engleski

Ionized calcium in serum – the influence of time periods from sampling to centrifugation, and from centrifugation until analysis

Introduction: After verification of serum as sample equivalent to arterial blood for ionized calcium (iCa) measurement, aim of our study was to evaluate the influence of time periods from sampling to centrifugation, and from centrifugation until analysis on the iCa in serum, in order to assess the urgency of analysis due to possible sample instability. Subjects and Methods: The influence of time periods from sampling to centrifugation was examined on 10 subjects ; 3 tubes of blood were collected and centrifuged 15 (Tube 1), 30 (Tube 2) and 60 minutes (Tube 3) after sampling, and analyzed within 10 minutes. The influence of time periods from centrifugation until analysis was examined on 15 subjects ; 3 tubes of blood were collected, centrifuged after 30 minutes of the sampling and analyzed at the following timing: 0-10 (Tube A), 30-40 (Tube B) and 90- 100 minutes (Tube C). Venous blood samples were collected in ‘’gel separator’’ serum tubes, all tubes were completely filled, centrifuged according to the manufacturer’s instructions, without temperature adjustment and left at room temperature until analysis. iCa was measured by potentiometric method on the RapidLab 348 analyzer (Siemens, Suffolk, UK). The obtained values were compared according to RiliBÄK’s criteria (acceptable deviation < 7.5%). Results: iCa deviations in Tube 2 and Tube 3 in relation to the values in Tube 1 were less than established criteria ; medium bias (range) ; 1.25% (-3.1-3.13) for Tube 2 ; 1.12% (-1.55- 3.91) for Tube 3. iCa deviations in Tube B and Tube C in relation to the values in Tube A were less than established criteria ; medium bias (range) ; 2.38% (-4.58- 2.34) for Tube B ; 2.79% (-4.72-4.80) for Tube C. Conclusion: Different time periods from sampling to centrifugation (up to 60 minutes) and from centrifugation until analysis (up to 90 minutes) did not influence the stability of the iCa in the serum.

ionised calcium ; specimen handling ; preanalytical phase

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