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


Mayssa Ben Ayed
Bochra Gharbi
Eya Jaouachi
Hela Baccouche
Sonia Mahjoub
Aya Chakroun


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.


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



  1. Schved JF, Monneret I, Levayer T, Lavabre-Bertrand C, Taib J. Étude des différentes méthodes de numération plaquettaire au laboratoire.: Application aux thrombopénies sévères. Rev Fr Lab. 1999;1999(312):95‑8.
  2. Lakos G, Mukhtar Z, Masi L, Valente S, Papa F. Alinity hq platelet count is not impacted by severe microcytosis. J Clin Lab Anal. 2022;36(4):e24218.
  3. Hummel K, Sachse M, Hoffmann JJML, van Dun LPJM. Comparative evaluation of platelet counts in two hematology analyzers and potential effects on prophylactic platelet transfusion decisions. Transfusion (Paris). 2018;58(10):2301‑8.
  4. Bavani s. Influence of Red Cell Microcytosis in the Accuracy of Platelet Counting by Automated Methods. Journal of Pharmaceutical Sciences and Research. 2019 [cité 11 déc 2023]; Disponible sur:
  5. Salignac S, Latger-Cannard V, Schlegel N, Lecompte TP. Platelet counting. Methods Mol Biol Clifton NJ. 2013;992:193‑205.
  6. Boulassel MR, Al-Farsi R, Al-Hashmi S, Al-Riyami H, Khan H, Al-Kindi S. Accuracy of Platelet Counting by Optical and Impedance Methods in Patients with Thrombocytopaenia and Microcytosis. Sultan Qaboos Univ Med J. 2015;15(4):e463-468.
  7. Tantanate C. Comparison of Impedance Platelet Count by Sysmex XE-5000 and Beckman Coulter LH 780 with Optical Fluorescent Platelet Count in Thalassemia Patients. Siriraj Med J. 2017;69(5):276‑82.
  8. Briggs C, Harrison P, Machin SJ. Continuing developments with the automated platelet count. Int J Lab Hematol. 2007;29(2):77‑91.
  9. Pan LL, Chen CM, Huang WT, Sun CK. Enhanced accuracy of optical platelet counts in microcytic anemia. Lab Med. 2014;45(1):32‑6.
  10. Pinkowski, R. Difference between impedance and optical platelet count methods in patients with microcytosis of red blood cells. Lab Hematol 5 22-27.
  11. Schoorl M, Schoorl M, Oomes J, van Pelt J. New fluorescent method (PLT-F) on Sysmex XN2000 hematology analyzer achieved higher accuracy in low platelet counting. Am J Clin Pathol. 2013;140(4):495‑9.
  12. Johannessen B, Haugen T, Stephen Scott C. Standardisation of platelet counting accuracy in blood banks by reference to an automated immunoplatelet procedure: comparative evaluation of Cell-Dyn CD4000 impedance and optical platelet counts. Transfus Apher Sci. 2001;25(2):93‑106.
  13. Tantanate C, Khowawisetsut L, Pattanapanyasat K. Performance Evaluation of Automated Impedance and Optical Fluorescence Platelet Counts Compared With International Reference Method in Patients With Thalassemia. Arch Pathol Lab Med. 2017;141(6):830‑6.
  14. Briggs C, Kunka S, Machin SJ. The most accurate platelet count on the Sysmex XE-2100. Optical or impedance? Clin Lab Haematol. avr 2004;26(2):157‑8.
  15. Cid J, Nascimento JD, Vicent A, Aguinaco R, Escoda L, Ugarriza A, et al. Evaluation of low platelet counts by optical, impedance, and CD61-immunoplatelet methods: estimation of possible inappropriate platelet transfusion. Transfusion (Paris). 2010;50(4):795‑800.