Medical Practice - Page 4
Laboratory Tests
The increase in the number, type, and
availability of laboratory tests has resulted in the
increased reliance on this approach for the
solution of clinical problems. It is essential to
bear in mind that laboratory tests are often
believed by physicians to be the final author-
ity, regardless of possible fallibility of the
tests, the individuals handling or interpreting
them, or of the instruments. Laboratory data
cannot replace observation of the patient.
Both the expense and possibilities of
misinterpretation of the lab tests ordered should be
taken into account by the physician. Laboratory
tests are rarely done individually, but
rather as batteries (24 up to 40). The various
combinations of lab tests are frequently
quite useful. The thoughtful use of screening
tests should not be confused with indis-
criminate lab testing. Screening tests are
useful because they enable the physician to
obtain a group of lab results conveniently,
utilizing a single specimen of blood, at rela-
tively low cost. Biochemical measurements,
together with simple lab tests, such as
blood counts, urine analyses, and sedimentation
rate often provide the principle clue to
the presence of a pathological process. The
physician must be alert for abnormalities in
screening test results that may not indicate
significant disease. An isolated laboratory
abnormality on an otherwise well patient should
not provoke an in-depth medical
workup. The lab test itself may bear repeating
to see if the results are reproducible. The
physician can then determine whether the
results are significant. Clinical judgment will
determine how to proceed if this
occurs.
Imaging Techniques
Over the past quarter of a century, the use of
imaging techniques as a diagnostic method
has become well established. This includes
ultrasonography, a method of examination
using soundwaves to visualize internal organs;
computerized axial tomography (CAT);
magnetic resonance imaging (MRI); and position
emission tomography (PET). This
major new diagnostic approach has frequently
replaced invasive techniques that require
insertion into the body of tubes, wires, or
catheters or surgical biopsy. The latter are fre-
quently painful and at times quite risky to the
patient. While very valuable, imaging
technique results need validation and are often
extremely expensive. Therefore, this
approach should be used judiciously, but not as
a supplement to invasive techniques.
DIAGNOSING DISEASE
Arriving at a diagnosis involves analysis and
synthesis--two aspects of logic. The
physician identifies all the problems raised
after hearing the patient's complaints, per-
forming a physical exam, and receiving lab
findings. Most physicians try to place the
medical problem they are dealing with into one
of several syndromes. A syndrome is a
group of symptoms associated with any disease
process, which constitutes together a
picture of the disease.
The syndrome incorporates a hypothesis
concerning a tissue, organ, or organ sys-
tem. For example, congestive heart failure will
produce a wide variety of symptoms, all
of which are connected to the single
pathophysiological mechanism, namely inadequacy
of the heart muscle. Similarly, identifying a
syndrome usually narrows down the number
of possibilities for an illness and suggests
ordering relevant clinical and lab studies.
Making a diagnosis is more difficult if one
cannot categorize the patient's signs and
symptoms. Nevertheless, the same logical
approach, starting with the symptoms, pro-
ceeding to the physical findings, and lab
results will usually lead to a diagnosis.
Diagnosing disease can prove at times very
challenging and require considerable
intellectual and physical effort. With the
advances in laboratory and imaging technol-
ogy, the task has been made much easier, but
there are times when even these modalities
do not provide satisfying answers. The
physician should not hesitate to consult a spe-
cialist to help establish a probable
diagnosis.
User Comments Add a comment…