In this episode, I’ll discuss Ockham’s Razor vs. Hickam’s Dictum.
Ockham’s Razor and Hickam’s Dictum are often referred to as opposing theories for diagnoses of disease. Pharmacists can use knowledge of these principles to understand a part of physicians’ thought process and to evaluate potential adverse effects of medications.
Ockham’s Razor
William of Ockham was an English philosopher and theologian who lived in the first half of the 14th century. His approach to problem-solving focused heavily on simplicity and has been called Ockham’s Razor. Ockham’s Razor states:
Among competing hypotheses, the one with the fewest assumptions should be selected.
To my knowledge, Ockham never applied this problem-solving concept to medicine, but many others have. The concept is also referred to as diagnostic parsimony. The idea being that correct diagnosis is the one with the fewest assumptions or the fewest possible causes for a given set of symptoms.
A good example of the application of Ockham’s razor was published in the Journal of the Royal Society of Medicine:
Imagine a patient presents to casualty complaining of a headache, neck stiffness, fever, and confusion – it is of course perfectly possible that he simultaneously developed a subarachnoid haemorrhage, torticollis, and hepatic encephalopathy. However, Ockham’s razor offers us a single diagnosis that fully accounts for this single presentation and guides us to a diagnosis of meningitis – the explanation that requires the fewest number of assumptions.
Hickam’s Dictum
Many times, however, a rare disease might explain a given set of symptoms, but so will two very common diseases. In such cases, blindly applying Ockham’s razor would lead to misdiagnosis. A counter-argument against this over simplification called Hickam’s Dictum is attributed to John Hickam, a US-based physician in the 1950’s. Hickam’s Dictum states:
Patients can have as many diseases as they damn well please.
Application in pharmacy
Rather than one concept applying all the time, diagnosis is a continuous effort of hypothesis generation and testing. Many times I can use my knowledge base to help a physician rule in or out medication-related causes of disease. Having the knowledge of these different problem-solving concepts helps me place my pharmacy-specific knowledge in the proper context.
You can see the balance between these problem-solving concepts at work in several pharmacy-related assessments. Here are two examples:
First, the 4Ts of heparin-induced thrombocytopenia. The 4T score (and therefore the pretest probability of heparin-induced thrombocytopenia) is affected by whether other causes for thrombocytopenia are present.
Second, the Naranjo algorithm for determining the likelihood a medication is responsible for an adverse effect. The Naranjo score is affected by whether there are alternative causes that could have caused the reaction in question.
If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.
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