Which of the following would not contribute to an elevated ESR result?

An elevated erythrocyte sedimentation rate (ESR) indicates inflammation or other conditions affecting blood components. In this context, the factor that does not contribute to an elevated ESR is polycythemia.

Polycythemia is a condition characterized by an increased number of red blood cells in circulation. This increase can lead to increased blood viscosity, which may actually make the red cells settle more slowly, resulting in a lower ESR rather than an elevated one. The tendency for red blood cells to aggregate and form stacks (rouleaux formation) is reduced when they are fewer in number proportionally, as seen in polycythemia.

In contrast, macrocytes, or enlarged red blood cells, can lead to an increased ESR due to their altered shape and increased surface area, which can promote aggregation. High fibrinogen levels also contribute to a higher ESR because fibrinogen, a protein involved in blood clotting, promotes the sticking together of red blood cells. Retention of blood cells can cause them to sediment more quickly, indirectly correlating with a higher ESR.

Understanding the biological mechanisms behind these conditions is crucial, as it illustrates how blood components interact and how specific pathologies influence laboratory results like the ESR.