Zebra – There is an old saying in medicine when you hear hoof beats think horses and not zebras. No we don’t think patients are horses it is just a saying to remind us to evaluate a patient’s signs and symptoms with the mindset that common things present commonly and uncommon things present uncommonly. An example is a patient that presents with a cough, low grade fever and mild shortness of breath. The “horse” is likely a common cold, bronchitis or maybe early pneumonia. The “zebra” would be an uncommon disease like sarcoidosis. The rule can go even farther and there is even the ever elusive unicorn. The “unicorn” is a disease seen once in a lifetime and occurs in only a few hundred patients. So what does this all mean, when evaluating patient’s think of common disease processes first and move on to zebras when the disease does not improve or specific clues appear. Finding a unicorn is super rare, the example I can think of now is the episode from Gray’s Anatomy TV show where they find a rare absorbed twin inside a patient. Another is pheochromocytoma, we look for it a lot in uncontrolled hypertension but rarely find it.
Now that we understand the zebra, how does it apply to the PANCE or PANRE exam?
The PANCE and PANRE is a test of zebras because it does not use actual clinical prevalence of a disease into account but ability to write a question. Common diseases would be bronchitis and hypertension, but since the PANCE and PANRE is not a clinical exam but a test of recall the use of zebras is quite common due to the ease in which questions can be written by the test writers. This means that diseases like sarcoidosis and scleroderma which have easily definable criteria are often questions to identify the disease but CHF is not a common question. When relating to CHF it is usually about a medication or the type but rarely diagnosis. Sarcoidosis on the other hand is easy to write about because of the specific clues to the disease identity.
An example of sarcoidosis-
A 34-year-old female presents with a 1 month cough, shortness of breath, elevated ESR and elevated ACE levels are noted on lab work. Her x-ray demonstrates bilateral hilar adenopathy, what is your initial diagnosis?
Systolic heart failure
Interstitial pulmonary fibrosis
A CHF question
A 55-year-old diabetic male presents with an acute exacerbation of shortness of breath at rest, exam reveals bilateral crackles, a PMI displaced downward and to the left and 2+ pedal edema. In addition to his lisinopril, furosemide and oxygen what medication should be added to his regimen?
Answer is Nitroglycerin
Beta blockers are contraindicated in acute CHF (they make it worse, negative inotrope), in this case Nitro should be added. Diltiazem would worsen the condition (negative inotrope), Amiodarone is an antiarrhythmic and Bumetatide is another diuretic.
So what have we learned?
The PANCE and PANRE is a test of zebras and it is necessary during the test to remember, that what you did on rotations or do in clinical practice differs greatly from the NCCPA exam. The Blueprint is over 550 topics with only about half the topics being tested in your session. One hint I often give is to review the orthopedics section with heavy emphasis on the rheumatology questions as they will make a bulk of the questions you will see in that blueprint area. Remember to think of the zebras when taking the exam. Also remember test writers don’t add useless information or write tricks into a question. Pick the best answer based on the information given, don’t what if or add information not there. Remember the question always has two correct answers you need to pick the best one just remember it is not a clinical prevalence based exam but a recall exam so keep the zebra in mind.