Impedance platelet count in severe microcytosis - study of 161 patients

IntroductionPlatelet count estimation is an important element of the diagnostic and treatment process in many disorders. The present study aims to determine the incidence of improper impedance platelet count in severe microcytosis and to state the sensitivity and specificity of various parameters like histogram, red cell distribution width (RDW), mean platelet volume (MPV), platelet flags Methods-Total 161 patients with mean corpuscular volume less than 60 femtoliter and impedance platelet count more than 150 x 10 /L were included. The samples were analyzed on CellDyn 3700 cell counter. Manual platelet count and stained peripheral smear review was done in each case. ROC (Receiver Operating Characteristics) analysis was used for MPV, RDW and histogram. Results-18.01 %(29/161) patients did not show corelation between impedance and manual platelet count. For “Do not corelate” group mean platelet volume(>12.7 femtoliter)showed 79.55% specificity and 55.17% sensitivity, Abnormal Platelet/RBC histogram(>40%) showed 76.51% specificity and 51.72 % sensitivity and RDW > 27 % showed 87.12 % sensitivity and 37.93 % specificity. Conclusion-Impedance platelet count is not always reliable in cases of severe microcytosis. Abnormal MPV and RBC/platelet histogram gives good hint for the same.