Medicine is a numbers game. We are always trying to guess what the percentage is that a patient is going to have a particular diagnosis. We use the history and physical exam to produces a pretest probability that a patient has a diagnosis. Depending on the mortality of the suspected diagnosis a threshold to order tests is created. If the pretest probability is above the threshold level we proceed with ordering a test.
In a high mortality diagnosis, we are only allowed to miss 2% of patients. That is why large studies that produce clinical scoring tools, like the PERC score, aim to miss < 2% of patients. The problem is that most of the classic presentations for diseases that we learn about in textbooks are only sensitive enough to catch greater than 10% of patients with a specific high-risk diagnosis. As a result, it is important to identify the risk factors for the outlier population that sit between 2% and 10%.
In patients with higher risk features the threshold for testing is lowered to ensure that a potentially life-threatening diagnosis is not missed.
So here is a list of wildcards to keep an eye out for
1. Super old patients
- These are patients that are >70 years old. Older patients may not present with a fever or elevated white blood cell count when they are septic. Their weak abdominal muscles may not be able to show signs of guarding or rigidity when there is an intraabdominal process going on.
- Chemo: patients that have received chemo 1 week prior to the presentation are at increased risk of being neutropenia
- Rheum patients: These patients are usually placed on immunosuppressants. Patients with Lupus are at increased risk of badness. Always consider the unexpected in Lupus patients.
- Transplant patients: These patients are typically on immunosuppressants (i.e. Tacrolimus)
- HIV/AIDS: CD4 count < 200.
- There is an increased rate of patients being prescribed novel oral anticoagulants. Liver failure patients are also at increased risk of bleeding. If an anticoagulated patient is hypotensive, look them all over to ensure that they are not hemorrhaging (i.e spontaneous intraabdominal bleeding).
When you see a patient with one of these wild cards, take a second to be extra thorough with your history and physical. Be sure to expect the unexpected and broaden your differential and work up.
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