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How Differential Diagnosis Can Improve Your Outcomes

Posted Dec 22nd, 2008 by Trisha Torrey

Symptoms sent you to your doctor.  Now you’ve suffered through the tests, and you may have been referred to a specialist. You’ve googled the little information they’ve provided so far – and it’s time for the verdict – your diagnosis.

"You have XYZ," the doctor tells you. "And this is how we usually treat it."

That’s the perfect world – a concise answer, and well-defined next steps, with the expectation that every word you are hearing is “THE TRUTH.”

But sometimes a diagnosis isn’t so clear – or even correct. So before you get into discussing treatment options with your doctor, there are five words that might make a huge difference in your future.

You need to ask your doctor, "What else might it be?"

For most patients, the suggestion that the doctor might not be telling you exactly what you need to know is a surprise.  But asking what the other possibilities are does not assume your doctor’s diagnosis is wrong. It’s actually a request to participate in a decision-making process your doctor uses every day called "differential diagnosis."

Differential diagnosis is the detective side of determining your diagnosis. It uses evidence and the process of elimination to hone in on the closest answer. Your doctor compares the results of your symptoms, your tests, your family history, her own experience and observation, to a list of possible diagnoses which are all related in some way, but have differences among them. That review should help her eliminate all but one or two answers, resulting in the diagnosis she gives you.

Obtaining a list of the other possibilities from your doctor will give you clues as to why that particular diagnosis was determined for you. You can also compare your doctor’s information to what you’ve learned on the Internet.  Further, it’s a confirmation step. It’s always possible that symptoms were recorded incorrectly, or that test results got filed incorrectly. If you find errors this early in the process, it allows you to correct the course early, before you waste time with wrong, or unnecessary treatment.

Be bold enough to ask the doctor about “differential diagnoses.”  She’ll know you are taking your health seriously enough to actually use her terminology.  Then write down the alternate diagnoses she gives you, and why she has eliminated them.   For example, she might diagnose you with pneumonia, when you think you have the flu.  She might say, “I considered that it might be influenza, but your chest x-ray clearly shows pneumonia, believed to be a bacterial form, which we can treat with an antibiotic.” 

Even after you’ve begun treatment, you may decide it’s not helping you. Your doctor’s original diagnosis may have been flawed. At that point you can study more about the other diagnoses on the list to determine whether one of them is a closer answer. Armed with this extra understanding, you’ll be able to discuss the alternatives intelligently when you return to your doctor, or when you seek a second opinion.

Sharp patients know that asking "what else might it be?" can make a huge difference in treatment success, and eventual health outcomes.


About the author

Trisha Torrey is Every Patient's Advocate. She is a newspaper columnist, radio talk show host, national speaker, and the guide to patient empowerment at

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