Page 327 - The Veterinary Laboratory and Field Manual 3rd Edition

296 Susan C. Cork and Roy Halliwell

immunological response and the nature of dis-
ease. Before evaluating haematology results,
consider the following questions and points.

1 What was the purpose of the test, that is, is
the animal unwell or has the sample been
sent for the purposes of general health screen-
ing? What is the presenting clinical problem,
that is, does the animal have anaemia or is
the submitter interested in the white cell
Figure 5.8 Equine blood smear viewed under oil response to infection?
immersion (Diff Quick 1000×) illustrating numerous 2 Check the submission form. Has the submit-
polymorph neutrophils (N), an eosinophil (E) and a ter only requested a general haematology
basophil (B). Diff Quick stain. RBC are also pres- screen or are specialized tests also requested?
TM
ent. See also Plate 23. Some more specialized tests, for example,
assessment for blood clotting disorders, may
need to be done at a referral laboratory.
3 Test results for each case should be compared
with the laboratory’s list of normal values.
4 Do the results fit with the submitting veteri-
narian’s list of differential diagnoses for the
case? If not, it may be important to discuss
the case further with the submitter to decide
whether additional tests are required or if tests
should be repeated on a fresh sample. Where
there are unusual or unexpected results it is
Figure 5.9 Equine blood smear viewed under oil important to check that the test results are
immersion 1000× illustrating granulocytes (E and accurate, that is, ensure that quality control
N) and agranulocytes (M and L). (E) Eosinophil, (N) measures have been complied with.
polymorph neutrophil. It is not always possible to
distinguish between monocytes and lymphocytes Haematology can be used to provide useful infor-
in blood smears. In this smear, the monocytes (M) mation about the health of an animal and about
are activated and are larger than dormant mono- the animal’s response to disease. However, the
cytes or lymphocytes (L). See text. Diff Quick interpretation of results can be challenging. In
TM
stain. RBC are also present. See also Plate 24. many cases sequential samples may be needed
to confirm a diagnosis. Sequential samples can
published ranges for common domestic species also be used to help the submitter assess the
are given above in Table 5.4. likely prognosis for a case, that is, is the ani-
mal’s immune system responding effectively?
Some common, non-specific, changes seen in the
5.7 Interpretation of results white cell fraction of the haematology profile are
outlined in Table 5.5.
Interpretation of results requires a good under- Haematology can provide a great deal of
standing of the haematopoietic system, the valuable information about a case but special-

Vet Lab.indb 296 26/03/2019 10:25