Multicenter verification of the Sysmex XN-Series

Verification of hemocytometry equipment deviates significantly from that of clinical chemistry equipment due to the absence of appropriate control material and the need for fresh material. In practice, verification is limited to comparison with the previously used equipment and determination of reproducibilities. Particularly in multicenter settings, harmonization of results is necessary. If the same equipment is used in several laboratory departments, calibration and uniformity are important issues.

In this study, seven Sysmex XN hematology modules distributed over three laboratories were evaluated with the same set of samples (n=160).

Results of each Sysmex XN hematology module were compared with the results of the Sysmex XE-2100 hematology analyzer using linear regression. Although excellent correlation coefficients were obtained, in many cases the criteria for slope and/or intercept were not met. Therefore, the same data were analyzed with Bland-Altman difference plots with three times the specified CV% of the parameter as limits of agreement. At least 90% of the determinations per parameter and per module must comply with those limits of agreement. Almost all parameters on each module fulfilled these criteria, and only RBC and Ht from respectively two and four XN modules had to be recalibrated. Reproducibility of each parameter was determined 10 times in patient samples with low, normal, and high levels. Reproducibility of all parameters was within the specifications of the manufacturer and the biological variability.

With this straightforward method, all seven Sysmex XN hematology modules demonstrated uniform results, which were identical to those of the previously used Sysmex XE-2100 hematology analyzer, the performance of which was well known.