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 20oC will decrease ESR
Temperature
above 27oC 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 3rd to 4th
month and does not return to normal until the 3rd or 4th
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.
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