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Ionized Calcium Measurement in Serum and Plasma by Ion Selective Electrodes: Comparison of Measured and Calculated Parameters

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Abstract

To determine the concentration of ionized calcium (iCa) collected in lithium heparin and gel tubes and to correlate the measured iCa with calculated iCa. Anaerobic fasting blood samples were simultaneously collected from healthy laboratory workers in lithium-heparin and gel tubes. iCa, pH, total calcium (CaT), total protein and albumin were measured. Ionized Ca was calculated with albumin and globulin values using an appropriate formula. Mean iCa in gel tubes showed a positive constant bias of 0.08 mmol/L (p < 0.001) when compared to lithium heparin results. The mean pH of blood taken in lithium heparin and gel tubes was non-significant (p = 0.3). Measured iCa poorly correlated with CaT (r = 0.2, p = 0.1) and calculated iCa (r = 0.2, p = 0.2). To evaluate the calcium status direct measurement of iCa must be done rather than using the formulae for iCa determination. In addition serum is recommended as the choice of sample for iCa determination in comparison to plasma samples.

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Abbreviations

iCa:

Ionized calcium

CaT:

Total calcium

ISE:

Ion selective electrode

PTH:

Parathyroid hormone

CLSI:

Clinical Laboratory Standards Institute

IFCC:

International Federation of Clinical Chemistry

SPSS:

Statistical Package of Social Sciences

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Conflict of interest

None.

Ethical standards

The study was given exemption by Ethical review committee (ERC) as per AKU ERC guidelines section B. http://www.aku.edu/res-office/res-erc.shtml.

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Authors and Affiliations

  1. Department of Pathology & Microbiology, Aga Khan University, Stadium Road, P.O. Box 3500, Karachi, 74800, Pakistan

    Lena Jafri & Aysha Habib Khan

  2. Clinical Chemistry Laboratory, Department of Pathology & Microbiology, Aga Khan University, Karachi, Pakistan

    Saba Azeem

Authors
  1. Lena Jafri
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  2. Aysha Habib Khan
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  3. Saba Azeem
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Correspondence to Lena Jafri.

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Jafri, L., Khan, A.H. & Azeem, S. Ionized Calcium Measurement in Serum and Plasma by Ion Selective Electrodes: Comparison of Measured and Calculated Parameters. Ind J Clin Biochem 29, 327–332 (2014). https://doi.org/10.1007/s12291-013-0360-x

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  • DOI: https://doi.org/10.1007/s12291-013-0360-x

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