Document Detail

Analytical and biological variation in measures of anemia and iron status in patients treated with maintenance hemodialysis.
MedLine Citation:
PMID:  20638166     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: To make informed decisions in dosing erythropoiesis-stimulating agents and intravenous iron therapy, clinicians must determine whether differences between current and previous test results for anemia and iron status markers reflect expected variation, a significant change, or an actual trend. STUDY DESIGN: Prospective observational cohort study. SETTING & PARTICIPANTS: 30 patients undergoing thrice-weekly in-center hemodialysis. PREDICTOR: Within-patient biological variations in hemoglobin (Hb) level, hematocrit (Hct), reticulocyte Hb content, transferrin saturation (TSAT), and ferritin level were determined over 12 consecutive treatment days. OUTCOMES & MEASUREMENTS: We separately measured same-sample analytical variation and within-patient biological variation (coefficient of variation), then calculated the number of sampling days needed to determine the true or homeostatic value for each analyte with 95% probability. We also evaluated whether results differed among the first, second, and third dialysis days of the week. RESULTS: Biological variation differed by analyte. Hb level (4.0%), Hct (4.0%), and reticulocyte Hb content (4.8%) showed much lower variation than TSAT (38.2%) or ferritin level (15.1%). Analytical variation ranged from 2.0%-6.9% for all analytes. We found that one sample day would be sufficient to establish the true mean Hb level or Hct within a level of closeness+/-20% and 95% probability. For the same levels of closeness and probability, one sample day would be needed for reticulocyte Hb content, 15 for TSAT, and 3 for ferritin level. No pairwise comparison for any of the 5 analytes yielded a significant difference between results obtained on the first, second, or third dialysis day of the week. LIMITATIONS: These findings may not apply to other patient populations. CONCLUSIONS: Low biological variation renders Hb level, Hct, and reticulocyte Hb content, but not TSAT and ferritin level, suitable for trend analysis using results from 2 successive samples. TSAT and ferritin test results, unlike reticulocyte Hb content, have limited value in evaluating changes in iron status within individual hemodialysis patients.
David B Van Wyck; Harry Alcorn; Resmi Gupta
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-07-16
Journal Detail:
Title:  American journal of kidney diseases : the official journal of the National Kidney Foundation     Volume:  56     ISSN:  1523-6838     ISO Abbreviation:  Am. J. Kidney Dis.     Publication Date:  2010 Sep 
Date Detail:
Created Date:  2010-08-23     Completed Date:  2010-09-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8110075     Medline TA:  Am J Kidney Dis     Country:  United States    
Other Details:
Languages:  eng     Pagination:  540-6     Citation Subset:  IM    
Copyright Information:
Copyright (c) 2010 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
DaVita Inc, Denver, CO, USA.
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MeSH Terms
Anemia / blood*,  epidemiology*
Iron / blood*
Longitudinal Studies
Middle Aged
Prospective Studies
Renal Dialysis*
Reg. No./Substance:

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