[Draft proposal to estimate true values of serum potassium in samples from patients with myeloproliferative...

The pseudohyperkalemia in thrombocytosis is assumed to be due to potassium released from blood cells during blood clotting as reported previously, but its mechanisms remain to be cleared. Although plasma potassium measurements with blood collection tubes containing heparin are performed in many hospitals to avoid pseudohyperkalemia, the burden on patients may come out with further blood sampling by another heparinized tube. Taken together, we investigated laboratory data possibly involved in pseudohyperkalemia in 184 samples from patients with myeloproliferative neoplasma (MPN), and studied estimation capability for true values of serum potassium, driving a correction formula by means of several laboratory data to explain the difference of measured potassium values (K-difference: serum value minus plasma value). Platelet count and mean corpuscular volume (MCV) were adopted as significant variables correlated to K-difference as a result of multiple regression analysis. A correction formula was driven by multiple regression equation with these two variables as follows: y = 0.0006 x 1+0.0004 x 2-0.177 (r= 0.885; x 1, platelet count; x 2, MPV). The correction formula was considered to be useful for estimating the true value of serum potassium in samples from patients with MPN because the corrected serum potassium value correlated highly with plasma potassium value (r = 0.885). These results propose that true values of serum potassium can be estimated by the correction of measured serum potassium values with platelet count and MCV, suggesting that not only quantitative factors but also qualitative factors may be involved in pseudohyperkalemia.