Packed Cell Volume (PCV)

Function

Packed Cell Volume (PCV), also known as hematocrit (Hct), measures the proportion of whole blood that is made up of red blood cells (RBCs). Its primary function is to assess the blood's ability to transport oxygen throughout the body. Because RBCs contain hemoglobin, which binds to oxygen, the PCV is a critical indicator of oxygen-carrying capacity.

Why it is Ordered

Physicians order a PCV test to screen for, diagnose, or monitor conditions affecting the red blood cells. It is a standard part of a Complete Blood Count (CBC). It is essential for:

• Evaluating unexplained fatigue, weakness, or pale skin (anemia).
• Monitoring patients with chronic lung or heart disease.
• Assessing dehydration levels.
• Checking for polycythemia vera (overproduction of RBCs).
• Monitoring response to treatments like erythropoietin or blood transfusions.

Associated Conditions

Abnormal PCV levels are associated with several clinical states. Low PCV is the hallmark of anemia, which can be caused by iron deficiency, B12/folate deficiency, chronic kidney disease, or blood loss. High PCV, or erythrocytosis, may indicate primary polycythemia vera or secondary causes like chronic hypoxia (common in smokers or high-altitude residents), dehydration, or erythropoietin-secreting tumors. Monitoring PCV is vital in trauma cases to assess internal bleeding and fluid resuscitation needs.