ERYTHROCYTE SEDIMENTATION RATE

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22 févr. 2014 (il y a 3 années et 5 mois)

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EXERCISE 1: Erythrocyte Sedimentation Rate MLAB 1315 Hematology




LAB EXERCISES MLAB 1315

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ERYTHROCYTE SEDIMENTATION RATE


LAB OBJECTIVE

The student will able to perform, within


2 mm/hr accuracy compared with the instructor’s
value, three erythrocyte sedimentation rates using the Westergren method.


PRINCIPLE

The erythrocyte sedimentat
ion rate (ESR), also called the sed rate, measures the settling of
erythrocytes in diluted human plasma over a specified time period. This numeric value is
determined (in millimeters) by measuring the distance from the bottom of the surface meniscus
to th
e top of erythrocyte sedimentation in a vertical column containing diluted whole blood that
has remained perpendicular to its base for 60 minutes. Various factors affect the ESR, such as
RBC size and shape, plasma fibrinogen, and globulin levels, as well
as mechanical and technical
factors.


The ESR is directly proportional to the RBC mass and inversely proportional to plasma viscosity.
In normal whole blood, RBCs do not form rouleaux; the RBC mass is small and therefore the
ESR is decreased (cells settle

out slowly). In abnormal conditions when RBCs can form
rouleaux, the RBC mass is greater, thus increasing the ESR (cells settle out faster).


The Westergren method is preferred by NCCLS standards because of its simplicity and greater
distance of sediment
ation measured in the longer Westergren tube. The straight tube is 30 cm
long, 2.5 mm in internal diameter, and calibrated in millimeters from 0
-
200. Approximately 1
mL of blood is required. The method it replaces is called the Wintrobe method.


SPECIMEN

Fresh anticoagulated blood collected in EDTA. Blood should be at room temperature and should
be no more than 2 hours old. If anticoagulated blood is refrigerated, the test must be set up
within 6 hours. Hemolyzed specimens cannot be used.


REAGENTS, SUPPLIES, AND EQUIPMENT

1.

Westergren tubes

2.

Westergren rack

3.

Disposable pipets

4.

0.5 ml sodium chloride in puncture ready vials

5.

Leveling plate for holding the Westergren rack

6.

Timer




EXERCISE 1: Erythrocyte Sedimentation Rate MLAB 1315 Hematology




LAB EXERCISES

MLAB 1315

Page
2

QUALITY CONTROL

Commercial controls are available for
this procedure. They will not be used for this exercise.


PROCEDURE


1.

Collect whol
e blood anticoagulated with EDTA.

2.

Label the puncture ready vial with the patient’s name.

3.

Remove cap from the puncture ready vial and add well mixed blood up to the line (see
illustration).

4.

Replace cap and invert 8 times making sure the blood and s
aline mix well.

5.

Carefully insert the Westergren tube into plungeable vial cap of blood/diluent mixture
twisting as you push the tube down.

6.

Place the tube in the Westergren rack to a vertical position and leave undisturbed for
exactly 1 hour.

7.

Set t
imer for 1 hour.

8.

After 1 hour has passed, read the distance in millimeters from the bottom of the plasma
meniscus to the top of the sedimented erythrocytes. Do not include the buffy coat in this
measurement. (The buffy coat is the layer of white cells

and platelets at the interface of
red cells and plasma. It is usually negligible, but may be noticeable in cases of
leukocytosis or thrombocytosis.)


REPORTING RESULTS

Normal values

Adult male

0
-
15 mm/hr

Adult female

0
-
20 mm/hr


PROCEDURE NOTES

Sources of error


1.

Age of specimen
-

must be less than 2 hours at room temperature, less than 6 hours
refrigerated.

2.

Temperature
-

must be between 20
-
25 C and blood must be at room temperature.

3.


temperatuare will cause a false ESR.

4.

Incorrect ratio of bl
ood to diluent

5.

Bubbles in the Westergren tube

6.

Tilting of the Westergren tube (accelerates the fall of the erythrocytes; an angle of even 3
degrees from vertical can accelerate sedimentation by as much as 30%)

7.

