Survey of serum potassium reference measurements

We compared the quality of reference measurements for serum potassium in fo ur reference laboratories from three different European countries, using a panel of 60 native patients' samples. The reference methods were based on e ither ion chromatography tone laboratory) or flame atomic emission spectrom etry (three laboratories). Performance specifications for serum potassium m easurements were defined as a maximum overall coefficient of variation (CV) of 1.5%, a maximum bias of 0.65% and a maximum total error of 3.0%. The ov erall imprecision for all laboratories was in the range of 0.7 to 1.3%, and was thus below the proposed specification of 1.5%. However, two laboratori es reported 12 and 13 quadruplicates with CVs exceeding this limit. The mea n bias (expressed as deviation from the overall mean of all laboratories) f or all reference laboratories was < 0.65%. In the lower concentration range , however, one laboratory exceeded this limit. No laboratory measured sampl es with a total error above 3.0%. From these results, it can be concluded t hat the reference measurements, and, thus, also the reference methodologies , based on ion chromatography and flame atomic emission spectrometry were e quivalent, and able to satisfy current analytical specifications for serum potassium measurements.