Estimation of platelet counts: auto analyzer versus counts from peripheral blood smear based on traditional and platelet: red blood cell ratio method

Abstract

Introduction: Accurate platelet counts are of utmost importance in clinical practice The methods used for estimating platelet count are: Manual method using counting chamber, Examination of a peripheral blood smear (PBS) and automated hematology analyzers Automated hematology analyzers produce erroneous results in the presence of particles of similar size and/or light scatter like fragmented red blood cells (RBC), microcytic RBCs and in the presence of giant platelets and platelet clumps. Aims and Objectives: Comparison of platelet count by three methods: 1. Automated six part analyzer. Traditional method: Counting average platelets per ten high power fields and multiplying the same by 15,000. 3. From smear by counting the number of platelets per 1000 RBCs and calculating the platelet count on the basis of platelet: RBC ratio. Methods: Ethylene Diamine Tetra-acetic acid (EDTA) samples for platelet counts over a period of two months were analyzed by the above-mentioned methods. Statistical software SPSS 2 and independent T tests were used to compare the variables between the groups. Sensitivity and specificity of the methods was calculated. Results: 250 EDTA samples were analyzed of which normal platelet counts were (56.4%) thrombocytopenic (35.2%) and thrombocytosis (8.4%). There was no significant difference between the platelet counts done by the auto analyzer compared with traditional (P value 0.50) and platelet: RBC ratio method (0.906). Specificity of the methods was 99.1% and the sensitivity was 92.5%. Conclusion: Platelet counts by traditional and platelet: RBC ratio can be used as alternate reliable methods as compared to the auto analyzers.