From the Guidelines
Elevated Hematocrit (Hct) and Mean Corpuscular Volume (MCV) levels are indicative of macrocytic polycythemia, a condition that requires prompt medical evaluation to determine the underlying cause and prevent potential complications, such as blood clots, which can significantly impact morbidity and mortality. The most recent and highest quality study, 1, suggests that targeting hematocrit levels to <45% can lower the risk of thrombosis in patients with polycythemia vera (PV).
Some common causes of high hematocrit and MCV levels include:
- Dehydration
- Smoking
- High altitude exposure
- Certain lung diseases
- Polycythemia vera (a bone marrow disorder)
- Vitamin B12/folate deficiency
If you have these abnormal lab values, you should consult with a healthcare provider promptly for proper diagnosis and treatment. Your doctor will likely order additional tests, such as:
- Complete blood count
- Peripheral blood smear
- Vitamin B12 and folate levels
- Possibly bone marrow examination
Treatment depends on the underlying cause, but may include:
- Phlebotomy (blood removal) to reduce blood thickness if hematocrit is dangerously high
- Smoking cessation
- Hydration
- Specific treatments for identified conditions
- For vitamin deficiencies, supplementation would be prescribed (typically vitamin B12 1000 mcg daily or folate 1-5 mg daily), as supported by previous guidelines 1.
It is essential to address these elevated values, as they can increase the risk of blood clots, which can have significant implications on morbidity and mortality, as highlighted in the study 1. Symptoms like headaches, dizziness, visual disturbances, or redness of skin should prompt immediate medical attention, as they may indicate complications requiring urgent intervention.
From the Research
Implications of Elevated Hematocrit (Hct) and Mean Corpuscular Volume (MCV) Levels
- Elevated Hematocrit (Hct) levels are associated with an increased risk of thrombosis, as stated in the study 2.
- An increased Hct can be caused by primary proliferative polycythemia, secondary polycythemia, relative polycythemia, or modifications of the red cell mass and plasma volume within their normal ranges 2.
- Hematocrit control below 45% is associated with a lower rate of thrombosis in polycythemia vera, as found in the study 3.
- Patients with polycythemia vera who require frequent phlebotomies have a higher risk of thrombosis and may need adjusted treatment, as shown in the study 3.
- Elevated Mean Corpuscular Volume (MCV) levels can be caused by various factors, including drug therapy, alcohol, liver disease, and reticulocytosis, as reported in the study 4.
- MCV values greater than 120 fL are usually caused by cobalamin deficiency, as stated in the study 4.
- The clinical significance of high MCV values can be difficult to establish, but they are often associated with underlying medical conditions, as discussed in the study 5.
- The need for blood volume studies is questionable in patients with obvious clinical or biological signs suggestive of polycythemia, but may be useful in patients with an increased hematocrit and no other clinical or biological signs, as mentioned in the study 2.