In polycythemia, which parameter is increased?

In polycythemia, which parameter is increased?

• A. White blood cell count
• B. Platelet count
• C. Hematocrit
• D. Serum iron

Answer: (C)

In polycythemia, the red blood cell mass is increased. Hematocrit is the fraction of blood volume made up by red blood cells, so when RBC mass rises, hematocrit rises as well. While white blood cell count and platelet count can be variable in some forms of myeloproliferative disorders, they are not the defining increase of polycythemia. Serum iron is not characteristically elevated and can be normal or low due to iron use for making more red cells. Therefore, the parameter that increases is hematocrit.

In polycythemia, the red blood cell mass is increased. Hematocrit is the fraction of blood volume made up by red blood cells, so when RBC mass rises, hematocrit rises as well. While white blood cell count and platelet count can be variable in some forms of myeloproliferative disorders, they are not the defining increase of polycythemia. Serum iron is not characteristically elevated and can be normal or low due to iron use for making more red cells. Therefore, the parameter that increases is hematocrit.