David W. Johnson

Bio: David W. Johnson is an academic researcher from University of Queensland. The author has contributed to research in topics: Peritoneal dialysis & Kidney disease. The author has an hindex of 160, co-authored 2714 publications receiving 140778 citations. Previous affiliations of David W. Johnson include Minnesota Department of Transportation & Open University.

Modification of cardiovascular risk in hemodialysis patients: an evidence-based review.

Abstract: Cardiovascular disease accounts for 40% to 50% of deaths in dialysis populations. Overall, the risk of cardiac mortality is 10-fold to 20-fold greater in dialysis patients than in age and sex-matched controls without chronic kidney disease. The aim of this paper is to review critically the evidence that cardiac outcomes in dialysis patients are modified by cardiovascular risk factor interventions. There is limited, but as yet inconclusive controlled trial evidence that cardiovascular outcomes in dialysis populations may be improved by antioxidants (vitamin E or acetylcysteine), ensuring that hemoglobin levels do not exceed 120 g/L (especially in the setting of known cardiovascular disease), prescribing carvedilol in the setting of dilated cardiomyopathy, and by using cinacalcet in uncontrolled secondary hyperparathyroidism. Similarly, there are a number of negative controlled trials, which have demonstrated that statins, high-dose folic acid, angiotensin-converting enzyme inhibitors, multiple risk factor intervention via multidisciplinary clinics, and high-dose or high-flux dialysis are ineffective in preventing cardiovascular disease. Although none of these studies could be considered conclusive, the negative trials to date should raise significant concerns about the heavy reliance of current clinical practice guidelines on extrapolation of findings from cardiovascular intervention trials in the general population. It may be that cardiovascular disease in dialysis populations is less amenable to intervention, either because of the advanced stage of chronic kidney disease or because the pathogenesis of cardiovascular disease in dialysis patients is different from that in the general population. Large, well-conducted, multicenter randomized-controlled trials in this area are urgently required.

Who comes back? Characteristics and predictors of return to emergency department services for pediatric mental health care.

Abstract: Objectives: The objective of this study was to investigate predictors of emergency department (ED) return visits for pediatric mental health care. The authors hypothesized that through the identification of clinical and health system variables that predict return ED visits, which children and adolescents would benefit from targeted interventions for persistent mental health needs could be determined. Methods: Data on 16,154 presentations by 12,589 pediatric patients (≤17 years old) were examined from 2002 to 2006, using the Ambulatory Care Classification System (ACCS), a provincewide database for Alberta, Canada. Multivariable logistic regressions identified predictors, while survival analyses estimated time to ED return. Results: In the multivariable analysis, there were four patient factors significantly associated with ED return. Male sex (odds ratio [OR] = 0.78; 99% confidence interval [CI] = 0.69 to 0.89) was associated with a lower rate of return, as was child age. The likelihood of ED return increased with age. Children ≤5 years (OR = 0.26; 99% CI = 0.14 to 0.46) and between ages 6 and 12 (OR = 0.64; 99% CI = 0.51 to 0.79) were less likely to return, compared to 13- to 17-year-olds. Patients with families receiving full assistance for covering government health care premiums were more likely to return compared to those with no assistance (OR = 1.59; 99% CI = 1.33 to 1.91). Patients were more likely to return if their initial presentation was for a mood disorder (OR = 1.72; 99% CI = 1.46 to 2.01) or psychotic-related illness (OR = 2.53; 99% CI = 1.80 to 3.56). There were two modest health care system predictors in the model. The likelihood of return decreased for patients triaged as nonurgent (OR = 0.62; 99% CI = 0.45 to 0.87) versus those triaged as urgent (level 3 acuity) and increased for patients with visits to general (vs. pediatric) EDs (OR = 1.25; 99% CI = 1.03 to 1.52). ED region (urban vs. rural) did not predict return. Within 72 hours of discharge, 6.1 and 8.7% of patients diagnosed with a mood disorder and psychotic-related illness, respectively, returned to the ED. Throughout the study period, 28.5 and 36.6% of these diagnostic populations, respectively, returned to the ED. Conclusions: Among children and adolescents who accessed the ED for mental health concerns, being female, older in age, in receipt of social assistance, and having an initial visit for a mood disorder or psychotic-related illness were associated with return for further care. How patient presentations were triaged and whether visits were made to a pediatric or general ED also affected the likelihood of return. ACADEMIC EMERGENCY MEDICINE 2010; 17:177–186 © 2010 by the Society for Academic Emergency Medicine

