I. Measurement/physiology
- ESR (Westergren) nl = age/2; add 5 if female
- Complex mechanism; approx. rate = 2ac (d1-d2) x g/7.65n
- a,c = radius, thickness of RBC
- d1,d2 = density of RBC, plasma
- g = force of gravity; n = plasma viscosity
- Nl blood: RBCs don't aggregate
- Abnl blood:
- Rouleaux formation occurs, due to reduction in "zeta potential" (charge on RBC membrane) caused by abundant asymmetrical macro-molecules, e.g. Ig's (Multiple Myeloma) or fibrinogen (tissue necrosis, inf., pregnancy)
- RBC agglutination (caused by G's in RBC membrane)
- These larger particles fall faster, so higher ESR
- Abnl RBC morph. can make rouleaux formation impossible & reduce ESR (e.g. SSA, acanthocytosis, anisocytosis, spherocytosis)
II. Differential dx
- ESR usually normal in:
- Osteoarthritis
- Typhoid fever
- Early pregnancy
- Angina
- Malaria
- PUD
- SSA (may be?)
- Polycyth. Vera
- Fever alone
- Mono
- Atopic conditions
- ESR usually high in:
- Infection
- Inflammation
- Neoplasm
- Pb poisoning
- Thyroiditis
- Menstruation (slightly elevated)
- Acute MI
- Very high ESR (> 100):
- 58% are Ca (Multiple Myeloma, lymphoma, metastatic)
- 25% inflamm/infectious
- 8% renal dis.