Concordance between platelet counts by impedance and optical technique during microcytic anemia: towards a threshold value of the mean corpuscular volume

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Figure 4. ROC curve of A, MCV and B, micro-R
Published May 30, 2024
https://doi.org/10.62438/tunismed.v102i6.4834
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Vol. 102 No. 6 (2024): Tunis med jun 2024

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Mayssa Ben Ayed
Hematology department, La Rabta University Hospital Center, Tunis, University of Tunis El Manar Faculty of Medicine of Tunis, Tunis, Tunisia
Bochra Gharbi
Higher School of Health Sciences and Techniques of Tunis, University of Tunis El Manar, Tunis, Tunisia
Eya Jaouachi
Higher School of Health Sciences and Techniques of Tunis, University of Tunis El Manar, Tunis, Tunisia
Hela Baccouche
Hematology department, La Rabta University Hospital Center, Tunis, University of Tunis El Manar Faculty of Medicine of Tunis, Tunis, Tunisia
Sonia Mahjoub
Hematology department, La Rabta University Hospital Center, Tunis, University of Tunis El Manar Faculty of Medicine of Tunis, Tunis, Tunisia
Aya Chakroun
Hematology department, La Rabta University Hospital Center, Tunis, University of Tunis El Manar Faculty of Medicine of Tunis, Tunis, Tunisia

Abstract

Introduction: Platelet count is crucial for clinical decision. In cases of microcytosis, platelet count based on impedance technique (PLT-I) may overestimate platelet count.


Aim: To compare PLT-I with platelet count using the optical technique (PLT-O) and establish a Mean Corpuscular Volume (MCV) threshold for considering PLT-O.


Methods: A prospective analytical study conducted over two months involved blood samples collected in standard K2 EDTA tubes for complete blood count analysis, revealing microcytosis (MCV<80 fL). PLT-O analysis in channel-Ret mode was performed using the Sysmex-XN1000 (Sysmex Corporation, Kobe, Japan).Percentage of fragmented red cells(FRC%) and percentage of microcytic red cells(Micro-R%) were recorded. Blood smears stained with May-Grünwald-Giemsa were examined for potential interfering particles.


Results: A strong correlation was observed between the two techniques for all platelet values as well as for PLT <150 x 109/L (correlation coefficient r = 0.971, 95% CI: [0.956-0.982]; P<10-3 and r = 0.90, 95% CI: [0.79-0.95]; P< 10-3). The Bland-Altman plot revealed a bias of 16.53 x 109/L between the two methods, with agreement limits between -55.8 and 88.8 x 109/L. A threshold MCV value indicating the use of the optical method, with a cut-off at 72.9fL, demonstrated promising performance consistent with litterature findings. However, less favorable performance was observed with Micro-R%.


Conclusion: Impedance could be employed in routine practice. However, for MCV<72.9 fL or in the presence of schizocytes, the hemogram validation procedure may incorporate the use of PLT-O.

Keywords:

platelets, impedance, optic , microcytosis, mean corpuscular volume, anemia

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