The influence of treatment modality and ethnicity on attitudes in type 2 diabetes

OBJECTIVE

The study examines diabetes attitude differences by treatment modality (insulin vs. no insulin), race/ethnicity, and the interaction of these two variables for people with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Data were collected with the Diabetes Care Profile (DCP), an instrument that assesses psychosocial factors related to diabetes. Participants (n = 672) were recruited in the metropolitan Detroit, Michigan, area from 1993 to 1996. A total of 68% of these participants were African-Americans with type 2 diabetes, and 32% were Caucasians with type 2 diabetes. Analyses of covariance were performed to examine the effects of race/ethnicity, treatment, and their interaction for each DCP scale.

RESULTS

The four patient categories (two ethnicities by two treatment modalities) differed by age, years with diabetes, education, and sex distribution. Treatment modality had a significant effect on 6 of the 16 DCP scales (Control, Social and Personal Factors, Positive Attitude, Negative Attitude, Self-Care Ability, and Exercise Barriers). Ethnicity was a significant effect for three scales (Control, Support, and Support Attitudes). The interaction of race/ethnicity and treatment modality was a significant effect for two related attitude scales (Positive Attitude and Negative Attitude).

CONCLUSIONS

The results suggest that attitudes toward diabetes are similar for African-American and Caucasian patients with type 2 diabetes. The results also suggest that treatment modality has a greater effect on attitudes than either race/ethnicity or the interaction effect. However, Caucasian patients using insulin differed from the other patient groups by having the least positive and the most negative attitudes regarding diabetes.

Assessing the cultural relevance of an education program for urban African Americans with diabetes

PURPOSE

This study was conducted to assess the cultural relevance of an education program for urban African Americans with diabetes.

METHODS

A set of 12 videotape vignettes were developed for use in diabetes education for urban African Americans with diabetes. Focus groups and questionnaires were used to determine if patients and diabetes educators would find the materials stimulating, culturally appropriate, and useful.

RESULTS

The videotape and discussion guide were perceived as valuable by both healthcare professionals and patients.

CONCLUSIONS

This education program could be a valuable resource for diabetes educators who want to provide culturally sensitive and relevant diabetes education for urban African Americans with diabetes.

The organizer factors Chordin and Noggin are required for mouse forebrain development

In mice, there is evidence suggesting that the development of head and trunk structures is organized by distinctly separated cell populations. The head organizer is located in the anterior visceral endoderm (AVE) and the trunk organizer in the node and anterior primitive streak. In amphibians, Spemann's organizer, which is homologous to the node, partially overlaps with anterior endoderm cells expressing homologues of the AVE markers cerberus, Hex and Hesx1. For mice, this raises the question of whether the AVE and node are independent of each other, as suggested by their anatomical separation, or functionally interdependent as is the case in amphibians. Chordin and Noggin are secreted bone morphogenetic protein (BMP) antagonists expressed in the mouse node, but not in the AVE. Here we show that mice double-homozygous mutants that are for chordin and noggin display severe defects in the development of the prosencephalon. The results show that BMP antagonists in the node and its derivatives are required for head development.

Feed-borne transmission and case clustering of BSE

An unresolved issue in the epidemiology of bovine spongiform encephalopathy (BSE) in the UK is what precisely determines the degree to which cases of disease in cattle are clustered within herds throughout the course of the epidemic. This paper presents an analysis of feed-borne transmission at the herd level and tests various models of case-clustering mechanisms, associated with heterogeneity in exposure to infectious feed, against observed epidemic pattern. We use an age-structured metapopulation framework in which the recycling of animal tissue between herds via feed producers is explicitly described. We explore two alternative assumptions for the scaling with herd size of the within-herd risk of exposure of an animal to infectious material. We find that whereas exposure heterogeneity caused by variation in feed and offal processing methods and by variation in per-animal feed uptake can explain the pattern of case clustering seen in the BSE epidemic, exposure heterogeneity due to the aggregation of infectivity within feed cannot.

