Pseudohyperkalaemia in Kawasaki disease.

Pseudohyperkalaemia was observed in 3 of 16 patients with Kawasaki disease showing remarkably increased platelet counts. Their plasma potassium concentration, which is not affected by in vitro coagulation, was in the normal range despite the increased serum level. A significant correlation was observed between the platelet count and the increase in the serum potassium level resulting from blood coagulation, which was estimated by subtracting the plasma potassium level from the serum level. This study indicates that pseudohyperkalaemia should be considered in patients with Kawasaki disease whose platelet counts are markedly increased.