated with an increased rate of improvement in URR included prolonged supervision of the selected facilities. We concluded that the sustained improvement in hemodialysis care that occurred after the inception of the ESRD Core Indicators Project was associated with specific ESRD Network interventions.

Adolescent↗
PubMed1999

Excess hospital admissions during the July 1995 heat wave in Chicago.

INTRODUCTION: This study describes medical conditions treated in all 47 non-VA hospitals in Cook County, IL during the 1995 heat wave. We characterize the underlying diseases of the susceptible population, with the goal of tailoring prevention efforts. METHODS: Primary and secondary discharge diagnoses made during the heat wave and comparison periods were obtained from computerized inpatient hospital discharge data to determine reasons for hospitalization, and comorbid conditions, respectively. RESULTS: During the week of the heat wave, there were 1072 (11%) more hospital admissions than average for comparison weeks and 838 (35%) more than expected among patients aged 65 years and older. The majority of this excess (59%) were treatments for dehydration, heat stroke, and heat exhaustion; with the exception of acute renal failure no other primary discharge diagnoses were significantly elevated. In contrast, analysis of comorbid conditions revealed 23% (p = 0.019) excess admissions of underlying cardiovascular diseases, 30% (p = 0.033) of diabetes, 52% (p = 0.011) of renal diseases, and 20% (p = 0.027) of nervous system disorders. Patient admissions for emphysema (p = 0.007) and epilepsy (p = 0.009) were also significantly elevated during the heat wave week. CONCLUSIONS: The majority of excess hospital admissions were due to dehydration, heat stroke, and heat exhaustion, among people with underlying medical conditions. Short-term public health interventions to reduce heat-related morbidity should be directed toward these individuals to assure access to air conditioning and adequate fluid intake. Long-term prevention efforts should aim to improve the general health condition of people at risk through, among other things, regular physician-approved exercise.

Cardiovascular Diseases↗
PubMed1999

A comparison of the Charlson comorbidity index derived from medical record data and administrative billing data.

The objective of this article is to compare the Charlson comorbidity index derived from medical record data (Chart Index) with the same index derived from billing data (ICD-9 Index) to determine how well each predicted inpatient and 30-day mortality, length of stay, and complications among Medicare beneficiaries hospitalized for carotid endarterectomy. Economic and time constraints have increased the need for risk adjusters derived from administrative data, yet few studies have compared these measures with those derived from chart review. Using logistic regression, the Chart Index was found to be a significant predictor of inpatient mortality, 30-day mortality, length of stay, and complications, after controlling for age, gender, and neurologic and medical risk factors (P values = 0.004, 0.056, 0.0001, and 0.042, respectively). The ICD-9 Index approached significance as a predictor of the outcomes (P values = 0.092, 0.100, 0.093, and 0.080, respectively). The Chart Index was shown to be superior to the ICD-9 Index within this patient sample.

Comorbidity↗
PubMed1999

Validation of the pneumonia severity index. Importance of study-specific recalibration.

OBJECTIVE: To evaluate the predictive validity and calibration of the pneumonia severity-of-illness index (PSI) in patients with community-acquired pneumonia (CAP). PATIENTS: Randomly selected patients (n = 1,024) admitted with CAP to 22 community hospitals. MEASUREMENTS AND MAIN RESULTS: Medical records were abstracted to obtain prognostic information used in the PSI. The discriminatory ability of the PSI to identify patients who died and the calibration of the PSI across deciles of risk were determined. The PSI discriminates well between patients with high risk of death and those with a lower risk. In contrast, calibration of the PSI was poor, and the PSI predicted about 2.4 times more deaths than actually occurred in our population of patients with CAP. CONCLUSIONS: We found that the PSI had good discriminatory ability. The original PSI overestimated absolute risk of death in our population. We describe a simple approach to recalibration, which corrected the overestimation in our population. Recalibration may be needed when transporting this prediction rule across populations.

Adult↗
PubMed1999

Case-only design to measure gene-gene interaction.

The case-only design is an efficient and valid approach to screening for gene-environment interaction under the assumption of the independence between exposure and genotype in the population. In this paper, we show that the case-only design is also a valid and efficient approach to measuring gene-gene interaction under the assumption that the frequencies of genes are independent in the population. Just as the case-only design requires fewer cases than the case-control design to measure gene-environment interaction, it also requires fewer cases to measure gene-gene interactions.

Epidemiologic Studies↗
PubMed1999

Occupational risk factors for sarcoma subtypes.

