Estimation of platelet count from peripheral blood smear based on platelet: red blood cell ratio. A prospective study in a tertiary care hospital

Accurate and reproducible platelet counts is essential for patient management. There are many methods for counting platelets. Study was conducted with the objectives of estimation of platelet count indirectly from peripheral blood smear (PBS) on the basis of platelet: red blood cell (RBC) ratio and using automated RBC count; and to verify the reliability of this method in comparison to automated platelet counts.

A prospective study was conducted in a tertiary care hospital on 200 Ethylene Diamine Tetra Acetic acid (EDTA) anticoagulated blood samples. Samples were evaluated by automated hematology analyser using impedance counting method and by examination of PBS. Number of platelets/1000 RBC in PBS was multiplied by automated RBC count in 10⁶/uL to get an estimate of platelet count in 10³/uL.

Two sample T test showed no significant difference between the two methods. Pearson correlation of the two methods showed high correlation.

Estimation of platelet count on the basis of platelet: RBC ratio is a reliable technique and can be used to validate automated platelet counts.