Science. Evaluation of factitious hyperkalemia in hemolytic samples: impact of the mean corpuscular hemoglobin concentration.

Background: Hemolyzed specimens are a relatively frequent occurrence in laboratory practice, accounting for nearly 60% of rejected specimens. Some formulas have been proposed as a means of making a quantitative correction of the effect of hemolysis. We assessed the accuracy of serum potassium determinations in hemolyzed samples, including the mean corpuscular hemoglobin concentration (MCHC) of each subject in the correction formula (rbcK+= [iK+ /MCHC]fsHb). Methods: The potassium values post-induction of hemolysis (hK+) were correlated with the potassium values obtained by combining/totaling the serum potassium (sK+) with the potassium released by the red cells after rupture (rbcK+), calculated with the above formula. Results: No statistically significant difference was found between the mean concentrations of hK+ and the potassium calculated with the above formula (calcK+); there was no significant deviation from linearity. Conclusions: The formula we propose produces more accurate measurements of potassium because it uses the MCHC value of each patient in the calculation, which may prevent the need for repeated serum collection and assays. [ABSTRACT FROM AUTHOR]