Complete Blood Count (CBC) Overview

Complete Blood Count (CBC)

• A CBC is a blood test used to assess overall health and identify various conditions like anemia and leukemia.
• It measures the number of all blood components, including red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.
• The CBC is a crucial part of any patient's complete blood work.

Red Blood Cell Count

• A red blood cell count (RBC count), or erythrocyte count, measures the number of red blood cells in the blood.
• This test is important because red blood cells contain hemoglobin, which carries oxygen throughout the body.
• Lower or higher than normal RBC counts can indicate potential medical issues.

Packed Cell Volume (PCV)

• Also known as Hematocrit (Hct).
• It's a measurement of the percentage of red blood cells in a blood sample.
• Commonly determined by centrifuging a blood sample and measuring the volume of red blood cells in relation to the total volume of the sample.
• Normal PCV ranges vary based on age, sex.

Why CBC and PCV are Performed?

• Part of a complete blood count (CBC) along with hemoglobin concentration.
• Simple screening test to check for anemia problems.
• To accurately measure Hemoglobin.
• To calculate a number of blood indices such as MCV, MCH, MCHC.

Microhematocrit Method

• A method used to estimate PCV using a capillary tube, centrifuge, and a reader to measure the percentage of red blood cells in the sample.
• Specific materials and instruments are needed to ensure accuracy of the method.

Principle of PCV Estimation

• Uncoagulated blood sample is centrifuged, separating the blood components into layers (plasma, buffy coat, packed red blood cells).
• The PCV is read directly from the graphic reader.
• The reading is presented in percentage.

Procedure for PCV Estimation

• Fill a heparinized capillary tube with blood up to 80% of its length.
• Seal one end of the capillary tube with clay.
• Centrifuge the tube for 3-5 minutes
• Use a graphic reader, or another appropriate method, to obtain the PCV reading, which is expressed in percentage.

Factors Affecting Test Accuracy

• Living at high altitudes, pregnancy, recent blood loss, blood transfusion, or severe dehydration can affect hematocrit test results.
• These factors may lead to inaccurate or misleading results.

Difference Between Hemoglobin and Hematocrit

• Hemoglobin is a protein; hematocrit is a measurement.
• Hemoglobin is part of hematocrit. Hematocrit measures the volume of red blood cells in total blood.
• Their values generally correlate (if one is low, the other is likely low too).

Physiological Causes of Increased/Decreased PCV

• Increased PCV: Chronic oxygen deprivation (high altitude), dehydration, immediately after exercise.
• Decreased PCV: Hemodilution (excess fluid in blood), pregnancy.

This quiz covers the essentials of Complete Blood Count (CBC) and its components, including red blood cell count, packed cell volume, and their significance in assessing health. Familiarize yourself with key terms and the importance of these measurements in diagnosing conditions like anemia and leukemia.