Role of peripheral blood smear examination and manual platelet counts as an adjunct to automated platelet counts

Abstract

Background: Assessment of platelet counts are an important part of the routine assessment of patients, especially in bleeding disorders, thrombocytopenia, and infections such as Dengue fever, which are associated with extremely low platelet counts. The platelet counts by automated Hematology counters are generally accurate, but at times, the machine cannot differentiate between platelets and non – platelet particles such as fragments of WBC, RBC and cellular debris. Objective: We estimated the accurate platelet counts obtained by automated machine using impedance technology, after verification with platelet counts obtained by assessment of peripheral blood smears and manual counts using Neubauer chamber. Methods: Blood samples of 236 patients reported to Malla Reddy Hospital Suraram Hyderabad, from 27 May 2019 to 09 June 2019 were studied. Patients were in the age of 4 days to 85 years, of both genders and had platelet counts below 1.5 × 103 / μl, estimated by Sysmex XNL 350. The counts thus obtained were verified by evaluation of Giemsa stained peripheral blood smears and manual platelet counts using improved Neubauer chamber. Results: The study revealed discordance between the machines generated platelet counts and manually evaluated platelet counts in 71 samples. In 63 samples the counts by Sysmex machine were lower than actual counts obtained by manual evaluation by a factor of 4 – 106 × 103/μl. In only 8 samples, the machine generated count was higher than the manual count by a similar factor. Conclusion: It is mandatory to verify abnormal platelet counts obtained by automated hematology analyzers, by examination of peripheral blood smears and manual counts using improved Neuberger's chamber.

Keywords

• accuracy of platelet counts
• pseudo thrombocytopenia
• platelet satellitism
• myloproliferative neoplasm
• giant platelets