Vibration such as from a nearby centri
fuge will cause a false ESR.






EXERCISE 1: Erythrocyte Sedimentation Rate MLAB 1315 Hematology




LAB EXERCISES MLAB 1
315

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Usefulness of the ESR

The ESR is not a specific test therefore it is used for screening for certain disease conditions. It
can be used to differentiate among diseases with similar symptoms or to monitor the course of a
n
existing disease. For example, early in the course of an uncomplicated viral infection, the ESR is
usually normal, but it may rise later with a superimposed bacterial infection. Within the first 24
hours of acute appendicitis, the ESR is not elevated,
but in the early stage of acute pelvic
inflammatory disease or ruptured ectopic pregnancy, it is elevated. The ESR is elevated in
established myocardial infarction but normal in angina pectoris. It is elevated in rheumatic fever,
rheumatoid arthritis, an
d pyogenic arthritis, but not in osteoarthritis. The ESR can be an index to
disease severity.


Biological factors affecting the ESR


1.

Plasma factors

Increased plasma concentration of fibrinogen, along with immunoglobulin, will result in
rouleaux formation and an inc
reased ESR. It can therefore be expected that disease states
that are characterized by hyperfibrinogenemia or elevated immunoglobulin levels will
result in an increased ESR.

2.

RBC factors

When rouleaux formation cannot occur, owing to the shape or size o
f the RBC, a
decreased or low ESR is expected. This is observed with sickle cells and spherocytes.
The ESR is of little diagnostic value in severe anemia or in hematologic states evidenced
by poikilocytosis.



Factors affecting the ESR

Increase

Decrease

Rouleaux formation

Microcytes

Elevated fibrinogen

Sickle cells

Excess immunoglobulin

Spherocytes


REFERENCES

Harmening., Denise,
Clinical Hematology and Fundamentals of Hemostasis
, 3
rd

edition, pp. 603
-
605.

Turgeon, Mary Louise,
Clinical Hematology
-

Theories and Procedures
, 3
rd

edition, pp 326.

EXERCISE 1: Erythrocyte Sedimentation Rate MLAB 1315 Hematology




LAB EXERCISES MLAB 1315

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Erythrocyte Sedimentation Rate Report Form for Lab Exercise




Student’s name:____________________________________________Date:________________


Westergren kit lot

#:_____________________________ Expiration Date:______________




Patient name

ID #

ESR
position
on rack

ESR
result

mm/hr

Instructor
result

Within
normal
range? Y/N




















EXERCISE 1: Erythrocyte Sedimentation Rate MLAB 1315 Hematology




LAB EXERCISES MLAB 1315

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STUDY QUESTIONS


Name_
_______________________________


Date_________________________________

1.
State the principle of the ESR.


(1 pt.)






2.
What is the normal range for ESR in (state reporting units)

(2 pts.)



Men? _________


Women? ______________



3.
State the specimen requirement for ESR and time limits for performing the test. (3 pts.)





4.
For how long do you time a sed rate? (1 pt.)



5.
State four (4) sources of error when performing an ESR. (4 pts.)








6.
The ESR can be used to differentiate appendicitis from: (4 pts.)




_____________________
_ and

_________________________


Circle
or highlight
the conditions(s) in which the ESR is elevated in the first 24 hours.





EXERCISE 1: Erythrocyte Sedimentation Rate MLAB 1315 Hematology




LAB EXERCISES

MLAB 1315

Page
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7.
The ESR can be used to differentiate anginia pecoris from: (
2

pt.)



____
______________________. Circle or highlight
the condition in which the ESR is
elevated.



8.
Which arthritis does not cause an elevated ESR?

(1 pt.)





9.
Is the ESR


or


in the f
ollowing conditions? (5 pts.)


A.

Sickle cells present


B.

Increased room temperature


C.

Unlevel ESR rack


D.

Nearby centrifuge in use


E.

Elevated plasma immunoglobulin


10. What is the name of the ESR method that the Westergren method replaces? (1 pt.)