Due to technological advancements, haematology analysers are becoming increasingly more complex. Before introducing new analyzers, laboratories must compare the agreement between the new and the old instruments. This study aimed to quantify the method agreement between Sysmex XT-4000i and Alinity hq analysers in order to establish whether they can be used interchangeably. A total of 415 complete blood counts (CBC) from adult patients of the Emergency Clinical County Hospital of Târgu Mureș, Romania, were analysed within 4 h from the collection on Sysmex XT-4000i (considered the reference method), then on Alinity hq. Statistical analysis consisted of outlier removal, Spearman Correlation, Bland-Altman test, and Passing-Bablok regression. For each CBC parameter, the analytical difference between methods was compared with the Reference Change Value (RCV) at medical decision levels (MDL). Despite using different technologies, the instruments have a good agreement regarding cell differentiation and counting. Cell counting and haemoglobin measurement showed a good agreement at all (Medical Decision Limits) MDLs. The analytical difference between methods surpassed the (Reference Change Value) RCV with 1.2% at the 14% MDL of HCT and with 0.2% at the 100 fL MDL of MCV. This study can not tell whether Sysmex or Alinity is superior, only if the two methods agree. The poorer agreement observed for RBC indices, especially MCHC, suggests an accumulation of differences caused by the different working principles of the two methods. However, it is reasonable to assume that such small differences will not affect clinical decision-making and patient outcome.
Keywords: Total quality management; complete blood counts; hematology; laboratory critical values; validation study.