Knowledge Check

True of false: the terms erythrocytosis and polycythemia are generally used interchangeably.

Red cell mass is rarely measured directly.

What 2 surrogate markers are used for red cell mass?

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1. Hb
2. Hct

Hemoglobin (Hb) and hematocrit (Hct) are expressed as weight of Hb or volume of red cells per volume of blood. Therefore, Hb and Hct values can increase in one of two ways:

1. The weight of Hb or the volume of red cells increase relative to the volume of plasma (increased numerator).
2. The volume of plasma decreases relative to the weight of Hb or volume of red cells (decreased denominator).

What terms are used to describe these two varieties of polycythemia?

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1. Absolute polycthyemia
2. Relative polycythemia

What is the difference between primary and secondary polycythemia/erythrocytosis?

What is Gaisbock’s Syndrome?

(see next slide)

• First described in 1905
• AKA:
  • Gaisbock’s polycythemia
  • Pseudo-polycythemia
  • Polycythemia of stress
  • Stress erythrocytosis
  • Polycythemia hypertonica
• Originally described as a syndrome of true polycythemia characterized by an elevation in hematocrit and presence of hypertension.
• Now refers to a type of relative polycythemia associated with normal red cell mass and decreased plasma volume.
• Risk factors include:
  • Male sex
  • Hypertension
  • Smoking
  • Diuretic therapy
  • Obesity
  • Emotional or physical stress
• Of these, hypertension (particularly diastolic hypertension) appears to be the most significant contributor to the polycythemia of Gaisbock’s syndrome

Additional reading:

• Arch Intern Med 1965;116:4-9
• Cardiol Rev 2022 Feb 7. doi: 10.1097

True or false: Gaisbock’s polycythemia can be thought of a chronic form of relative polycythemia, as distinct from transient causes such as as diarrhea, vomiting and diuretics.