There are many misconceptions about the role of clinical
pathology. Some clinicians undervalue clinical pathology data, using it
only to attempt to confirm something which clinical acumen has already discovered.
Equally, there is a tendency to place too much emphasis on clinical pathology
data, regarding it as a definitive diagnostic tool to be relied upon when
acumen has failed entirely. Clinical pathology data can indeed be definitive
but this approach leads to disappointment when the data is equivocal, or
worse, completely uninformative. In short, clinical pathology data is integral
to nearly all diagnostic investigations. Searching a profile for evidence
of a disease pattern is as important a part of the database for each patient
as the physical examination and history. Profiles are designed to evaluate
the status and function of the internal organs and the blood. There are
some body systems, for example, the central nervous system, the cardio-respiratory
system and the gastrointestinal tract, for which there are few relevant
biochemical and haematological parameters. Other body systems are well represented
in correctly designed profiles. Beware of using a limited profile e.g. a
kidney profile, as the primary database for a new investigation; the missing
information may return to haunt you at a later date!
Pattern recognition is the foundation of the clinical pathologist's
art and forms the basis for the interpretation of data, blood films and
cytology. Pattern recognition also helps to overcome some of the eccentricities
of reference ranges and sampling artefacts. Remember that reference ranges
are never more than guidelines, since variables such as the definition of
a normal animal, differing methods of analysis, and the huge diversity of
veterinary species under investigation render many ranges absolutely meaningless
unless interpreted in the context of a pattern of clinical signs, history
and data.
Some diseases produce consistent patterns which can be
interpreted with relative ease but mixed patterns featuring more than one
primary pathological process and diverse secondary effects, frequently occur.
Certain types of sample artefacts e.g. sample ageing, may complicate pattern
interpretation. Many of these ageing artefacts leave recognisable footprints
which are specific to the laboratory and the methods of analysis being used.
One of the most challenging aspects of diagnostic interpretation
is the fourth dimension "time". Disease processes develop over
time and each sample is effectively a single frame from a moving picture.
Incomplete patterns abound and recognising them takes experience. Often,
further samples taken at a later date provide the missing information and
secure the diagnosis. This is particularly true of diseases involving the
haematopoietic and endocrine systems. The time interval before re?sampling
may be crucial and it is advisable to seek the advice of an experienced
clinical pathologist.
The provision and interpretation of results which are precise
and true are the hallmarks of a quality clinical pathology service. Quality
assurance will not be discussed in detail here but it is clear that medical
decisions based on results which are not subjected to rigorous quality control
procedures may at best be rash, and at worst disastrous.
Complete quality assurance requires internal monitoring
of controls, calibrators and standards (precise results) and also comparison
of results with those from other laboratories using the same external samples
(true results). When you use data from a professional Clinical Pathology
Laboratory such as Axiom you know that, although human error can never be
absolutely prevented, the results are constantly scrutinised by qualified
technicians and clinical pathologists to ensure that values are both precise
and true. |