LAP3

LAB3
Determination of Erythrocyte Sedimentation Rate (E.S.R.)
Is the rate of sink the R.B.Cs in graduated tube fixed vertically for a given time and expressed as millimeters per hour (mm./h)
If anticoagulated blood is allowed to stand for some time, the R.B.Cs gradually sink and the plasma upward. The rate of this action is constant in healthy human and is known as ESR.
in certain conditions this rate is increased because the R.B.Cs align face to face in columns like a stack or coins this called a rouleaux and this proportional to ESR.
ESR is affected by two factors :-
1- The number, size and density of R.B.Cs.
2- The composition of plasma especially the protein
3- Plasma viscosity
4- Room temperature
We try to discuss each of them :-
* When cells are suspended in normal plasma, rouleaux formation is minimal and the sedimentation of cells is low, the changes occur in the R.B.Cs numbers like anemia leads to increase rouleaux formation and accelerate the ESR, but there is some changes not correlate with this state like some special conditions of anemia, ex: Spherocytic anemia these, usually do not exhibit increased sedimentation, so normal & even reduced ESR. Why ?
* The principle cause of rouleaux formation is the composition of plasma, especially the protein (Albumin & Globulins).
* Plasma viscosity is affected by the concentration of large proteins (fibrinogen & some immunoglobins)
Lower levels of plasma viscosity are seen in neonates because of low levels of proteins particularly fibrinogen, while there is a slight increase in viscosity is not affected by anemia unlike ESR.