Korean J Intern Med.  2014 Mar;29(2):226-230. 10.3904/kjim.2014.29.2.226.

Whole blood versus serum ionized calcium concentrations in dialysis patients

• Kang SH
• Cho KH
• Park JW
• Yoon KW
• Do JY

• KMID: 1792039
• DOI: http://doi.org/10.3904/kjim.2014.29.2.226

Abstract

BACKGROUND/AIMS
The aim of this study is to measure the difference of ionized calcium between heparinized whole blood and serum.
METHODS
We recruited 107 maintenance hemodialysis (HD) patients from our hospital HD unit. The clinical and laboratory data included ionized calcium in serum and in whole blood (reference, 4.07 to 5.17 mg/dL).
RESULTS
The level of ionized calcium in serum was higher than that in whole blood (p < 0.001). Bland-Altman analysis showed that difference for ionized calcium was 0.5027. For the difference, the nonstandardized beta was -0.4389 (p < 0.001) and the intercept was 2.2418 (p < 0.001). There was a significant difference in the distribution of categories of ionized calcium level between two methods (kappa, 0.279; p < 0.001).
CONCLUSIONS
This study demonstrates that whole blood ionized calcium is underestimated compared with serum ionized calcium. Positive difference increases as whole blood ionized calcium decreases. Therefore, significant hypocalcemia in whole blood ionized calcium should be verified by serum ionized calcium.

Keyword

Renal dialysis; Heparin; Hypocalcemia

MeSH Terms

Aged
Biological Markers/blood
Calcium/*blood
Female
Humans
Hypercalcemia/blood/*diagnosis/etiology
Hypocalcemia/blood/*diagnosis/etiology
Kidney Diseases/blood/complications/diagnosis/*therapy
Male
Middle Aged
Predictive Value of Tests
*Renal Dialysis/adverse effects
Reproducibility of Results
Specimen Handling/*methods
Biological Markers
Calcium