Belief or disbelief does not alter the truth. Clinical impressions are inherently unreliable, generally conforming to our
preconceived biases. However, strong preconceptions are not a substitute for objective evidence. We must use caution not to
ignore data because it does not coincide with our beliefs. Rather than interpreting facts in light of preconceived conclusions,
we must train ourselves to allow reproducible observations (facts) to lead us to reasonable conclusions.
There is a difference between diagnostic possibilities and diagnostic probabilities. In general, collection and interpretation
of relevant clinical data about a patient's illness allows us to reduce numerous diagnostic possibilities to a few or one
diagnostic probability. However, diagnoses are often a matter of educated opinion rather than a matter of fact. It is one
thing to make a diagnosis and another thing to substantiate it. Absence of clinical evidence of suspected diseases is not
always synonymous with evidence of absence of these diseases. Likewise, detection of evidence that is consistent with a specific
type of disease is not always pathognomonic for that specific disease. It follows that we as veterinarians should convey to
our clients that our diagnoses (and prognoses) are based on probability, and therefore are not infallible.
Waiting to pursue the diagnosis of the underlying cause(s) of various diseases until the patient does not respond to symptomatic
shotgun therapy is like saying, "Ready! Fire! Aim!" Not only does this approach to diagnosis often result in use of drugs
that miss the therapeutic target, it often results in iatrogenic errors that can compromise the health of our patients further.
Not all diagnostic plans benefit patients in context of the balance of associated risks and benefits, and the resources that
are required to implement them. Therefore, we should not confuse activity with accomplishment. Why do efficiently that which
should not be done at all?
Formulate prognoses as if we were the patients.
Consider the following corollaries of Rule No. 3:
Prognosis of diseases requires judgment in the absence of certainty. Therefore, when making prognoses, we must remember that
almost right is still wrong.
For some patients, prognoses are life saving; for others they are a death sentence. Therefore, our decisions about the care
of our patients should be based on the same conscientious, explicit and judicious use of current best evidence (so-called
evidence-based medicine) that we would desire physicians to use in caring for us if we were in a similar situation. Putting
evidence-based medicine into practice means integrating our individual clinical expertise with the best available external
clinical evidence derived from systematic research.
The following scheme is recommended to score the strength and the quality of available external evidence (McGowan et al: Journal
of Infectious Diseases, Vol. 165, pages 1-13, 1992). Grade "I" Evidence is defined as the highest quality evidence. It is
derived from at least one properly randomized controlled clinical study. Grade "II" Evidence may be data obtained from:
1) at least one well-designed clinical study without randomization;
2) cohort or case-controlled analytic studies;
3) studies using acceptable laboratory models or simulations in the target species, preferably from more than one center;
4) multiple time series;
5) or dramatic results in uncontrolled studies. Grade "III" Evidence is defined as the weakest form of evidence, and may be
- opinions from respected authorities on the basis of clinical experience;
- descriptive studies;
- studies in other species;
- pathophysiological justification;
- reports of expert committees.
Treat others as we want to be treated.