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Concordance between platelet counts by impedance and optical technique during microcytic anemia: towards a threshold
Mayssa Ben Ayed1,2,3, Bochra Gharbi4,2, Eya Jaouachi4,2
1La Rabta University Hospital Center, Hematology department, Tunis, Tunisia.
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 literature 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.
Insights
In microcytosis cases, impedance platelet counts may be inaccurate. Optical platelet counts are recommended for MCV < 72.9 fL or when schizocytes are present for reliable results.
Area of Science:
- Hematology
- Clinical Pathology
- Laboratory Medicine
Background:
- Platelet count is critical for clinical decisions.
- Impedance-based platelet counts (PLT-I) can overestimate platelet levels in microcytic conditions.
Purpose of the Study:
- Compare impedance (PLT-I) and optical (PLT-O) platelet counting techniques.
- Determine a Mean Corpuscular Volume (MCV) threshold for utilizing PLT-O.
Main Methods:
- Prospective analytical study over two months.
- Collected blood samples in K2 EDTA tubes for complete blood count analysis.
- Utilized Sysmex-XN1000 for PLT-O analysis in channel-Ret mode.
- Recorded fragmented red cells (FRC%) and microcytic red cells (Micro-R%).
- Examined blood smears for interfering particles.
Main Results:
- Strong correlation between PLT-I and PLT-O (r=0.971 for all, r=0.90 for PLT <150 x 10^9/L).
- Bland-Altman analysis showed a bias of 16.53 x 10^9/L.
- An MCV cut-off of 72.9 fL demonstrated promising performance for recommending PLT-O.
- Less favorable results were observed with Micro-R% analysis.
Conclusions:
- Impedance platelet counting is suitable for routine use.
- Employ PLT-O for validation when MCV < 72.9 fL or schizocytes are detected.
- Optical method enhances accuracy in specific microcytic scenarios.
