Erythrocyte Sedimentation Rate(ESR)

choppedspleenMechanics

Feb 21, 2014 (3 years and 8 months ago)

94 views

Erythrocyte Sedimentation Rate

(ESR)


The erythrocyte sedimentation rate (ESR) is a
nonspecific measurement used to detect and
monitor an inflammatory response to tissue
injury (an acute phase) in which there is a
change in the plasma concentration of several
proteins (termed acute phase proteins).


This procedure, very simply, consist of allowing
a specific amount of blood to sit in a vertical
position for a period of time (usually one hour).
The distance, in millimeters, that the red cells
fall during this time period is the erythrocyte
sedimentation rate and is reported in mm/hr.


The ESR is affected by three factors:
erythrocytes, plasma composition, and
mechanical/technical factors.

I.
Erythrocytes


A
factor of chief importance in determining the distance the
RBCs fall is the size or mass of the falling particle. The
larger the particle, the faster its rate of fall.


In normal blood, the RBCs remain more or less separated.
They are negatively charged and, therefore repel each
other.


In certain diseases, however, plasma protein concentration
may be altered, causing a reduction in the negative charge
of the RBCs and consequent formation of rouleaux. This
leads to a larger mass and an increased sedimentation
velocity.


Agglutination of RBCs due to change in the erythrocyte
surface also leads to an increased RBC mass and a more
rapid sedimentation rate.

I.
Erythrocytes


Macrocytes tend to settle more rapidly than microcytes.
RBCs show an alteration in shape, such as sickle cells and
spherocytes, are unable to aggregate or form rouleaux and
the sedimentation rate is decreased.


Anisocytosis and poikilocytosis reduce the ability of RBCs to
form large aggregates and there by tend to falsely lower
ESR.


In severe anemia, the ESR is markedly elevated: the
concentration of RBCs is decreased, aggregation and
rouleaux formation are increased, and they therefore, settle
out more easily and rapidly.


In polycythemia, in which the RBCs count is high, the ESR is
generally normal.

II.
Plasma composition



The plasma composition is the most important factor
determining the ESR. Rouleaux and aggregation of the
RBCs are controlled primarily by the levels of acute phase
proteins (most notable fibrinogen,

-
1 globulin, and

-
2
globulin); increasing these three plasma protein levels are
increased in the plasma.


As the concentration of protein increases so does the
viscosity of the plasma. Although an increased plasma
viscosity will tend to inhibit the fall of the RBCs, the increase
in plasma proteins are generally those which cause rouleaux
and aggregation of the RBCs, which affects the ESR more
greatly than does the increased plasma viscosity. Increased
concentrations of albumin will tend to lower the ESR.

III.
Mechanical/Technical factors



It is important that the ESR tube be exactly perpendicular.
A tilt of
30
can cause errors up to
30
%.


Also, the rack holding the tubes should not be subject to
any movement or vibration.


Minor, everyday variations in room temperature do not
significantly affect the ESR. With large changes in
temperature, however, the sedimentation rate increases as
the temperature increases.


The length and inner diameter of the ESR tube also affect
the final test results. ESR tubes with a narrower than
standard bore will generally yield lower sedimentation
rates.


Normal values:


Adult male


0
-
15 mm/hr


Adult female


0
-
20 mm/hr

Significance of the ESR




The ESR represents a nonspecific response to
tissue damage and inflammation and denotes the
presence of disease, but not its severity.


It primarily reflects changes in the plasma
proteins that accompany most the acute and
chronic infections, tumors, and degenerative
diseases. It may be used to follow the progress
of certain diseases such as tuberculosis and
rheumatoid arthritis.


An elevated ESR may be found in
:

1.
Pregnancy (after the third month).

2.
Acute and chronic infections.

3.
Rheumatic fever.

4.
Rheumatoid arthritis.

5.
Myocardial infection.

6.
Nephrosis.

7.
Acute hepatitis.

8.
Menstruation.

9.
Tuberculosis.

10.
Hypothyroidism.

11.
Hyperthyroidism.


Adults over 60 years of age frequently have a
slightly higher ESR value due primarily to
decreased concentrations of plasma albumin.


A decreased ESR will be present in
:

1.
Polycythemia.

2.
Congestive heart failure.

3.
Hypofibrinogenemia.

4.
The presence of red blood cell abnormalities
(poikilocytosis, spherocytes, and sickle cells
).

Westergren method



Reagents and Equipment:

1)
Westergren pipette calibrated in millimeters. The
National Committee for clinical laboratory standards
has set specific dimensions for the pipettes to be used:


Length = 300.5mm (+/
-
0.5mm) (in order to fit into standard
racks)


External diameter = 5.5mm (+/
-
0.5mm)


Internal bore = 2.65mm (=/
-
0.15mm)


Graduated scale on pipette = 200mm (+/
-

0.35mm) (Graduated
lines of uniform thickness 0.2mm)


3
-
westergern pipette rack. All racks should contain a leveling
bulb in order to ensure that the position of tubes is vertical (+/
-
2o).

Reagents and Equipment

2)
Westergren rack.

3)
Disposable pipettes

4)
Leveling plate for
holding the
Westergren rack

5)
Timer.


Specimen


Whole blood (4 volumes) diluted with 0.109 M
trisodium citrate (1 volume). Alternatively, 3ml
whole blood anticoagulated with EDTA. (If this
specimen type is used the whole blood [2.0ml]
must be diluted with 0.85% w/v sodium chloride
[0.5ml] prior testing).

