Which factor does NOT influence the erythrocyte sedimentation rate (ESR)?

The erythrocyte sedimentation rate (ESR) is influenced by various factors, primarily related to the properties of the blood components and the conditions under which the blood sample is collected and processed.

When blood is drawn into a sodium citrate tube, the anticoagulant helps preserve the sample but does not directly influence the sedimentation rate itself. The ESR is generally impacted by factors such as the shape and size of erythrocytes (red blood cells), the viscosity of the plasma, and the concentration of certain plasma proteins—especially acute-phase reactants.

In contrast, anisocytosis and poikilocytosis, which refer to variations in the size and shape of red blood cells, respectively, can have a significant effect on how quickly the cells settle in a stationary state. Plasma proteins, particularly fibrinogen and immunoglobulins, also play a crucial role as they can increase the aggregation of red blood cells, thereby affecting the ESR.

The caliber of the tube used for the ESR test matters because wider tubes may produce different sedimentation outcomes compared to narrower ones due to variations in how cells interact within the tube.

Thus, while the choice involving sodium citrate relates to sample handling and anticoagulation rather than direct influence on