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Articles by A. J Collins
Total Records ( 3 ) for A. J Collins
  J. M Young , N Terrin , X Wang , T Greene , G. J Beck , J. W Kusek , A. J Collins , M. J Sarnak and V. Menon

Background and objectives: Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, reduces bioavailability of nitric oxide and induces endothelial dysfunction. This dimethylated amino acid accumulates in chronic kidney disease and may be involved in the pathophysiology of cardiovascular disease (CVD) in this population.

Design, settings, participants, & methods: The Modification of Diet in Renal Disease Study was a randomized, controlled trial conducted between 1989 and 1993. We measured ADMA in frozen samples collected at baseline (n = 820) and obtained survival status, up to December 31, 2000, from the National Death Index. We examined the relationship of ADMA with prevalent CVD and performed multivariable Cox models to examine the relationship of ADMA with all-cause and CVD mortality.

Results: Mean (SD) age was 52 (12) yr, GFR was 32 ± 12 ml/min per 1.73 m2, and ADMA was 0.70 ± 0.25 µmol/L. A 1-SD increase in ADMA was associated with a 31% increased odds of prevalent CVD in an adjusted logistic regression model. During the 10-yr follow-up period, 202 (25%) participants died of any cause, 122 (15%) from CVD, and 545 (66%) reached kidney failure. In multivariable Cox models, a 1-SD increase in ADMA was associated with a 9% increased risk for all-cause and 19% increased risk for CVD mortality.

Conclusions: In this cohort of patients with predominantly nondiabetic, stages 3 to 4 chronic kidney disease, there was a strong association of ADMA with prevalent CVD and a modest association with all-cause and CVD mortality.

  B. M Chavers , C. A Solid , F. X Daniels , S. C Chen , A. J Collins , D. L Frankenfield and C. A. Herzog

Background and objectives: Data are limited regarding BP distribution and the prevalence of hypertension in pediatric long-term dialysis patients. This study aimed to examine BP distribution in U.S. pediatric long-term hemodialysis patients.

Design, setting, participants, & measurements: This cross-sectional study of all U.S. pediatric (aged 0-< 18 yr, n = 624) long-term hemodialysis patients was performed as part of the Centers for Medicare & Medicaid Services End-Stage Renal Disease (ESRD) Clinical Performance Measures Project. BP and clinical information were collected monthly in October, November, and December 2001. Hypertension was defined as the mean of pre- and postdialysis systolic or diastolic BP above the 95th percentile for age, height, and sex, or antihypertensive medication use. Results were calculated by age, sex, race, ethnicity, ESRD duration, body mass index percentile, primary cause of ESRD, and laboratory data.

Results: Hypertension was present in 79% of patients; 62% used antihypertensive medication. Five percent of patients were prehypertensive (mean BP at 90th to 95th percentile). Hypertension was uncontrolled in 74% of treated patients. Characteristics associated with hypertension included acquired kidney disease, shorter duration of ESRD, and lower mean hemoglobin and calcium values. Characteristics associated with uncontrolled hypertension were younger age and shorter duration of ESRD.

Conclusions: Hypertension is common in U.S. pediatric long-term hemodialysis patients, uncontrolled in 74% of treated patients, and untreated in 21% of hypertensive patients. It is concluded that a more aggressive approach to treatment of hypertension is warranted in pediatric long-term hemodialysis patients.

  O Wang , R. D Kilpatrick , C. W Critchlow , X Ling , B. D Bradbury , D. T Gilbertson , A. J Collins , K. J Rothman and J. F. Acquavella

Background and objectives: Observational studies relating epoetin alfa (EPO) dose and mortality frequently use analytic methods that do not control time-dependent confounding by indication (CBI). The relationship between EPO dose and 1-year mortality, adjusting for the effects of time-dependent CBI, was examined using a marginal structural model.

Design, setting, participants, & measurements: This retrospective cohort study included 27,791 hemodialysis patients between July 2000 and June 2002. Patients were grouped at successive 2-wk intervals into a zero-dose category or four nonzero-dose categories. Ordinal regression was used to calculate inverse probability of treatment weights of patients receiving their own dose level given their covariate and treatment history. Three treatment models with an increasing number of treatment predictors were evaluated to assess the effect of model specification. A small number of excessively large patient weights were truncated. Relative hazards for higher-dose groups compared with the lowest nonzero-dose group varied by treatment model specification and by level of weight truncation.

Results: Results differed appreciably between the simplest treatment model, which incorporated only hemoglobin and EPO dosing history with 2% weight truncation (hazard ratio: 1.51; 95% confidence interval: 1.09, 1.89 for highest-dose patients), and the most comprehensive treatment model with 1% weight truncation (hazard ratio: 0.98; 95% confidence interval: 0.76, 1.74).

Conclusions: There is appreciable CBI at higher EPO doses, and EPO dose was not associated with increased mortality in marginal structural model analyses that more completely addressed this confounding.

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