Evaluation and management of leukolysis-mediated pseudohyperkalemia in paediatric leukemic samples

Introduction: Leukolysis-related pseudohyperkalemia due to preanalytical procedures may lead to erroneous (or absence of) treatment based on an invalid lab test result. We aimed to obtain a leukocyte threshold above which leukolysis-related pseudohyperkalemia becomes clinical relevant. Secondly, temporal dynamics of treatment-induced leukocyte decrease were studied to allow tailored implementation of laboratory information system (LIS) decision rules based on the leukocyte threshold to avoid leukolysis-related pseudohyperkalemia. Materials and methods: Potassium results of AU5811 routine chemistry (Beckman Coulter, Brea, California, USA) and iStat point of care (POC) (Abbott Diagnostics, Chicago, Illinois, USA) analysers were compared, the latter method being insensitive to leukolysis caused by pre-analytical procedures. Potassium results were combined with leukocyte counts obtained using a Cell-Dyn Sapphire haematology analyser (Abbott Diagnostics, Santa Clara, California, USA), resulting in 132 unique data triplets. Regression analysis was performed to establish a leukocyte threshold. The Reference Change Value (√2 x Z x √(CV 2 a + CV _i2 )) was used to calculate maximum allowable difference between routine analyser and POC potassium results (delta _max + 0.58 mmol/L). Temporal analysis on the treatment-induced leukocyte decrease was performed by plotting leukocyte counts in time for all patients above the threshold leukocyte count (N = 41). Results: Established leukocyte threshold was 63 x10 ⁹/L. Temporal analysis showed leukocyte counts below the threshold within 8 days of treatment for all patients. Conclusions: Based on performed analyses we were able to implement LIS decision rules to reduce pseudohyperkalemia due to preanalytical pro-cedures. This implementation can contribute to a reduction in erroneous (or absence of) treatments in the clinic.