Clinical performance of Swelab Lumi hematology analyzer compared with reference instrument
Hematological tests can be used to help diagnose and monitor numerous blood-related conditions, including anemia, infections, and certain forms of cancer. Although manual microscopy is often considered the ultimate method for cellular and morphological analyses, automated hematology analyzers are routinely used for complete blood counts (CBC) and white blood cell (WBC) differentials in clinical laboratories. In addition, automated analyzers can provide much more information than a manual count.
Swelab Lumi is a 5-part hematology analyzer from Boule Diagnostics (Figure 1). The analyzer provides information on 29 parameters—20 parameters for in vitro diagnostic (IVD) use and 9 parameters for research use (RUO) only—for the CBC, including red blood cells (RBC) and platelets (PLT), hemoglobin (HGB), and for the 5-part differential of white blood cells (WBC).
Figure 1. Swelab Lumi is an entry-level 5-part hematology analyzer intended for the cost-minded clinical laboratory. The user-friendly design makes system operations easy. Robust software and hardware components ensure a reliable system performance. With its small footprint, Swelab Lumi is well suited for the typical physician office laboratory.
As most hematology analyzers, Swelab Lumi uses electrical impedance for CBC and spectrophotometry for determination of HGB. For the WBC differential, however, measurement methods differ between analyzers. Swelab Lumi uses a tri-angle laser-scatter method for the 5-part differential of WBC (Figure 2).
Figure 2. Swelab Lumi uses laser-based flow cytometry for WBC, with separate channels for 4-part and BASO differential. Low angle signal (about 1° to 5°) represents the cell volume information, middle angle signal (about 7° to 20°) represents the cell nucleus information, high angle signal (about 90°) represents the cell nucleus and cytoplasm information.
This study validates the performance of Swelab Lumi against a reference system for the 20 IVD parameters, using normal and abnormal fresh whole blood samples collected from patients for routine analysis.
Comparison of test and reference systems
The performance of the Swelab Lumi 5-part hematology analyzer (test system) was compared to that of the Sysmex™ XN-1000 5-part hematology analyzer (reference system). Swelab Lumi operates with the same technology as the reference analyzer, except for the WBC differential count, where the reference analyzer uses fluorescence flow cytometry. In general, the results show good correlations and relatively low bias estimates between the test and reference systems, indicating that the systems are in good agreement (Figure 3). Any significant difference in the observed means can most likely be attributed to the different detection and calculation methods between the two systems.
Comparison of test and reference system with manual microscopy
The WBC differential using the test and reference systems agreed well with manual microscopy, except for BASO and MONO. With high WCB counts, it can be difficult for the analyzer to differentiate the subpopulations. As shown for MONO in Figure 4, for example, when removing samples with WBC counts above 50 × 109/L, the correlation between the systems improves. Although a bias between the systems, Swelab Lumi was closer to manual microscopy than the reference system. As laboratories are obliged to establish and maintain reference intervals for measurands, this will mitigate the observed bias.
Figure 4. Agreement of the MONO count between (A) the test and the reference system, (B) the test system and manual microscopy, and (C) the reference system and manual microscopy using samples with WBC < 50 × 109/L (n = 138). In the regression plots, the gray line corresponds to identity (x = y) and the red line corresponds to best fit.