Pseudohyperkalaemia in leukaemic patients: the effect of test tube type and form of transport to the laboratory

Abstract

Background The present study was aimed at determining the effect of the tube type used for primary sample collection and the manner of transport prior to assessment (either manual or by pneumatic tube) on the degree of pseudohyperkalaemia in leukaemic patients. Methods Blood from six leukaemic patients was collected into seven primary sample tubes (Monovette®, Sarstedt): sample A, heparinized blood gas syringe (potassium reference value); sample B, plasma Li-heparin without separator gel; sample C, plasma Li-heparin with separator gel; and sample D, serum with separator gel. The primary sample tubes designated B, C and D were transported to the laboratory manually. Duplicates of the same sample tubes, BPT, CPT and DPT, were sent to the laboratory by pneumatic tube. Results In patients with chronic lymphocytic leukaemia (CLL), there was no increase in the concentration of potassium in samples B, C and D when compared to the reference value. Transport of the samples by pneumatic tube led to a pronounced increase in potassium concentration in samples BPT and CPT, whereas there was no increase in sample DPT when compared to the reference value. In the patient with chronic myeloid leukaemia (CML), an increase in potassium concentration occurred in sample D and in samples BPT, CPT and DPT. A similar finding was observed in the patient with acute lymphocytic leukaemia (ALL), furthermore with an extremely high concentration of potassium in samples C and CPT. Conclusions Manual transport of non-coagulable blood (plasma Li-heparin without separator gel) to the laboratory results in the least possible artificial increase in potassium concentration in the sample.