Comparison of platelet counts by sysmex XE 2100 and LH-750 with the international flow reference method in thrombocytopenic patients

BACKGROUND: There are several methods for counting platelets, of which the international flow reference method (IRM) is considered to be the gold standard. We compared the platelet count given by this method to the count given by automated analyzers using other methods, such as optical fluorescence and impedance. AIMS: The aim of this study is to compare the platelet counts obtained by Sysmex XE 2100 by Impedance (Sysmex-I), optical florescence (Sysmex-O) and reported (Sysmex-R) based on the switching algorithm and LH-750 by Impedance (LH-750) with the IRM in thrombocytopenic blood samples. To calculate the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of various technologies at the clinically relevant transfusion thresholds of 10 × 10 9 /l and 20 × 10 9 /l. MATERIALS AND METHODS: A total of 118 blood samples with platelet count of <50 × 10 9 /l were selected for the study. Platelet counts of all samples were analyzed by all methods using the Sysmex analyzer, LH-750 and IRM in parallel within 6 h of collection. STATISTICAL ANALYSIS USED: Pearson correlation, bland Altman analysis, sensitivity and specificity, PPV and NPV. RESULTS AND CONCLUSIONS: Sysmex-R had the least Bias and 95% limits of agreement (95%LA) range and thus correlated best with IRM values. LH-750 had a higher Bias compared to Sysmex-O and Sysmex-R, but a strikingly similar 95% LA ensures similar results in all three methods. In fact, in the oncology subset, it had the narrowest 95% LA, which made it the best performer in this subgroup. Of the three Sysmex results, Sysmex-I had the highest bias, widest 95% LA and highest potential risk of over transfusion. Hence, Sysmex-R and LH-750 were found to be reliable tools for estimation of platelet count in thrombocytopenic patients.