Erythrocyte Sedimentation Rate (ESR) Basics

Erythrocyte Sedimentation Rate (ESR)

• ESR is the rate at which red blood cells sediment when blood is placed vertically in a narrow tube.
• Westergren Apparatus is used to measure ESR, with a calibration of 0-200 mm from above to downward.
• The red cells settle at a faster rate in the presence of increased proteins, particularly immunoglobulins, which neutralize the negative charge of RBCs.
• Normal ESR values are:
  • Males: 4-6 mm/h up to 15 mm/h.
  • Females: 8-10 mm/h up to 20 mm/h (due to lower red cell count).
• ESR is not a specific or diagnostic test, but it confirms the presence or absence of inflammatory activity and monitors its progression or response to treatment.
• ESR increases physiologically in females during pregnancy, menstruation, and lactation.
• ESR increases in pathological conditions such as tonsillitis, fractures, myocardial infarction, and rheumatoid arthritis.

Hematocrit Value (Hct)

• Hematocrit is the percentage of blood volume that is made up of red blood cells.
• Methods for detection include:
  • Macro hematocrit method using a Wintrobe hematocrit tube.
  • Micro hematocrit method using a heparinized microhaematocrit capillary tube.
• Normal hematocrit values are:
  • Males: average 42-52%.
  • Females: average 37-47%.
• Hematocrit increases in dehydration and polycythemia.
• Hematocrit decreases in overhydration and anemia.

Complete Blood Picture (CBC)

• CBC is the calculation of the cellular elements of blood.
• Automated hematology analyzer is used to determine the different components of blood in less than a minute.
• CBC is used to determine general health status, screen for, diagnose, or monitor diseases and conditions that affect blood cells, such as anemia, infection, and bleeding disorders.
• Red Blood Indices include:
  • Mean Cell Volume (MCV): the average volume of red blood cell measured by femtoliters (fl).
  • Mean Cell Hemoglobin (MCH): the average amount of Hb in a single red blood cell measured by picogram (pg).
  • Mean Cell Hb Concentration (MCHC): the concentration of Hb per 100 ml of RBC measured in g/dl.

Osmotic Fragility Test

• Osmotic Fragility Test measures erythrocyte resistance to hemolysis while being exposed to varying levels of dilution of a saline solution.
• The sooner hemolysis occurs, the greater the osmotic fragility of the cells.
• The biconcave shape of RBCs allows 45-65% increases in their volume before they rupture.
• The test is used to detect:
  • Enzymatic deficiency (G-6-P-D deficiency).
  • Hereditary spherocytosis.
  • Iron deficiency anemia: red cells are flattened but not fragile.
  • Thalassemia.
  • Sickle cell anemia.