Are elevated hemoglobin and hematocrit levels significant?

Evaluation of Elevated Hemoglobin and Hematocrit in a 26-Year-Old

A hemoglobin of 18.1 g/dL and hematocrit of 53.3% in a 26-year-old is significant and warrants further evaluation to rule out pathologic causes of erythrocytosis. 1, 2

Significance of These Values

• These values exceed normal ranges for a young adult, with hemoglobin >18.0 g/dL and hematocrit >52% in males considered elevated and potentially indicative of erythrocytosis 3
• Elevated hemoglobin and hematocrit increase blood viscosity, which can potentially lead to thrombotic complications and impaired tissue perfusion 4
• While these values would be considered normal at high altitude (>4000m), they are abnormal at standard elevation 5

Diagnostic Algorithm

1. First, distinguish between relative and absolute erythrocytosis:

   • Rule out dehydration as a cause of relative polycythemia by assessing hydration status and rechecking CBC after adequate hydration 1, 2
   • If values remain elevated after hydration, proceed with evaluation for absolute erythrocytosis 2

2. Initial laboratory workup should include:

   • Complete blood count with red cell indices and reticulocyte count
   • Serum ferritin, iron, TIBC, and transferrin saturation
   • Erythropoietin level
   • Arterial blood gas analysis (to assess oxygen saturation)
   • C-reactive protein 2

3. If initial workup suggests absolute erythrocytosis:

   • Test for JAK2 mutations (both exon 14 and exon 12) to evaluate for polycythemia vera 2
   • Consider sleep study if nocturnal hypoxemia is suspected 3
   • Evaluate for potential secondary causes (smoking, COPD, sleep apnea, renal disease) 3

Clinical Implications

• Elevated hematocrit increases blood viscosity, which can impair microcirculation and tissue perfusion 4
• Studies have shown that elevated hematocrit is associated with reduced reperfusion and increased risk of thrombotic events 4
• The combination of elevated hemoglobin and hematocrit may indicate an underlying condition requiring treatment 3

Management Considerations

• If dehydration is confirmed as the cause, increasing fluid intake is the appropriate management 1
• For absolute erythrocytosis, management depends on the underlying cause:
  • For primary polycythemia (e.g., polycythemia vera): referral to hematology is indicated 2
  • For secondary causes: treatment of the underlying condition 3
• Therapeutic phlebotomy is generally reserved for significantly higher values (hemoglobin >20 g/dL or hematocrit >65%) with symptoms of hyperviscosity 2

Common Pitfalls and Caveats

• Avoid assuming these values are normal without further investigation, even in an asymptomatic young adult 1, 2
• Hemoglobin and hematocrit should be interpreted together, as discordance between these values can occur in approximately 40-50% of cases 6
• Do not initiate therapeutic phlebotomy based solely on these values without establishing a diagnosis, as unnecessary phlebotomy can lead to iron deficiency 2
• Remember that testosterone use (prescribed or unprescribed) can cause erythrocytosis and should be considered in the differential diagnosis in a young adult 3