Principle


Whole blood (
4
volumes) anticoagulated with
0.109
M
trisodium citrate (
1
volume), or EDTA anticoagulated
blood (
4
volumes) diluted with
0.85
% sodium chloride (
1
volume) is mixed, placed in a Westergren pipette, and
allowed to stand for exactly
1
hour in a vertical position.
The number of millimeters the red blood cells fall during
this timed period constitutes the ESR.



The normal values

for the modified Westergren ESR are
0
to
15
mm/hour for women,
0
to
10
mm/hour for men, and
0
to
10
mm/hour for children.

Procedures


1)
1
-
Mix the diluted blood for at least 2 minutes on a rotator.
(The blood should be at room temperature). Check the
tube for clots using two applicator sticks.

2)
2
-
Make certain the Westergren ESR rack is exactly level.

3)
3
-

Fill the Westergren pipette to exactly the 0 mark.
Making certain there are no air bubbles in the blood.

4)
4
-
Place the pipette in the rack. Be certain the pipette fits
snugly and evenly into the grooves provided.

5)
5
-
Allow the pipette to stand for exactly 60 minutes.

6)
6
-
At the end of 60 minutes records the number of
millimeters the red blood cells have fallen. This result is
the erythrocyte sedimentation rate in millimeters/hour

Wintrobe and Landsberg method


Reagent and equipment:


Wintrobe tube, calibrated in millimeters


Wintrobe pipette rack.


Disposable capillary pipette.


Applicator sticks


Specimen:


Whole blood,
1
ml, using EDTA as the
anticoagulant.



Principle:


Well
-
mixed, whole blood is placed in a Wintrobe
tube and allowed to stand for
1
hour. The
number of millimeters the red blood cells fall
during time constitutes the ESR. In the Wintrobe
and Landsberg method, normal values for
women are
0
to
20
mm/hour and
0
to
9
mm/hour
for men.


Procedure:

1.
Mix the whole blood for at least 2 minutes on a
rotator. (Make certain the blood is at room
temperature). Check the tube for clots using
tow applicator sticks.

2.
With a capillary pipette, fill the Wintrobe tube to
the 0 mark.

3.
Place the tube in an exactly vertical position in
the rack. Time for 60 minutes.

4.
At the end of 60 minutes, record the level of the
erythrocyte column. This result is the
erythrocyte sedimentation rate in
millimeters/hour.

Discussion


1.
The sedimentation of red blood cells takes place
in three stages:

i.
In the first
10
minutes
(lag phase)
rouleaux formation
occurs and the sedimentation rate is slight.

ii.
Sedimentation then occurs for a period of
approximately
40
minutes at a more rapid and
constant rate
(decanation)
.

iii.
During the last
10
minutes, the sedimentation rate is
slow because of the accumulation of RBCs in bottom
of the tube. The longer the tube the longer the stage
two will last, and therefore the higher the ESR result.

Discussion

2.
Although care may be taken in filling the sedimentation
tube to the 0 mark, occasionally the upper level of the
blood may only reach the 1 or 2 mm mark. In such
case, care should be taken when making the final
reading. Subtract the 1 or 2 mm from the final result.
For example, if the ESR tube is filled to the 2 mm mark
and the RBCs fall to the 18mm mark, the ESR is
reported as 16mm/hour. If the level of blood falls below
the 5 mm mark, the test should be repeated to ensure
that valid results are obtained. If the upper level of the
blood is below 0 due to leakage of the blood from the
bottom of the tube (Westergren method) the test must
be repeated from step 1. leakage of blood from the
bottom of the tube invalidates the test result.

Discussion

3.
All the sedimentation racks should be equipped with
leveling screws and a spirit level.

4.
Mechanical sources of error:

i.
If the concentration of EDTA is greater than recommended, the
ESR will be falsely low.

ii.
The anticoagulants sodium or potassium oxalate and heparin
cause the RBCs to shrink and the ESR will be falsely high.

iii.
If the ESR stands for more than
60
minutes, the results will be
falsely elevated. If the test is timed for less than
60
minutes,
invalidly low values are obtained.

iv.
A marked increase (or decrease) in room temperature leads to
increased (or decreased) ESR result.

v.
Tilting of the ESR tube increases the ESR.

vi.
Bubbles in blood cause invalid results.

vii.
Fibrin clots present in the blood invalidate the test results.

Discussion

5.
The ESR should be set up within 2 hours of blood
collection. If EDTA is used as the anticoagulant, the
test may be set up within 6 hours if the blood has been
refrigerated.

6.
The Wintrobe ESR technique is thought to be more
sensitive when the ESR is low, whereas the
Westergren procedure more accurately reflects the
patient’s disorder when the results are high. The
Westergern method has been chosen as the standard
method by the International Committee for
Standardization in Hematology.

Discussion

7.
When reading the ESR results on bloods with an
extremely high WBCs or platelet count, the buffy
coat should be excluded from the reading.

8.
If there is poor separation of the RBCs and
plasma layers this may be due to an
increased number of reticulocytes and has
been termed “stratified sedimentation”.

9.
The internal bore and the length of the
graduated scale on the Westergern pipette
are critical measurements.

Disposable ESR



commercial kits are now available for a
disposable ESR test. Several kits include
safety caps for the pipettes that allow the
blood to precisely fill to the zero mark. This
makes the pipette a closed system and
eliminates the error involved with manually
setting the blood at the zero mark.