Multi-site comparison of Yumizen H2500 Large Platelet Fraction quantified by optical extinction method with Sysmex XN Immature Platelet Fraction measured by fluorescence method

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Marion EVEILLARD¹, Mathias CHEA², Eldad HOD³, Michelle HEGE⁴, Andrea TORRES⁴, Desrick J. PINKNEY⁴, Amin MOHAMMAD^{4
1}Nantes University hospital (FRANCE), ²Nîmes University hospital (FRANCE), ³Columbia University Irving Medical Center (USA), ⁴Baylor Scott & White Healthcare (USA)

Introduction

Platelets are involved in many different biological processes. Indeed, circulating platelets mainly differ by size and density. The normal range for platelet size is between 5-10 fL. Therefore, Large Platelet Fraction (LPF) corresponds to the platelet population with a size superior to 20 fL.
This population is mostly composed of large young platelets also called reticulated platelets or immature platelets in physiological situation.
These newly large released platelets in blood flow are thought to be more reactive.
In this multicentric study, we evaluated the LPF count accuracy of the HORIBA Yumizen H2500 analyzers compared to the SYSMEX XN-10 Immature Platelet Fraction (IPF) on whole blood samples from pediatric and adult patients. Because no international reference method exists yet to count large platelets, we performed a method comparison between the analyzers.

Methods

Yumizen H2500 analyzers count LPF using a combination of resistive (cell volume) and optical extinction measurement into a hydrodynamic focusing flow cell.
The LPF count quantified in the optical chamber is a fluorescent free method. SYSMEX IPF is measured using cell volume and fluorescent dimensions.
This international multicentric study enrolled 794 whole blood samples (from 4 different hospitals centers: Nantes, Nîmes, New York, Baylor).

Results

Once all outliers (flagged results) sorted from statistics (as defined by CLSI EP09c), 655 samples were analyzed. All LPF results are between 0.4 to 23.3% (13% of patients are lower than 2% LPF, 55% from 2 to 10% LPF, 19% from 6 to 10% LPF and 13% higher than 10% LPF).
The comparison between LPF and IPF showed a good correlation (R²=0.71) as shown in figure 1 and figure 2.

Figure 1: Passing bablok regression on 655 samples

Figure 2: Bland Altman plots on 655 samples

Conclusion

Due to the absence of international reference method to measure the proportion of large platelets, customers can only rely on inter-analyzer comparison to assess the accuracy of the large platelet count.
LPF/IPF comparison results demonstrated a good correlation between optical and fluorescent methods highlighting the interchangeability between both analyzers for clinical utility and desired applications.

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