Format

Send to

Choose Destination
See comment in PubMed Commons below
Am J Kidney Dis. 2010 Sep;56(3):540-6. doi: 10.1053/j.ajkd.2010.05.009. Epub 2010 Jul 16.

Analytical and biological variation in measures of anemia and iron status in patients treated with maintenance hemodialysis.

Author information

1
DaVita Inc, Denver, CO, USA. david.vanwyck@davita.com

Abstract

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.

PMID:
20638166
DOI:
10.1053/j.ajkd.2010.05.009
[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science
    Loading ...
    Support Center