Makindo Medical Notes

The principle of ESR is based on the fact that during inflammation, red blood cells (RBCs) tend to clump together due to the presence of acute-phase reactants such as fibrinogen. These clumps are denser than individual RBCs, causing them to settle more rapidly.

About

• ESR the rate (mm/hour) at which erythrocytes settle when placed in a vertical tube
• Depends largely upon the plasma concentration of fibrinogen
• These alter the standard electrical charge of red blood cells, and this results in rouleaux formation

Normal Values

• Males < 15 mm/hr with increases with age
• Females < 20 mm/hr with increases with age

Causes of a High ESR often > 100 mm/hr

Low ESR

• Extreme leukocytosis, Reduced fibrinogen
• Polycythaemia, Spherocytosis, Acanthocytosis
• Congestive cardiac failure - often quoted but is wrong
• Sickle cell anaemia

Difficulties in interpretation

• ESR is a non-specific test, meaning it cannot pinpoint the exact cause of inflammation.
• Simple factors like age, gender, and technical aspects can increase the ESR
• Slower Response: It changes more slowly in response than other markers like C-reactive protein (CRP).