The Korean journal of internal medicine

The Korean Association of Internal Medicine (대한내과학회)
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Whole blood versus serum ionized calcium concentrations in dialysis patients

  • Kang, Seok Hui (Division of Nephrology, Department of Internal Medicine, Yeungnam University Medical Center) ;
  • Cho, Kyu Hyang (Division of Nephrology, Department of Internal Medicine, Yeungnam University Medical Center) ;
  • Park, Jong Won (Division of Nephrology, Department of Internal Medicine, Yeungnam University Medical Center) ;
  • Yoon, Kyung Woo (Division of Nephrology, Department of Internal Medicine, Yeungnam University Medical Center) ;
  • Do, Jun Young (Division of Nephrology, Department of Internal Medicine, Yeungnam University Medical Center)
  • Received : 2012.09.13
  • Accepted : 2012.12.07
  • Published : 2014.03.01
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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.

Keywords

References

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