Patient and Caregiver Priorities for Outcomes in Peritoneal Dialysis: Multinational Nominal Group Technique Study

Abstract: BACKGROUND AND OBJECTIVES: The absence of accepted patient-centered outcomes in research can limit shared decision-making in peritoneal dialysis (PD), particularly because PD-related treatments can be associated with mortality, technique failure, and complications that can impair quality of life. We aimed to identify patient and caregiver priorities for outcomes in PD, and to describe the reasons for their choices. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Patients on PD and their caregivers were purposively sampled from nine dialysis units across Australia, the United States, and Hong Kong. Using nominal group technique, participants identified and ranked outcomes, and discussed the reasons for their choices. An importance score (scale 0-1) was calculated for each outcome. Qualitative data were analyzed thematically. RESULTS: Across 14 groups, 126 participants (81 patients, 45 caregivers), aged 18-84 (mean 54, SD 15) years, identified 56 outcomes. The ten highest ranked outcomes were PD infection (importance score, 0.27), mortality (0.25), fatigue (0.25), flexibility with time (0.18), BP (0.17), PD failure (0.16), ability to travel (0.15), sleep (0.14), ability to work (0.14), and effect on family (0.12). Mortality was ranked first in Australia, second in Hong Kong, and 15th in the United States. The five themes were serious and cascading consequences on health, current and impending relevance, maintaining role and social functioning, requiring constant vigilance, and beyond control and responsibility. CONCLUSIONS: For patients on PD and their caregivers, PD-related infection, mortality, and fatigue were of highest priority, and were focused on health, maintaining lifestyle, and self-management. Reporting these patient-centered outcomes may enhance the relevance of research to inform shared decision-making.

Impact of obesity on renal transplant outcomes.

Abstract: Obesity is a frequent and important consideration to be taken into account when assessing patient suitability for renal transplantation. In addition, posttransplant obesity continues to represent a significant challenge to health care professionals caring for renal transplant recipients. Despite the vast amount of evidence that exists on the effect of pretransplant obesity on renal transplant outcomes, there are still conflicting views regarding whether obese renal transplant recipients have a worse outcome, in terms of short- and long-term graft survival and patient survival, compared with their non-obese counterparts. It is well established that any association of obesity with reduced patient survival in renal transplant recipients is mediated in part by its clustering with traditional cardiovascular risk factors such as hypertension, dyslipidaemia, insulin resistance and posttransplant diabetes mellitus, but what is not understood is what mediates the association of obesity with graft failure. Whether it is the higher incidence of cardiovascular comorbidities jeopardising the graft or factors specific to obesity, such as hyperfiltration and glomerulopathy, that might be implicated, currently remains unknown. It can be concluded, however, that pre- and posttransplant obesity should be targeted as aggressively as the more well-established cardiovascular risk factors in order to optimize long-term renal transplant outcomes.

Positive End-Expiratory Pressure Increases the Right-to-Left Shunt in Mechanically Ventilated Patients with Patent Foramen Ovale

Abstract: Objective: To determine the effect of the presence of a patent foramen ovale on the right-to-left shunt in patients with respiratory failure who receive positive end-expiratory pressure (PEEP). Des...

Initial sequencing and analysis of the human genome.

Abstract: The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The social identity theory of intergroup behavior

Abstract: This chapter presents an outline of a theory of intergroup conflict and some preliminary data relating to the theory. Much of the work on the social psychology of intergroup relations has focused on patterns of individual prejudices and discrimination and on the motivational sequences of interpersonal interaction. The intensity of explicit intergroup conflicts of interests is closely related in human cultures to the degree of opprobrium attached to the notion of "renegade" or "traitor." The basic and highly reliable finding is that the trivial, ad hoc intergroup categorization leads to in-group favoritism and discrimination against the out-group. Many orthodox definitions of "social groups" are unduly restrictive when applied to the context of intergroup relations. The equation of social competition and intergroup conflict rests on the assumptions concerning an "ideal type" of social stratification in which the salient dimensions of intergroup differentiation are those involving scarce resources.