Biomedical subjects

Kenneth Chen

Publications and source records attributed to Kenneth Chen.

4 recordsLinked to original sources

PubMed2005

Kidney transplantation and wait-listing rates from the international Dialysis Outcomes and Practice Patterns Study (DOPPS).

BACKGROUND: The international Dialysis Outcomes and Practice Patterns Study (DOPPS I and II) allows description of variations in kidney transplantation and wait-listing from nationally representative samples of 18- to 65-year-old hemodialysis patients. The present study examines the health status and socioeconomic characteristics of United States patients, the role of for-profit versus not-for-profit status of dialysis facilities, and the likelihood of transplant wait-listing and transplantation rates. METHODS: Analyses of transplantation rates were based on 5267 randomly selected DOPPS I patients in dialysis units in the United States, Europe, and Japan who received chronic hemodialysis therapy for at least 90 days in 2000. Left-truncated Cox regression was used to assess time to kidney transplantation. Logistic regression determined the odds of being transplant wait-listed for a cross-section of 1323 hemodialysis patients in the United States in 2000. Furthermore, kidney transplant wait-listing was determined in 12 countries from cross-sectional samples of DOPPS II hemodialysis patients in 2002 to 2003 (N= 4274). RESULTS: Transplantation rates varied widely, from very low in Japan to 25-fold higher in the United States and 75-fold higher in Spain (both P values <0.0001). Factors associated with higher rates of transplantation included younger age, nonblack race, less comorbidity, fewer years on dialysis, higher income, and higher education levels. The likelihood of being wait-listed showed wide variation internationally and by United States region but not by for-profit dialysis unit status within the United States. CONCLUSION: DOPPS I and II confirmed large variations in kidney transplantation rates by country, even after adjusting for differences in case mix. Facility size and, in the United States, profit status, were not associated with varying transplantation rates. International results consistently showed higher transplantation rates for younger, healthier, better-educated, and higher income patients.

Adolescent↗

PubMed2004

Timing of first cannulation and vascular access failure in haemodialysis: an analysis of practice patterns at dialysis facilities in the DOPPS.

BACKGROUND: Optimal waiting time before first use of vascular access is not known. METHODS: Two practices-first cannulation time for fistulae and grafts, and blood flow rate-were examined as potential predictors of vascular access failure in the Dialysis Outcomes and Practice Patterns Study (DOPPS). Access failure (defined as time to first failure or first salvage intervention) was modelled using Cox regression. RESULTS: Among 309 haemodialysis facilities, 2730 grafts and 2154 fistulae were studied. For grafts, first cannulation typically occurred within 2-4 weeks at 62% of US, 61% of European and 42% of Japanese facilities. For fistulae, first cannulation occurred <2 months after placement in 36% of US, 79% of European and 98% of Japanese facilities. Overall, the relative risk (RR) of graft failure in Europe was lower compared with the USA (RR = 0.69, P = 0.04). The RR of graft failure (reference group = first cannulation at 2-3 weeks) was 0.84 with first cannulation at <2 weeks (P = 0.11), 0.94 with first cannulation at 3-4 weeks (P = 0.48) and 0.93 with first cannulation at >4 weeks (P = 0.48). The RR of fistula failure was 0.72 with first cannulation at <4 weeks (P = 0.08), 0.91 at 2-3 months (P = 0.43) and 0.87 at >3 months (P = 0.31) (reference group = first cannulation at 1-2 months). Facility median blood flow rate was not a significant predictor of access failure. CONCLUSIONS: Earlier cannulation of a newly placed vascular access at the haemodialysis facility level was not associated with increased risk of vascular access failure. Potential for confounding due to selection bias cannot be excluded, implying the importance of clinical judgement in determining time to first use of vascular access.

Arteriovenous Shunt, Surgical↗

PubMed2004

The 3'-untranslated region of the beta2-adrenergic receptor mRNA regulates receptor synthesis.

beta(2)-Adrenergic receptors (beta(2)-ARs) are low abundance integral membrane proteins that mediate the effects of catecholamines at the cell surface. Post-transcriptional regulation of beta(2)-AR is dependent, in part, on sequences within the 5'- and 3'-untranslated regions (UTRs) of the receptor mRNA. In this work, we demonstrate that 3'-UTR sequences regulate the translation of the receptor mRNA. Deletion of the 3'-UTR sequences resulted in 2-2.5-fold increases in receptor expression. The steadystate levels of beta(2)-AR mRNA did not change significantly in the presence or absence of the 3'-UTR, suggesting that the translation of the receptor mRNA is suppressed by 3'-UTR sequences. Introduction of the receptor 3'-UTR sequences into the 3'-UTR of a heterologous reporter gene (luciferase) resulted in a 70% decrease in reporter gene expression without significant changes in luciferase mRNA levels. Sucrose density gradient fractionation of cytoplasmic extracts from Chinese hamster ovary cells transfected with full-length receptor cDNA demonstrated that the receptor transcripts were distributed between polysomal and non-polysomal fractions. Deletion of 3'-UTR sequences from the receptor cDNA resulted in a clear shift in the distribution of receptor mRNA toward the polysomal fractions, favoring increased translation. The 3'-UTR sequences of the receptor mRNA were sufficient to shift the distribution of luciferase mRNA from predominantly polysomal fractions toward non-polysomal fractions in cells transfected with the chimeric luciferase construct. Taken together, our results provide the first evidence for translational control of beta(2)-AR expression by 3'-UTR sequences. Presumably, this occurs by affecting the receptor mRNA localization.

3' Untranslated Regions↗

PubMed2004

The Dialysis Outcomes and Practice Patterns Study (DOPPS): design, data elements, and methodology.

The Dialysis Outcomes and Practice Patterns Study (DOPPS) is a prospective, observational study designed to elucidate aspects of hemodialysis practice that are associated with the best outcomes for hemodialysis patients. In DOPPS I, 308 hemodialysis units from 7 countries participated, including 145 facilities from the United States (1996-2001), 62 facilities from Japan (1999-2001), and 101 facilities from France, Germany, Italy, Spain, and the United Kingdom (all 1998-2000). DOPPS II (2002-2004) has included 320 hemodialysis units and more than 12,400 hemodialysis patients from the 7 DOPPS I countries as well as Australia, Belgium, Canada, New Zealand, and Sweden. Dialysis units are chosen via a stratified random selection procedure to provide proportional sampling by region and type of facility within each country. In DOPPS I and II, longitudinal data have been collected from both a prevalent (cross-sectional) patient sample and an incident patient sample. Data have also been collected on numerous facility practice patterns. Most DOPPS analyses incorporate both facility- and patient-level data in regression-based analyses to investigate predictors of survival, hospitalization, quality of life, vascular access type, and other outcomes. DOPPS longitudinal data also help identify trends in subject characteristics, practice indicators, medication use, and outcomes. The DOPPS remains a unique source of data on hemodialysis patients and facilities. It continues to refine its methods of data collection and analysis with the goal of improving hemodialysis practice and end-stage renal disease patient lives worldwide.

Humans↗