Priority of diagnostic plans
Where does the DAMN IT acronym fit into the diagnostic process? When formulating diagnostic plans, we routinely follow this
sequence of steps:
1. Verify or confirm the presence of problems, especially those defined by clients.
2. Localize problems to an organ or body system.
3. Consider the most probable pathophysiologic mechanisms associated with the identified problems (DAMN IT acronym; Table
4. Based on the probable (in contrast to the possible) pathophysiologic mechanisms present in the patient, formulate specific
diagnostic rule-outs (tentative diagnoses) that would explain the underlying cause of the problems, and implement diagnostic
tests to confirm them.
By using the DAMN IT acronym when considering diagnostic rule-outs, numerous diagnostic possibilities can be logically reduced
to a few diagnostic probabilities.
The DAMN IT acronym
Each letter in the acronym represents one or more pathophysiologic disease processes. Examine Table 1 and begin with the letter
"D," which may stimulate your recall of pathophysiologic mechanisms such as degenerative osteoarthritis or degenerative aging
to explain severe lameness localized to both coxofemoral joints of a 10-year-old German shepherd. The letter "D" may also
stimulate your recall of developmental or congenital disorders, such as glomerulonephropathy to explain unthriftyness, progressive
azotemia, severe proteinuria, isosthenuria, etc., in an English cocker spaniel.
The letter "M" could prompt one to think of a metabolic disorder, such as diabetes mellitus to explain progressive vomiting,
marked dehydration, impaired urine concentrating capacity and extreme depression.
If we routinely use it, the DAMN IT acronym rapidly becomes part of our memory. When used in conjunction with the history,
physical examination and other diagnostic data, the acronym facilitates rapid and reproducible formulation of probable rule-outs
(i.e., as tentative diagnoses) for each of a patient's undiagnosed problems. In 1962 when I was a sophomore veterinary student,
I created the DAMN IT acronym as an aid to taking examinations. I have added a few pathophysiologic mechanisms since that
time (Table 1). As an iterative memory aid, some of the pathophysiologic mechanisms listed with different letters in the DAMN
IT acronym overlap (i.e., autoimmune and immune; developmental, anomalous and inherited).
What is next?
After developing a list of pathophysiologic mechanisms likely to be causing the clinical problems, the most probable causes
of these problems should be ruled in or ruled out by implementing appropriate diagnostic plans. The specific diagnostic tests
and procedures chosen to evaluate each problem, and the rate and frequency with which these tests are implemented, depend
on several factors, especially the patient's status.
If a patient is admitted with an acute onset of rapidly changing problems that are assessed to be an immediate threat to life,
diagnostic plans for several rule-outs should be implemented simultaneously. For example, if a critically ill patient is admitted
because of rapidly progressing vomiting, dehydration, impaired urine concentrating capacity and extreme depression, it's advisable
to simultaneously implement diagnostic plans to rule out renal failure, diabetic ketoacidosis, hypoadrenocorticism, pyometra,
hepatic dysfunction and systemic toxicity.
If a priority list of investigation is established so you don't evaluate the second rule-out until the first rule-out has
been eliminated, and follow-up plans are implemented to rule out only one problem at a time (i.e., in series), the patient
may die before a specific diagnosis is established. In contrast, if a patient has had intermittent progressive urinary incontinence
for the past seven months, one can initially justify a less comprehensive diagnostic approach associated with the expenditure
of less duplication of resources.
Diagnoses should not be overstated by guessing their underlying cause based on insufficient evidence. They should be stated
at the level of refinement that can be reasonably justified based on current knowledge about the patient. Why? Because if
the diagnosis is overstated, then misdiagnosis, misprognosis and formulation of ineffective or contraindicated therapy can
result. No patient should be worse for having seen the doctor.
Dr. Osborne, a diplomate of the American College of Veterinary Internal Medicine, is professor of medicine in the Department of Small
Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota.