Biomedical subjects

W D Flanders

Publications and source records attributed to W D Flanders.

At least 19 recordsLinked to original sources

PubMed2004

Is readmission to hospital an indicator of poor process of care for patients with heart failure?

BACKGROUND: Controversy exists about the appropriateness of using readmission as an indicator of the quality of care. A study was undertaken to measure the validity and predictive ability of readmission in this context. METHODS: An evaluation study was performed in patients discharged alive with heart failure from three Swiss academic medical centres. Process quality indicators were derived from evidence based guidelines for the management and treatment of heart failure. Readmissions were calculated from hospital administrative data. The predictive ability of readmissions was evaluated using bivariate and multivariate analyses, and validity by calculating sensitivity, specificity, positive and negative predictive value, using process indicators as the "gold standard". RESULTS: Of 1055 eligible patients discharged alive, 139 (13.2%) were readmitted within 30 days. The adjusted odds ratio (OR) for absence of measurement of left ventricular function was 0.70 (95% CI 0.45 to 1.08) for readmissions. In patients with left ventricular systolic dysfunction, three dose categories of angiotensin converting enzyme inhibitor were examined using ordinal logistic regression. The adjusted OR for these categories was 1.07 (95% CI 0.56 to 2.06) for readmissions. When using process indicators as the gold standard to assess the validity of readmissions, sensitivity ranged from 0.08 to 0.17 and specificity from 0.86 to 0.93. CONCLUSIONS: Readmission did not predict and was not a valid indicator of the quality of care for patients with heart failure admitted to three Swiss university hospitals.

Aged↗

PubMed2003

Assessment of two self-reporting questionnaires for eating disorders in women.

OBJECTIVE: The goals of this study were to evaluate how well the Eating Disorder Inventory (EDI) predicted specific eating disorders as identified by the Survey of Eating Disorders (SED), and to identify the most predictive EDI scales. An additional goal was to evaluate the EDI as a screening instrument for eating disorders among a large non-clinical group of women. METHOD: The community-based study sample consisted of 1245 Norwegian women between age 18 and 50 years (mean 23). Subjects filled out the EDI and the SED. RESULTS: The strongest predictors of SED-defined eating disorders were the EDI scales bulimia (BN) and drive of thinness (DT) and body mass index (BMI). When we classified women with an EDI sum score of 40 or higher as having an eating disorder (ED), the sensitivity was 38% and the specificity was 90%, compared to the SED diagnosis of ED. DISCUSSION: Our findings suggest modest agreement between the EDI and the SED, and modest sensitivity and specificity of the EDI. While these instruments, perhaps with some modification, may be adequate for use in selected research applications, they should probably be supplemented with additional information in a clinical or treatment setting.

Adolescent↗

PubMed2002

Eating disorder behavior in physically active Norwegian women.

Competitive female athletes may have higher risk of eating disorders (ED) than recreational athletes, in part because low body fat may be advantageous in sports. However, women who participate in sports or physical activities might also do this for weight reduction, altering body shape, and for other food related reasons. This study was conducted to evaluate the association between hours of leisure time physical activity (PA) and prevalence of ED, and whether the association between the Eating Disorders Inventory (EDI) scales and ED, as classified by the Survey of Eating Disorders (SED), was the same among women with high vs. low physical activity levels. The community-based study sample consisted of 898 female students aged 18-50 years. Subjects filled out the EDI, the SED, and a questionnaire concerning physical activity and demographic data. Physical activity was not associated with increased risk of having a SED-defined diagnosis of an ED or of having an EDI score greater than 40, which is sometimes used to define women at risk for having an eating disorder. Women with a SED-defined ED had higher scores on all subscales of the EDI, but did not differ with respect to age, BMI or hours of weekly activity. The strongest predictors of having a SED-defined ED were body mass index (BMI), two EDI scales, drive of thinness and Bulimia Nervosa, with no differences between the two PA groups. Among women with a SED-defined ED, those with more than 5 h weekly PA did not differ from others with respect to scoring on the EDI or BMI. Results suggest that hours of physical activity may not increase risk of developing ED. Effective interventions are needed to help the growing numbers of persons with body-image and eating difficulties. For some, moderate physical training might be helpful.

Adolescent↗

PubMed2001

New estimator of the genotype risk ratio for use in case-parental control studies.

Estimation of the genotype risk ratio can be an important part of studying the role of genetics in disease causation. For example, one might estimate risk among persons with genotype DD compared with risk among those with genotype Dd, where the candidate locus has alleles D and d, with D representing the disease susceptibility allele. In this paper, the authors propose a modified method of analysis for case-parental control studies that can improve efficiency. They show how investigators can use information from families in which both parents are observed to improve the estimator created by Sun et al., which applies when only one parent and an affected offspring have been observed. Since this information is not used by the conditional approach of Schaid and Sommer, the authors' approach allows for more complete use of available information, leading to a smaller mean squared error of the genotype risk ratio estimators. The authors also suggest a way to combine estimates from families in which one parent and one offspring are observed and estimates from families in which both parents and one offspring are observed.

Alleles↗

PubMed2001

Accounting for unmeasured population substructure in case-control studies of genetic association using a novel latent-class model.

We propose a novel latent-class approach to detect and account for population stratification in a case-control study of association between a candidate gene and a disease. In our approach, population substructure is detected and accounted for using data on additional loci that are in linkage equilibrium within subpopulations but have alleles that vary in frequency between subpopulations. We have tested our approach using simulated data based on allele frequencies in 12 short tandem repeat (STR) loci in four populations in Argentina.

Alleles↗

PubMed2001

Statistical models to predict the need for postoperative intensive care and hospitalization in pediatric surgical patients.

OBJECTIVE: To develop statistical models for predicting postoperative hospital and ICU stay in pediatric surgical patients based on preoperative clinical characteristics and operative factors related to the degree of surgical stress. We hypothesized that preoperative and operative factors will predict the need for ICU admission and may be used to forecast the length of ICU stay or postoperative hospital stay. DESIGN: Prospective data collection from 1,763 patients. SETTING: Tertiary care children's hospital. PATIENTS AND PARTICIPANTS: All pediatric surgical patients, including those undergoing day surgery. Patients undergoing dental or ophthalmologic surgical procedures were excluded. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: A logistic regression model predicting ICU admission was developed from all patients. Poissonregression models were developed from 1,161 randomly selected patients and validated from the remaining 602 patients. The logistic regression model for ICU admission was highlypredictive (area under the receiver operating characteristics (ROC) curve = 0.981). In the data set used for development of Poisson regression models, significant correlations occurred between the observed and predicted ICU stay (Pearson r = 0.468, p < 0.0001, n = 131) and between the observed and predicted hospital stay for patients undergoing general (r = 0.695, p < 0.0001), orthopedic (r = 0.717, p < 0.0001), cardiothoracic (r = 0.746, p < 0.0001), urologic (r = 0.458, p < 0.0001), otorhinolaryngologic (r = 0.962, p < 0.0001), neurosurgical (r = 0.7084, p < 0.0001) and plastic surgical (r = 0.854, p < 0.0001) procedures. In the validation data set, correlations between predicted and observed hospital stay were significant for general (p < 0.0001), orthopedic (p < 0.0001), cardiothoracic (p = 0.0321) and urologic surgery (p = 0.0383). The Poisson models for length of ICU stay, otorhinolaryngology, neurosurgery or plastic surgery could not be validated because of small numbers of patients. CONCLUSIONS: Preoperative and operative factors may be used to develop statistical models predicting the need for ICU admission in pediatric surgical patients, and hospital stay following general surgical, orthopedic, cardiothoracic and urologic procedures. These statistical models need to be refined and validatedfurther, perhaps using data collection from multiple institutions.

Arkansas↗

PubMed2000

Predictors of correct treatment of children with fever seen at outpatient health facilities in the Central African Republic.

To identify factors associated with improved performance of health care workers who treat ill children in developing countries, the authors analyzed a sample of consultations of children with malaria (defined as any fever) from a national health facility survey conducted in the Central African Republic from December 1995 to January 1996. Twenty-eight health care workers and 204 children were studied. A univariate analysis revealed the following significant predictors of correct treatment, as defined by the Central African malaria control program: high fever (odds ratio (OR) = 3.25, 95% confidence interval (CI): 1.47, 7.17); correct health care worker diagnosis (OR = 2.59, 95% CI: 1.39, 4.85); and the caregiver's reporting the child's fever to the health care worker (OR = 2.18, 95% CI: 1.32, 3.62). There was an unexpected inverse association between the presence of a fever treatment chart and correct treatment (OR = 0.19, 95% CI: 0.04, 0.91). Correct treatment was marginally associated with a longer consultation time (p value for trend = 0.058). Neither in-service training in the treatment of fever nor supervision was significantly associated with correct treatment. For child health programs to improve, targeted studies are needed to understand which factors, alone or in combination, improve health care worker performance.

Ambulatory Care↗

PubMed2000

Bias associated with study protocols in epidemiologic studies of disease familial aggregation.

The effect of selection bias has not been well evaluated in epidemiologic studies which focus on familial aggregation. The authors illustrate this type of bias for a reconstructed cohort study. With the reconstructed cohort design, cases and controls are first selected from the population and their relatives form the exposed and unexposed cohorts, respectively. The recurrence risk ratio (RRR) is calculated to assess and measure familial aggregation. The ways of utilizing information from relatives affects the estimate of RRR, and the authors show that a traditional method used in epidemiologic studies can yield a severely biased estimate of the RRR. However, this traditional approach can give approximately unbiased estimates under special conditions. A novel selection approach is proposed which yields an unbiased estimate of RRR. In conclusion, when relatives are identified through cases or controls, they should be included and counted in the study cohorts each time a case or control is selected, even if they or other family members have already been included.

Bias↗

PubMed2000

A model to estimate the probability of hepatitis B- and Haemophilus influenzae type b-vaccine uptake into national vaccination programs.

Most countries have been slow to adopt new vaccines into national vaccination schedules, despite recommendations from global multi-lateral agencies. Characteristics of countries that have adopted hepatitis B (HB) vaccine were analysed and used to formulate a logistic regression model. The model was applied to country-specific data to predict HB and Haemophilus influenzae type b (Hib) vaccine uptake. The greatest predictors of HB uptake were coverage rates of other vaccines, vaccine cost relative to the economy, and perceived disease burden. The logistic regression model's probability estimate of vaccine uptake agreed well with observed data for HB and Hib, (c-statistic 85 and 82%, respectively). Application of this model to other antigens may aid in predicting potential national markets to better plan new vaccine supply and demand.

Bacterial Capsules↗

PubMed2000

Occurrence of primary cancers in association with multiple myeloma and Kaposi's sarcoma in the United States, 1973-1995.

The causes of multiple myeloma (MM) are obscure, but a laboratory association was recently reported between MM and human herpesvirus 8 (HHV-8), the probable etiologic agent of Kaposi's sarcoma (KS). Although there has been some additional laboratory corroboration, most laboratory studies have found no association between MM and HHV-8. We looked for indirect evidence of an HHV-8/MM association by evaluating whether MM is associated with KS in the United States. Cancer incidence and survival data were obtained from the Surveillance, Epidemiology, and End Results (SEER) program for the years 1973-1995. Strength of association was assessed for a number of cancer pairs using standardized incidence ratios (SIRs) (observed/expected double cancers). KS was strongly associated (SIR > 15) with non-Hodgkin's lymphoma and anal cancer, was modestly associated (2.5 < SIR < 5.5) with MM, Hodgkin's disease, and testicular cancer and was not significantly associated with 6 other cancers. Besides being associated with KS, MM was weakly associated (1.7 < SIR < 2.3) with Hodgkin's disease and testicular cancer. The SIRs for 7 other cancers paired with MM were all less than 1.6. Factors that might be responsible for the KS/MM association include MM-related immune dysfunction, HIV and HHV-8, but the role of these factors cannot be directly assessed through the SEER database. Although we cannot rule out the possibility that HHV-8 is linked to a small proportion of MM cases, the modest KS/MM association is evidence that the vast majority of MM cases are not likely to be associated with HHV-8.

Adolescent↗

PubMed2000

Transmission/disequilibrium tests for quantitative traits.

The transmission/disequilibrium test (TDT) is a powerful method of locating disease genes. The TDT was originally proposed for use in studies of qualitative traits in families with both parents available. Recently, the TDT has been extended to studies of qualitative traits in sibships without parents available and in families with one parent available. It has also been extended for use in studies of quantitative traits in families with both parents available and in sibships with multiple offspring. In this paper, we first propose a new class of TDT-type tests for linkage in the presence of linkage disequilibrium for use in studies of families with both parents available. The TDT of Spielman et al. (1993) for qualitative traits and the TDT of Rabinowitz (1997) for quantitative traits are special cases of the new tests. Second, we propose a new class of TDT-type tests for linkage for use in studies of families with one parent available. Third, we study the validity and the power of the tests using simulations. Finally, we propose a method of combining data from different types of families. The combined test is valuable and allows researchers full use of the available data in detecting linkage between a marker locus and an unobservable quantitative trait locus. An important feature of the tests proposed in this paper is that no assumptions on the distribution of the quantitative traits are needed.

Computer Simulation↗

PubMed1999

Evaluating the exposure and disease relationship with adjustment for different types of exposure misclassification: a regression approach.

Misclassification of exposure can lead to biased results in the epidemiologic research. Available methods accounting for misclassification often require the use of a gold standard or assume non-differential misclassification of exposure. We present a regression approach which can detect and account for different types of misclassification when estimating the exposure and disease relationship. This approach uses two imperfect measures of a dichotomous exposure and does not require a gold standard. Standard statistical packages with a logistic regression module can be used for estimation of parameters through the EM algorithm process. Two examples are used to illustrate the methodology.

Algorithms↗

PubMed1999

Transmission disequilibrium test (TDT) when only one parent is available: the 1-TDT.

The transmission disequilibrium test (TDT) is a useful method to locate mutations linked to disease genes associated with complex diseases. TDT requires genotypes of affected individuals and their parents. Recently, Ewens and Spielman (Am J Hum Genet 1998;62:450-8) extended the TDT for use in sibships with at least one affected and one unaffected individual and devised a new test called the sib transmission/disequilibrium test (S-TDT). The S-TDT can be applied to diseases with late age at onset such as non-insulin-dependent diabetes mellitus, psychiatric disorders, and diseases related to aging. For some disorders, it might be relatively easy to obtain the genotype of one parent either because the other parent is not available for study or he/she is not cooperative. Curtis and Sham (Ann Hum Genet 1995;59:323-36) showed that bias in transmitting certain alleles is introduced if only heterozygous parents and homozygous offspring are used in the TDT. In this paper, the authors propose a new test, the 1-TDT, to detect linkage between a candidate locus and a disease locus using genotypes of affected individuals and only one available parent for each affected individual. The test is not biased under the null hypothesis of no linkage or association. The authors validate their test using both simulated and real data sets. Finally, they show how to combine data from different types of families.

Age of Onset↗

PubMed1999

Effects of temperature and snowfall on mortality in Pennsylvania.

The relation between exposure to severe cold weather and mortality is examined in a retrospective study of deaths occurring during the month of January from 1991 to 1996 in Pennsylvania. Using division-days as units of observation (n = 1,560) aggregated from death certificates and geographic divisions, the authors estimated mortality rates for total deaths and deaths due to ischemic heart disease, cerebrovascular diseases, and respiratory diseases by analyses based on generalized estimating equations. Total mortality increased on days of "extreme" climatic conditions, that is, when snowfall was greater than 3 cm and when temperatures were below -7 degrees C (rate ratio (RR) = 1.27, 95 percent confidence interval (CI) 1.12-1.44). On days of extreme conditions, mortality due to ischemic heart diseases tripled among males aged 35-49 years (RR = 3.54, 95 percent CI 2.35-5.35), increased for men aged 50-64 years (RR = 1.77, 95 percent CI 1.32-2.38), and rose for males aged 65 years and older (RR = 1.58, 95 percent CI 1.37-1.82), when compared with milder conditions. Among females, mortality for those aged 65 years and older increased for respiratory causes (RR = 1.68, 95 percent CI 1.28-2.21) and cerebrovascular causes (RR = 1.47, 95 percent CI 1.13-1.91). Cold and snow exposure may be hazardous among men as young as 35 years.

Aged↗

PubMed1999

Using case-control designs for genome-wide screening for associations between genetic markers and disease susceptibility loci.

We used a case-control design to scan the genome for any associations between genetic markers and disease susceptibility loci using the first two replicates of the Mycenaean population from the GAW11 (Problem 2) data. Using a case-control approach, we constructed a series of 2-by-3 tables for each allele of every marker on all six chromosomes. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated for all alleles of every marker. We selected the one allele for which the estimated OR had the minimum p-value to plot in the graph. Among these selected ORs, we calculated 95% CI for those that had a p-value < or = adjusted alpha level. Significantly high ORs were taken to indicate an association between a marker locus and a suspected disease-susceptibility gene. For the Mycenaean population, the case-control design identified allele number 1 of marker 24 on chromosome 1 to be associated with a disease susceptibility gene, OR = 2.10 (95% CI 1.66-2.62). Our approach failed to show any other significant association between case-control status and genetic markers. Stratified analysis on the environmental risk factor (E1) provided no further evidence of significant association other than allele 1 of marker 24 on chromosome 1. These data indicate the absence of linkage disequilibrium for markers flanking loci A, B, and C. Finally, we examined the effect of gene x environment (G x E) interaction for the identified allele. Our results provided no evidence of G x E interaction, but suggested that the environmental exposure alone was a risk factor for the disease.

Alleles↗

PubMed1999

Whole genome association studies for genes affecting alcohol dependence.

We applied the transmission/disequilibrium test (TDT) for sibs (S-TDT) and for families with one parent (1-TDT), to the Collaborative Study on the Genetics of Alcoholism data set. The combined test is used to screen the whole genome to locate genes responsible for alcohol dependence. This analysis supports the previous finding that the region close to GABRB1 on chromosome 4 might be associated with alcohol dependence. The regions close to D6S474 and D11S1998 are also of particular interest. We found segregation distortion at the GR1K1 locus. The segregation distortion might be due to the binning method used in genotyping at this locus.

Alcoholism↗

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↗