Herbicides, chlorophenols, and other occupational exposures are suspected risk factors for soft-tissue sarcoma, but the epidemiologic evidence is inconsistent. Given that soft-tissue sarcomas represent a heterogeneous mix of cancer subtypes and that these subtypes have different disease patterns by race, sex, and age at diagnosis, studying all soft-tissue sarcomas combined may mask subtype-specific associations. Using the Selected Cancers Study, a large population-based case-control study of sarcoma conducted among U.S. men aged 30 to 60 in 1984 to 1988, we explored the occupational risk factors for soft-tissue sarcoma subtypes and skeletal sarcoma. The analysis included 251 living sarcoma cases (48 dermatofibrosarcoma protuberans, 32 malignant fibrohistiocytic sarcoma, 67 leiomyosarcoma, 53 liposarcoma, and 51 skeletal sarcoma) and 1908 living controls. Exact conditional logistic regression models suggested patterns of subtype specificity for occupational exposures. Self-reported herbicide use was associated with malignant fibrohistiocytic sarcoma (OR = 2.9, 95% CI = 1.1-7.3). We found elevated risks for chlorophenol exposure and cutting oil exposure and malignant fibrohistiocytic sarcoma and leiomyosarcoma. We found no occupational risk factor for liposarcoma. Polytomous regression models identified different odds ratios across subtypes for plywood exposure and exposure to wood and saw dust. Although exploratory, this analysis suggests that occupational risk factors for sarcoma are not uniform across subtypes.

Adult↗
PubMed1998

A new method for estimating the risk ratio in studies using case-parental control design.

The authors describe a new simple noniterative, yet efficient method to estimate the risk ratio in studies using case-parental control design. The new method is compared with two other noniterative methods, Khoury's method and Flanders and Khoury's method, and with a maximum likelihood-based method of Schaid and Sommer. The authors found that the variance of the new estimation method is usually smaller than that of Khoury's method or Flanders and Khoury's method and that it is slightly larger than that of the maximum likelihood-based method of Schaid and Sommer. Despite the slightly large variance of the new estimator compared with that of the maximum likelihood-based method, the simplicity of the new estimator and its variance makes the new method appealing. When genotypic information for only one parent is available, the authors also describe a method to estimate the risk ratio without assuming Hardy-Weinberg equilibrium or random mating. A simple formula for the variance of the estimator is given.

Alleles↗
PubMed1998

Family history score as a predictor of breast cancer mortality: prospective data from the Cancer Prevention Study II, United States, 1982-1991.

A consistent predictor of a woman's risk for breast cancer is a family history of the disease. Most studies of family history and breast cancer have used the number of affected relatives in the family to calculate relative risk, but they have not considered the heterogeneity of the familial risk for breast cancer in a systematic way. With the use of data from a large prospective mortality study of US adults, the authors compared simple classification of family history of breast cancer (yes/no) to the method of using a quantitative family history score method, which takes into account the effects of family structure, age, and birth cohort as predictors of breast cancer mortality. After 9 years of follow-up, 1,428 cases of fatal breast cancer were observed among 453,073 women with complete information on number and age of siblings and family history. With the use of the family history score, about one-third of women with a positive family history of breast cancer were at no higher risk for breast cancer mortality than those without a family history of the disease. As a quantitative measure of relative risk for each family, family history score gave a better fit to the data, and it provided an incremental improvement of predictive accuracy of developing fatal breast cancer. Family history score can also be used as a categorical variable to stratify families. This allows researchers to focus on which risk groups would benefit from conducting further genetic analysis and to test the effects of genetic factors, environmental exposure, and gene-environment interactions on the etiology of the development of breast cancer.

Adult↗
PubMed1998

Carotid endarterectomy among Medicare beneficiaries: a statewide evaluation of appropriateness and outcome.

BACKGROUND AND PURPOSE: We sought to examine the appropriateness and the surgical outcomes of carotid endarterectomy (CE) in unselected community hospitals to identify opportunities for improvement. METHODS: We performed a retrospective review of all CEs performed on Medicare beneficiaries in Georgia in 1993 (n = 1945). Conclusions regarding appropriateness were based on current guidelines as interpreted by a physician reviewer and were supported by the aggregate results of structured, blinded overreading by clinicians with relevant expertise. Adverse outcomes were confirmed and rated as to severity by a physician. Outcomes were correlated with demography, vascular anatomic findings, comorbidity, surgical techniques, and hospital characteristics. RESULTS: The majority of the patients (51%) were asymptomatic at presentation. CEs were performed appropriately in 96.1% of the cases in accordance with current guidelines. There was no significant difference in the rate of appropriateness between the symptomatic (96%) and the asymptomatic patients (96.4%). Survival without stroke or myocardial infarction (MI) was 94.3%. The 30-day mortality was 1.9%; moderate to severe strokes occurred in 1.8%, stroke-related death in 0.7%, MI in 1.1%, and MI-related death in 0.5%. Those hospitals performing <10 CEs in the observed year had a statistically significant higher morbidity and mortality as well as an increase in less severe complications such as hematomas, wound dehiscence, wound infection, and pneumonia than did hospitals with higher volume of CEs.. Older patients and women had statistically significantly higher morbidity and mortality. Patients with a Charlson Severity Index score of > or =1 had a risk for adverse outcomes 3.4 times higher than patients with a score of 0 after adjustment for age and sex. CONCLUSIONS: The great majority of CEs performed in Georgia on Medicare patients were appropriate, according to current guidelines. Slightly more than half of the patients were asymptomatic as defined in the Asymptomatic Carotid Atherosclerosis Study. In hospitals performing <CEs in the index year, we noted higher morbidity and mortality, as well as an increase in less severe complications. This relationship between the volume of surgery and outcome was confirmed in the analysis of the 30-day mortality for all Medicare cases (n = 10,569) performed in Georgia from 1991 to 1995. This was the most important opportunity for improvement identified in this study. In view of the increased use of CE, it is important to continue to monitor the patterns of practice for this procedure to improve outcomes.

Age Factors↗
PubMed1998

Mortality in end-stage renal disease is associated with facility-to-facility differences in adequacy of hemodialysis.

Death rates of end-stage renal disease (ESRD) patients treated with hemodialysis vary substantially among treatment centers. The association between facility-to-facility differences in delivered hemodialysis dose and facility-specific mortality rates was examined among 5817 randomly selected patients treated with hemodialysis on October 1, 1994, from all 213 hemodialysis treatment centers reporting to ESRD Network 6. The mean urea reduction ratio (URR) for each treatment center, a measure of hemodialysis adequacy, was calculated for each facility, using measurements made by center staff members during one treatment for each of the randomly selected patients. During 7 mo of follow-up (ending April 30, 1995), 441 (7.6%) patients died. The average URR among the treatment centers was 64.9%. There was a strong, inverse association between increasing treatment center URR and adjusted mortality count (P = 0.009). Other treatment center characteristics associated with increased mortality included free-standing status (P = 0.009) and decreasing frequency of reported physician supervision of care (P = 0.01). It was concluded that lower average levels of dialysis adequacy in treatment centers are associated with higher rates of death, and this association persists after controlling for facility-to-facility differences in patient and nonpatient characteristics.

Adolescent↗
PubMed1997

Cigarette smoking and changes in the histopathology of lung cancer.

BACKGROUND: Adenocarcinoma of the lung, once considered minimally related to cigarette smoking, has become the most common type of lung cancer in the United States. The increased incidence of this cancer might be explained by advances in diagnostic technology (i.e., increased ability to perform biopsies on tumors in smaller, more distal airways), changes in cigarette design (e.g., the adoption of filtertips), or changes in smoking practices. We examined data from the Connecticut Tumor Registry and two American Cancer Society studies to explore these possibilities. METHODS: Connecticut Tumor Registry data from 1959 through 1991 were analyzed to determine whether the increase in lung adenocarcinoma observed during that period could be best described by birth cohort effects (i.e., generational changes in cigarette smoking) or calendar period effects (i.e., diagnostic advances). Associations between cigarette smoking and death from specific types of lung cancer during the first 2 years of follow-up in Cancer Prevention Study I (CPS-I), initiated in 1959) and Cancer Prevention Study II (CPS-II, initiated in 1982) were also examined. RESULTS: Adenocarcinoma incidence in Connecticut increased nearly 17-fold in women and nearly 10-fold in men from 1959 through 1991. The increases followed a clear birth cohort pattern, paralleling gender and generational changes in smoking more than diagnostic advances. Cigarette smoking became more strongly associated with death from lung adenocarcinoma in CPS-II compared with CPS-I, with relative risks of 19.0 (95% confidence interval [CI] = 8.3-47.7) for men and 8.1 (95% CI = 4.5-14.6) for women in CPS-II and 4.6 (95% CI = 1.7-12.6) for men and 1.5 (0.3-7.7) for women in CPS-I. CONCLUSIONS: The increase in lung adenocarcinoma since the 1950s is more consistent with changes in smoking behavior and cigarette design than with diagnostic advances.

Adenocarcinoma↗
PubMed1997

Sample size requirements in case-only designs to detect gene-environment interaction.

With advances in molecular genetic technology, more studies will examine gene-environment interaction in disease etiology. If the primary purpose of the study is to estimate the effect of gene-environment interaction in disease etiology, one can do so without employing controls. The case-only design has been promoted as an efficient and valid method for screening for gene-environment interaction. The authors derive a method for estimating sample size requirements, present sample size estimates, and compare minimum sample size requirements to detect gene-environment interaction in case-only studies with case-control studies. Assuming independence between exposure and genotype in the population, the authors believe that the case-only design is more efficient than a case-control design in detecting gene-environment interaction. They also illustrate a method to estimate sample size when information on marginal effects (relative risk) of exposure and genotype is available from previous studies.

