Blood smear

Blood smear

1. BLOOD SMEARS
RAJESH MOHESS, CLT

2. BLOOD SMEARS
•Peripheral blood smear is a very important tool in the
hematology lab
•It provides rapid, reliable access to information about a
variety of hematologic disorders
•Examination of the peripheral blood smear is an inexpensive
but powerful diagnostic tool in both children and adults
•The smear offers a window into the functional status of the
bone marrow
•Review of the smear is an important adjunct to other clinical
data; in some cases, the peripheral smear alone is sufficient to
establish a diagnosis

3. BLOOD SMEARS
•An examination of the blood smear (or film) may be
requested by physicians based on medical history or
initiated by laboratory staff as part of their protocol
•Majority of cases for blood smears are from laboratory
protocol
•With the development of sophisticated automated blood-
cell analyzers, the proportion of blood-count samples that
require a blood smear has steadily diminished and in many
clinical settings is now 10 to 15 percent or less.
•Nevertheless, the blood smear remains a crucial diagnostic
aid

4. BLOOD SMEARS
•For a true morphological interpretation, a trained
person is required to review the smear, as automation
in hematology will normally generalize the morphology
•The indications for smear review differ according to the
age and sex of the patient, whether the request is an
initial or a subsequent one, and whether there has
been a clinically significant change from a previous
validated result (referred to as a failed delta check).
•All laboratories should have a protocol for the
examination of a laboratory-initiated blood smear

5. BLOOD SMEARS
•Not all hematological disorder requires a
peripheral blood smears for diagnosis.
•Some conditions can be diagnosed by other
laboratory data also.
•For example, Iron deficiency anemia can be
diagnosed by MCV, iron and ferritin levels

6. BLOOD SMEARS
•There are numerous valid reasons for a clinician to request
a blood smear and these differ somewhat from the reasons
why laboratory workers initiate a blood-smear examination.
•Sometimes it is possible for a definitive diagnosis to be
made from a blood smear.
•More often, the smear is an important tool in the provision
of a differential diagnosis and the indication of further
necessary tests.
•The blood smear can have an important part in the speedy
diagnosis of certain specific infections.
•Otherwise, its major roles are in the differential diagnosis
of anemia and thrombocytopenia and in the identification
and characterization of leukemia and lymphoma.

7. BLOOD SMEARS
Anemia:
•In patients with anemia, physician-initiated
examinations of blood smears are usually
performed in response to clinical features or to a
previously abnormal complete blood count
•Laboratory-initiated examinations of blood
smears for patients with anemia are usually the
result of a laboratory policy according to which a
blood smear is ordered whenever the
hemoglobin concentration is unexpectedly low

8. BLOOD SMEARS
Hemolytic Anemia:
•In the hemolytic anemias, red-cell shape is of
considerable diagnostic importance.
•Some types of hemolytic anemia yield such a
distinctive blood smear that the smear is often
sufficient for diagnosis.
•This is true of hereditary elliptocytosis, and
ovalocytosis.
•The presence of bite cells points to a Heinz body
hemolytic anemia

9. BLOOD SMEARS
Macrocytic Anemia:
•Patients with vitamin B
12or folic acid
deficiency, the blood smear shows
macrocytes.
•It may also show oval macrocytes and
hypersegmented neutrophils.
•When the anemia is more severe, there may
be marked poikilocytosis, with teardrop and
red-cell fragments

10. BLOOD SMEARS
Microcytic Anemia:
•Blood smear not very significant in diagnosis,
although very useful.
•Most common cause is iron deficiency anemia
which can be diagnosed by other blood tests
Sickle cells/Thalassemia:
•A blood smear is useful. Usually shows target
cells sickle cells

11. BLOOD SMEARS
Thrombocytopenia/Thrombocytosis:
•A blood smear should always be examined for
patients with thrombocytopenia.
•This is done to both confirm the
thrombocytopenia and to look for the
underlying cause.
•Falsely low platelet counts may be the result
of small clots, platelet clumping, platelet
satellitism or abnormally large platelets

12. BLOOD SMEARS
White Cell Disorders
(Leukemia/Lymphoma/Bone Marrow Failure):
•The precise disease classification may rely upon
evaluation of abnormal circulating cells.
•Blood smears must always be examined when
there is unexplained leukocytosis, lymphocytosis,
or monocytosis or when the flagging system of an
automated instrument suggests the presence of
blast cells
•For example, the presence of Auer rods in a blast
form in patients with acute myeloid leukemia

