Accuracy of Platelet Counting by Optical and Impedance Methods in Patients with Thrombocytopaenia and Microcytosis
Journal Title: Sultan Qaboos University Medical Journal - Year 2015, Vol 15, Issue 4
Abstract
Objectives: Obtaining accurate platelet counts in microcytic blood samples is challenging, even with the most reliable automated haematology analysers. Te CELL-DYN™ Sapphire (Abbott Laboratories, Chicago, Illinois, USA) analyser uses both optical density and electronic impedance methods for platelet counting. Tis study aimed to evaluate the accuracy of optical density and electrical impedance methods in determining true platelet counts in thrombocytopaenic samples with microcytosis as defned by low mean corpuscular volume (MCV) of red blood cells. Additionally, the impact of microcytosis on platelet count accuracy was evaluated. Methods: Tis study was carried out between February and December 2014 at the Haematology Laboratory of the Sultan Qaboos University Hospital in Muscat, Oman. Blood samples were collected and analysed from 189 patients with thrombocytopaenia and MCV values of <76 femtolitres. Platelet counts were tested using both optical and impedance methods. Stained peripheral blood flms for each sample were then reviewed as a reference method to confrm platelet counts. Results: Te platelet counts estimated by the impedance method were on average 30% higher than those estimated by the optical method (P <0.001). Te estimated intraclass correlation coefcient was 0.52 (95% confdence interval: 0.41–0.62), indicating moderate reliability between the methods. Te degree of agreement between methods ranged from -85.5 to 24.3 with an estimated bias of -30, suggesting that these methods generate different platelet results. Conclusion: Te impedance method signifcantly overestimated platelet counts in microcytic and thrombocytopaenic blood samples. Further attention is therefore needed to improve the accuracy of platelet counts, particularly for patients with conditions associated with microcytosis.
Authors and Affiliations
Mohamed-Rachid Boulassel| Departments of Allied Health Sciences, Haematology, College of Medicine & Health Sciences, Sultan Qaboos University, Raya Al-Farsi| Department of Haematology, Sultan Qaboos University Hospital, Muscat, Oman, Sulaiman Al-Hashmi| Departments of Genetics, College of Medicine & Health Sciences, Sultan Qaboos University, Hamad Al-Riyami| Departments of Genetics, College of Medicine & Health Sciences, Sultan Qaboos University, Hammad Khan| Department of Haematology, Sultan Qaboos University Hospital, Muscat, Oman, Salam Al-Kindi| Departments of Haematology , College of Medicine & Health Sciences, Sultan Qaboos University
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