Lecture #7: Erythrocyte Sedimentation Rate

Erythrocyte sedimentation rate (ESR) refers to the speed of fall of the erythrocyte to settle down from their plasma. It may also mean the velocity of erythrocyte sedimentation. The ESR may also be referred to by the following terms: sed rate, suspension stability of erythrocytes. It is directly proportional to red cell mass and inversely proportional to plasma viscosity.

Importance of ESR

1. Used as an index in the presence of and active disease

2. Measure the suspension stability of RBC’s

3. Measure the abnormal concentration of fibrinogen and serum globulin

ESR may be measured in two ways

1. By measuring the length of fall of the top of the column of RBC in a specified period of time.

2. By determining the time required for the red cells to reach a specified point.

Phases or stages in the erythrocyte sedimentation rate

1. Agglomeration phase – initial period of aggregation

In this first phase, a few cells sink under gravity but the majority form agglomerates (rouleaux) of various sizes. This takes place during the first 10 minutes.

2. Phase of fast settling

In this second phase, the agglomerates sink rapidly, the rate of fall depending on their size; lack of uniformity in the size of the agglomerates may result in blurring of the level of the settle erythrocytes. This takes place for about 40 minutes.

3. Final phase of packing

In this third phase, the rate of settling is slow owing to “clogging” of the agglomerates and takes place during the last 10 minutes.

Factors affecting the erythrocyte sedimentation rate

The rate of fall of the red cells is influenced by a number of interacting factors. Basically, it depends upon the difference in specific gravity between the red cells and plasma, but the actual rate of fall is influenced very greatly by the extent to which the red cells form rouleaux, which sediment more rapidly than single cells.

A.     Intrinsic Factors

1. Plasma factors

Increased fibrinogen concentration accelerates ESR

Increased globulin concentration accelerates ESR

Cholesterol increases ESR

Increased albumin retards ESR

Lecithin retards ESR

Removal of fibrinogen by defibrination lowers the ESR

Extreme increase in plasma viscosity slows down ESR

2. Red cell factors

a. Number of red cells

(1)   Anemia (lesser) cells increases ESR

(2)   Polycythemia (more) cells decreases ESR

b. Size of red cells

(1)   Macrocytes (large cells) increases ESR

(2)   Microcytes (smaller cells) increases ESR

c. Shape of red cells

(1)   Rouleaux formation does not occur with abnormally shaped red cells, so any abnormality in the shape of RBC will decrease the ESR. Poikilocytosis decreases ESR.

d. Hemolyzed red cells

(1)   Hemolysis accelerates ESR

B.     Extrinsic factors

1. Mechanical, technical and physical factors

a. Time of examination and observation

The test should be done in two hours after the blood has been collected, since red cells tend to be more spherical on standing and a delay will slow down the ESR.

b. Anticoagulants

Excess of dry anticoagulants slows down ESR

Increased concentration of anticoagulant retards ESR

c. Temperature

Temperature below 20^oC will decrease ESR

Temperature above 27^oC will increase ESR

Refrigerated blood should be placed at room temperature prior to the test

d. Length of tube

The longer the tube, the faster the ESR

e. Bore of the tube

Less than 2mm diameter slows down ESR

Larger than 3.75 mm diameter increases ESR

f. Position of the tube

Inclination or tilting of the tube accelerates ESR

g. Dilution of the blood

The greater the dilution, the faster the ESR

h. Volume of the blood

The more blood, the more cells, the slower the ESR

The lesser blood, the lesser cells, the higher the ESR

i.  Inaccurate reporting or recording of the result will either increase or decrease the ESR

j.  Presence of air bubbles – causes lesser cells in the blood column, so it increases ESR

k. Defibrination slows down ESR

l.  Presence of blood clots will increase ESR

m.   Use of wet glasswares will cause hemolysis and hemolysis accelerate ESR

n. Use of dirty glasswares will cause the formation of blood clots, thereby causing the decrease ESR

Methods of ESR determination

A. Macromethods of ESR determination

1. Wintrobe and Landsberg method

Anticoagulant used:         Double oxalate

Tube used:            Length:            calibrated up to 100 mm or 10 cm

                              Bore:               3 mm

The wintrobe tube may also be used for hematocrit determination

Normal values:     Men – 0 – 10 mm/hr

                              Women – 0 – 15 mm/hr

                              Children – 1 – 15 mm/hr

2. Westergren method

Anticoagulant used          :           3.8% sodium citrate

Length of tube                  :           calibration is up to 200 mm

Bore of tube                     :           2.5 mm

Normal value                    :           Men – 3 – 5 mm/hr

                                                      Women – 4 – 7 mm/hr

3. Graphic and cutler method

Anticoagulant used          :           3% or 3.8% sodium citrate

Length of tube                  :           calibration is from 0 – 50 mm

Normal values                  :           Men – 3 – 5 mm/hr

                                                      Women – 4 – 7 mm/hr

4. Linzenmeir method

Anticoagulant used          :           3.7 or 3.8% sodium citrate

Length of tube                  :           65 mm with two calibrations at 1 mm and 18 mm

Bore of tube                     :           5 mm diameter

Normal values                  :           Men – 350 – 600 minutes

                                                      Women – 300 – 600 minutes

In this method, cells are allowed to settle up to mark 18 mm and the time required to reach that specified point is the ESR reading in minutes.

5. Rowrke–Ernsten method

Anticoagulant used:                     Heparin

6. Brays

Anticoagulant used:                     Double oxalate

B. Micromethods of ESR determination

1. Micro Landau

Anticoagulant used          :           Sodium citrate

Length of tube                  :           12 cm

Bore of tube                     :           1 mm

Calibration of tube          :           12.5 mm and 62.5 mm

Normal values                  :           Men – 1–5 mm/hr

                                                      Women – 1–8 mm/hr

2. Smith method

Anticoagulant used          :           5% Sodium citrate

Capillary pipette              :           230 mm long with 1 mm internal bore

Normal values                  :           Men – 1–5 mm/hr

                                                      Women – 1–8 mm/hr

3. Hellige–Volmer or Crista method

Anticoagulant used          :           5% Sodium citrate

Normal values                  :           Children – 8 – 10 mm/hr

                                                      Adults – 6 – 8 mm/hr

ZETA SEDIMENTATION RATE

Principle:

A centrifugal device (zetafuge) spins capillary tubes in a vertical position in four 45 second cycles. This result in controlled compaction and dispersion of erythrocytes, allowing roleaux to form and sediment in this three minute period of time. The capillary tube is then read as if it were a standard hematocrit tube, giving a value referred to as zetacrit. The true hematocrit is divided by the zetacrit, and the result expressed as percentage, is the Zeta Sedimentation Rate (ZSR).

            ZSR (%)                        =          Hct %   x          100

                                                               Zct %

Reference range         40 – 51%                     – for both sexes

                                    51 – 54                        – borderline normal

                                    55 – 59                        – mildly elevated

                                    60 – 64                        – moderately elevated

                                    Above 65                    – markedly elevated

Correction for anemia

One of the controversial points about the sedimentation concerns the correction for anemia. Because anemia and increased sedimentation rate are often associated and because it is known that the sedimentation rate of red cells diluted with plasma from the same individual fall faster than do the undiluted cells, attempts have been made to correct the ESR for anemia.

        Reasons for not correcting ESR for anemia are:

1. In certain anemias (hypochromic microcytic, sickle cell anemia and anemia characterized by marked poikilocytosis) the ESR is not increased.

2. In numerous patients with anemia and tissue changes known to be associated with an increased ESR such as active TB, the ESR is abnormal, but when corrected for anemia, normal values are obtained.

3. In a given patient, the ESR and / or degree of anemia may change without correlation

Therefore, correction for anemia is not accurate, is not necessary and often, misleading. Because of the difference in opinion concerning anemia, it is advisable to report ESR as it is observed and stating the method used.

Variation in ESR values

A. Physiologic variations

1. ESR is more constant in men than in women

2. In pregnancy, ESR begins to increase at the 3^rd to 4^th month and does not return to normal until the 3^rd or 4^th week post partum

3. In newborn, ESR is greatly reduced, in older adults, rather high

B. Pathologic variations

1. ESR is reduced in polycythemia, congestive heart failure, diseases of the liver parenchyma, hyperbilirubinemia, hemolytic jaundice, sickle cell anemia, presence of ACTH, high cholesterol, high FBS, presence of clots.

2. ESR is increased in all inflammatory conditions, in acute and chronic infections like TB, in diseases accompanies by necrosis or tissue breakdown, in the presence of tumors, after exposure to ultraviolet lights or X–rays, after stimulation therapy, connective tissue disease like rheumatoid arthritis and rheumatoid fever, in severe toxicity, in coronary thrombosis, hyperfibrinogenemia, in gonorrhea and syphilis, multiple myeloma, macroglobulinemia, severe polyclonal hyperglobulinemia.

Measurement of ESR provides an opportunity of examining the plasma for color and clarity; golden yellow in hemolysis, straw colored in pernicious anemia; cloudy in increased fat content and protein changes.