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Articles by B. D Bradbury
Total Records ( 2 ) for B. D Bradbury
  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.

  E. V Lawler , B. D Bradbury , J. R Fonda , J. M Gaziano and D. R. Gagnon
 

Background and objectives: Although well-described for patients who require dialysis, information on transfusion burden related to anemia in the nondialysis patient population with chronic kidney disease (CKD) is lacking.

Design, settings, participants, & measurements: A retrospective study was conducted of patients with CKD and chronic anemia from 2002 through 2007 in the Veterans Administration Healthcare System. Included patients had stage 3 CKD or higher and anemia (one or more hemoglobin [Hb] levels <11 g/dl or received anemia therapy [erythropoiesis-stimulating agents [ESAs], iron, or both]). The outcome of interest was transfusion events, which was evaluated in relation to the absolute Hb level and changes in Hb levels overall and according to the type of treatment received (no treatment, iron therapy, ESA therapy, or ESA and iron therapy) concurrent with each Hb measurement.

Results: Among 97,636 patients with CKD and anemia, we observed 68,556 transfusion events (61 events per 100 person-years), 86.6% of which occurred in inpatient settings. At all Hb levels, transfusion events were highest during periods of no treatment and increased with declining Hb levels. Between an Hb of 10.0 and 10.9 g/dl, the transfusion rate was 2.0% for those who received an ESA, iron, or both and 22% for those who received no treatment; at an Hb level of 7.0 to 7.9 g/dl, the transfusion rate was 10 to 12% for treated and 58% for untreated patients. Low absolute Hb levels but not Hb changes was most predictive of a transfusion even after adjustment for patient case mix.

Conclusions: Transfusions are still used to treat anemia in patients who have CKD and do not require dialysis, although they occur considerably less frequently in patients who receive other available anemia therapies.

 
 
 
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