Spurious Hyperkalemia Without Hemolysis: A Case-Based Presentation of Preanalytical Errors and Diagnostic Pitfalls

Background and Clinical significance: Potassium is one of the most frequently measured laboratory parameters used to assess a patient's clinical status and is also one of the analytes most commonly affected by preanalytical errors. Case Presentation: A potassium test was ordered for a 63-year-old male patient. The result obtained was 6.4 mmol/L, indicating hyperkalemia, and a medical consultation was recommended in the laboratory report. As the potassium result was inconsistent with the patient's clinical status, a new blood sample was analyzed the next day. This yielded a result that was 1.3 mmol/L (20%) lower. A detailed interview with the patient and the staff responsible for blood sample collection revealed that the spurious hyperkalemia was most likely caused by prolonged storage of the blood sample in a refrigerator implemented because of high ambient temperatures. Further analysis demonstrated that after storage of blood samples at low temperature, potassium concentration increased significantly on average by 5% and 20% at the 4 h and 8 h time points, respectively. Conclusions: Low temperature and prolonged blood sample storage before analysis significantly affect potassium results. Since even a slight alteration in potassium levels can have a severe impact on a patient's health and may require immediate action, obtaining accurate potassium results requires ensuring appropriate conditions for sample storage and transport, and proper sample handling. This is particularly important in laboratories serving large geographical areas, where prolonged storage and transportation of blood samples can considerably extend the preanalytical phase.