hematocrit (Hct, Packed red blood cell volume, Packed cell volume [PCV])
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p487-489
2025-05-25
696
Type of test Blood
Normal findings
Male: 42%-52% or 0.42-0.52 volume fraction (SI units)
Female: 37%-47% or 0.37-0.47 volume fraction (SI units)
Pregnant female: > 33%
Elderly: values may be slightly decreased
Children (%)
Newborn: 44-64 , 2-8 weeks: 39-59 , 2-6 months: 35-50 , 6 months-1 year: 29-43 1-6 years: 30-40 6-18 years: 32-44
Possible critical values
< 15% or > 60%
Test explanation and related physiology
The Hct is a measure of the percentage of the total blood volume that is made up by the RBCs. The height of the RBC column is measured after centrifugation. It is compared with the height of the column of the total whole blood (Figure 1). The ratio of the height of the RBC column compared with the original total blood column is multiplied by 100%. This is the Hct value. It is routinely performed as part of a complete blood count. The Hct closely reflects the Hgb and RBC values. The Hct in percentage points usually is approximately three times the Hgb concentration in grams per deciliter when RBCs are of nor mal size and contain normal amounts of Hgb.
Fig1. Tubes showing hematocrit levels of normal blood, blood with evidence of anemia, and blood with evidence of polycythemia. Note the buffy coat located between the packed red blood cells (RBCs) and the plasma. A, Normal percentage of RBCs. B, Anemia (low percentage of RBCs). C, Polycythemia (high percentage of RBCs). WBC, White blood cell.
Abnormal values indicate the same pathologic states as abnormal RBC counts and Hgb concentrations (see next test). Decreased levels indicate anemia (reduced number of RBCs). Increased levels can indicate erythrocytosis. Like other RBC values, the Hct can be altered by many factors, such as hydration status and RBC morphology.
Interfering factors
• Abnormalities in RBC size may alter Hct values.
• Extremely elevated white blood cell counts may affect values.
• Hemodilution and dehydration may affect the Hct level.
• Pregnancy usually causes slightly decreased values because of hemodilution.
• Living in high altitudes causes increased values.
• Values may not be reliable immediately after hemorrhage.
* Drugs that may cause decreased levels include chloramphenicol and penicillin.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: lavender
Abnormal findings
Increased levels
- Congenital heart disease
- Polycythemia vera
- Severe dehydration
- Erythrocytosis
- Eclampsia
- Burns
- Chronic obstructive pulmonary disease
Decreased levels
- Anemia
-Hyperthyroidism
-Cirrhosis
- Hemolytic reaction
-Hemorrhage
-Dietary deficiency
-Bone marrow failure
- Normal pregnancy
-Rheumatoid arthritis
-Multiple myeloma
-Leukemia
-Hemoglobinopathy
-Prosthetic valves
-Renal disease
-Lymphoma
-Hodgkin disease
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