Assessment of the prevalence of vCJD through testing tonsils and appendices for abnormal prion protein

The objective of this study was to determine the age group or groups which will provide the most information on the potential size of the vCJD epidemic in Great Britain via the sampling of tonsil and appendix material to detect the presence of abnormal prion protein (PrP(Sc)). A subsidiary aim was to determine the degree to which such an anonymous age-stratified testing programme will reduce current uncertainties in the size of the epidemic in future years. A cohort- and time-stratified model was used to generate epidemic scenarios consistent with the observed vCJD case incidence. These scenarios, together with data on the age distribution of tonsillectomies and appendectomies, were used to evaluate the optimal age group and calendar time for undertaking testing and to calculate the range of epidemic sizes consistent with different outcomes. The analyses suggested that the optimal five-year age group to test is 25-29 years, although a random sample of appendix tissue from all age groups is nearly as informative. A random sample of tonsil tissue from all age groups is less informative, but the information content is improved if sampling is restricted to tissues removed from those over ten years of age. Based on the assumption that the test is able to detect infection in the last 75% of the incubation period, zero detected infections in an initial random sample of 1000 tissues would suggest that the epidemic will be less than 870,000 cases. If infections are detected, then the model prediction suggests that both relatively small epidemics (800+ cases if one is detected or 8300+ if two are detected) and larger epidemics (21,000+ cases if three or more are detected) are possible. It was concluded that testing will be most informative if undertaken using appendix tissues or tonsil tissues removed from those over ten years of age. Large epidemics can only be excluded if a small number of infections are detected and the test is able to detect infection early in the incubation period.

Complex chromosome aberrations in peripheral blood lymphocytes as a potential biomarker of exposure to high-LET alpha-particles

PURPOSE

To determine the induction and transmission, to second and third division cells, of complex chromosome aberrations in peripheral blood lymphocytes after exposure to high-LET alpha-particles in vitro.

MATERIALS AND METHODS

Separated peripheral blood lymphocytes collected from four healthy donors were irradiated in vitro with either high-LET alpha-particles (121 keV/microm; 0.5 Gy) or low-LET X-rays (250kV constant potential; 3 Gy). Cells were harvested in first, second and third division post-irradiation and chromosome aberrations observed at each cell division were analysed by combining the techniques of FISH and DAPI/Hoechst 33258 harlequin staining. Whole chromosome probes were used for chromosomes 1, 2 and 5, together with a pan-centromeric probe and the resulting chromosome 'painting' patterns were classified according to the Savage and Simpson (S & S) scheme (Savage and Simpson 1994a, Savage and Tucker 1996).

RESULTS

A greater proportion of complex chromosome aberrations was observed, defined as involving three or more breaks in two or more chromosomes, relative to total exchanges, after exposure to 0.5 Gy alpha-particles (mean 1 track/cell) than after the high reference dose of 3 Gy X-rays (49-56% and 20-22%, respectively). Qualitatively, alpha-particles induced chromosome aberrations of far greater complexity than those observed after X-rays. This was reflected by both the rapid reduction in the percentage of damaged cells between first and second division indicative of cell death, and the spectrum of aberration types observed in second and third division cells post-irradiation. Regardless of this complexity, 15% of the complexes induced by alpha-particles at first division were potentially transmissible and by third division, transmissible-type complexes, specifically insertions, represented the predominant complex type (65%).

CONCLUSION

Transmissible-type complexes were observed, specifically insertions, in both second and third division cells after exposure to high-LET alpha-particles (0.5 Gy) in vitro. The authors predict these cells to be stable and to be capable of persisting through many cell generations. Considering that the induction of complex chromosome aberrations by low-LET radiation is strongly dependent on dose, so that they are expected to be undetectable at environmental exposures, insertions are much more likely to be a characteristic feature of high-LET radiation at all doses. From this the usefulness of insertions as biomarkers of past exposure to environmentally relevant doses of high-LET alpha-particles is supported.

Antigen-driven CD4+ T cell and HIV-1 dynamics: residual viral replication under highly active antiretroviral therapy

Antigen-induced stimulation of the immune system can generate heterogeneity in CD4+ T cell division rates capable of explaining the temporal patterns seen in the decay of HIV-1 plasma RNA levels during highly active antiretroviral therapy. Posttreatment increases in peripheral CD4+ T cell counts are consistent with a mathematical model in which host cell redistribution between lymph nodes and peripheral blood is a function of viral burden. Model fits to patient data suggest that, although therapy reduces HIV replication below replacement levels, substantial residual replication continues. This residual replication has important consequences for long-term therapy and the evolution of drug resistance and represents a challenge for future treatment strategies.

Population structure of pathogens: the role of immune selection

Sunetra Gupta and Roy Anderson discuss how the balance between host immune responses against conserved and variable antigens shapes the population structure of pathogens. At one extreme, immune selection against polymorphic determinants can cause pathogen populations to self-organize spontaneously into discrete antigenic types that may either be maintained over long periods or undergo cyclical or chaotic fluctuations. At the other extreme, diversity may be drastically reduced by competition induced by a strong immune response against a conserved determinant. Where does each pathogen lie along this continuum? How would this knowledge influence our attempts to control an infectious disease?

