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Robert W. Burnett, Arthur K. Covington, Niels Fogh-Andersen, Wolf R. Külpmann, Andrzej Lewenstam, Anton H.J. Maas, Oswald Müller-Plathe, Charles Sachs, Ole Siggaard-Andersen, Antonius L. VanKessel, Willem G. Zijlstra
Recommendations for Measurement of and Conventions for Reporting Sodium and Potassium by Ion-Selective Electrodes in Undiluted Serum, Plasma or Whole Blood
Ion-selective electrodes (ISEs) respond to ion-activity
and therefore do not sense substance concentration directly. However, it is recognized that sodium and
potassium in plasma will continue to be expressed for
clinical purposes in terms of substance concentration
(mmol/l). A convention is proposed whereby for routine
clinical purposes results of ISE measurements
of sodium and potassium in undiluted plasma should
be reported in terms of substance concentration
(mmol/l). In specimens with normal concentrations of
plasma water, total CO2, lipids, protein and pH, the values
will concur with the total substance concentration
as determined for example by flame atomic emission
spectrometry (FAES) or ISE measurements on diluted
samples. In specimens with abnormal concentrations
of plasma water, the results will differ. However, under
these circumstances, measurements of sodium and
potassium by ISE in the undiluted sample will more
appropriately reflect the activity of sodium and potassium
and are therefore clinically more relevant than
the determination in diluted samples. Detailed recommendations
are made about practical procedures to
achieve this. The recommended name for this quantity
is the substance concentration of
Clinical Chemical Laboratory Medicine, Walter de Gruyter
Print ISSN: 1434-6621
Volume: 38, 10/2000
Pages: 1065 - 1071