Sawtooth Potassium and Hemoglobin Results

A 5-year-old boy was admitted with dyspnea, fever, night sweats, and unexplained bruising. Radiography revealed several pulmonary consolidations, and laboratory investigations showed marked hyperleukocytosis with 90% blasts. He was diagnosed with T-cell acute lymphoblastic leukemia. Hemoglobin (Hb)2 and potassium results in the subsequent days, during therapy, showed a sawtooth pattern [Fig. 1: central lab, solid dots; point of care (POC), open...