Why the study?
Does temperature affect the measurement of plasma ionized calcium in whole blood in vitro?
Does temperature affect the measurement of plasma ionized calcium in whole blood in vitro?
Temperature has a small but significant negative correlation with measured plasma ionized calcium, suggesting fresh samples should be measured at body temperature for highest accuracy.
May necessitate temperature standardization for ionized calcium assays; leaves open clinical relevance of this small effect.
Plasma calcium ion concentration (cCa2+) in samples from 50 healthy volunteers was measured at four temperatures (21, 26, 31 and 37 degrees C) using a calcium electrode based on a neutral carrier ligand. A small negative correlation was found between temperature and cCa2+, the coefficient being -0.0017 mmol . l-1 . degrees C-1 (P less than 0.001). The significance of this in clinical, physiological and instrumentation fields is discussed. The effect on measured cCa2+ of overnight storage at 4 degrees C was slight, but did increase the variance of the results. It is suggested that the most accurate results of cCa2+ will be obtained from fresh samples measured at body temperature.
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Heining et al. (1983) studied this question.
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