I agree that we need to define what levels of potassium we are concerned
with in clinical terms, but, even then, it is useful to know whether we
are dealing with a plasma or serum potassium value. The data in the
paper by Hartland and Neary, Clin Chem 1999, 45, 1091-1092 causes
concern, especially if we are still using plasma reference ranges.
After reading this paper I am not sure that only using SST tubes solves
the problem. One could argue that the best potassium values are plasma
values and we have a quality problem if we do not only use plasma values
for potassium.
John Evans
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