A novel method to estimate platelet counts from peripheral smears: A study comparing a new method of platelet estimation with existing methods.

Background: Automated hematology analyzers have a low degree of accuracy in predicting platelet counts in patients with thrombocytopenia. Hence automated platelet counts should be crosschecked by reviewing the peripheral blood smear in cases of thrombocytopenia. However existing methods for platelet count estimation from peripheral blood smears have certain drawbacks. Hence we suggest a new method to estimate platelet count from peripheral smear and compared it with the existing methods. Methods: Platelet count was estimated by four different methods in 200 blood samples and compared with the platelet count obtained from automated analyzer Sysmex XT-1800i. Method A was based on the platelet/Red Blood cell (RBC) ratio in ten oil immersion fields and multiplying it by total RBC count, Methods B, C and D were based on the average number of platelets per oil immersion field. Platelet count was obtained by multiplying by 15000 in Method B, by 20000 in Method C, by hemoglobin value X 1000 in Method D. Results were analyzed by ANOVA, student’s t test and correlation coefficient.Result: Results of Method A had a strong correlation with the automated blood counts (0.973). The results were not significantly different from the automated blood counts (p value of 0.798). Results of other methods were significantly different from automated platelet counts (p<0.05).Conclusion: Platelet count estimation based on platelet/RBC ratio in ten oil immersion fields and total RBC count is a simple and reliable method to estimate platelet counts from peripheral smears. DOI: 10.21276/apalm.2017.1159