Ahmed, Zeeshan Ansar

Khan, Noor Rahman

Shaikh, Muhammad Shariq

English

eCommons@AKU

eCommons@AKUDepartment of Pathology and Laboratory Medicine Medical College, PakistanApril 2018Adequacy of platelet counting by automatedhaematology analyzers: An insight on currentmethodologiesMuhammad Shariq ShaikhAga Khan University, muhammad.shariq@aku.eduNoor Rahman KhanAga Khan UniversityZeeshan Ansar AhmedAga Khan University, zeeshan.ansar@aku.eduFollow this and additional works at: https://ecommons.aku.edu/pakistan_fhs_mc_pathol_microbiolPart of the Hematology Commons, and the Pathology CommonsRecommended CitationShaikh, M. S., Khan, N. R., Ahmed, Z. A. (2018). Adequacy of platelet counting by automated haematology analyzers: An insight oncurrent methodologies. Journal of the Pakistan Medical Association, 68(4), 675-676.Available at: https://ecommons.aku.edu/pakistan_fhs_mc_pathol_microbiol/727Madam, in normal haemostasis, the platelets along withblood vessels and coagulation proteins are the keybiological components required to arrest bleeding froman injured blood vessel. Platelets are cytoplasmicfragments of megakaryocytes of the bone marrow andhave a diameter of 1-3µm with mean platelet volume(MPV) of 2-20 femtoliter (fL). Approximately 70 to 80 %of platelets circulate in the blood, 20 to 30 % are pooledin the spleen. A normal platelet count ranges from150,000 to 410,000 platelets per microliter of blood.Platelet count is one of the three important cell lineagesthat are stated in every complete blood count (CBC)report. In several clinical conditions, important clinicaldecisions are based on platelet count reported by thelaboratory. This is particularly important in patientswho are at risk of bleeding where judicious transfusioncan save the patient's life.Both The International Council for Standardization inHaematology (ICSH) and the International Society ofLaboratory Haematology (ISLH) recommend flowcytometric enumeration of platelets utilizingmonoclonal antibodies directed against plateletantigens as a reference method (IRM).1 However, owingto its high cost and rather complicated methodology,this method is not routinely available and restricted to arelatively smaller number of laboratories. In under-developed countries like Pakistan with limited healthresources, utilization of methods which are more cost-effective and require minimal technical expertiseshould be utilized. Other methods for plateletestimation in use include 1) microscopy using ahaemocytometer, 2) impedance method and 3)fluorescent optical method.In impedance measurement, cells are made to pass oneafter the other through a capillary opening. Theresistance produced by the passing cell is measured aselectronic signal which is directly proportional to thesize of cell.  Whereas in fluorescent optical method,platelet RNA is first stained with a fluorescent dyefollowed by flow cytometric counting utilizing semi-conductor laser technology. Due to high specificity offluorescent dye for platelet RNA, accurate and preciseestimation of platelets is obtained regardless of the sizeof platelets or presence of other interferingsubstances.2Based on differences in principles of two methods,fluorescent optical method is specifically indicatedwhere interferences in impedance method may lead toinaccurate platelet counts. These conditions includepresence of: 1) reticulated and large/giant platelets as inBernard-Soulier syndrome, Gray platelet syndrome,essential thrombocythemia and immunethrombocytopenia 2) fragments of white and red bloodcells2 as in myelodysplastic syndromes andmicroangiopathic haemolytic anaemias likedisseminated intravascular coagulation and thromboticthrombocytopenic purpura / Haemolytic uremicsyndrome (TTP/HUS), 3) significant RBC microcytosis as insevere iron deficiency anaemia and thalassemiasyndromes.3 Other interferences that may produceinaccurate platelet counts by impedance method includemicro clots, blood parasites and reagent contamination.Since fluorescent dye in optical method binds specificallyto platelet RNA, accurate platelet count is obtained indisorders of platelet granules as well. Good correlationbetween fluorescent optical method and IRM has beenreported for platelet counts up to 30,000 per microliter ofblood.4 Additionally, Coefficient of variation (CV) valuesof less than 5% for samples with platelet count less than20,000 per microliter of blood are well documented inthe literature.4,5Although, majority of currently available analyzers areequipped with impedance technique, fluorescentoptical technique is increasingly being incorporated innewer models. When both the techniques are present inthe same analyzer, software can automatically switchbetween the two based on pre-defined criteria. Thus, incompliance with good laboratory practice, accurateplatelet count can be reported 24/7.Vol. 68, No. 4, April 2018675LETTER TO THE EDITORAdequacy of platelet counting by automated haematology analyzers: An insighton current methodologiesMuhammad Shariq Shaikh, Noor Rahman Khan, Zeeshan Ansar AhmedAga Khan University, Karachi.Correspondence:Muhammad Shariq Shaikh.Email: muhammad.shariq@aku.eduDisclaimer: The manuscript has not been previouslypresented or published in a conference and was notpart of a research, PhD or thesis project.Conflict of Interests: The authors declare no conflict ofinterest.Funding Sources: None.References1. International Council for Standardization in HaematologyExpert Panel on Cytometry and International Society ofLaboratory Hematology Task Force on Platelet Counting.Platelet Counting by the RBC/Platelet Ratio Method AReference Method. Am J Clin Pathol 2001; 115: 460-4.2. Wada A, Takagi Y, Kono M, Morikawa T. Accuracy of a NewPlatelet Count System (PLT-F) Depends on the StainingProperty of Its Reagents. PLoS One 2015; 10: e0141311.3. Pan LL, Chen CM, Huang WT, Sun CK. Enhanced Accuracy of OpticalPlatelet Counts in Microcytic Anemia. Lab Med 2014; 45: 32-6.4. Briggs C, Longair I, Kumar P, Singh D, Machin SJ. Performanceevaluation of the Sysmex haematology XN modular system. JClin Pathol 2012; 65: 1024-30.5. Schoorl M, Schoorl M, Oomes J, van Pelt J. New fluorescentmethod (PLT-F) on Sysmex XN2000 hematology analyzerachieved higher accuracy in low platelet counting. Am J ClinPathol 2013; 140: 495-9.J Pak Med Assoc676 M. S. Shaikh, N. R. Khan, Z. A. Ahmed

Adequacy of platelet counting by automated haematology analyzers: An insight on current methodologies

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Adequacy of platelet counting by automated haematology analyzers: An insight on current methodologies

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