“How can you be sure?”
That question stopped our discussion for a second.
During some down time, several nurses and I were talking about childhood coughs. Her 6 month old child had just started daycare 2 weeks ago and has been coughing ever since. The child was put on amoxicillin and then Zithromax by her pediatrician but … [GASP] … her cough wasn’t getting any better. The nurse thought her child had pneumonia.
“What should she be taking now?”
I was in a particularly snarky mood, so, with a smirk, I said “probably vancomycin … maybe add gentamycin just for the gram negative coverage, too.”
“I’m being serious. She’s not getting better with antibiotics.”
“BINGO! That’s because she has a virus infection and antibiotics don’t kill viruses any more than RAID kills dandelions.”
“But a virus infection isn’t going to last for two weeks.”
“Neither is bacterial pneumonia. The fact that she isn’t getting better with antibiotics should tell you that she has a chest cold. It’s a virus.”
“How can you be sure?”
There’s just no good response to that question. The truth is that we can’t be “sure” that there isn’t a bacterial infection present. We can’t be “sure” she didn’t aspirate a foreign body. We can’t be “sure” that she doesn’t have tracheomalacia. There is just no way that we can ever give a Flo’s Progressive Insurance 100% guarantee that a given set of symptoms is being caused by a given disease process and nothing else. The problem is that often patients expect this kind of diagnostic accuracy and get upset when there’s a misdiagnosis. Unfortunately, medicine is an inexact science at best. One of the things that I always found ironic is that many patients and even some medical experts expect doctors to “prove” their diagnoses do exist or to “rule out” other diagnoses by showing that those diagnoses couldn’t possibly exist. However, in court, when a doctor is accused of wrongdoing, an expert is required to testify to “a reasonable degree of medical certainty” which in most cases means that something is “more likely than not.” In other words, court testimony demands only 50.001% certainty while clinical practice often demands a much higher level of certainty.
Our discussion transitioned from snark to reality.
“Most of the time you can’t be ‘sure’ of a medical diagnosis – especially a diagnosis with a symptom as vague as a cough.”
“Well patients want certainty. If I bring my child to the doctor, I want to KNOW what’s wrong, not get some wastebasket diagnosis like a viral infection when my baby could have pneumonia.”
I nodded my head. Then I went to the cafeteria to get some lunch and I mulled that last statement while walking down the hall. How could I explain the concepts of pre-test probability and futility without getting too far into the weeds? The runny cottage cheese at the salad bar gave me an idea.
I got back to the ED and asked the nurse
“Have you ever given your child poisoned food?”
“Of course not.”
“But how can you be sure? How do you know that the formula doesn’t have contaminants in it – like that Chinese infant formula contamination back in 2008?”
“That’s completely different from diagnosing pneumonia.”
“True, but it’s the same concept. We assume that a healthy-appearing child with a runny nose and cough in the middle of winter has a head cold the same way we assume that the food we eat is not contaminated. If there are signs of complications with a coughing child, we may do further testing to see if there are other problems. If there are signs of food spoilage, we may choose not to eat the food.”
“Not the same thing.”
“Hear me out. We naturally eat food without examining it much because the likelihood of it being poisoned is quite small. However, if we wanted to be “sure” that the food wasn’t contaminated or poisoned, then we could do a bunch of microbiological testing before we eat every bite to make “sure” that the food wasn’t poisoned. But because the likelihood of poisoning is so small, all of the expenses of the extra testing probably would be a waste of money.”
“Not the same.”
“Even worse, if we do a bunch of testing on a well-appearing child with a runny nose and cough, there may be some complications from the testing or complications/side effects from the treatment for a disease that may not be present. People can get resistant infections or bad diarrhea from antibiotics for a “pneumonia” that was over-read on a chest x-ray.”
“I’ll say. My daughter has had diarrhea for a week.”
“Exactly my point. She’d probably be doing better with nasal saline, suction, and perhaps some … OTC cough medications” – a cringeworthy concept for most pediatricians.
I was convinced I had prevailed in our little discussion until she asked “Can children take Levaquin?”
“Only for bacterial infections.”
“No. Just no.”