13. BLOOD SMEARS
The role of the blood smear in the diagnosis
of leukemia and lymphoma is to suggest:
•A likely diagnosis or range of diagnoses
•To indicate which additional tests should be
performed
•To provide a morphologic context without
which immunophenotyping and other
sophisticated investigations cannot be
interpreted

14. BLOOD SMEARS
Summary
•The blood smear remains an important diagnostic tool,
even in this age of molecular analysis
•Physicians may and should request a blood smear
when there are clinical indications for it.
•The Laboratory technologist should make and examine
a blood smear whenever the results of the CBC indicate
that a blood smear is necessary for the validation or to
further investigate an abnormality
•To avoid errors and miss any diagnoses, hematological
disorders should be investigated by both clinical data
and the peripheral smear

15. PREPARATION OF A BLOOD SMEAR
Principle:
•A peripheral smear may be requested by the clinician.
•It may also be performed as part of the laboratory
protocol from reflex or if there are discrepancies from
prior results.
•We will discuss the ‘Wedge Smear’
•Smears are prepared by placing a drop of blood on a
clean glass slide and spreading the drop using another
glass slide at an angle.
•The slide is then stained and observed microscopically,
mainly to determine differential count and morphology
study

16. PREPARATION OF A BLOOD SMEAR
Principle:
•A well-stained peripheral smear will show the red cell
background as red orange.
•White cells will appear with blue purple nuclei with red
purple granules throughout the cytoplasm.
•A well made, well distributed peripheral smear will have a
counting area at the thin portion of the wedge smear which
is approximately 200 red cells not touching.
•A good counting area is an essential ingredient in a
peripheral smear for evaluating the numbers of and types
of white cells present and evaluating red cell and platelet
morphology.

17. PREPARATION OF A BLOOD SMEAR
Principle:
•Functions of the peripheral blood smear are:
-provide information for diagnosis
-provide information for further testing or to
establish diagnosis
-used as a guide for therapy
-Used as an indicator to monitor the harmful
effects for chemotherapy and radiation therapy

18. PREPARATION OF A BLOOD SMEAR
Materials:
-Glass slides
-Applicator sticks
-Capillary tubes
-EDTA specimen (smear should be made within 4
hours of blood collection)
-Capillary blood specimen collected in
heparinized tubes

19. BLOOD SMEAR PROCEDURE
•Mix blood properly
•Place a small drop of blood (about 2-3 mm) about 1 cm from
the frosted end of a clean slide (slide must be completely
clean)
•Using a spreader (another slide), draw backwards into the
drop of blood (while applying pressure) –maintain an angle of
30-45 degrees

20. BLOOD SMEAR PROCEDURE
•When the spreader touches the blood, allow the
blood to spread across the edge of the spreader
•Move the spreader forward on the slide (in one
smooth motion), so a smear is made
approximately 3 to 4 cm in length.
•The smear should be half the size of the slide,
with no ridges, and a “feather edge” should be
toward the end of the smear.

21. BLOOD SMEAR PROCEDURE

22. BLOOD SMEAR PROCEDURE
•Label the frosted end of the slide with the
patient’s last name and first initial, specimen
number, and the date
•Allow the smear to air dry completely (about 5
minutes)
•Specimen can now be stained

23. BLOOD SMEAR PROCEDURE

24. BLOOD SMEAR
Good smear
A good smear should have the following
appearance:
•Appear smooth and uninterrupted
•Start thick and gradually thinning out (feather-
edge)
•The film should take up ½ to ¾ the length of
the slide

25. BLOOD SMEAR LIMITATIONS
•The angle between the slides is dependent upon the size of the
blood drop and viscosity of the blood.
The optimal angle is 45 degrees
•The larger the drop of blood and lower the hematocrit, the higher
the angle needs to be so the blood smear is not too long
•Blood with a higher hematocrit needs to have a lower angle so the
smear is not too short and thick
•Glass slides must be clean; otherwise, this results in imperfect
distribution of cells and improper staining
•Smears should not be made from blood remaining on the tube
stopper as the lubricant on the stoppers can interfere with the
drying process

26. BLOOD SMEAR LIMITATIONS
•Once the drop of blood has contact on the slide, the smear
needs to be made immediately.
•Otherwise, the blood will clump and dry, again resulting in
uneven distribution of WBC and platelets (granulocytes will
accumulate at the edges)

27. POOR SMEARS
Poor smears can results from a number of
reasons, such as:
•Too large or small blood drop
•Not pushing the spreader in an even motion
•Pressing down heavily on the spreader
•Too great or small an angle of the spreader
•Speed of stroke used to move the spreader
•Clots in the blood
•Dirty (oily) slides

28. BLOOD SMEAR

29. BLOOD SMEAR

30. BLOOD SMEAR
THE END