Theory is the cart, vision is the horse: reflections on research in diabetes patient education

PURPOSE

In this paper, we examine the nature of vision and the role it plays in helping educators identify and use theories productively. We also discuss the role of theory in diabetes education and provide criteria for selecting appropriate theories.

METHODS

The vision of diabetes education developed at the Michigan Diabetes Research and Training Center was used to illustrate how our vision has influenced our use of educational and behavioral theories.

RESULTS

Both our vision and our theoretical assumptions should be articulated, discussed, debated, and studied.

CONCLUSIONS

Diabetes patient education research can systematically contribute to the development of a sound, coherent, and progressive body of knowledge that will truly serve diabetes patient education.

A second operator is involved in Pseudomonas aeruginosa elastase (lasB) activation

Pseudomonas aeruginosa LasB elastase gene (lasB) transcription is controlled by the two-component quorum-sensing system of LasR, and the autoinducer, 3OC(12)-HSL (N-3-[oxododecanoyl]homoserine lactone). LasR and 3OC(12)-HSL-mediated lasB activation requires a functional operator sequence (OP1) in the lasB promoter region. Optimal activation of lasB, however, requires a second sequence of 70% identity to OP1, named OP2, located 43 bp upstream of OP1. In this study, we used sequence substitutions and insertion mutations in lasBp-lacZ fusion plasmids to explore the role of OP2 in lasB activation. Our results demonstrate that (i) OP1 and OP2 synergistically mediate lasB activation; (ii) OP2, like OP1, responds to LasR and 3OC(12)-HSL; and (iii) the putative autoinducer-binding domain of LasR is not required for synergistic activation from OP1 and OP2.

Simulation studies of phase III clinical trials to test the efficacy of a candidate HIV-1 vaccine

One question of particular importance in phase III HIV vaccine trials is the choice of efficacy measure (EM) to validly and precisely estimate the true vaccinal efficacy. Traditional EMs, based on hazard rate ratio (HRR) or cumulative incidence ratio (CIR) are time-sensitive to mode of vaccine action and population heterogeneities. Through Monte-Carlo simulation, the performance of HRR and CIR based EMs are examined across different trial designs and vaccine and population characteristics. A new EM based on log-spline hazard regression (HARE) is proposed. Given that vaccinal properties (mode of action, time-lag, waning) are unknown a priori, appropriate selection of EM is problematic, and HRR and CIR can be unreliable to estimate the true maximum efficacy of candidate products. Non-random sexual mixing can exacerbate biases in HRR and CIR. HARE can offer valid estimation across different modes of vaccine action and in presence of frailty effects, contrary to its traditional counterparts. Our simulation studies highlight the weaknesses of widely used EMs while offering guidelines for trial design and suggesting new avenues for statistical analysis.

Apostles and Zionists: the influence of religion on demographic change in rural Zimbabwe

Religion has acted as a brake on demographic transition in a number of historical and contemporary populations. In a study in two rural areas of Zimbabwe, we found substantial differences in recent demographic trends between Mission and Independent or "Spirit-type" churches. Birth rates are higher in some Spirit-type churches and, until recently, infant mortality was also higher. Recent increases in mortality were seen within Mission churches but not in Spirit-type churches. Missiological and ethnographic data indicate that differences in religious teaching on healthcare-seeking and sexual behaviour and differences in church regulation could explain this contrast in demographic patterns. More restrictive norms on alcohol consumption and extra-marital relationships in Spirit-type churches may limit the spread of HIV and thereby reduce its impact on mortality. These contrasting trends will influence the future religious and demographic profile of rural populations in Zimbabwe.

Vancomycin-resistant enterococci in intensive-care hospital settings: transmission dynamics, persistence, and the impact of infection control programs

Vancomycin-resistant enterococci (VRE) recently have emerged as a nosocomial pathogen especially in intensive-care units (ICUs) worldwide. Transmission via the hands of health-care workers is an important determinant of spread and persistence in a VRE-endemic ICU. We describe the transmission of nosocomial pathogens by using a micro-epidemiological framework based on the transmission dynamics of vector-borne diseases. By using the concept of a basic reproductive number, R0, defined as the average number of secondary cases generated by one primary case, we show quantitatively how infection control measures such as hand washing, cohorting, and antibiotic restriction affect nosocomial cross-transmission. By using detailed molecular epidemiological surveillance and compliance monitoring, we found that the estimated basic reproductive number for VRE during a study at the Cook County Hospital, Chicago, was approximately 3-4 without infection control and 0.7 when infection control measures were included. The impact of infection control was to reduce the prevalence from a predicted 79% to an observed 36%. Hand washing and staff cohorting are the most powerful control measures although their efficacy depends on the magnitude of R0. Under the circumstances tested, endemicity of VRE was stabilized despite infection control measures, by the constant introduction of colonized patients. Multiple stochastic simulations of the model revealed excellent agreement with observed pattern. In conjunction with detailed microbiological surveillance, a mathematical framework provides a precise template to describe the colonization dynamics of VRE in ICUs and impact of infection control measures. Our analyses suggest that compliance for hand washing significantly in excess of reported levels, or the cohorting of nursing staff, are needed to prevent nosocomial transmission of VRE in endemic settings.

Sexual mixing patterns in the spread of gonococcal and chlamydial infections

OBJECTIVES

This study sought to define, among sexually transmitted disease (STD) clinic attendees, (1) patterns of sex partner selection, (2) relative risks for gonococcal or chlamydial infection associated with each mixing pattern, and (3) selected links and potential and actual bridge populations.

METHODS

Mixing matrices were computed based on characteristics of the study participants and their partners. Risk of infection was determined in study participants with various types of partners, and odds ratios were used to estimate relative risk of infection for discordant vs concordant partnerships.

RESULTS

Partnerships discordant in terms of race/ethnicity, age, education, and number of partners were associated with significant risk for gonorrhea and chlamydial infection. In low-prevalence subpopulations, within-subpopulation mixing was associated with chlamydial infection, and direct links with high-prevalence subpopulations were associated with gonorrhea.

CONCLUSIONS

Mixing patterns influence the risk of specific infections, and they should be included in risk assessments for individuals and in the design of screening, health education, and partner notification strategies for populations.

Transmission dynamics and epidemiology of dengue: insights from age-stratified sero-prevalence surveys

The relationship between infection with the four major serotypes of dengue virus and the occurrence of different forms of disease is complex and not fully understood. Interpreting longitudinal records of the incidence of serious disease to gain insight into the transmission dynamics and epidemiology of the virus is therefore complicated. Since age reflects duration of exposure, age-stratified, strain-specific serological surveys carried out at one point in time, or over a short time interval, can potentially provide a rich source of information on longitudinal patterns. This paper describes the development and application (to data collected in Thailand) of statistically rigorous methods designed to estimate time-varying, strain-specific forces of infection, and thus basic reproduction numbers, from cross-sectional serological data. The analyses provide support for the hypothesis that antibody-dependent enhancement of transmission influences observed epidemiological pattern. Age-stratified serological data also reveal evidence of a propensity for the annual incidence of infection to oscillate over time with a frequency of several years. The latter observation is consistent with the predictions of simple mathematical models of the transmission dynamics of the virus. The estimates of the basic reproduction numbers obtained are similar in magnitude for each dengue serotype, being in the range of four to six. Such values are higher than those obtained from earlier analyses, and the implications of this for dengue control are discussed.

Studies of antibiotic resistance within the patient, hospitals and the community using simple mathematical models

The emergence of antibiotic resistance in a wide variety of important pathogens of humans presents a worldwide threat to public health. This paper describes recent work on the use of mathematical models of the emergence and spread of resistance bacteria, on scales ranging from within the patient, in hospitals and within communities of people. Model development starts within the treated patient, and pharmacokinetic and pharmacodynamic principles are melded within a framework that mirrors the interaction between bacterial population growth, drug treatment and the immunological responses targeted at the pathogen. The model helps identify areas in which more precise information is needed, particularly in the context of how drugs influence pathogen birth and death rates (pharmacodynamics). The next area addressed is the spread of multiply drug-resistant bacteria in hospital settings. Models of the transmission dynamics of the pathogen provide a framework for assessing the relative merits of different forms of intervention, and provide criteria for control or eradication. The model is applied to the spread of vancomycin-resistant enterococci in an intensive care setting. This model framework is generalized to consider the spread of resistant organisms between hospitals. The model framework allows for heterogeneity in hospital size and highlights the importance of large hospitals in the maintenance of resistant organisms within a defined country. The spread of methicillin resistant Staphylococcus aureus (MRSA) in England and Wales provides a template for model construction and analysis. The final section addresses the emergence and spread of resistant organisms in communities of people and the dependence on the intensity of selection as measured by the volume or rate of drug use. Model output is fitted to data for Finland and Iceland and conclusions drawn concerning the key factors determining the rate of spread and decay once drug pressure is relaxed.

Transmission dynamics of epidemic methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci in England and Wales

A simple epidemiological framework for the analysis of the transmission dynamics of hospital outbreaks of epidemic methicillin-resistant Staphylococcus aureus (EMRSA) and vancomycin-resistant enterococci (VRE) in hospitals in England and Wales is presented. Epidemic strains EMRSA-15 and EMRSA-16 are becoming endemic in hospitals in the United Kingdom, and theory predicts that EMRSA-15 and EMRSA-16 will reach respective endemic levels of 158 (95% confidence interval [CI], 143-173) and 116 (95% CI, 109-123) affected hospitals with stochastic fluctuations of up to 30 hospitals in each case. An epidemic of VRE is still at an early stage, and the incidence of hospitals newly affected by VRE is growing exponentially at a rate r=0.51/year (95% CI, 0.48-0.54). The likely impact of introducing surveillance policies if action is taken sufficiently early is estimated. Finally, the role of heterogeneity in hospital size is considered: "Super-spreader hospitals" may increase transmission by 40%-132% above the expected mean.

Some important issues in the planning of phase III HIV vaccine efficacy trials

Given that interesting HIV vaccine candidates, including live preparations and DNA plasmids, exist and that the first phase III vaccine (AIDSVAX) testing is due to begin this summer, 1998, in the U.S., adequately addressing trial preparedness is a pressing issue. Despite double-blind randomized controlled clinical trial design, there may be difficulties with interpretation and use of the usual measures of vaccinal efficacy and calculation of sample size. Difficulties arise from vaccine characteristics (e.g. mode of action, time-lag, waning) and population heterogeneities (e.g. differences in susceptibility, sexual behaviour, mixing preferences) causing frailty effects that can exacerbate bias and time-dependent effects already known to exist in simple cases. Since vaccine properties, particularly mode of action, are unlikely to be known before the onset of clinical trials, choosing an efficacy measure and the associated analyses and sample size calculations will be problematic. Interim analyses designed to decide whether a study will be prolonged may be tenuous if based on a time-dependent measure and will influence sample size determination. Despite shortcomings, general recommendations can be made to minimise pernicious effects. The objectives of this paper are principally to review the current state of knowledge of the different stages in the preparation of large phase III HIV vaccine efficacy trials, the methodological difficulties related to their design, and the analysis of data collected from them. Mathematical models and trial simulations are used to demonstrate that further research is necessary to study the behaviour of vaccine efficacy measures under heterogeneous conditions of population, vaccine action, and trial design and identify a time-independent efficacy measure. Alternative methods to validate sample size calculations have to be developed in older to reduce the chances of unnecessary economic and human cost in phase III HIV vaccine trials.

The relationship between the volume of antimicrobial consumption in human communities and the frequency of resistance

The threat to human health posed by antibiotic resistance is of growing concern. Many commensal and pathogenic organisms have developed resistance to well established and newer antibiotics. The major selection pressure driving changes in the frequency of antibiotic resistance is the volume of drug use. However, establishing a quantitative relationship between the frequency of resistance and volume of drug use has proved difficult. Using population genetic methods and epidemiological observations, we report an analysis of the influence of the selective pressure imposed by the volume of drug use on temporal changes in resistance. Analytical expressions are derived to delineate key relationships between resistance and drug consumption. The analyses indicate that the time scale for emergence of resistance under a constant selective pressure is typically much shorter than the decay time after cessation or decline in the volume of drug use and that significant reductions in resistance require equally significant reductions in drug consumption. These results highlight the need for early intervention once resistance is detected.

Estimation of the basic reproduction number of BSE: the intensity of transmission in British cattle

The basic reproduction number, R0, of an infectious agent is a key factor determining the rate of spread and the proportion of the host population affected. We formulate a general mathematical framework to describe the transmission dynamics of long incubation period diseases with complex pathogenesis. This is used to derive expressions for R0 of bovine spongiform encephalopathy (BSE) in British cattle, and back-calculation methods are used to estimate R0 throughout the time-course of the BSE epidemic. We show that the 1988 meat and bonemeal ban was effective in rapidly reducing R0 below 1, and demonstrate that this indicates that BSE will be unable to become endemic in the UK cattle population even when case clustering is taken into account. The analysis provides some insight into absolute infectiousness for bovine-to-bovine transmission, indicating maximally infectious animals may have infected up to 400 animals each. The relationship between R0 and the early stages of the BSE epidemic and the requirements for additional research are also discussed.