Blood
film, also known as peripheral blood smear is a thin layer of blood smeared on
a microscope slide and then stained in such a way to allow the various blood
cells to be examined microscopically. Blood films are usually examined to
investigate hematological problems (disorders of the blood) and occasional to
look for parasites within the blood such as malaria and filaria. (Pallister, 2006).
Blood
film provides valuable information on the status of blood cells and presence of
parasitic elements. The
blood film is the only permanent record of hematological investigation.
Therefore, a well-made, well-stained smear is essential it is common practice
to prepare at least 2 blood films from each specimen, one stained and the other
kept in reserve, to be stained if and when necessary.
Capillary
blood is ideal for preparing a blood smear. If venous blood is used, EDTA is
the anticoagulant of choice because it retains the morphological features of
blood cells and also prevents clumping of platelets (Ochei and Kolhatkar, 2007).
In
blood film, it must be noted that capillary blood sample although of great
value in children and in adult with difficult veins are subject to increased
sampling error relative to various blood and produce different results for some
tests. Further disadvantages are that it may be impossible to repeat tests in
the laboratory as the whole sample may have been used and additional tests
which may be required cannot be performed without a second sample being taken.
Capillary blood samples are unsuitable for test which require volumes of blood
greater than 1ml (Baker et al., 2009).
TYPES OF
BLOOD FILMS:
In
haematology, we have two (2) basic analytical blood films and some others.
·
Thin
film
·
Thick
film
Wet films (for
conducting sickling test, white blood cell count, etc).