Erythrocyte Sedimentation Rate & C-Reactive Protein

ESR

The Erythrocyte Sedimentation Rate (ESR), or 'sed rate' is a crude measure of inflammation. An elevated ESR (ie over 100) suggests inflammatory process- infectious, immunologic or neoplastic (ie multiple myeloma).

The rate at which a RBC falls to the bottom of the test tube. If there is increased immunoglobulins or plasma proteins (paraproteins), then the red blood cells stack together forming rouleaux. These are heavier and fall to the bottom of the tube faster.

A rule (to be used with great caution) to calculate upper limits of normal:

• (men’s age)/2 =
• (woman’s age + 10)/2=

 

Mechanism of ESR

Fibrinogen or antibodies neutralize the negative charges of RBCs, allowing their interaction and accelerated settling.

ESR increases with age, anemia, renal failure and in pregnancy.

ESR decreases with changes in RBC morphology, congestive heart rate and cryoglobulinemia.

C-Reactive Protein

 

The Protein is synthesized by the liver promptly after tissue injury. Plasma levels increase as early as 4 hours after an injury, increasing more than 1000x and peaks within 48 hours. It clears within 18 hours.

Normal levels are between 0-8 mg/dl.

Interpretation
Synthesis of CRP requires sufficient concentration of inflammatory mediators to reach the liver. It is a more timely indicator of inflammation, being unaffected by age, anemia, pregnancy, as

 

CRP is not usually increased in multiple myeloma or diseases with polyclonal gammopathy.