Case-Control Studies↗
PubMed1997

Black/white differences in leukocyte subpopulations in men.

BACKGROUND: Although counts of leukocytes differ substantially between blacks and whites, and are predictive of ischaemic heart disease (IHD), racial differences in counts of leukocyte subpopulations have received less attention. METHODS: We examined black/white differences in leukocyte subpopulations among 3467 white and 493 black 31-45 year-old-men who had previously served in the US Army. Laboratory determinations were performed at a central location during 1985-1986. RESULTS: Black men had an 840 cell/microliter (or 15%) lower mean total leukocyte count than did white men, largely due to a 960 cell/microliter (or 25%) lower mean neutrophil count. Although black men also had a 20% lower mean monocyte count (= 70 cells/microliter) than did white men, their mean lymphocyte count was 10% higher (approximately = 200 cells/microliter). Counts of various leukocyte subpopulations were associated with cigarette smoking, haemoglobin levels, platelet counts, and several other characteristics, but black/white differences in counts of neutrophils, lymphocytes, monocytes and other subpopulations could not be attributed to any of the examined covariates. CONCLUSIONS: Despite the relatively low counts of leukocytes and neutrophils among black men, their lymphocyte counts are generally higher than those among white men. It is possible that black/white differences in counts of various cell types may influence race-specific rates of IHD, and future studies should attempt to assess the importance of leukocyte subpopulations in the development of clinical disease.

Adult↗
PubMed1997

Estimating health risks from natural hazards using risk assessment and epidemiology.

Risk assessment is the process of estimating the likelihood that an adverse effect may result from exposure to a specific health hazard. The process traditionally involves hazard identification, dose-response assessment, exposure assessment, and risk characterization to answer "How many excess cases of disease A will occur in a population of size B due to exposure to agent C at dose level D?" For natural hazards, however, we modify the risk assessment paradigm to answer "How many excess cases of outcome Y will occur in a population of size B due to natural hazard event E of severity D?" Using a modified version involving hazard identification, risk factor characterization, exposure characterization, and risk characterization, we demonstrate that epidemiologic modeling and measures of risk can quantify the risks from natural hazard events. We further extend the paradigm to address mitigation, the equivalent of risk management, to answer "What is the risk for outcome Y in the presence of prevention intervention X relative to the risk for Y in the absence of X?" We use the preventable fraction to estimate the efficacy of mitigation, or reduction in adverse health outcomes as a result of a prevention strategy under ideal circumstances, and further estimate the effectiveness of mitigation, or reduction in adverse health outcomes under typical community-based settings. By relating socioeconomic costs of mitigation to measures of risk, we we illustrate that prevention effectiveness is useful for developing cost-effective risk management options.

Disaster Planning↗
PubMed1996

Analysis of case-parental control studies: method for the study of associations between disease and genetic markers.

Case-control studies using parents of case subjects as the control subjects provide an innovative way to study associations of genetic markers with disease risk. This approach, sometimes called the haplotype-relative risk method, has received recent attention because the use of parents as control subjects may reduce or eliminate the confounding associated with differences in race, ethnicity, or genetic background. We provide a new method for analysis of such case-parental control studies. The method of analysis is noniterative and yields simple estimates of risk ratios associated with genetic markers. It easily accommodates the situation in which data are available from only one parent. Although we illustrate the approach for a locus with two alleles, the analyses extend immediately to loci with multiple alleles.

Alleles↗
PubMed1996

Nontraditional epidemiologic approaches in the analysis of gene-environment interaction: case-control studies with no controls!

Although case-control studies are suitable for assessing gene-environment interactions, choosing appropriate control subjects is a valid concern in these studies. The authors review three nontraditional study designs that do not include a control group: 1) the case-only study, 2) the case-parental control study, and 3) the affected relative-pair method. In case-only studies, one can examine the association between an exposure and a genotype among case subjects only. Odds ratios are interpreted as a synergy index on a multiplicative scale, with independence assumed between the exposure and the genotype. In case-parental control studies, one can compare the genotypic distribution of case subjects with the expected distribution based on parental genotypes when there is no association between genotype and disease; the effect of a genotype can be stratified according to case subjects' exposure status. In affected relative-pair studies, the distribution of alleles identical by descent between pairs of affected relatives is compared with the expected distribution based on the absence of genetic linkage between the locus and the disease; the analysis can be stratified according to exposure status. Some or all of these methods have certain limitations, including linkage disequilibrium, confounding, assumptions of Mendelian transmission, an inability to measure exposure effects directly, and the use of a multiplicative scale to test for interaction. Nevertheless, they provide important tools to assess gene-environment interaction in disease etiology.

Case-Control Studies↗