Page 362 - The Veterinary Laboratory and Field Manual 3rd Edition

Clinical chemistry 331

local hospital. Most of these dip-stick type tests
require collection of a very small drop of blood
that remains in contact with a colour reagent
strip for a specified period of time. The colour
strip is then washed and the colour change
read alongside a colour chart which relates to a
known amount of urea or glucose in the blood.
Some systems, for example, B-M test glycaemie,
produced by BCL utilize double colour blocks
which may give a more accurate result, and these
systems may be read using a special reference
system. Similar tests are also available for test-
ing urine and other samples (Figure 7.1). Figure 7.1 Chemstrip® uG/K are test strips used
When using commercial reagent strips the in human medicine for the semi-quantitative deter-
instruction sheets should be read carefully mination of glucose in urine and for the detection
to ensure that the correct test parameters are of ketone bodies (for example, acetone) in urine.
used. Before use it is advisable to check that the Similar products are available for veterinary use. In
reagent strips are (1) not out of date and (2) human medicine these strips can be easily used
that they are stored correctly. Most dip-stick by patients to monitor diabetes control. The test is
tests come with detailed information about the based on dipping the reaction area of the test strip
optimal test method and how to interpret the into freshly voided urine. There are two test reaction
colour change. Interpretation of the test result pads on these strips that change colour in proportion
will also depend on the presumptive diagnosis to the amount of glucose or ketones respectively,
based on clinical history and examination of the present in the sample. In normal healthy individuals
animal. If test results do not fall within expected neither of the reaction pads on the test strip will
parameters it may be necessary to reconsider the change colour. Any colour change noted after the
diagnosis but it is possible that the test result recommended test reaction time is read against a
is incorrect, particularly if the sample has not colour coded key provided on the container. Similar
been collected or handled correctly. If results are test strips are available for testing blood and serum
doubtful it is best to repeat the test on a fresh samples for the presence of glucose, creatinine and
sample. blood urea nitrogen. When used correctly these
strips are fairly accurate and provide a good supple-
ment to other diagnostic tests. Photo: Dr Susan
Photometer methods Cork, University of Calgary, Canada.

Most, if not all, biochemistry test systems are laboratories where large numbers of biochemi-
based on colorimetry in one form or another. cal tests are performed regularly these systems
The principles and methodology of quantitative would be worth considering but they may not
biochemical tests are explained in section 7.4. be justified where the budget is restricted or
There are a range of automated high through- where technical support for servicing repair is
put systems available (see Chapter 2) some of unreliable. There are also some newer and less
which require a large initial expenditure and expensive kit test systems which could be con-
have fairly high maintenance costs with ongoing sidered for smaller veterinary laboratories where
requirements for reagent kits and servicing. In cost recovery is an option.

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