Erythrocyte Sedimentation Rate: Meaning and Variation | Blood | Biology

In this article we will discuss about the meaning and physiological variation of erythrocyte sedimentation rate (ESR).

Meaning of Erythrocyte Sedimentation Rate (ESR):

While in circulation, the red cells remain uniformly suspended in the plasma. If an anticoagulant is added to a specimen of blood and let stand it in a glass tube, the corpuscles (being heavier than plasma) are found to sediment gradually at the bottom of the tube, while the plasma remains as a clear supernatant fluid. This process is called sedimentation and the rate of settling down or sedimentation is known as the erythrocyte sedimentation rate (ESR).

Sedimentation Continues in Three Phases:

(1) A short stage of aggregation with a little fall,

(2) True sedimen­tation following maximum velocity of fall, and

(3) Finally slowing until packing is complete leaving an upper layer of clear plasma.

It depends upon:

(a) On the differences in densities between red blood corpuscles and plasma,

(b) On the degree of adherence of red blood corpuscles to one another (rouleaux formation) related to the plasma protein content, and

(c) On the resistance that plasma exerts on the red cell surface.

Red cells carry a negative charge, and hence any condition which increases the positive charge in plasma accelerates ESR.

ESR is increased with:

(a) Rise in O₂

(b) Rise in cholesterol,

(c) Rise in fibrinogen, and

(d) Rise in a-globulin.

It is decreased with:

(a) Rise in CO₂,

(b) Rise in albumin,

(c) Rise in nucleoprotein, and

(d) Rise in lecithin.

ESR constitutes a guide to the progress of a disease. It is measured either in relation to a fixed time or distance by the methods of Wintrobe, Westergren or Cutler. The tube is put in a vertical position, the lower end of which is placed on a rubber cap and the upper end remains open. Height of supernatant plasma in mm separated out at the top of the vertical column of blood after an hour is noted. This is expressed as the erythrocyte sedimentation rate.

Normal ESR values by Wintrobe’s method is 0.0-6.5 mm per hour for males, average being 3.7 mm per hour and 0.0-15.0 mm per hour for females, average being 9.6 mm per hour.

Physiological Variations in Erythrocyte Sedimentation Rate (ESR):

i. Lowest in new-born, 0.0-2.0 mm per hour. In children it is from 3.0 to 13.0 mm/hour, average 9.0 mm/hour.

ii. In pregnancy there is a definite acceleration beginning from the tenth to twelfth week. The rate gradually increases and reaches normal level only at third or fourth week postpartum.

iii. In old age the ESR increases.

It is a non-specific reaction, and gives information of a general character, but is useful supplement when temperature, pulse, etc., show no clinical disorder. ESR is increased in all acute general infections.

One of the most important uses of the test is in calling attention to the presence of more or less occult disease. It also useful as an aid in differential diagnosis. Other things being equal, an accelerated rate suggests organic disease rather than functional disorder. It acts as a guide to the progress of a disease.